Sample records for stream flow rates
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Natural stream flow-rates measurements by tracer techniques
International Nuclear Information System (INIS)
Cuellar Mansilla, J.
1982-01-01
This paper presents the study of the precision obtained measuring the natural stream flow rates by tracer techniques, especially when the system presents a great slope and a bed constituted by large and extended particle size. The experiences were realized in laboratory pilot channels with flow-rates between 15 and 130 [1/s]; and in natural streams with flow-rates from 1 to 25 m 3 /s. Tracer used were In-133m and Br-82 for laboratory and field measurements respectively. In both cases the tracer was injected as a pulse and its dilution measured collecting samples in the measured section, at constant flow-rates, of 5[1] in laboratory experiences and 60[1] of water in field experiences. Precisions obtained at a 95% confidence level were about 2% for laboratory and 3% for field. (I.V.)
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Linear growth rates of resistive tearing modes with sub-Alfvénic streaming flow
International Nuclear Information System (INIS)
Wu, L. N.; Ma, Z. W.
2014-01-01
The tearing instability with sub-Alfvénic streaming flow along the external magnetic field is investigated using resistive MHD simulation. It is found that the growth rate of the tearing mode instability is larger than that without the streaming flow. With the streaming flow, there exist two Alfvén resonance layers near the central current sheet. The larger perturbation of the magnetic field in two closer Alfvén resonance layers could lead to formation of the observed cone structure and can largely enhance the development of the tearing mode for a narrower streaming flow. For a broader streaming flow, a larger separation of Alfvén resonance layers reduces the magnetic reconnection. The linear growth rate decreases with increase of the streaming flow thickness. The growth rate of the tearing instability also depends on the plasma beta (β). When the streaming flow is embedded in the current sheet, the growth rate increases with β if β s , but decreases if β > β s . The existence of the specific value β s can be attributed to competition between the suppressing effect of β and the enhancing effect of the streaming flow on the magnetic reconnection. The critical value β s increases with increase of the streaming flow strength
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Method of measuring the mass flow rate of a substance entering a cocurrent fluid stream
International Nuclear Information System (INIS)
Cochran, H.D. Jr.
1978-01-01
An improved method of monitoring the mass flow rate of a substance entering a coherent fluid stream is described. The method very basically consists of heating equal sections of the fluid stream above and below the point of entry of the substance to be monitored, and measuring and comparing the resulting change in temperature of the sections. Advantage is taken of the difference in thermal characteristics of the fluid and the substance to be measured to correlate temperature differences in the sections above and below the substance feed point for providing an indication of the mass flow rate of the substance
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International Nuclear Information System (INIS)
Chen, K.F.
1996-01-01
The Environmental Transport Group of the Environmental Technology Section was requested to predict the seven-day ten-year low flow (7Q10 flow) for the SRS streams based on historical stream flow records. Most of the historical flow records for the SRS streams include reactor coolant water discharged from the reactors and process water released from the process facilities. The most straight forward way to estimate the stream daily natural flow is to subtract the measured upstream reactor and/or facility daily effluents from the measured downstream daily flow. Unfortunately, this method does not always work, as indicated by the fact that sometimes the measured downstream volumetric flow rates are lower than the reactor effluent volumetric flow rates. For those cases that cannot be analyzed with the simple subtracting method, an alternative method was used to estimate the stream natural flows by statistically separating reactor coolant and process water flow data. The correlation between the calculated 7Q10 flows and the watershed areas for Four Mile Branch and Pen Branch agrees with that calculated by the USGS for Upper Three Runs and Lower Three Runs Creeks. The agreement between these two independent calculations lends confidence to the 7Q10 flow calculations presented in this report
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Peterson, James T.; Shea, C.P.
2015-01-01
Fishery biologists are increasingly recognizing the importance of considering the dynamic nature of streams when developing streamflow policies. Such approaches require information on how flow regimes influence the physical environment and how those factors, in turn, affect species-specific demographic rates. A more cost-effective alternative could be the use of dynamic occupancy models to predict how species are likely to respond to changes in flow. To appraise the efficacy of this approach, we evaluated relative support for hypothesized effects of seasonal streamflow components, stream channel characteristics, and fish species traits on local extinction, colonization, and recruitment (meta-demographic rates) of stream fishes. We used 4 years of seasonal fish collection data from 23 streams to fit multistate, multiseason occupancy models for 42 fish species in the lower Flint River Basin, Georgia. Modelling results suggested that meta-demographic rates were influenced by streamflows, particularly short-term (10-day) flows. Flow effects on meta-demographic rates also varied with stream size, channel morphology, and fish species traits. Small-bodied species with generalized life-history characteristics were more resilient to flow variability than large-bodied species with specialized life-history characteristics. Using this approach, we simplified the modelling framework, thereby facilitating the development of dynamic, spatially explicit evaluations of the ecological consequences of water resource development activities over broad geographic areas. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
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Shock formation and structure in magnetic reconnection with a streaming flow.
Wu, Liangneng; Ma, Zhiwei; Zhang, Haowei
2017-08-18
The features of magnetic reconnection with a streaming flow have been investigated on the basis of compressible resistive magnetohydrodynamic (MHD) model. The super-Alfvenic streaming flow largely enhances magnetic reconnection. The maximum reconnection rate is almost four times larger with super-Alfvenic streaming flow than sub-Alfvénic streaming flow. In the nonlinear stage, it is found that there is a pair of shocks observed in the inflow region, which are manifested to be slow shocks for sub-Alfvénic streaming flow, and fast shocks for super-Alfvénic streaming flow. The quasi-period oscillation of reconnection rates in the decaying phase for super-Alfvénic streaming flow is resulted from the different drifting velocities of the shock and the X point.
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Sullivan, C.; Good, R. G. R.; Binns, A. D.
2017-12-01
Sediment transport processes in streams provides valuable insight into the temporal evolution of planform and bedform geometry. The majority of previous experimental research in the literature has focused on bedload transport and corresponding bedform development in rectangular, confined channels, which does not consider planform adjustment processes in streams. In contrast, research conducted with laboratory streams having movable banks can investigate planform development in addition to bedform development, which is more representative of natural streams. The goal of this research is to explore the relationship between bedload transport rates and the morphological adjustments in meandering streams. To accomplish this, a series of experimental runs were conducted in a 5.6 m by 1.9 m river basin flume at the University of Guelph to analyze the bedload impacts on bed formations and planform adjustments in response to varying flow conditions. In total, three experimental runs were conducted: two runs using steady state conditions and one run using unsteady flow conditions in the form of a symmetrical hydrograph implementing quasi steady state flow. The runs were performed in a series of time-steps in order to monitor the evolution of the stream morphology and the bedload transport rates. Structure from motion (SfM) was utilized to capture the channel morphology after each time-step, and Agisoft PhotoScan software was used to produce digital elevation models to analyze the morphological evolution of the channel with time. Bedload transport rates were quantified using a sediment catch at the end of the flume. Although total flow volumes were similar for each run, the morphological evolution and bedload transport rates in each run varied. The observed bedload transport rates from the flume are compared with existing bedload transport formulas to assess their accuracy with respect to sediment transport in unconfined meandering channels. The measured sediment transport
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Optimized open-flow mixing: insights from microbubble streaming
Rallabandi, Bhargav; Wang, Cheng; Guo, Lin; Hilgenfeldt, Sascha
2015-11-01
Microbubble streaming has been developed into a robust and powerful flow actuation technique in microfluidics. Here, we study it as a paradigmatic system for microfluidic mixing under a continuous throughput of fluid (open-flow mixing), providing a systematic optimization of the device parameters in this practically important situation. Focusing on two-dimensional advective stirring (neglecting diffusion), we show through numerical simulation and analytical theory that mixing in steady streaming vortices becomes ineffective beyond a characteristic time scale, necessitating the introduction of unsteadiness. By duty cycling the streaming, such unsteadiness is introduced in a controlled fashion, leading to exponential refinement of the advection structures. The rate of refinement is then optimized for particular parameters of the time modulation, i.e. a particular combination of times for which the streaming is turned ``on'' and ``off''. The optimized protocol can be understood theoretically using the properties of the streaming vortices and the throughput Poiseuille flow. We can thus infer simple design principles for practical open flow micromixing applications, consistent with experiments. Current Address: Mechanical and Aerospace Engineering, Princeton University.
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Lightbody, A.; Sotiropoulos, F.; Kang, S.; Diplas, P.
2009-12-01
Despite their widespread application to prevent lateral river migration, stabilize banks, and promote aquatic habitat, shallow transverse flow training structures such as rock vanes and stream barbs lack quantitative design guidelines. Due to the lack of fundamental knowledge about the interaction of the flow field with the sediment bed, existing engineering standards are typically based on various subjective criteria or on cross-sectionally-averaged shear stresses rather than local values. Here, we examine the performance and stability of in-stream structures within a field-scale single-threaded sand-bed meandering stream channel in the newly developed Outdoor StreamLab (OSL) at the St. Anthony Falls Laboratory (SAFL). Before and after the installation of a rock vane along the outer bank of the middle meander bend, high-resolution topography data were obtained for the entire 50-m-long reach at 1-cm spatial scale in the horizontal and sub-millimeter spatial scale in the vertical. In addition, detailed measurements of flow and turbulence were obtained using acoustic Doppler velocimetry at twelve cross-sections focused on the vicinity of the structure. Measurements were repeated at a range of extreme events, including in-bank flows with an approximate flow rate of 44 L/s (1.4 cfs) and bankfull floods with an approximate flow rate of 280 L/s (10 cfs). Under both flow rates, the structure reduced near-bank shear stresses and resulted in both a deeper thalweg and near-bank aggradation. The resulting comprehensive dataset has been used to validate a large eddy simulation carried out by SAFL’s computational fluid dynamics model, the Virtual StreamLab (VSL). This versatile computational framework is able to efficiently simulate 3D unsteady turbulent flows in natural streams with complex in-stream structures and as a result holds promise for the development of much-needed quantitative design guidelines.
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Jensen, C.; McGuire, K. J.
2017-12-01
Headwater streams are spatially extensive, accounting for a majority of global stream length, and supply downstream water bodies with water, sediment, organic matter, and pollutants. Much of this transmission occurs episodically during storms when stream flow and connectivity are high. Many headwaters are temporary streams that expand and contract in length in response to storms and seasonality. Understanding where and when streams carry flow is critical for conserving headwaters and protecting downstream water quality, but storm events are difficult to study in small catchments. The rise and fall of stream flow occurs rapidly in headwaters, making observation of the entire stream network difficult. Stream intermittency sensors that detect the presence or absence of water can reveal wetting and drying patterns over short time scales. We installed 50 intermittency sensors along the channel network of a small catchment (35 ha) in the Valley and Ridge of southwest Virginia. Previous work shows stream length is highly variable in this shale catchment, as the drainage density spans two orders of magnitude. The sensors record data every 15 minutes for one year to capture different seasons, antecedent moisture conditions, and precipitation rates. We seek to determine whether hysteresis between stream flow and network length occurs on the rising and falling limbs of events and if reach-scale characteristics such as valley width explain spatial patterns of flow duration. Our results indicate reaches with a wide, sediment-filled valley floor carry water for shorter periods of time than confined channel segments with steep valley side slopes. During earlier field mapping surveys, we only observed flow in a few of the tributaries for the wettest conditions mapped. The sensors now show that these tributaries flow more frequently during much smaller storms, but only for brief periods of time (hour). The high temporal sampling resolution of the sensors permits a more realistic
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Ambient groundwater flow diminishes nitrogen cycling in streams
Azizian, M.; Grant, S. B.; Rippy, M.; Detwiler, R. L.; Boano, F.; Cook, P. L. M.
2017-12-01
Modeling and experimental studies demonstrate that ambient groundwater reduces hyporheic exchange, but the implications of this observation for stream N-cycling is not yet clear. We utilized a simple process-based model (the Pumping and Streamline Segregation or PASS model) to evaluate N- cycling over two scales of hyporheic exchange (fluvial ripples and riffle-pool sequences), ten ambient groundwater and stream flow scenarios (five gaining and losing conditions and two stream discharges), and three biogeochemical settings (identified based on a principal component analysis of previously published measurements in streams throughout the United States). Model-data comparisons indicate that our model provides realistic estimates for direct denitrification of stream nitrate, but overpredicts nitrification and coupled nitrification-denitrification. Riffle-pool sequences are responsible for most of the N-processing, despite the fact that fluvial ripples generate 3-11 times more hyporheic exchange flux. Across all scenarios, hyporheic exchange flux and the Damkohler Number emerge as primary controls on stream N-cycling; the former regulates trafficking of nutrients and oxygen across the sediment-water interface, while the latter quantifies the relative rates of organic carbon mineralization and advective transport in streambed sediments. Vertical groundwater flux modulates both of these master variables in ways that tend to diminish stream N-cycling. Thus, anthropogenic perturbations of ambient groundwater flows (e.g., by urbanization, agricultural activities, groundwater mining, and/or climate change) may compromise some of the key ecosystem services provided by streams.
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Hydroelectric plant turbine, stream and spillway flow measurement
Energy Technology Data Exchange (ETDEWEB)
Lampa, J.; Lemon, D.; Buermans, J. [ASL AQ Flow Inc., Sidney, BC (Canada)
2004-07-01
This presentation provided schematics of the turbine flow measurements and typical bulb installations at the Kootenay Canal and Wells hydroelectric power facilities in British Columbia. A typical arrangement for measuring stream flow using acoustic scintillation was also illustrated. Acoustic scintillation is portable, non-intrusive, suitable for short intakes, requires minimal maintenance and is cost effective and accurate. A comparison between current meters and acoustic scintillation was also presented. Stream flow measurement is valuable in evaluating downstream areas that are environmentally important for fish habitat. Stream flow measurement makes it possible to define circulation. The effects of any changes can be assessed by combining field measurements and numerical modelling. The presentation also demonstrated that computational fluid dynamics modelling appears promising in determining stream flow and turbulent flow at spillways. tabs., figs.
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Stream Tracker: Crowd sourcing and remote sensing to monitor stream flow intermittence
Puntenney, K.; Kampf, S. K.; Newman, G.; Lefsky, M. A.; Weber, R.; Gerlich, J.
2017-12-01
Streams that do not flow continuously in time and space support diverse aquatic life and can be critical contributors to downstream water supply. However, these intermittent streams are rarely monitored and poorly mapped. Stream Tracker is a community powered stream monitoring project that pairs citizen contributed observations of streamflow presence or absence with a network of streamflow sensors and remotely sensed data from satellites to track when and where water is flowing in intermittent stream channels. Citizens can visit sites on roads and trails to track flow and contribute their observations to the project site hosted by CitSci.org. Data can be entered using either a mobile application with offline capabilities or an online data entry portal. The sensor network provides a consistent record of streamflow and flow presence/absence across a range of elevations and drainage areas. Capacitance, resistance, and laser sensors have been deployed to determine the most reliable, low cost sensor that could be mass distributed to track streamflow intermittence over a larger number of sites. Streamflow presence or absence observations from the citizen and sensor networks are then compared to satellite imagery to improve flow detection algorithms using remotely sensed data from Landsat. In the first two months of this project, 1,287 observations have been made at 241 sites by 24 project members across northern and western Colorado.
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Schwab, Michael; Klaus, Julian; Pfister, Laurent; Weiler, Markus
2015-04-01
Diurnal fluctuations in stream-flow are commonly explained as being triggered by the daily evapotranspiration cycle in the riparian zone, leading to stream flow minima in the afternoon. While this trigger effect must necessarily be constrained by the extent of the growing season of vegetation, we here show evidence of daily stream flow maxima in the afternoon in a small headwater stream during the dormant season. We hypothesize that the afternoon maxima in stream flow are induced by viscosity changes of riparian water that is caused by diurnal temperature variations of the near surface groundwater in the riparian zone. The patterns were observed in the Weierbach headwater catchment in Luxembourg. The catchment is covering an area of 0.45 km2, is entirely covered by forest and is dominated by a schistous substratum. DOC concentration at the outlet of the catchment was measured with the field deployable UV-Vis spectrometer spectro::lyser (scan Messtechnik GmbH) with a high frequency of 15 minutes over several months. Discharge was measured with an ISCO 4120 Flow Logger. During the growing season, stream flow shows a frequently observed diurnal pattern with discharge minima in the afternoon. During the dormant season, a long dry period with daily air temperature amplitudes of around 10 ° C occurred in March and April 2014, with discharge maxima in the afternoon. The daily air temperature amplitude led to diurnal variations in the water temperature of the upper 10 cm of the riparian zone. Higher riparian water temperatures cause a decrease in water viscosity and according to the Hagen-Poiseuille equation, the volumetric flow rate is inversely proportional to viscosity. Based on the Hagen-Poiseuille equation and the viscosity changes of water, we calculated higher flow rates of near surface groundwater through the riparian zone into the stream in the afternoon which explains the stream flow maxima in the afternoon. With the start of the growing season, the viscosity
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High rates of organic carbon processing in the hyporheic zone of intermittent streams.
Burrows, Ryan M; Rutlidge, Helen; Bond, Nick R; Eberhard, Stefan M; Auhl, Alexandra; Andersen, Martin S; Valdez, Dominic G; Kennard, Mark J
2017-10-16
Organic carbon cycling is a fundamental process that underpins energy transfer through the biosphere. However, little is known about the rates of particulate organic carbon processing in the hyporheic zone of intermittent streams, which is often the only wetted environment remaining when surface flows cease. We used leaf litter and cotton decomposition assays, as well as rates of microbial respiration, to quantify rates of organic carbon processing in surface and hyporheic environments of intermittent and perennial streams under a range of substrate saturation conditions. Leaf litter processing was 48% greater, and cotton processing 124% greater, in the hyporheic zone compared to surface environments when calculated over multiple substrate saturation conditions. Processing was also greater in more saturated surface environments (i.e. pools). Further, rates of microbial respiration on incubated substrates in the hyporheic zone were similar to, or greater than, rates in surface environments. Our results highlight that intermittent streams are important locations for particulate organic carbon processing and that the hyporheic zone sustains this fundamental process even without surface flow. Not accounting for carbon processing in the hyporheic zone of intermittent streams may lead to an underestimation of its local ecological significance and collective contribution to landscape carbon processes.
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Improving H-Q rating curves in temprorary streams by using Acoustic Doppler Current meters
Marchand, P.; Salles, C.; Rodier, C.; Hernandez, F.; Gayrard, E.; Tournoud, M.-G.
2012-04-01
Intermittent rivers pose different challenges to stream rating due to high spatial and temporal gradients. Long dry periods, cut by short duration flush flood events explain the difficulty to obtain reliable discharge data, for low flows as well as for floods: problems occur with standard gauging, zero flow period, etc. Our study aims to test the use of an acoustic Doppler currentmeter (ADC) for improving stream rating curves in small catchments subject to large variations of discharge, solid transport and high eutrophication levels. The study is conducted at the outlet of the river Vène, a small coastal river (67 km2) located close to the city of Montpellier (France). The low flow period lasts for more than 6 month; during this period the river flow is sustained by effluents from urban sewage systems, which allows development of algae and macrophytes in the riverbed. The ADC device (Sontek ®Argonaut SW) is a pulsed Doppler current profiling system designed for measuring water velocity profiles and levels that are used to compute volumetric flow rates. It is designed for shallow waters (less than 4 meter depth). Its main advantages are its low cost and high accuracy (±1% of the measured velocity or ±0.05 m/sec, as reported by the manufacturer). The study will evaluate the improvement in rating curves in an intermittent flow context and the effect of differences in sensitivity between low and high water level, by comparing mean flow velocity obtained by ADC to direct discharges measurements. The study will also report long-term use of ADC device, by considering effects of biofilms, algae and macrophytes, as well as solid transport on the accuracy of the measurements. In conclusion, we show the possibility to improve stream rating and continuous data collection of an intermittent river by using a ADC with some precautions.
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Directory of Open Access Journals (Sweden)
Ivan Arismendi
2017-12-01
Full Text Available Intermittent and ephemeral streams represent more than half of the length of the global river network. Dryland freshwater ecosystems are especially vulnerable to changes in human-related water uses as well as shifts in terrestrial climates. Yet, the description and quantification of patterns of flow permanence in these systems is challenging mostly due to difficulties in instrumentation. Here, we took advantage of existing stream temperature datasets in dryland streams in the northwest Great Basin desert, USA, to extract critical information on climate-sensitive patterns of flow permanence. We used a signal detection technique, Hidden Markov Models (HMMs, to extract information from daily time series of stream temperature to diagnose patterns of stream drying. Specifically, we applied HMMs to time series of daily standard deviation (SD of stream temperature (i.e., dry stream channels typically display highly variable daily temperature records compared to wet stream channels between April and August (2015–2016. We used information from paired stream and air temperature data loggers as well as co-located stream temperature data loggers with electrical resistors as confirmatory sources of the timing of stream drying. We expanded our approach to an entire stream network to illustrate the utility of the method to detect patterns of flow permanence over a broader spatial extent. We successfully identified and separated signals characteristic of wet and dry stream conditions and their shifts over time. Most of our study sites within the entire stream network exhibited a single state over the entire season (80%, but a portion of them showed one or more shifts among states (17%. We provide recommendations to use this approach based on a series of simple steps. Our findings illustrate a successful method that can be used to rigorously quantify flow permanence regimes in streams using existing records of stream temperature.
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Arismendi, Ivan; Dunham, Jason B.; Heck, Michael; Schultz, Luke; Hockman-Wert, David
2017-01-01
Intermittent and ephemeral streams represent more than half of the length of the global river network. Dryland freshwater ecosystems are especially vulnerable to changes in human-related water uses as well as shifts in terrestrial climates. Yet, the description and quantification of patterns of flow permanence in these systems is challenging mostly due to difficulties in instrumentation. Here, we took advantage of existing stream temperature datasets in dryland streams in the northwest Great Basin desert, USA, to extract critical information on climate-sensitive patterns of flow permanence. We used a signal detection technique, Hidden Markov Models (HMMs), to extract information from daily time series of stream temperature to diagnose patterns of stream drying. Specifically, we applied HMMs to time series of daily standard deviation (SD) of stream temperature (i.e., dry stream channels typically display highly variable daily temperature records compared to wet stream channels) between April and August (2015–2016). We used information from paired stream and air temperature data loggers as well as co-located stream temperature data loggers with electrical resistors as confirmatory sources of the timing of stream drying. We expanded our approach to an entire stream network to illustrate the utility of the method to detect patterns of flow permanence over a broader spatial extent. We successfully identified and separated signals characteristic of wet and dry stream conditions and their shifts over time. Most of our study sites within the entire stream network exhibited a single state over the entire season (80%), but a portion of them showed one or more shifts among states (17%). We provide recommendations to use this approach based on a series of simple steps. Our findings illustrate a successful method that can be used to rigorously quantify flow permanence regimes in streams using existing records of stream temperature.
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Flow Field and Acoustic Predictions for Three-Stream Jets
Simmons, Shaun Patrick; Henderson, Brenda S.; Khavaran, Abbas
2014-01-01
Computational fluid dynamics was used to analyze a three-stream nozzle parametric design space. The study varied bypass-to-core area ratio, tertiary-to-core area ratio and jet operating conditions. The flowfield solutions from the Reynolds-Averaged Navier-Stokes (RANS) code Overflow 2.2e were used to pre-screen experimental models for a future test in the Aero-Acoustic Propulsion Laboratory (AAPL) at the NASA Glenn Research Center (GRC). Flowfield solutions were considered in conjunction with the jet-noise-prediction code JeNo to screen the design concepts. A two-stream versus three-stream computation based on equal mass flow rates showed a reduction in peak turbulent kinetic energy (TKE) for the three-stream jet relative to that for the two-stream jet which resulted in reduced acoustic emission. Additional three-stream solutions were analyzed for salient flowfield features expected to impact farfield noise. As tertiary power settings were increased there was a corresponding near nozzle increase in shear rate that resulted in an increase in high frequency noise and a reduction in peak TKE. As tertiary-to-core area ratio was increased the tertiary potential core elongated and the peak TKE was reduced. The most noticeable change occurred as secondary-to-core area ratio was increased thickening the secondary potential core, elongating the primary potential core and reducing peak TKE. As forward flight Mach number was increased the jet plume region decreased and reduced peak TKE.
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Tesoriero, Anthony J.
2012-01-01
Groundwater age and water chemistry data along flow paths from recharge areas to streams were used to evaluate the trends and transformations of agricultural chemicals. Results from this analysis indicate that median nitrate recharge concentrations in these agricultural areas have increased markedly over the last 50 years from 4 mg N/L in samples collected prior to 1983 to 7.5 mg N/L in samples collected since 1983. The effect that nitrate accumulation in shallow aquifers will have on drinking water quality and stream ecosystems is dependent on the rate of redox reactions along flow paths and on the age distribution of nitrate discharging to supply wells and streams.
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Entropy resistance analyses of a two-stream parallel flow heat exchanger with viscous heating
International Nuclear Information System (INIS)
Cheng Xue-Tao; Liang Xin-Gang
2013-01-01
Heat exchangers are widely used in industry, and analyses and optimizations of the performance of heat exchangers are important topics. In this paper, we define the concept of entropy resistance based on the entropy generation analyses of a one-dimensional heat transfer process. With this concept, a two-stream parallel flow heat exchanger with viscous heating is analyzed and discussed. It is found that the minimization of entropy resistance always leads to the maximum heat transfer rate for the discussed two-stream parallel flow heat exchanger, while the minimizations of entropy generation rate, entropy generation numbers, and revised entropy generation number do not always. (general)
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Flow effects on benthic stream invertebrates and ecological processes
Koprivsek, Maja; Brilly, Mitja
2010-05-01
Flow is the main abiotic factor in the streams. Flow affects the organisms in many direct and indirect ways. The organisms are directly affected by various hydrodynamic forces and mass transfer processes like drag forces, drift, shear stress, food and gases supply and washing metabolites away. Indirect effects on the organisms are determining and distribution of the particle size and structure of the substrate and determining the morphology of riverbeds. Flow does not affect only on individual organism, but also on many ecological effects. To expose just the most important: dispersal of the organisms, habitat use, resource acquisition, competition and predator-prey interactions. Stream invertebrates are adapted to the various flow conditions in many kinds of way. Some of them are avoiding the high flow with living in a hyporeic zone, while the others are adapted to flow with physical adaptations (the way of feeding, respiration, osmoregulation and resistance to draught), morphological adaptations (dorsoventrally flattened shape of organism, streamlined shape of organism, heterogeneous suckers, silk, claws, swimming hair, bristles and ballast gravel) or with behaviour. As the flow characteristics in a particular stream vary over a broad range of space and time scales, it is necessary to measure accurately the velocity in places where the organisms are present to determine the actual impact of flow on aquatic organisms. By measuring the mean flow at individual vertical in a single cross-section, we cannot get any information about the velocity situation close to the bottom of the riverbed where the stream invertebrates are living. Just measuring the velocity near the bottom is a major problem, as technologies for measuring the velocity and flow of natural watercourses is not adapted to measure so close to the bottom. New researches in the last two decades has shown that the thickness of laminar border layer of stones in the stream is only a few 100 micrometers, what
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Dispersal and colonisation of plants in lowland streams: success rates and bottlenecks
DEFF Research Database (Denmark)
Riis, Tenna
2008-01-01
-rich lowland streams. Rather, I conclude that primary colonisation is the main constraint to regaining vegetation in lowland streams in general and in vegetation-free rehabilitated streams in particular. Therefore, if plant colonisation is a target for stream rehabilitation, it is important to enhance......Plant dispersal and colonisation, including rates of dispersal, retention, colonisation and survival of dispersed propagules (shoots and seeds), were studied in a 300-m stream reach in a macrophyte-rich lowland stream during one growing season. Relationships between colonisation processes...... and simple flow parameters were tested. Each fortnight during a growing season, the number of dispersed plant propagules and the number of new and lost plant colonisations since the last sampling day were recorded. The retention of dispersing shoots was tested on two occasions during the growing season...
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Coupling nutrient uptake and energy flow in headwater streams
Energy Technology Data Exchange (ETDEWEB)
Mulholland, Patrick J [ORNL; Fellows, Christine [Griffith University, Nathan, Queensland, Australia; Valett, H. Maurice [Virginia Polytechnic Institute and State University (Virginia Tech); Dahm, Cliff [University of New Mexico, Albuquerque; Thomas, Steve [University of Nebraska
2006-08-01
Nutrient cycling and energy flow in ecosystems are tightly linked through the metabolic processes of organisms. Greater uptake of inorganic nutrients is expected to be associated with higher rates of metabolism [gross primary production (GPP) and respiration (R)], due to assimilatory demand of both autotrophs and heterotrophs. However, relationships between uptake and metabolism should vary with the relative contribution of autochthonous and allochthonous sources of organic matter. To investigate the relationship between metabolism and nutrient uptake, we used whole-stream and benthic chamber methods to measure rates of nitrate-nitrogen (NO{sub 3}-N) uptake and metabolism in four headwater streams chosen to span a range of light availability and therefore differing rates of GPP and contributions of autochthonous carbon. We coupled whole-stream metabolism with measures of NO{sub 3}-N uptake conducted repeatedly over the same stream reach during both day and night, as well as incubating benthic sediments under both light and dark conditions. NO{sub 3}-N uptake was generally greater in daylight compared to dark conditions, and although day-night differences in whole-stream uptake were not significant, light-dark differences in benthic chambers were significant at three of the four sites. Estimates of N demand indicated that assimilation by photoautotrophs could account for the majority of NO{sub 3}-N uptake at the two sites with relatively open canopies. Contrary to expectations, photoautotrophs contributed substantially to NO{sub 3}-N uptake even at the two closed-canopy sites, which had low values of GPP/R and relied heavily on allochthonous carbon to fuel R.
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Switch of flow direction in an Antarctic ice stream.
Conway, H; Catania, G; Raymond, C F; Gades, A M; Scambos, T A; Engelhardt, H
2002-10-03
Fast-flowing ice streams transport ice from the interior of West Antarctica to the ocean, and fluctuations in their activity control the mass balance of the ice sheet. The mass balance of the Ross Sea sector of the West Antarctic ice sheet is now positive--that is, it is growing--mainly because one of the ice streams (ice stream C) slowed down about 150 years ago. Here we present evidence from both surface measurements and remote sensing that demonstrates the highly dynamic nature of the Ross drainage system. We show that the flow in an area that once discharged into ice stream C has changed direction, now draining into the Whillans ice stream (formerly ice stream B). This switch in flow direction is a result of continuing thinning of the Whillans ice stream and recent thickening of ice stream C. Further abrupt reorganization of the activity and configuration of the ice streams over short timescales is to be expected in the future as the surface topography of the ice sheet responds to the combined effects of internal dynamics and long-term climate change. We suggest that caution is needed when using observations of short-term mass changes to draw conclusions about the large-scale mass balance of the ice sheet.
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Unsteady Flows Control Hydrologic Turnover Rates in Antarctic Hyporheic Zones
Wlostowski, A. N.; Gooseff, M. N.; McKnight, D. M.; Lyons, W. B.; Saelens, E.
2016-12-01
Hydrologic turnover of the hyporheic zone (HZ) is the process of HZ flowpaths receiving water and solutes from the stream channel while simultaneously contributing water and solutes from the HZ back to the stream channel. The influence of hydrologic turnover on HZ solute storage depends on the relative magnitude of hyporheic exchange rates (i.e. physical transport) and biogeochemical reaction rates. Because both exchange rates and reaction rates are unsteady in natural systems, the availability of solutes in the HZ is controlled by the legacy of hydraulic and biological conditions. In this study, we quantify the influence of unsteady flows on hydrologic turnover of the HZ. We study a glacial melt stream in the McMurdo Dry Valleys of Antarctica (MDVs). The MDVs provide an ideal setting for investigating hydrologic and chemical storage characteristics of HZs, because nearly all streamflow is generated from glacier melt and the HZ is vertically bounded by continuous permafrost. A dense network of shallow groundwater wells and piezometers was installed along a 60-meter reach of Von Guerard Stream. 12 days of continuous water level data in each well was used to compute the magnitude and direction of 2D hydraulic gradients between the stream channel and lateral hyporheic aquifer. Piezometers were sampled daily for stable isotope abundances. The direction and magnitude of the cross-valley (CV), perpendicular to the thalweg, component of hydraulic gradients is sensitive to daily flood events and exhibits significant spatial heterogeneity. CV gradients are consistently oriented from the hyporheic aquifer towards the stream channel on 2 sections of the study reach, whereas CV gradients are consistently oriented from the stream channel towards the hyporheic aquifer on 1 section. Three sections show diel changes in orientation of CV gradients, coincident with the passage of daily flood events. During a 4-day period of low flows, the HZ is isotopically distinct from the stream
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Acoustic streaming in pulsating flows through porous media
International Nuclear Information System (INIS)
Valverde, J.M.; Dura'n-Olivencia, F.J.
2014-01-01
When a body immersed in a viscous fluid is subjected to a sound wave (or, equivalently, the body oscillates in the fluid otherwise at rest) a rotational fluid stream develops across a boundary layer nearby the fluid-body interphase. This so-called acoustic streaming phenomenon is responsible for a notable enhancement of heat, mass and momentum transfer and takes place in any process involving two phases subjected to relative oscillations. Understanding the fundamental mechanisms governing acoustic streaming in two-phase flows is of great interest for a wide range of applications such as sonoprocessed fluidized bed reactors, thermoacoustic refrigerators/engines, pulsatile flows through veins/arteries, hemodialysis devices, pipes in off-shore platforms, offshore piers, vibrating structures in the power-generating industry, lab-on-a-chip microfluidics and microgravity acoustic levitation, and solar thermal collectors to name a few. The aim of engineering studies on this vast diversity of systems is oriented towards maximizing the efficiency of each particular process. Even though practical problems are usually approached from disparate disciplines without any apparent linkage, the behavior of these systems is influenced by the same underlying physics. In general, acoustic streaming occurs within the interstices of porous media and usually in the presence of externally imposed steady fluid flows, which gives rise to important effects arising from the interference between viscous boundary layers developed around nearby solid surfaces and the nonlinear coupling between the oscillating and steady flows. This paper is mainly devoted to highlighting the fundamental physics behind acoustic streaming in porous media in order to provide a simple instrument to assess the relevance of this phenomenon in each particular application. The exact microscopic Navier-Stokes equations will be numerically solved for a simplified 2D system consisting of a regular array of oscillating
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Low-flow characteristics of streams in the Puget Sound region, Washington
Hidaka, F.T.
1973-01-01
Periods of low streamflow are usually the most critical factor in relation to most water uses. The purpose of this report is to present data on low-flow characteristics of streams in the Puget Sound region, Washington, and to briefly explain some of the factors that influence low flow in the various basins. Presented are data on low-flow frequencies of streams in the Puget Sound region, as gathered at 150 gaging stations. Four indexes were computed from the flow-flow-frequency curves and were used as a basis to compare the low-flow characteristics of the streams. The indexes are the (1) low-flow-yield index, expressed in unit runoff per square mile; (2) base-flow index, or the ratio of the median 7-day low flow to the average discharge; (3) slope index, or slope of annual 7-day low-flow-frequency curve; and (4) spacing index, or spread between the 7-day and 183-day low-flow-frequency curves. The indexes showed a wide variation between streams due to the complex interrelation between climate, topography, and geology. The largest low-flow-yield indexes determined--greater than 1.5 cfs (cubic feet per second) per square mile--were for streams that head at high altitudes in the Cascade and Olympic Mountains and have their sources at glaciers. The smallest low-flow-yield indexes--less than 0.5 cfs per square mile--were for the small streams that drain the lowlands adjacent to Puget Sound. Indexes between the two extremes were for nonglacial streams that head at fairly high altitudes in areas of abundant precipitation. The base-flow index has variations that can be attributed to a basin's hydrogeology, with very little influence from climate. The largest base-flow indexes were obtained for streams draining permeable unconsolidated glacial and alluvial sediments in parts of the lowlands adjacent to Puget Sound. Large volume of ground water in these materials sustain flows during late summer. The smallest indexes were computed for streams draining areas underlain by
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Low-flow characteristics of Virginia streams
Austin, Samuel H.; Krstolic, Jennifer L.; Wiegand, Ute
2011-01-01
Low-flow annual non-exceedance probabilities (ANEP), called probability-percent chance (P-percent chance) flow estimates, regional regression equations, and transfer methods are provided describing the low-flow characteristics of Virginia streams. Statistical methods are used to evaluate streamflow data. Analysis of Virginia streamflow data collected from 1895 through 2007 is summarized. Methods are provided for estimating low-flow characteristics of gaged and ungaged streams. The 1-, 4-, 7-, and 30-day average streamgaging station low-flow characteristics for 290 long-term, continuous-record, streamgaging stations are determined, adjusted for instances of zero flow using a conditional probability adjustment method, and presented for non-exceedance probabilities of 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, 0.02, 0.01, and 0.005. Stream basin characteristics computed using spatial data and a geographic information system are used as explanatory variables in regional regression equations to estimate annual non-exceedance probabilities at gaged and ungaged sites and are summarized for 290 long-term, continuous-record streamgaging stations, 136 short-term, continuous-record streamgaging stations, and 613 partial-record streamgaging stations. Regional regression equations for six physiographic regions use basin characteristics to estimate 1-, 4-, 7-, and 30-day average low-flow annual non-exceedance probabilities at gaged and ungaged sites. Weighted low-flow values that combine computed streamgaging station low-flow characteristics and annual non-exceedance probabilities from regional regression equations provide improved low-flow estimates. Regression equations developed using the Maintenance of Variance with Extension (MOVE.1) method describe the line of organic correlation (LOC) with an appropriate index site for low-flow characteristics at 136 short-term, continuous-record streamgaging stations and 613 partial-record streamgaging stations. Monthly
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A spatial assessment of stream-flow characteristics and hydrologic ...
African Journals Online (AJOL)
The global hydrologic regime has been intensively altered through activities such as dam construction, water abstraction, and inter-basin transfers. This paper uses the Range of Variability Approach (RVA) and daily stream flow records from nine gauging stations to characterize stream-flow post dam construction in the ...
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The impact of Indian Ocean high pressure system on rainfall and stream flow
International Nuclear Information System (INIS)
Rehman, S.; Nasir, H.; Zia, S.S.; Ansari, W.A.; Salam, K.; Tayyab, N.
2012-01-01
Centre of Action approach is very useful in getting insight of rainfall and stream flow variability of specific region. Hameed et al. showed that Inter-annual variability of Gulf Stream north wall is influenced by low Icelandic pressure system and has more statistically significant correlation than North Atlantic Oscillation (NAO) with longitude of Icelandic low. This study also aims to explore possible relationships between rainfall and stream flow in Collie river catchment in Southwest Western Australia (SWWA) with Indian Ocean high pressure dynamics. The relationship between rainfall and stream flow with Indian Ocean high pressure system have been investigated using correlation analysis for early winter season (MJJA), lag correlation for MJJA versus SOND rainfall and stream flow are also calculated and found significant at 95% confidence level. By investigating the relationship between COA indices with rainfall and stream flow over the period 1976-2008, significant correlations suggests that rainfall and stream flow in Collie river basin is strongly influenced by COA indices. Multiple correlations between rainfall and stream flow with Indian Ocean high pressure (IOHPS and IOHLN) is 0.7 and 0.6 respectively. Centers of Action (COA) indices explain 51% and 36% of rainfall and stream flow respectively. The correlation between rainfall and stream flow with IOHPS is -0.4 and -0.3 whereas, with IOHLN is -0.47 and -0.52 respectively. (author)
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Diamond, Kelly M; Schoenfuss, Heiko L; Walker, Jeffrey A; Blob, Richard W
2016-10-01
Experimental measurements of escape performance in fishes have typically been conducted in still water; however, many fishes inhabit environments with flow that could impact escape behavior. We examined the influences of flow and predator attack direction on the escape behavior of fish, using juveniles of the amphidromous Hawaiian goby Sicyopterus stimpsoni In nature, these fish must escape ambush predation while moving through streams with high-velocity flow. We measured the escape performance of juvenile gobies while exposing them to a range of water velocities encountered in natural streams and stimulating fish from three different directions. Frequency of response across treatments indicated strong effects of flow conditions and attack direction. Juvenile S. stimpsoni had uniformly high response rates for attacks from a caudal direction (opposite flow); however, response rates for attacks from a cranial direction (matching flow) decreased dramatically as flow speed increased. Mechanical stimuli produced by predators attacking in the same direction as flow might be masked by the flow environment, impairing the ability of prey to detect attacks. Thus, the likelihood of successful escape performance in fishes can depend critically on environmental context. © 2016. Published by The Company of Biologists Ltd.
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Directory of Open Access Journals (Sweden)
P. Gao
2013-03-01
Full Text Available Reduced stream flow and increased sediment discharge are a major concern in the Yellow River basin of China, which supplies water for agriculture, industry and the growing populations located along the river. Similar concerns exist in the Wei River basin, which is the largest tributary of the Yellow River basin and comprises the highly eroded Loess Plateau. Better understanding of the drivers of stream flow and sediment discharge dynamics in the Wei River basin is needed for development of effective management strategies for the region and entire Yellow River basin. In this regard we analysed long-term trends for water and sediment discharge during the flood season in the Wei River basin, China. Stream flow and sediment discharge data for 1932 to 2008 from existing hydrological stations located in two subcatchments and at two points in the Wei River were analysed. Precipitation and air temperature data were analysed from corresponding meteorological stations. We identified change-points or transition years for the trends by the Pettitt method and, using double mass curves, we diagnosed whether they were caused by precipitation changes, human intervention, or both. We found significant decreasing trends for stream flow and sediment discharge during the flood season in both subcatchments and in the Wei River itself. Change-point analyses further revealed that transition years existed and that rapid decline in stream flow began in 1968 (P P P P P < 0.05, respectively. The impact of precipitation or human activity on the reduction amount after the transition years was estimated by double mass curves of precipitation vs. stream flow (sediment. For reductions in stream flow and sediment discharge, the contribution rate of human activity was found to be 82.80 and 95.56%, respectively, and was significantly stronger than the contribution rate of precipitation. This evidence clearly suggests that, in the absence of significant decreases in precipitation
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The long term response of stream flow to climatic warming in headwater streams of interior Alaska
Jeremy B. Jones; Amanda J. Rinehart
2010-01-01
Warming in the boreal forest of interior Alaska will have fundamental impacts on stream ecosystems through changes in stream hydrology resulting from upslope loss of permafrost, alteration of availability of soil moisture, and the distribution of vegetation. We examined stream flow in three headwater streams of the Caribou-Poker Creeks Research Watershed (CPCRW) in...
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Smith, S. Jerrod; Esralew, Rachel A.
2010-01-01
drainage-basin outlet for the period 1961-1990, 10-85 channel slope (slope between points located at 10 percent and 85 percent of the longest flow-path length upstream from the outlet), and percent impervious area. The Oklahoma StreamStats application interacts with the National Streamflow Statistics database, which contains the peak-flow regression equations in a previously published report. Fourteen peak-flow (flood) frequency statistics are available for computation in the Oklahoma StreamStats application. These statistics include the peak flow at 2-, 5-, 10-, 25-, 50-, 100-, and 500-year recurrence intervals for rural, unregulated streams; and the peak flow at 2-, 5-, 10-, 25-, 50-, 100-, and 500-year recurrence intervals for rural streams that are regulated by Natural Resources Conservation Service floodwater retarding structures. Basin characteristics and streamflow statistics cannot be computed for locations in playa basins (mostly in the Oklahoma Panhandle) and along main stems of the largest river systems in the state, namely the Arkansas, Canadian, Cimarron, Neosho, Red, and Verdigris Rivers, because parts of the drainage areas extend outside of the processed hydrologic units.
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Altered stream-flow regimes and invasive plant species: The Tamarix case
Stromberg, J.C.; Lite, S.J.; Marler, R.; Paradzick, C.; Shafroth, P.B.; Shorrock, D.; White, J.M.; White, M.S.
2007-01-01
Aim: To test the hypothesis that anthropogenic alteration of stream-flow regimes is a key driver of compositional shifts from native to introduced riparian plant species. Location: The arid south-western United States; 24 river reaches in the Gila and Lower Colorado drainage basins of Arizona. Methods: We compared the abundance of three dominant woody riparian taxa (native Populus fremontii and Salix gooddingii, and introduced Tamarix) between river reaches that varied in stream-flow permanence (perennial vs. intermittent), presence or absence of an upstream flow-regulating dam, and presence or absence of municipal effluent as a stream water source. Results: Populus and Salix were the dominant pioneer trees along the reaches with perennial flow and a natural flood regime. In contrast, Tamarix had high abundance (patch area and basal area) along reaches with intermittent stream flows (caused by natural and cultural factors), as well as those with dam-regulated flows. Main conclusions: Stream-flow regimes are strong determinants of riparian vegetation structure, and hydrological alterations can drive dominance shifts to introduced species that have an adaptive suite of traits. Deep alluvial groundwater on intermittent rivers favours the deep-rooted, stress-adapted Tamarix over the shallower-rooted and more competitive Populus and Salix. On flow-regulated rivers, shifts in flood timing favour the reproductively opportunistic Tamarix over Populus and Salix, both of which have narrow germination windows. The prevailing hydrological conditions thus favour a new dominant pioneer species in the riparian corridors of the American Southwest. These results reaffirm the importance of reinstating stream-flow regimes (inclusive of groundwater flows) for re-establishing the native pioneer trees as the dominant forest type. ?? 2007 The Authors Journal compilation ?? 2007 Blackwell Publishing Ltd.
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Methods for estimating flow-duration and annual mean-flow statistics for ungaged streams in Oklahoma
Esralew, Rachel A.; Smith, S. Jerrod
2010-01-01
Flow statistics can be used to provide decision makers with surface-water information needed for activities such as water-supply permitting, flow regulation, and other water rights issues. Flow statistics could be needed at any location along a stream. Most often, streamflow statistics are needed at ungaged sites, where no flow data are available to compute the statistics. Methods are presented in this report for estimating flow-duration and annual mean-flow statistics for ungaged streams in Oklahoma. Flow statistics included the (1) annual (period of record), (2) seasonal (summer-autumn and winter-spring), and (3) 12 monthly duration statistics, including the 20th, 50th, 80th, 90th, and 95th percentile flow exceedances, and the annual mean-flow (mean of daily flows for the period of record). Flow statistics were calculated from daily streamflow information collected from 235 streamflow-gaging stations throughout Oklahoma and areas in adjacent states. A drainage-area ratio method is the preferred method for estimating flow statistics at an ungaged location that is on a stream near a gage. The method generally is reliable only if the drainage-area ratio of the two sites is between 0.5 and 1.5. Regression equations that relate flow statistics to drainage-basin characteristics were developed for the purpose of estimating selected flow-duration and annual mean-flow statistics for ungaged streams that are not near gaging stations on the same stream. Regression equations were developed from flow statistics and drainage-basin characteristics for 113 unregulated gaging stations. Separate regression equations were developed by using U.S. Geological Survey streamflow-gaging stations in regions with similar drainage-basin characteristics. These equations can increase the accuracy of regression equations used for estimating flow-duration and annual mean-flow statistics at ungaged stream locations in Oklahoma. Streamflow-gaging stations were grouped by selected drainage
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DEFF Research Database (Denmark)
Prahl, C.; Jeppesen, E.; Sand-Jensen, Kaj
1991-01-01
on the stream bank, consists of several macrophyte and sediment chambers equipped with a double-flow system that ensures an internal water velocity close to that in the stream and which, by continuously renewing the water, mimics diel fluctuation in stream temperature and water chemistry. Water temperature...... production and dark respiration occurred at similar rates (6-7g O2 m-2 day-1), net balance being about zero. Inorganic nitrogen was consumed both by the sediment and to a greater extent by the macrophytes, the diel average consumption being 1g N m-2 day-1. 3. The sum of the activity in the macrophyte...... and sediment chambers corresponded to the overall activity of the stream section as determined by upstream/downstream mass balance. This indicates that the results obtained with the continuous-flow chambers realistically describe the oxygen and the nitrogen metabolism of the stream....
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Particle migration and sorting in microbubble streaming flows
Thameem, Raqeeb; Hilgenfeldt, Sascha
2016-01-01
Ultrasonic driving of semicylindrical microbubbles generates strong streaming flows that are robust over a wide range of driving frequencies. We show that in microchannels, these streaming flow patterns can be combined with Poiseuille flows to achieve two distinctive, highly tunable methods for size-sensitive sorting and trapping of particles much smaller than the bubble itself. This method allows higher throughput than typical passive sorting techniques, since it does not require the inclusion of device features on the order of the particle size. We propose a simple mechanism, based on channel and flow geometry, which reliably describes and predicts the sorting behavior observed in experiment. It is also shown that an asymptotic theory that incorporates the device geometry and superimposed channel flow accurately models key flow features such as peak speeds and particle trajectories, provided it is appropriately modified to account for 3D effects caused by the axial confinement of the bubble. PMID:26958103
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Three-dimensional microbubble streaming flows
Rallabandi, Bhargav; Marin, Alvaro; Rossi, Massimiliano; Kaehler, Christian; Hilgenfeldt, Sascha
2014-11-01
Streaming due to acoustically excited bubbles has been used successfully for applications such as size-sorting, trapping and focusing of particles, as well as fluid mixing. Many of these applications involve the precise control of particle trajectories, typically achieved using cylindrical bubbles, which establish planar flows. Using astigmatic particle tracking velocimetry (APTV), we show that, while this two-dimensional picture is a useful description of the flow over short times, a systematic three-dimensional flow structure is evident over long time scales. We demonstrate that this long-time three-dimensional fluid motion can be understood through asymptotic theory, superimposing secondary axial flows (induced by boundary conditions at the device walls) onto the two-dimensional description. This leads to a general framework that describes three-dimensional flows in confined microstreaming systems, guiding the design of applications that profit from minimizing or maximizing these effects.
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Riparian indicators of flow frequency in a tropical montante stream network
Andrew S. Pike; Frederick N. Scatena
2010-01-01
Many field indicators have been used to approximate the magnitude and frequency of flows in a variety of streams and rivers, yet due to a scarcity of long-term flow records in tropical mountain streams, little to no work has been done to establish such relationships between field features and the flow regime in these environments. Furthermore, the transition between...
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Laser streaming: Turning a laser beam into a flow of liquid.
Wang, Yanan; Zhang, Qiuhui; Zhu, Zhuan; Lin, Feng; Deng, Jiangdong; Ku, Geng; Dong, Suchuan; Song, Shuo; Alam, Md Kamrul; Liu, Dong; Wang, Zhiming; Bao, Jiming
2017-09-01
Transforming a laser beam into a mass flow has been a challenge both scientifically and technologically. We report the discovery of a new optofluidic principle and demonstrate the generation of a steady-state water flow by a pulsed laser beam through a glass window. To generate a flow or stream in the same path as the refracted laser beam in pure water from an arbitrary spot on the window, we first fill a glass cuvette with an aqueous solution of Au nanoparticles. A flow will emerge from the focused laser spot on the window after the laser is turned on for a few to tens of minutes; the flow remains after the colloidal solution is completely replaced by pure water. Microscopically, this transformation is made possible by an underlying plasmonic nanoparticle-decorated cavity, which is self-fabricated on the glass by nanoparticle-assisted laser etching and exhibits size and shape uniquely tailored to the incident beam profile. Hydrophone signals indicate that the flow is driven via acoustic streaming by a long-lasting ultrasound wave that is resonantly generated by the laser and the cavity through the photoacoustic effect. The principle of this light-driven flow via ultrasound, that is, photoacoustic streaming by coupling photoacoustics to acoustic streaming, is general and can be applied to any liquid, opening up new research and applications in optofluidics as well as traditional photoacoustics and acoustic streaming.
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Dunkerley, David; Brown, Kate
1999-08-01
The behaviour of a discrete sub-bank-full flow event in a small desert stream in western NSW, Australia, is analysed from direct observation and sediment sampling during the flow event and from later channel surveys. The flow event, the result of an isolated afternoon thunderstorm, had a peak discharge of 9 m3/s at an upstream station. Transmission loss totally consumed the flow over the following 7·6 km. Suspended sediment concentration was highest at the flow front (not the discharge peak) and declined linearly with the log of time since passage of the flow front, regardless of discharge variation. The transmission loss responsible for the waning and eventual cessation of flow occurred at a mean rate of 13.2% per km. This is quite rapid, and is more than twice the corresponding figure for bank-full flows estimated by Dunkerley (1992) on the same stream system. It is proposed that transmission losses in ephemeral streams of the kind studied may be minimized in flows near bank-full stage, and be higher in both sub-bank-full and overbank flows. Factors contributing to enhanced flow loss in the sub-bank-full flow studied included abstractions of flow to pools, scour holes and other low points along the channel, and overflow abstractions into channel filaments that did not rejoin the main flow. On the other hand, losses were curtailed by the shallow depth of banks wetted and by extensive mud drapes that were set down over sand bars and other porous channel materials during the flow. Thus, in contrast with the relatively regular pattern of transmission loss inferred from large floods, losses from low flows exhibit marked spatial variability and depend to a considerable extent on streamwise variations in channel geometry, in addition to the depth and porosity of channel perimeter sediments.
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Fine particle retention within stream storage areas at base flow and in response to a storm event
Drummond, J. D.; Larsen, L. G.; González-Pinzón, R.; Packman, A. I.; Harvey, Judson
2017-01-01
Fine particles (1–100 µm), including particulate organic carbon (POC) and fine sediment, influence stream ecological functioning because they may contain or have a high affinity to sorb nitrogen and phosphorus. These particles are immobilized within stream storage areas, especially hyporheic sediments and benthic biofilms. However, fine particles are also known to remobilize under all flow conditions. This combination of downstream transport and transient retention, influenced by stream geomorphology, controls the distribution of residence times over which fine particles influence stream ecosystems. The main objective of this study was to quantify immobilization and remobilization rates of fine particles in a third-order sand-and-gravel bed stream (Difficult Run, Virginia, USA) within different geomorphic units of the stream (i.e., pool, lateral cavity, and thalweg). During our field injection experiment, a thunderstorm-driven spate allowed us to observe fine particle dynamics during both base flow and in response to increased flow. Solute and fine particles were measured within stream surface waters, pore waters, sediment cores, and biofilms on cobbles. Measurements were taken at four different subsurface locations with varying geomorphology and at multiple depths. Approximately 68% of injected fine particles were retained during base flow until the onset of the spate. Retention was evident even after the spate, with 15.4% of the fine particles deposited during base flow still retained within benthic biofilms on cobbles and 14.9% within hyporheic sediment after the spate. Thus, through the combination of short-term remobilization and long-term retention, fine particles can serve as sources of carbon and nutrients to downstream ecosystems over a range of time scales.
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Fine particle retention within stream storage areas at base flow and in response to a storm event
Drummond, J. D.; Larsen, L. G.; González-Pinzón, R.; Packman, A. I.; Harvey, J. W.
2017-07-01
Fine particles (1-100 µm), including particulate organic carbon (POC) and fine sediment, influence stream ecological functioning because they may contain or have a high affinity to sorb nitrogen and phosphorus. These particles are immobilized within stream storage areas, especially hyporheic sediments and benthic biofilms. However, fine particles are also known to remobilize under all flow conditions. This combination of downstream transport and transient retention, influenced by stream geomorphology, controls the distribution of residence times over which fine particles influence stream ecosystems. The main objective of this study was to quantify immobilization and remobilization rates of fine particles in a third-order sand-and-gravel bed stream (Difficult Run, Virginia, USA) within different geomorphic units of the stream (i.e., pool, lateral cavity, and thalweg). During our field injection experiment, a thunderstorm-driven spate allowed us to observe fine particle dynamics during both base flow and in response to increased flow. Solute and fine particles were measured within stream surface waters, pore waters, sediment cores, and biofilms on cobbles. Measurements were taken at four different subsurface locations with varying geomorphology and at multiple depths. Approximately 68% of injected fine particles were retained during base flow until the onset of the spate. Retention was evident even after the spate, with 15.4% of the fine particles deposited during base flow still retained within benthic biofilms on cobbles and 14.9% within hyporheic sediment after the spate. Thus, through the combination of short-term remobilization and long-term retention, fine particles can serve as sources of carbon and nutrients to downstream ecosystems over a range of time scales.
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Steady streaming: A key mixing mechanism in low-Reynolds-number acinar flows
Kumar, Haribalan; Tawhai, Merryn H.; Hoffman, Eric A.; Lin, Ching-Long
2011-01-01
Study of mixing is important in understanding transport of submicron sized particles in the acinar region of the lung. In this article, we investigate transport in view of advective mixing utilizing Lagrangian particle tracking techniques: tracer advection, stretch rate and dispersion analysis. The phenomenon of steady streaming in an oscillatory flow is found to hold the key to the origin of kinematic mixing in the alveolus, the alveolar mouth and the alveolated duct. This mechanism provides the common route to folding of material lines and surfaces in any region of the acinar flow, and has no bearing on whether the geometry is expanding or if flow separates within the cavity or not. All analyses consistently indicate a significant decrease in mixing with decreasing Reynolds number (Re). For a given Re, dispersion is found to increase with degree of alveolation, indicating that geometry effects are important. These effects of Re and geometry can also be explained by the streaming mechanism. Based on flow conditions and resultant convective mixing measures, we conclude that significant convective mixing in the duct and within an alveolus could originate only in the first few generations of the acinar tree as a result of nonzero inertia, flow asymmetry, and large Keulegan–Carpenter (KC) number. PMID:21580803
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Rožman, Marko; Acuña, Vicenç; Petrović, Mira
2018-02-01
A mesocosm case study was conducted to gain understanding and practical knowledge on biofilm emerging contaminants biodegradation capacity under stressor and multiple stressor conditions. Two real life scenarios: I) biodegradation in a pristine intermittent stream experiencing acute pollution and II) biodegradation in a chronically polluted intermittent stream, were examined via a multifactorial experiment using an artificial stream facility. Stream biofilms were exposed to different water flow conditions i.e. permanent and intermittent water flow. Venlafaxine, a readily biodegradable pharmaceutical was used as a measure of biodegradation capacity while pollution was simulated by a mixture of four emerging contaminants (erythromycin, sulfisoxazole, diclofenac and imidacloprid in addition to venlafaxine) in environmentally relevant concentrations. Biodegradation kinetics monitored via LC-MS/MS was established, statistically evaluated, and used to link biodegradation with stress events. The results suggest that the effects of intermittent flow do not hinder and may even stimulate pristine biofilm biodegradation capacity. Chronic pollution completely reduced biodegradation in permanent water flow experimental treatments while no change in intermittent streams was observed. A combined effect of water flow conditions and emerging contaminants exposure on biodegradation was found. The decrease in biodegradation due to exposure to emerging contaminants is significantly greater in streams with permanent water flow suggesting that the short and medium term biodegradation capacity in intermittent systems may be preserved or even greater than in perennial streams. Copyright © 2017 Elsevier Ltd. All rights reserved.
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Selective particle and cell capture in a continuous flow using micro-vortex acoustic streaming.
Collins, David J; Khoo, Bee Luan; Ma, Zhichao; Winkler, Andreas; Weser, Robert; Schmidt, Hagen; Han, Jongyoon; Ai, Ye
2017-05-16
Acoustic streaming has emerged as a promising technique for refined microscale manipulation, where strong rotational flow can give rise to particle and cell capture. In contrast to hydrodynamically generated vortices, acoustic streaming is rapidly tunable, highly scalable and requires no external pressure source. Though streaming is typically ignored or minimized in most acoustofluidic systems that utilize other acoustofluidic effects, we maximize the effect of acoustic streaming in a continuous flow using a high-frequency (381 MHz), narrow-beam focused surface acoustic wave. This results in rapid fluid streaming, with velocities orders of magnitude greater than that of the lateral flow, to generate fluid vortices that extend the entire width of a 400 μm wide microfluidic channel. We characterize the forces relevant for vortex formation in a combined streaming/lateral flow system, and use these acoustic streaming vortices to selectively capture 2 μm from a mixed suspension with 1 μm particles and human breast adenocarcinoma cells (MDA-231) from red blood cells.
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Can Low-Resolution Airborne Laser Scanning Data Be Used to Model Stream Rating Curves?
Directory of Open Access Journals (Sweden)
Steve W. Lyon
2015-03-01
Full Text Available This pilot study explores the potential of using low-resolution (0.2 points/m2 airborne laser scanning (ALS-derived elevation data to model stream rating curves. Rating curves, which allow the functional translation of stream water depth into discharge, making them integral to water resource monitoring efforts, were modeled using a physics-based approach that captures basic geometric measurements to establish flow resistance due to implicit channel roughness. We tested synthetically thinned high-resolution (more than 2 points/m2 ALS data as a proxy for low-resolution data at a point density equivalent to that obtained within most national-scale ALS strategies. Our results show that the errors incurred due to the effect of low-resolution versus high-resolution ALS data were less than those due to flow measurement and empirical rating curve fitting uncertainties. As such, although there likely are scale and technical limitations to consider, it is theoretically possible to generate rating curves in a river network from ALS data of the resolution anticipated within national-scale ALS schemes (at least for rivers with relatively simple geometries. This is promising, since generating rating curves from ALS scans would greatly enhance our ability to monitor streamflow by simplifying the overall effort required.
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Can low-resolution airborne laser scanning data be used to model stream rating curves?
Lyon, Steve; Nathanson, Marcus; Lam, Norris; Dahlke, Helen; Rutzinger, Martin; Kean, Jason W.; Laudon, Hjalmar
2015-01-01
This pilot study explores the potential of using low-resolution (0.2 points/m2) airborne laser scanning (ALS)-derived elevation data to model stream rating curves. Rating curves, which allow the functional translation of stream water depth into discharge, making them integral to water resource monitoring efforts, were modeled using a physics-based approach that captures basic geometric measurements to establish flow resistance due to implicit channel roughness. We tested synthetically thinned high-resolution (more than 2 points/m2) ALS data as a proxy for low-resolution data at a point density equivalent to that obtained within most national-scale ALS strategies. Our results show that the errors incurred due to the effect of low-resolution versus high-resolution ALS data were less than those due to flow measurement and empirical rating curve fitting uncertainties. As such, although there likely are scale and technical limitations to consider, it is theoretically possible to generate rating curves in a river network from ALS data of the resolution anticipated within national-scale ALS schemes (at least for rivers with relatively simple geometries). This is promising, since generating rating curves from ALS scans would greatly enhance our ability to monitor streamflow by simplifying the overall effort required.
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Yillia, Paul T.; Kreuzinger, Norbert; Mathooko, Jude M.
For shallow streams in sub-Saharan Africa, in-stream activities could be described as the actions by people and livestock, which take place within or besides stream channels. This study examined the nature of in-stream activities along a rural stream in Kenya and established the inequality in water allocation for various livelihood needs, as well as the negative impact they have on dry weather stream flow and chemical water quality. Seven locations along the stream were studied in wet and dry weather of 2006. Enumeration consisted of making head counts of people and livestock and tallying visitors at hourly intervals from 6 a.m. to 7 p.m. To estimate water abstraction, filled containers of known volume were counted and the stream was sampled to examine the impact on water quality. Water samples were obtained upstream and downstream of in-stream activities before (6 a.m.) and during (11 a.m., 6 p.m.) activities. Samples were analyzed for suspended solids, turbidity, BOD 5, total nitrogen and total phosphorus. The daily total abstraction at the middle reaches during dry weather was 120-150 m 3 day -1. More than 60% of abstraction was done by water vendors. Vended water from the stream was sold at US 3.5-7.5 per m 3 and vendors earned between US 3-6 a day. Abstracted water contributed approximately 40-60% of the total daily consumptive water use in the riparian area during dry weather but >30% of the morning stream flow was abstracted thereby upsetting stream flow in the lower reaches. The daily total water abstraction correlated positively ( R2, 0.98) and significantly ( p < 0.05) with the daily total human visit, which was diurnally periodic with two peaks, occurring between 9 a.m. and 10 a.m. and from 4 p.m. to 5 p.m. This diurnal pattern of visits and the corresponding in-stream activities affected water quality. In particular, suspended solids, turbidity and BOD 5 levels increased significantly ( p < 0.05) downstream during in-stream activities. It was concluded
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Rice, Jacelyn; Westerhoff, Paul
2017-08-01
Wastewater discharges from publicly owned treatment works are a significant source of endocrine disruptors and other contaminants to the aquatic environment in the US. Although remaining pollutants in wastewater pose environmental risks, treated wastewater is also a primary source of stream flow, which in turn is critical in maintaining many aquatic and riparian wildlife habitats. Here we calculate the dilution factor--the ratio of flow in the stream receiving discharge to the flow of wastewater discharge--for over 14,000 receiving streams in the continental US using streamflow observations and a spatially explicit watershed-scale hydraulic model. We found that wastewater discharges make up more than 50% of in-stream flow for over 900 streams. However, in 1,049 streams that experienced exceptional low-flow conditions, the dilution factors in 635 of those streams fell so low during those conditions that the safety threshold for concentrations of one endocrine disrupting compound was exceeded, and in roughly a third of those streams, the threshold was exceeded for two compounds. We suggest that streams are vulnerable to public wastewater discharge of contaminants under low-flow conditions, at a time when wastewater discharges are likely to be most important for maintaining stream flow for smaller sized river systems.
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Directory of Open Access Journals (Sweden)
Castillo M.M.
2013-03-01
Full Text Available We studied the effects of land use changes on flow regime and water chemistry of headwater streams in the highlands of Chiapas, a region in southern Mexico that has experienced high rates of deforestation in the last decades. Samples for water chemistry were collected and discharge was measured between September 2007 and August 2008 at eight streams that differed in the land uses of their riparian and catchment areas, including streams draining protected forested areas. Streams with high forest cover (>70% in their catchments maintained flow through the year. Streams draining more disturbed catchments exhibited reduced or no flow for 4 − 6 months during the dry season. Nitrate concentrations were lower at streams draining forested catchments while highest concentrations were measured where conventional agriculture covered a high proportion of the catchment and riparian zone. Highest phosphorus concentrations occurred at the catchment where poultry manure was applied as fertilizer. Differences between forest streams and those draining disturbed areas were correlated with the proportion of forest and agriculture in the riparian zone. Variation in stream variables among sampling dates was lower at the forest sites than at the more disturbed study streams. Conversion of forest into agriculture and urban areas is affecting flow regime and increasing nutrient concentrations, although the magnitude of the impacts are influenced by the type of agricultural practices and the alteration of the riparian zone.
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International Nuclear Information System (INIS)
Yamasaki, K; Iwayama, T; Yajima, T
2011-01-01
The Okubo-Weiss field, frequently used for partitioning incompressible two-dimensional (2D) fluids into coherent and incoherent regions, corresponds to the Gaussian curvature of the stream function. Therefore, we consider the differential geometric structures of stream functions and calculate the Gaussian curvatures of some basic flows. We find the following. (I) The vorticity corresponds to the mean curvature of the stream function. Thus, the stream-function surface for an irrotational flow and that for a parallel shear flow correspond to the minimal surface and a developable surface, respectively. (II) The relationship between the coherency and the magnitude of the vorticity is interpreted by the curvatures. (III) Using the Gaussian curvature, stability of single and double point vortex streets is analyzed. The results of this analysis are compared with the well-known linear stability analysis. (IV) Conformal mapping in fluid mechanics is the physical expression of the geometric fact that the sign of the Gaussian curvature does not change in conformal mapping. These findings suggest that the curvatures of stream functions are useful for understanding the geometric structure of an incompressible 2D flow.
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Stream flow - its estimation, uncertainty and interaction with groundwater and floodplains
DEFF Research Database (Denmark)
Poulsen, Jane Bang
, floodplain hydraulics and sedimentation patterns has been investigated along a restored channel section of Odense stream, Denmark. Collected samples of deposited sediment, organic matter and phosphorus on the floodplain were compared with results from a 2D dynamic flow model. Three stage dependent flow...... regimes were predicted by the flow model with shifting primary overbank flow and zones of flow confluence. These dynamic flow patterns were found to correlate with the spatial deposition of total phosphorus (11.4 g m-2), organic matter (0.65 kg m-2) and sediment (4.72 kg m-2), and zones of major total...... sediment deposition coincided with the flow confluence zones. The revealed complex spatially and temporally changing floodplain flow pattern was found to play a decisive role for the deposition processes. The interaction between stream flow and groundwater from catchment to point scale has been...
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Flow-covariate prediction of stream pesticide concentrations.
Mosquin, Paul L; Aldworth, Jeremy; Chen, Wenlin
2018-01-01
Potential peak functions (e.g., maximum rolling averages over a given duration) of annual pesticide concentrations in the aquatic environment are important exposure parameters (or target quantities) for ecological risk assessments. These target quantities require accurate concentration estimates on nonsampled days in a monitoring program. We examined stream flow as a covariate via universal kriging to improve predictions of maximum m-day (m = 1, 7, 14, 30, 60) rolling averages and the 95th percentiles of atrazine concentration in streams where data were collected every 7 or 14 d. The universal kriging predictions were evaluated against the target quantities calculated directly from the daily (or near daily) measured atrazine concentration at 32 sites (89 site-yr) as part of the Atrazine Ecological Monitoring Program in the US corn belt region (2008-2013) and 4 sites (62 site-yr) in Ohio by the National Center for Water Quality Research (1993-2008). Because stream flow data are strongly skewed to the right, 3 transformations of the flow covariate were considered: log transformation, short-term flow anomaly, and normalized Box-Cox transformation. The normalized Box-Cox transformation resulted in predictions of the target quantities that were comparable to those obtained from log-linear interpolation (i.e., linear interpolation on the log scale) for 7-d sampling. However, the predictions appeared to be negatively affected by variability in regression coefficient estimates across different sample realizations of the concentration time series. Therefore, revised models incorporating seasonal covariates and partially or fully constrained regression parameters were investigated, and they were found to provide much improved predictions in comparison with those from log-linear interpolation for all rolling average measures. Environ Toxicol Chem 2018;37:260-273. © 2017 SETAC. © 2017 SETAC.
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Branco, Paulo; Santos, José M.; Katopodis, Christos; Pinheiro, António; Ferreira, Maria T.
2013-01-01
Fish are particularly sensitive to connectivity loss as their ability to reach spawning grounds is seriously affected. The most common way to circumvent a barrier to longitudinal connectivity, and to mitigate its impacts, is to implement a fish passage device. However, these structures are often non-effective for species with different morphological and ecological characteristics so there is a need to determine optimum dimensioning values and hydraulic parameters. The aim of this work is to study the behaviour and performance of two species with different ecological characteristics (Iberian barbel Luciobarbus bocagei–bottom oriented, and Iberian chub Squalius pyrenaicus–water column) in a full-scale experimental pool-type fishway that offers two different flow regimes–plunging and streaming. Results showed that both species passed through the surface notch more readily during streaming flow than during plunging flow. The surface oriented species used the surface notch more readily in streaming flow, and both species were more successful in moving upstream in streaming flow than in plunging flow. Streaming flow enhances upstream movement of both species, and seems the most suitable for fishways in river systems where a wide range of fish morpho-ecological traits are found. PMID:23741465
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Size-selective sorting in bubble streaming flows: Particle migration on fast time scales
Thameem, Raqeeb; Rallabandi, Bhargav; Hilgenfeldt, Sascha
2015-11-01
Steady streaming from ultrasonically driven microbubbles is an increasingly popular technique in microfluidics because such devices are easily manufactured and generate powerful and highly controllable flows. Combining streaming and Poiseuille transport flows allows for passive size-sensitive sorting at particle sizes and selectivities much smaller than the bubble radius. The crucial particle deflection and separation takes place over very small times (milliseconds) and length scales (20-30 microns) and can be rationalized using a simplified geometric mechanism. A quantitative theoretical description is achieved through the application of recent results on three-dimensional streaming flow field contributions. To develop a more fundamental understanding of the particle dynamics, we use high-speed photography of trajectories in polydisperse particle suspensions, recording the particle motion on the time scale of the bubble oscillation. Our data reveal the dependence of particle displacement on driving phase, particle size, oscillatory flow speed, and streaming speed. With this information, the effective repulsive force exerted by the bubble on the particle can be quantified, showing for the first time how fast, selective particle migration is effected in a streaming flow. We acknowledge support by the National Science Foundation under grant number CBET-1236141.
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Artificial intelligence based models for stream-flow forecasting: 2000-2015
Yaseen, Zaher Mundher; El-shafie, Ahmed; Jaafar, Othman; Afan, Haitham Abdulmohsin; Sayl, Khamis Naba
2015-11-01
The use of Artificial Intelligence (AI) has increased since the middle of the 20th century as seen in its application in a wide range of engineering and science problems. The last two decades, for example, has seen a dramatic increase in the development and application of various types of AI approaches for stream-flow forecasting. Generally speaking, AI has exhibited significant progress in forecasting and modeling non-linear hydrological applications and in capturing the noise complexity in the dataset. This paper explores the state-of-the-art application of AI in stream-flow forecasting, focusing on defining the data-driven of AI, the advantages of complementary models, as well as the literature and their possible future application in modeling and forecasting stream-flow. The review also identifies the major challenges and opportunities for prospective research, including, a new scheme for modeling the inflow, a novel method for preprocessing time series frequency based on Fast Orthogonal Search (FOS) techniques, and Swarm Intelligence (SI) as an optimization approach.
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Frequency dependence and frequency control of microbubble streaming flows
Wang, Cheng; Rallabandi, Bhargav; Hilgenfeldt, Sascha
2013-02-01
Steady streaming from oscillating microbubbles is a powerful actuating mechanism in microfluidics, enjoying increased use due to its simplicity of manufacture, ease of integration, low heat generation, and unprecedented control over the flow field and particle transport. As the streaming flow patterns are caused by oscillations of microbubbles in contact with walls of the set-up, an understanding of the bubble dynamics is crucial. Here we experimentally characterize the oscillation modes and the frequency response spectrum of such cylindrical bubbles, driven by a pressure variation resulting from ultrasound in the range of 1 kHz raisebox {-.9ex{stackrel{textstyle <}{˜ }} }f raisebox {-.9ex{stackrel{textstyle <}{˜ }} } 100 kHz. We find that (i) the appearance of 2D streaming flow patterns is governed by the relative amplitudes of bubble azimuthal surface modes (normalized by the volume response), (ii) distinct, robust resonance patterns occur independent of details of the set-up, and (iii) the position and width of the resonance peaks can be understood using an asymptotic theory approach. This theory describes, for the first time, the shape oscillations of a pinned cylindrical bubble at a wall and gives insight into necessary mode couplings that shape the response spectrum. Having thus correlated relative mode strengths and observed flow patterns, we demonstrate that the performance of a bubble micromixer can be optimized by making use of such flow variations when modulating the driving frequency.
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Counter-streaming flows in a giant quiet-Sun filament observed in the extreme ultraviolet
Diercke, A.; Kuckein, C.; Verma, M.; Denker, C.
2018-03-01
Aim. The giant solar filament was visible on the solar surface from 2011 November 8-23. Multiwavelength data from the Solar Dynamics Observatory (SDO) were used to examine counter-streaming flows within the spine of the filament. Methods: We use data from two SDO instruments, the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI), covering the whole filament, which stretched over more than half a solar diameter. Hα images from the Kanzelhöhe Solar Observatory (KSO) provide context information of where the spine of the filament is defined and the barbs are located. We apply local correlation tracking (LCT) to a two-hour time series on 2011 November 16 of the AIA images to derive horizontal flow velocities of the filament. To enhance the contrast of the AIA images, noise adaptive fuzzy equalization (NAFE) is employed, which allows us to identify and quantify counter-streaming flows in the filament. We observe the same cool filament plasma in absorption in both Hα and EUV images. Hence, the counter-streaming flows are directly related to this filament material in the spine. In addition, we use directional flow maps to highlight the counter-streaming flows. Results: We detect counter-streaming flows in the filament, which are visible in the time-lapse movies in all four examined AIA wavelength bands (λ171 Å, λ193 Å, λ304 Å, and λ211 Å). In the time-lapse movies we see that these persistent flows lasted for at least two hours, although they became less prominent towards the end of the time series. Furthermore, by applying LCT to the images we clearly determine counter-streaming flows in time series of λ171 Å and λ193 Å images. In the λ304 Å wavelength band, we only see minor indications for counter-streaming flows with LCT, while in the λ211 Å wavelength band the counter-streaming flows are not detectable with this method. The diverse morphology of the filament in Hα and EUV images is caused by different absorption
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Headwater streams represent a large proportion of river networks and many have temporary flow. Litigation has questioned whether these streams are jurisdictional under the Clean Water Act. Our goal was to identify indicators of flow permanence by comparing invertebrate assemblage...
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Low-flow characteristics of streams in South Carolina
Feaster, Toby D.; Guimaraes, Wladmir B.
2017-09-22
An ongoing understanding of streamflow characteristics of the rivers and streams in South Carolina is important for the protection and preservation of the State’s water resources. Information concerning the low-flow characteristics of streams is especially important during critical flow periods, such as during the historic droughts that South Carolina has experienced in the past few decades.Between 2008 and 2016, the U.S. Geological Survey, in cooperation with the South Carolina Department of Health and Environmental Control, updated low-flow statistics at 106 continuous-record streamgages operated by the U.S. Geological Survey for the eight major river basins in South Carolina. The low-flow frequency statistics included the annual minimum 1-, 3-, 7-, 14-, 30-, 60-, and 90-day mean flows with recurrence intervals of 2, 5, 10, 20, 30, and 50 years, depending on the length of record available at the streamflow-gaging station. Computations of daily mean flow durations for the 5-, 10-, 25-, 50-, 75-, 90-, and 95-percent probability of exceedance also were included.This report summarizes the findings from publications generated during the 2008 to 2016 investigations. Trend analyses for the annual minimum 7-day average flows are provided as well as trend assessments of long-term annual precipitation data. Statewide variability in the annual minimum 7-day average flow is assessed at eight long-term (record lengths from 55 to 78 years) streamgages. If previous low-flow statistics were available, comparisons with the updated annual minimum 7-day average flow, having a 10-year recurrence interval, were made. In addition, methods for estimating low-flow statistics at ungaged locations near a gaged location are described.
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A multiphase flow meter for the on-line determination of the flow rates of oil, water and gas
International Nuclear Information System (INIS)
Roach, G.J.; Watt, J.S.
1997-01-01
Multiphase mixtures of crude oil, formation water and gas are carried in pipelines from oil wells to production facilities. Multiphase flow meters (MFMs) are being developed to determine the flow rates of each component of the heterogeneous mixture in the pipeline. CSIRO Minerals has developed and field tested a gamma-ray MFM for the on-line determination of the flow rates of heterogeneous mixtures of oil, water and gas in pipelines. It consists of two specialised gamma-ray transmission gauges, and pressure and temperature sensors, mounted on the pipeline carrying the full flow of the production stream. The MFM separately measures liquids and gas flow rates, and the volume ratio of water and liquids (water cut). The MFM has been trialled at three offshore production facilities in Australia. In each, the MFM was mounted on the pipeline between the test manifold and the test separator. The multiphase streams from the various wells feeding to the platform were sequentially routed past the MFM. The MFM and test separator outputs were compared using regression analysis. The flow rates of oil, water and gas were each determined to relative errors in the range of 5-10% . The MFM has been in routine use on the West Kingfish platform in the Bass Strait since November 1994. The MFM was recently tested over a wide range of flow conditions at a Texaco flow facility near Houston. Water cut, based on pre-trial calibration, was determined to 2% rms over the range 0-100% water cut. The liquids and gas flow results were interpreted based on slip correlations obtained from comparison of the MFM and Texaco flows. Using these, the relative errors were respectively 6.6% for liquid flow, 6.2% for gas, 8% for oil and 8% for water. The MFM is licensed to Kvaerner FSSL of Aberdeen. Kvaerner will supply the gamma-ray MFM for both platform and subsea use. Technology transfer commenced in December 1996, and Kvaerner completed the manufacture of the first MFM in August 1997
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Ziegeweid, Jeffrey R.; Lorenz, David L.; Sanocki, Chris A.; Czuba, Christiana R.
2015-12-24
Knowledge of the magnitude and frequency of low flows in streams, which are flows in a stream during prolonged dry weather, is fundamental for water-supply planning and design; waste-load allocation; reservoir storage design; and maintenance of water quality and quantity for irrigation, recreation, and wildlife conservation. This report presents the results of a statewide study for which regional regression equations were developed for estimating 13 flow-duration curve statistics and 10 low-flow frequency statistics at ungaged stream locations in Minnesota. The 13 flow-duration curve statistics estimated by regression equations include the 0.0001, 0.001, 0.02, 0.05, 0.1, 0.25, 0.50, 0.75, 0.9, 0.95, 0.99, 0.999, and 0.9999 exceedance-probability quantiles. The low-flow frequency statistics include annual and seasonal (spring, summer, fall, winter) 7-day mean low flows, seasonal 30-day mean low flows, and summer 122-day mean low flows for a recurrence interval of 10 years. Estimates of the 13 flow-duration curve statistics and the 10 low-flow frequency statistics are provided for 196 U.S. Geological Survey continuous-record streamgages using streamflow data collected through September 30, 2012.
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Impact of lateral flow on the transition from connected to disconnected stream-aquifer systems
Xian, Yang; Jin, Menggui; Liu, Yanfeng; Si, Aonan
2017-05-01
Understanding the mechanisms by which stream water infiltrates through streambeds to recharge groundwater systems is essential to sustainable management of scarce water resources in arid and semi-arid areas. An inverted water table (IWT) can develop under a stream in response to the desaturation between the stream and underlying aquifer as the system changes from a connected to disconnected status. However, previous studies have suggested that the IWT can only occur at the bottom of a low permeability streambed in which only the vertical flow between the stream and groundwater during disconnection was assumed. In the present study, numerical simulations revealed that the lateral flow induced by capillarity or heterogeneity also plays an essential role on interactions between streams and aquifers. Three pathways were identified for the transition from connection to disconnection in homogenous systems; notably, the lowest point of an IWT can develop not only at the bottom of the streambed but also within the streambed or the aquifer in response to the initial desaturation at, above, or below the interface between the streambed and aquifer (IBSA), respectively. A sensitivity analysis indicated that in wide streams, the lowest point of an IWT only occurs at the bottom of the streambed; however, for a stream half width of 1 m above a 6 m thick sandy loam streambed, the lowest point occurs in the streambed as stream depth is less than 0.5 m. This critical stream depth increases with streambed thickness and decreases with stream width. Thus, in narrow streams the lowest point can also develop in a thick streambed under a shallow stream. In narrow streams, the lowest point also forms in the aquifer if the ratio of the hydraulic conductivity of the streambed to that of the aquifer is greater than the ratio of the streambed thickness to the sum of the stream depth and the streambed thickness; correspondingly, the streambed is thin but relatively permeable and the stream is
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Flow of a stream through a reservoir
International Nuclear Information System (INIS)
Sauerwein, K.
1967-01-01
If a reservoir is fed from a single source, which may not always be pure, the extent to which the inflowing stream mixes with the water in the reservoir is important for the quality of the water supplied by the reservoir. This question was investigated at the Lingese Reservoir, containing between one and two million cubic metres of water, in the Bergisches Land (North Rhine-Westphalia). The investigation was carried out at four different seasons so that the varying effects of the stream-water temperatures could be studied in relation to the temperature of the reservoir water. The stream was radioactively labelled at the point of inflow into the reservoir, and its flow through the reservoir was measured in length and depth from boats, by means of 1-m-long Geiger counters. In two cases the radioactivity of the outflowing water was also measured at fixed points. A considerable variety of intermixing phenomena were observed; these were mainly of limnological interest. The results of four experiments corresponding to the four different seasons are described in detail. They were as follows: (1) The mid-October experiment where the stream, with a temperature of 8.0 deg. C, was a good 5 deg. C colder than the water of the reservoir, whose temperature was almost uniform, ranging from 13.2 deg. C at the bed to 13.6 deg. C at the surface. (2) The spring experiment (second half of March), when the stream temperature was only 0.3 deg. C below that of the reservoir surface (7.8 deg. C), while the temperature of the bed was 5.8 deg. C. (3) The winter experiment (early December) where at first the temperature of the stream was approximately the same as that of the surface so that, once again, the stream at first flowed 1/2 - 1 m below the surface. During the almost wind-free night a sudden fall in temperature occurred, and the air temperature dropped from 0 deg. C to -12 deg. C. (4) The summer experiment (end of July to mid-August) when the stream was nearly 1 deg. C colder than
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Effect of β-PVDF Piezoelectric Transducers’ Positioning on the Acoustic Streaming Flows
Directory of Open Access Journals (Sweden)
Susana O. Catarino
2014-09-01
Full Text Available This paper reports the numerical and experimental analysis of the acoustic streaming effect in a fluidic domain. The actuation of a piezoelectric transducer generates acoustic waves that propagate to the fluids, generating pressure gradients that induce the flow. The number and positioning of the transducers affect the pressure gradients and, consequently, the resultant flow profile. Two actuation conditions were considered: (1 acoustic streaming generated by a 28 μm thick β-poly(vinylidene fluoride (β-PVDF piezoelectric transducer placed asymmetrically relative to the fluidic domain and (2 acoustic streaming generated by two 28 μm thick β-PVDF piezoelectric transducers placed perpendicularly to each other. The transducers were fixed to the lower left corner of a poly(methyl methacrylate (PMMAcuvette and were actuated with a 24 Vpp and 34.2 MHz sinusoidal voltage. The results show that the number of transducers and their positioning affects the shape and number of recirculation areas in the acoustic streaming flows. The obtained global flows show great potential for mixing and pumping, being an alternative to the previous geometries studied by the authors, namely, a single transducer placed symmetrically under a fluidic domain.
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Control characteristics of cryogenic distillation column with a feedback stream for fusion reactor
International Nuclear Information System (INIS)
Yamanishi, Toshihiko; Okuno, Kenji
1997-01-01
The control characteristics of the cryogenic distillation column with a feedback stream have been discussed based on computer simulation results. This column plays an important role in fusion reactor. A new control system was proposed from the simulation results. The flow rate of top product is determined from the composition and flow rate of a main feed stream by a feedforward control loop. The flow rates of the feedback stream and vapor stream within the column are proportionally changed with a corresponding change of feed flow rate. The flow rate of vapor stream within the column is further adjusted to maintain product purity by a feedback control loop. The proposed system can control the product purity for a large fluctuation of feed composition, a change of feed flow rate, and an increase or decrease of the number of total theoretical stages of the column. The control system should be designed for each column by considering its operating conditions and function. The present study gives us a basic procedure for the design method of the control system of the cryogenic distillation column. (author)
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Monteith, Corey E; Brunner, Matthew E; Djagaeva, Inna; Bielecki, Anthony M; Deutsch, Joshua M; Saxton, William M
2016-05-10
The transport of cytoplasmic components can be profoundly affected by hydrodynamics. Cytoplasmic streaming in Drosophila oocytes offers a striking example. Forces on fluid from kinesin-1 are initially directed by a disordered meshwork of microtubules, generating minor slow cytoplasmic flows. Subsequently, to mix incoming nurse cell cytoplasm with ooplasm, a subcortical layer of microtubules forms parallel arrays that support long-range, fast flows. To analyze the streaming mechanism, we combined observations of microtubule and organelle motions with detailed mathematical modeling. In the fast state, microtubules tethered to the cortex form a thin subcortical layer and undergo correlated sinusoidal bending. Organelles moving in flows along the arrays show velocities that are slow near the cortex and fast on the inward side of the subcortical microtubule layer. Starting with fundamental physical principles suggested by qualitative hypotheses, and with published values for microtubule stiffness, kinesin velocity, and cytoplasmic viscosity, we developed a quantitative coupled hydrodynamic model for streaming. The fully detailed mathematical model and its simulations identify key variables that can shift the system between disordered (slow) and ordered (fast) states. Measurements of array curvature, wave period, and the effects of diminished kinesin velocity on flow rates, as well as prior observations on f-actin perturbation, support the model. This establishes a concrete mechanistic framework for the ooplasmic streaming process. The self-organizing fast phase is a result of viscous drag on kinesin-driven cargoes that mediates equal and opposite forces on cytoplasmic fluid and on microtubules whose minus ends are tethered to the cortex. Fluid moves toward plus ends and microtubules are forced backward toward their minus ends, resulting in buckling. Under certain conditions, the buckling microtubules self-organize into parallel bending arrays, guiding varying directions
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Size-sensitive particle trajectories in three-dimensional micro-bubble acoustic streaming flows
Volk, Andreas; Rossi, Massimiliano; Hilgenfeldt, Sascha; Rallabandi, Bhargav; Kähler, Christian; Marin, Alvaro
2015-11-01
Oscillating microbubbles generate steady streaming flows with interesting features and promising applications for microparticle manipulation. The flow around oscillating semi-cylindrical bubbles has been typically assumed to be independent of the axial coordinate. However, it has been recently revealed that particle motion is strongly three-dimensional: Small tracer particles follow vortical trajectories with pronounced axial displacements near the bubble, weaving a toroidal stream-surface. A well-known consequence of bubble streaming flows is size-dependent particle migration, which can be exploited for sorting and trapping of microparticles in microfluidic devices. In this talk, we will show how the three-dimensional toroidal topology found for small tracer particles is modified as the particle size increases up to 1/3 of the bubble radius. Our results show size-sensitive particle positioning along the axis of the semi-cylindrical bubble. In order to analyze the three-dimensional sorting and trapping capabilities of the system, experiments with an imposed flow and polydisperse particle solutions are also shown.
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Interactions between hyporheic flow produced by stream meanders, bars, and dunes
Stonedahl, Susa H.; Harvey, Judson W.; Packman, Aaron I.
2013-01-01
Stream channel morphology from grain-scale roughness to large meanders drives hyporheic exchange flow. In practice, it is difficult to model hyporheic flow over the wide spectrum of topographic features typically found in rivers. As a result, many studies only characterize isolated exchange processes at a single spatial scale. In this work, we simulated hyporheic flows induced by a range of geomorphic features including meanders, bars and dunes in sand bed streams. Twenty cases were examined with 5 degrees of river meandering. Each meandering river model was run initially without any small topographic features. Models were run again after superimposing only bars and then only dunes, and then run a final time after including all scales of topographic features. This allowed us to investigate the relative importance and interactions between flows induced by different scales of topography. We found that dunes typically contributed more to hyporheic exchange than bars and meanders. Furthermore, our simulations show that the volume of water exchanged and the distributions of hyporheic residence times resulting from various scales of topographic features are close to, but not linearly additive. These findings can potentially be used to develop scaling laws for hyporheic flow that can be widely applied in streams and rivers.
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Interaction between stream temperature, streamflow, and groundwater exchanges in alpine streams
Constantz, James E.
1998-01-01
Four alpine streams were monitored to continuously collect stream temperature and streamflow for periods ranging from a week to a year. In a small stream in the Colorado Rockies, diurnal variations in both stream temperature and streamflow were significantly greater in losing reaches than in gaining reaches, with minimum streamflow losses occurring early in the day and maximum losses occurring early in the evening. Using measured stream temperature changes, diurnal streambed infiltration rates were predicted to increase as much as 35% during the day (based on a heat and water transport groundwater model), while the measured increase in streamflow loss was 40%. For two large streams in the Sierra Nevada Mountains, annual stream temperature variations ranged from 0° to 25°C. In summer months, diurnal stream temperature variations were 30–40% of annual stream temperature variations, owing to reduced streamflows and increased atmospheric heating. Previous reports document that one Sierra stream site generally gains groundwater during low flows, while the second Sierra stream site may lose water during low flows. For August the diurnal streamflow variation was 11% at the gaining stream site and 30% at the losing stream site. On the basis of measured diurnal stream temperature variations, streambed infiltration rates were predicted to vary diurnally as much as 20% at the losing stream site. Analysis of results suggests that evapotranspiration losses determined diurnal streamflow variations in the gaining reaches, while in the losing reaches, evapotranspiration losses were compounded by diurnal variations in streambed infiltration. Diurnal variations in stream temperature were reduced in the gaining reaches as a result of discharging groundwater of relatively constant temperature. For the Sierra sites, comparison of results with those from a small tributary demonstrated that stream temperature patterns were useful in delineating discharges of bank storage following
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Franssen, Nathan R; Stewart, Laura K; Schaefer, Jacob F
2013-11-01
Understanding population-level responses to human-induced changes to habitats can elucidate the evolutionary consequences of rapid habitat alteration. Reservoirs constructed on streams expose stream fishes to novel selective pressures in these habitats. Assessing the drivers of trait divergence facilitated by these habitats will help identify evolutionary and ecological consequences of reservoir habitats. We tested for morphological divergence in a stream fish that occupies both stream and reservoir habitats. To assess contributions of genetic-level differences and phenotypic plasticity induced by flow variation, we spawned and reared individuals from both habitats types in flow and no flow conditions. Body shape significantly and consistently diverged in reservoir habitats compared with streams; individuals from reservoirs were shallower bodied with smaller heads compared with individuals from streams. Significant population-level differences in morphology persisted in offspring but morphological variation compared with field-collected individuals was limited to the head region. Populations demonstrated dissimilar flow-induced phenotypic plasticity when reared under flow, but phenotypic plasticity in response to flow variation was an unlikely explanation for observed phenotypic divergence in the field. Our results, together with previous investigations, suggest the environmental conditions currently thought to drive morphological change in reservoirs (i.e., predation and flow regimes) may not be the sole drivers of phenotypic change.
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Application of support vector regression (SVR) for stream flow prediction on the Amazon basin
CSIR Research Space (South Africa)
Du Toit, Melise
2016-10-01
Full Text Available regression technique is used in this study to analyse historical stream flow occurrences and predict stream flow values for the Amazon basin. Up to twelve month predictions are made and the coefficient of determination and root-mean-square error are used...
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Riverman, K. L.; Anandakrishnan, S.; Alley, R. B.; Peters, L. E.; Christianson, K. A.; Muto, A.
2013-12-01
Northeast Greenland Ice Stream (NEGIS) is the largest ice stream in Greenland, draining approximately 8.4% of the ice sheet's area. The flow pattern and stability mechanism of this ice stream are unique to others in Greenland and Antarctica, and merit further study to ascertain the sensitivity of this ice stream to future climate change. Geophysical methods are valuable tools for this application, but their results are sensitive to the structure of the firn and any spatial variations in firn properties across a given study region. Here we present firn data from a 40-km-long seismic profile across the upper reaches of NEGIS, collected in the summer of 2012 as part of an integrated ground-based geophysical survey. We find considerable variations in firn thickness that are coincident with the ice stream shear margins, where a thinner firn layer is present within the margins, and a thicker, more uniform firn layer is present elsewhere in our study region. Higher accumulation rates in the marginal surface troughs due to drift-snow trapping can account for some of this increased densification; however, our seismic results also highlight enhanced anisotropy within the firn and upper ice column that is confined to narrow bands within the shear margins. We thus interpret these large firn thickness variations and abrupt changes in anisotropy as indicators of firn densification dependent on the effective stress state as well as the overburden pressure, suggesting that the strain rate increases nonlinearly with stress across the shear margins. A GPS strain grid maintained for three weeks across both margins observed strong side shearing, with rapid stretching and then compression along particle paths, indicating large deviatoric stresses in the margins. This work demonstrates the importance of developing a high-resolution firn densification model when conducting geophysical field work in regions possessing a complex ice flow history; it also motivates the need for a more
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The Effects of the Impedance of the Flow Source on the Design of Tidal Stream Generators
Salter, S.
2011-12-01
The maximum performance of a wind turbine is set by the well-known Betz limit. If the designer of a wind turbine uses too fast a rotation, too large a blade chord or too high an angle of blade pitch, the air flow can take an easier path over or around the rotor. Most estimates of the tidal stream resource use equations borrowed from wind and would be reasonably accurate for a single unit. But water cannot flow through the seabed or over rotors which reach to the surface. If contra-rotating, vertical-axis turbines with a rectangular flow-window are placed close to one another and reach from the surface close to the seabed, the leakage path is blocked and they become more like turbines in a closed duct. Instead of an equation with area times velocity-cubed we should use the first power of volume flow rate though the rotor times the pressure difference across it. A long channel with a rough bed will already be losing lots of energy and will behave more like a high impedance flow. Attempts to block it with closely-packed turbines will increase the head across the turbines with only a small effect on flow rate. The same thing will occur if a close-packed line of turbines is built out to sea from a headland. It is necessary to understand the impedance of the flow source all the way out to mid-ocean. In deep seas where the current velocities at the seabed are too slow to disturb the ooze the friction coefficients will be similar to those of gloss paint, perhaps 0.0025. But the higher velocities in shallow water will remove ooze and quite large sediments leaving rough, bare rock and leading to higher friction-coefficients. Energy dissipation will be set by the higher friction coefficients and the cube of the higher velocities. The presence of turbines will reduce seabed losses and about one third of the present loss can be converted to electricity. The velocity reduction would be about 10%. In many sites the energy output will be far higher than the wind turbine equations
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Whiteley, Andrew R; Coombs, Jason A; Cembrola, Matthew; O'Donnell, Matthew J; Hudy, Mark; Nislow, Keith H; Letcher, Benjamin H
2015-07-01
The effective number of breeders that give rise to a cohort (N(b)) is a promising metric for genetic monitoring of species with overlapping generations; however, more work is needed to understand factors that contribute to variation in this measure in natural populations. We tested hypotheses related to interannual variation in N(b) in two long-term studies of brook trout populations. We found no supporting evidence for our initial hypothesis that N^(b) reflects N^(c) (defined as the number of adults in a population at the time of reproduction). N^(b) was stable relative to N^(C) and did not follow trends in abundance (one stream negative, the other positive). We used stream flow estimates to test the alternative hypothesis that environmental factors constrain N(b). We observed an intermediate optimum autumn stream flow for both N^(b) (R(2) = 0.73, P = 0.02) and full-sibling family evenness (R(2) = 0.77, P = 0.01) in one population and a negative correlation between autumn stream flow and full-sib family evenness in the other population (r = -0.95, P = 0.02). Evidence for greater reproductive skew at the lowest and highest autumn flow was consistent with suboptimal conditions at flow extremes. A series of additional tests provided no supporting evidence for a related hypothesis that density-dependent reproductive success was responsible for the lack of relationship between N(b) and N(C) (so-called genetic compensation). This work provides evidence that N(b) is a useful metric of population-specific individual reproductive contribution for genetic monitoring across populations and the link we provide between stream flow and N(b) could be used to help predict population resilience to environmental change. © 2015 John Wiley & Sons Ltd.
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Fine-Grained Rate Shaping for Video Streaming over Wireless Networks
Directory of Open Access Journals (Sweden)
Chen Tsuhan
2004-01-01
Full Text Available Video streaming over wireless networks faces challenges of time-varying packet loss rate and fluctuating bandwidth. In this paper, we focus on streaming precoded video that is both source and channel coded. Dynamic rate shaping has been proposed to shape the precompressed video to adapt to the fluctuating bandwidth. In our earlier work, rate shaping was extended to shape the channel coded precompressed video, and to take into account the time-varying packet loss rate as well as the fluctuating bandwidth of the wireless networks. However, prior work on rate shaping can only adjust the rate oarsely. In this paper, we propose fine-grained rate shaping (FGRS to allow for bandwidth adaptation over a wide range of bandwidth and packet loss rate in fine granularities. The video is precoded with fine granularity scalability (FGS followed by channel coding. Utilizing the fine granularity property of FGS and channel coding, FGRS selectively drops part of the precoded video and still yields decodable bit-stream at the decoder. Moreover, FGRS optimizes video streaming rather than achieves heuristic objectives as conventional methods. A two-stage rate-distortion (RD optimization algorithm is proposed for FGRS. Promising results of FGRS are shown.
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Energy Technology Data Exchange (ETDEWEB)
Kotas, Charlotte W [ORNL; Rogers, Peter [Georgia Institute of Technology; Yoda, Minami [Georgia Institute of Technology
2011-01-01
The ears of fishes are remarkable sensors for the small acoustic disturbances associated with underwater sound. For example, each ear of the Atlantic cod (Gadus morhua) has three dense bony bodies (otoliths) surrounded by fluid and tissue, and detects sounds at frequencies from 30 to 500 Hz. Atlantic cod have also been shown to localize sounds. However, how their ears perform these functions is not fully understood. Steady streaming, or time-independent, flows near a 350% scale model Atlantic cod otolith immersed in a viscous fluid were studied to determine if these fluid flows contain acoustically relevant information that could be detected by the ear s sensory hair cells. The otolith was oscillated sinusoidally at various orientations at frequencies of 8 24 Hz, corresponding to an actual frequency range of 280 830 Hz. Phaselocked particle pathline visualizations of the resulting flows give velocity, vorticity, and rate of strain fields over a single plane of this mainly two-dimensional flow. Although the streaming flows contain acoustically relevant information, the displacements due to these flows are likely too small to explain Atlantic cod hearing abilities near threshold. The results, however, may suggest a possible mechanism for detection of ultrasound in some fish species.
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Anwar, Y.; Setyasih, I.; Setiawan, M. A.; Christanto, N.
2018-04-01
Evaluation study for such a regional spatial plan (RTRW) in Indonesia has not been evaluated for its effectiveness in controlling the surface run off that contributed to streamflow. This necessity can be accomplishsed by applying a modeling approach, such as Soil Water Assessment Tool (SWAT). The objectives of this research are 1) to simulate the streamflow of Wakung watershed based on actual landuse, 2) to predict streamflow of Wakung watershed based on RTRW, and 3) to evaluate the effectiveness of the RTRW of Pemalang District in controling streamflow rate at Wakung Watershed. ArcSWAT model was used to determine the erosion rate prediction. The model was then calibrated by using SWATCUP. Model performance were tested by using R2 and ENS. The calibration and validation results showed that R2 and ENS (monthly) > 0.5. The result of SWAT simulation in Wakung sub-watershed reaching 161 - 4950 m3/s/years for W-A scenario (actual landuse and weather data of 2013), for scenario W-R (RTRW and weather data of 2013), 330 - 4919 m3/s/year. The comparison between actual and spatial plan land use data for stream flow is showing that the W-A scenario is lower than the W-R scenario in 19 sub watersheds. This is because there are many plans for adding land use for urban and intensive horticulture land in areas with steep slopes (> 25%). This condition is caused by the demands of fulfilling the needs of settlement and food for people in the Wakung watershed.
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Ivan Arismendi; Mohammad Safeeq; Sherri L. Johnson; Jason B Dunham; Roy Haggerty
2013-01-01
Flow and temperature are strongly linked environmental factors driving ecosystem processes in streams. Stream temperature maxima (Tmax_w) and stream flow minima (Qmin) can create periods of stress for aquatic organisms. In mountainous areas, such as western North America, recent shifts toward an earlier spring peak flow and...
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Nasir Mahmood, Muhammad; Schmidt, Christian; Trauth, Nico
2017-04-01
Stream morphological features, in combination with hydrological variability play a key role in water and solute exchange across surface and subsurface waters. Meanders are prominent morphological features within stream systems which exhibit unique hydrodynamics. The water surface elevation difference across the inner bank of a meander induces lateral hyporheic exchange within the intra-meander region. This hyporheic flow is characterized by considerably prolonged flow paths and residence times (RT) compared to smaller scales of hyporheic exchange. In this study we examine the impact of different meander geometries on the intra-meander hyporheic flow field and solute mobilization under both steady state and transient flow conditions. We developed a number of artificial meander shape scenarios, representing various meander evolution stages, ranging from a typical initial to advanced stage (near cut off ) meander. Three dimensional steady state numerical groundwater flow simulations including the unsaturated zone were performed for the intra-meander region. The meandering stream was implemented in the model by adjusting the top layers of the modelling domain to the streambed elevation and assigning linearly decreasing head boundary conditions to the streambed cells. Residence times for the intra-meander region were computed by advective particle tracking across the inner bank of meander. Selected steady state cases were extended to transient flow simulations to evaluate the impact of stream discharge events on the temporal behavior of the water exchange and solute transport in the intra-meander region. The transient stream discharge was simulated for a number of discharge events of variable duration and peak height using the surface water model HEC-RAS. Transient hydraulic heads obtained from the surface water model were applied as transient head boundary conditions to the streambed cells of the groundwater model. A solute concentration source was added in the
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Lagrangian mass-flow investigations of inorganic contaminants in wastewater-impacted streams
Barber, L.B.; Antweiler, Ronald C.; Flynn, J.L.; Keefe, S.H.; Kolpin, D.W.; Roth, D.A.; Schnoebelen, D.J.; Taylor, Howard E.; Verplanck, P.L.
2011-01-01
Understanding the potential effects of increased reliance on wastewater treatment plant (WWTP) effluents to meet municipal, agricultural, and environmental flow requires an understanding of the complex chemical loading characteristics of the WWTPs and the assimilative capacity of receiving waters. Stream ecosystem effects are linked to proportions of WWTP effluent under low-flow conditions as well as the nature of the effluent chemical mixtures. This study quantifies the loading of 58 inorganic constituents (nutrients to rare earth elements) from WWTP discharges relative to upstream landscape-based sources. Stream assimilation capacity was evaluated by Lagrangian sampling, using flow velocities determined from tracer experiments to track the same parcel of water as it moved downstream. Boulder Creek, Colorado and Fourmile Creek, Iowa, representing two different geologic and hydrologic landscapes, were sampled under low-flow conditions in the summer and spring. One-half of the constituents had greater loads from the WWTP effluents than the upstream drainages, and once introduced into the streams, dilution was the predominant assimilation mechanism. Only ammonium and bismuth had significant decreases in mass load downstream from the WWTPs during all samplings. The link between hydrology and water chemistry inherent in Lagrangian sampling allows quantitative assessment of chemical fate across different landscapes. ?? 2011 American Chemical Society.
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Subsurface Controls on Stream Intermittency in a Semi-Arid Landscape
Dohman, J.; Godsey, S.; Thackray, G. D.; Hale, R. L.; Wright, K.; Martinez, D.
2017-12-01
Intermittent streams currently constitute 30% to greater than 50% of the global river network. In addition, the number of intermittent streams is expected to increase due to changes in land use and climate. These streams provide important ecosystem services, such as water for irrigation, increased biodiversity, and high rates of nutrient cycling. Many hydrological studies have focused on mapping current intermittent flow regimes or evaluating long-term flow records, but very few have investigated the underlying causes of stream intermittency. The disconnection and reconnection of surface flow reflects the capacity of the subsurface to accommodate flow, so characterizing subsurface flow is key to understanding stream drying. We assess how subsurface flow paths control local surface flows during low-flow periods, including intermittency. Water table dynamics were monitored in an intermittent reach of Gibson Jack Creek in southeastern Idaho. Four transects were delineated with a groundwater well located in the hillslope, riparian zone, and in the stream, for a total of 12 groundwater wells. The presence or absence of surface flow was determined by frequent visual observations as well as in situ loggers every 30m along the 200m study reach. The rate of surface water drying was measured in conjunction with temperature, precipitation, subsurface hydraulic conductivity, hillslope-riparian-stream connectivity and subsurface travel time. Initial results during an unusually wet year suggest different responses in reaches that were previously observed to occasionally cease flowing. Flows in the intermittent reaches had less coherent and lower amplitude diel variations during base flow periods than reaches that had never been observed to dry out. Our findings will help contribute to our understanding of mechanisms driving expansion and contraction cycles in intermittent streams, increase our ability to predict how land use and climate change will affect flow regimes, and
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Directory of Open Access Journals (Sweden)
Chaojun Gu
2016-12-01
Full Text Available The Poyang Lake Basin has been suffering from severe water problems such as floods and droughts. This has led to great adverse impacts on local ecosystems and water resource utilization. It is therefore important to understand stream flow changes and their driving factors. In this paper, the dynamics of stream flow and precipitation in the Poyang Lake Basin between 1961 and 2012 were evaluated with the Mann–Kendall test, Theil–Sen approaches, Pettitt test, and Pearson’s correlation. Stream flow was measured at the outlets of five major tributaries of Poyang Lake, while precipitation was recorded by fourteen meteorological stations located within the Poyang Lake Basin. Results showed that annual stream flow of all tributaries and the precipitation over the study area had insignificant (P > 0.1 temporal trends and change points, while significant trends and shifts were found in monthly scale. Stream flow concentration indices (SCI at Waizhou, Meigang, and Wanjiabu stations showed significant (P < 0.05 decreasing trends with change points emerging in 1984 at Waizhou and 1978 at Wanjiabu, while there was no significant temporal trend and change point detected for the precipitation concentration indices (PCI. Correlation analysis indicated that area-average stream flow was closely related to area-average precipitation, but area-average SCI was insignificantly correlated with area-average PCI after change point (1984. El Niño/Southern Oscillation (ENSO had greater impacts on stream flow than other climate indices, and La Niña events played a more important role in stream flow changes than EI Niño. Human activities, particularly in terms of reservoir constructions, largely altered the intra-annual distribution of stream flow but its effects on the amount of stream flow were relatively low. Results of this study provided a useful reference to regional water resource management and the prevention of flood and drought disasters.
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Eddy-current flow rate meter for measuring sodium flow rates
International Nuclear Information System (INIS)
Knaak, J.
1976-01-01
For safety reasons flow rate meters for monitoring coolant flow rates are inserted in the core of sodium-cooled fast breeder reactors. These are so-called eddy-current flow rate meters which can be mounted directly above the fuel elements. In the present contribution the principle of measurement, the mechanical construction and the circuit design of the flow rate measuring device are described. Special problems and their solution on developing the measuring system are pointed out. Finally, results of measurement and experience with the apparatus in several experiments are reported, where also further possibilities of application were tested. (orig./TK) [de
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IOD and ENSO impacts on the extreme stream-flows of Citarum river in Indonesia
Energy Technology Data Exchange (ETDEWEB)
Sahu, Netrananda; Yamashiki, Yosuke; Takara, Kaoru [Kyoto University, Disaster Prevention Research Institute, Innovative Disaster Prevention Technology and Policy Research Laboratory, Gokasho, Uji City, Kyoto (Japan); Behera, Swadhin K. [JAMSTEC, Research Institute for Global Change, Yokohama, Kanagawa (Japan); JAMSTEC, Application Laboratory, Yokohama (Japan); Yamagata, Toshio [University of Tokyo, School of Science, Bunkyo-ku, Tokyo (Japan); JAMSTEC, Application Laboratory, Yokohama (Japan)
2012-10-15
Extreme stream-flow events of Citarum River are derived from the daily stream-flows at the Nanjung gauge station. Those events are identified based on their persistently extreme flows for 6 or more days during boreal fall when the seasonal mean stream-flow starts peaking-up from the lowest seasonal flows of June-August. Most of the extreme events of high-streamflows were related to La Nina conditions of tropical Pacific. A few of them were also associated with the negative phases of IOD and the newly identified El Nino Modoki. Unlike the cases of extreme high streamflows, extreme low streamflow events are seen to be associated with the positive IODs. Nevertheless, it was also found that the low-stream-flow events related to positive IOD events were also associated with El Nino events except for one independent event of 1977. Because the occurrence season coincides the peak season of IOD, not only the picked extreme events are seen to fall under the IOD seasons but also there exists a statistically significant correlation of 0.51 between the seasonal IOD index and the seasonal streamflows. There also exists a significant lag correlation when IOD of June-August season leads the streamflows of September-November. A significant but lower correlation coefficient (0.39) is also found between the seasonal streamflow and El Nino for September-November season only. (orig.)
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Three-dimensional features on oscillating microbubbles streaming flows
Rossi, Massimiliano; Marin, Alvaro G.; Wang, Cheng; Hilgenfeldt, Sascha; Kähler, Christian J.
2013-11-01
Ultrasound-driven oscillating micro-bubbles have been used as active actuators in microfluidic devices to perform manifold tasks such as mixing, sorting and manipulation of microparticles. A common configuration consists in side-bubbles, created by trapping air pockets in blind channels perpendicular to the main channel direction. This configuration results in bubbles with a semi-cylindrical shape that creates a streaming flow generally considered quasi two-dimensional. However, recent experiments performed with three-dimensional velocimetry methods have shown how microparticles can present significant three-dimensional trajectories, especially in regions close to the bubble interface. Several reasons will be discussed such as boundary effects of the bottom/top wall, deformation of the bubble interface leading to more complex vibrational modes, or bubble-particle interactions. In the present investigation, precise measurements of particle trajectories close to the bubble interface will be performed by means of 3D Astigmatic Particle Tracking Velocimetry. The results will allow us to characterize quantitatively the three-dimensional features of the streaming flow and to estimate its implications in practical applications as particle trapping, sorting or mixing.
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Corcoll, Natàlia; Casellas, Maria; Huerta, Belinda; Guasch, Helena; Acuña, Vicenç; Rodríguez-Mozaz, Sara; Serra-Compte, Albert; Barceló, Damià; Sabater, Sergi
2015-01-15
Increasing concentrations of pharmaceutical compounds occur in many rivers, but their environmental risk remains poorly studied in stream biofilms. Flow intermittency shapes the structure and functions of ecosystems, and may enhance their sensitivity to toxicants. This study evaluates the effects of a long-term exposure of biofilm communities to a mixture of pharmaceutical compounds at environmental concentrations on biofilm bioaccumulation capacity, the structure and metabolic processes of algae and bacteria communities, and how their potential effects were enhanced or not by the occurrence of flow intermittency. To assess the interaction between those two stressors, an experiment with artificial streams was performed. Stream biofilms were exposed to a mixture of pharmaceuticals, as well as to a short period of flow intermittency. Results indicate that biofilms were negatively affected by pharmaceuticals. The algal biomass and taxa richness decreased and unicellular green algae relatively increased. The structure of the bacterial (based on denaturing gradient gel electrophoresis of amplified 16S rRNA genes) changed and showed a reduction of the operational taxonomic units (OTUs) richness. Exposed biofilms showed higher rates of metabolic processes, such as primary production and community respiration, attributed to pharmaceuticals stimulated an increase of green algae and heterotrophs, respectively. Flow intermittency modulated the effects of chemicals on natural communities. The algal community became more sensitive to short-term exposure of pharmaceuticals (lower EC50 value) when exposed to water intermittency, indicating cumulative effects between the two assessed stressors. In contrast to algae, the bacterial community became less sensitive to short-term exposure of pharmaceuticals (higher EC50) when exposed to water intermittency, indicating co-tolerance phenomena. According to the observed effects, the environmental risk of pharmaceuticals in nature is high
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Degefu, Mekonnen Adnew; Bewket, Woldeamlak
2017-04-01
This study assesses variability, trends, and teleconnections of stream flow with large-scale climate signals (global sea surface temperatures (SSTs)) for the Omo-Ghibe River Basin of Ethiopia. Fourteen hydrological indices of variability and extremes were defined from daily stream flow data series and analyzed for two common periods, which are 1972-2006 for 5 stations and 1982-2006 for 15 stations. The Mann-Kendall's test was used to detect trends at 0.05 significance level, and simple correlation analysis was applied to evaluate associations between the selected stream flow indices and SSTs. We found weak and mixed (upward and downward) trend signals for annual and wet (Kiremt) season flows. Indices generated for high-flow (flood) magnitudes showed the same weak trend signals. However, trend tests for flood frequencies and low-flow magnitudes showed little evidences of increasing change. It was also found that El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are the major anomalies affecting stream flow variability in the Omo-Ghibe Basin. The strongest associations are observed between ENSO/Niño3.4 and the stream flow in August and September, mean Kiremt flow (July-September), and flood frequency (peak over threshold on average three peaks per year (POT3_Fre)). The findings of this study provide a general overview on the long-term stream flow variability and predictability of stream flows for the Omo-Ghibe River Basin.
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Dynamic Programming Optimization of Multi-rate Multicast Video-Streaming Services
Directory of Open Access Journals (Sweden)
Nestor Michael Caños Tiglao
2010-06-01
Full Text Available In large scale IP Television (IPTV and Mobile TV distributions, the video signal is typically encoded and transmitted using several quality streams, over IP Multicast channels, to several groups of receivers, which are classified in terms of their reception rate. As the number of video streams is usually constrained by both the number of TV channels and the maximum capacity of the content distribution network, it is necessary to find the selection of video stream transmission rates that maximizes the overall user satisfaction. In order to efficiently solve this problem, this paper proposes the Dynamic Programming Multi-rate Optimization (DPMO algorithm. The latter was comparatively evaluated considering several user distributions, featuring different access rate patterns. The experimental results reveal that DPMO is significantly more efficient than exhaustive search, while presenting slightly higher execution times than the non-optimal Multi-rate Step Search (MSS algorithm.
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Identifying hidden voice and video streams
Fan, Jieyan; Wu, Dapeng; Nucci, Antonio; Keralapura, Ram; Gao, Lixin
2009-04-01
Given the rising popularity of voice and video services over the Internet, accurately identifying voice and video traffic that traverse their networks has become a critical task for Internet service providers (ISPs). As the number of proprietary applications that deliver voice and video services to end users increases over time, the search for the one methodology that can accurately detect such services while being application independent still remains open. This problem becomes even more complicated when voice and video service providers like Skype, Microsoft, and Google bundle their voice and video services with other services like file transfer and chat. For example, a bundled Skype session can contain both voice stream and file transfer stream in the same layer-3/layer-4 flow. In this context, traditional techniques to identify voice and video streams do not work. In this paper, we propose a novel self-learning classifier, called VVS-I , that detects the presence of voice and video streams in flows with minimum manual intervention. Our classifier works in two phases: training phase and detection phase. In the training phase, VVS-I first extracts the relevant features, and subsequently constructs a fingerprint of a flow using the power spectral density (PSD) analysis. In the detection phase, it compares the fingerprint of a flow to the existing fingerprints learned during the training phase, and subsequently classifies the flow. Our classifier is not only capable of detecting voice and video streams that are hidden in different flows, but is also capable of detecting different applications (like Skype, MSN, etc.) that generate these voice/video streams. We show that our classifier can achieve close to 100% detection rate while keeping the false positive rate to less that 1%.
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Strong enhancement of streaming current power by application of two phase flow
Xie, Yanbo; Sherwood, John D.; Shui, Lingling; van den Berg, Albert; Eijkel, Jan C.T.
2011-01-01
We show that the performance of a streaming-potential based microfluidic energy conversion system can be strongly en-hanced by the use of two phase flow. In single-phase systems, the internal conduction current induced by the streaming poten-tial limits the output power, while in a two-phase system
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Numerical and experimental modelling of back stream flow during close-coupled gas atomization
Motaman, S; Mullis, AM; Borman, DJ; Cochrane, RF; McCarthy, IN
2013-01-01
This paper reports the numerical and experimental investigation into the effects of different gas jet mis-match angles (for an external melt nozzle wall) on the back-stream flow in close coupled gas atomization. The Pulse Laser Imaging (PLI) technique was applied for visualising the back-stream melt flow phenomena with an analogue water atomizer and the associated PLI images compared with numerical results. In the investigation a Convergent–Divergent (C–D) discrete gas jet die at five differe...
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Low-flow characteristics for selected streams in Indiana
Fowler, Kathleen K.; Wilson, John T.
2015-01-01
The management and availability of Indiana’s water resources increase in importance every year. Specifically, information on low-flow characteristics of streams is essential to State water-management agencies. These agencies need low-flow information when working with issues related to irrigation, municipal and industrial water supplies, fish and wildlife protection, and the dilution of waste. Industrial, municipal, and other facilities must obtain National Pollutant Discharge Elimination System (NPDES) permits if their discharges go directly to surface waters. The Indiana Department of Environmental Management (IDEM) requires low-flow statistics in order to administer the NPDES permit program. Low-flow-frequency characteristics were computed for 272 continuous-record stations. The information includes low-flow-frequency analysis, flow-duration analysis, and harmonic mean for the continuous-record stations. For those stations affected by some form of regulation, low-flow frequency curves are based on the longest period of homogeneous record under current conditions. Low-flow-frequency values and harmonic mean flow (if sufficient data were available) were estimated for the 166 partial-record stations. Partial-record stations are ungaged sites where streamflow measurements were made at base flow.
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IOD and ENSO impacts on the extreme stream-flows of Citarum river in Indonesia
Sahu, Netrananda; Behera, Swadhin K.; Yamashiki, Yosuke; Takara, Kaoru; Yamagata, Toshio
2012-10-01
Extreme stream-flow events of Citarum River are derived from the daily stream-flows at the Nanjung gauge station. Those events are identified based on their persistently extreme flows for 6 or more days during boreal fall when the seasonal mean stream-flow starts peaking-up from the lowest seasonal flows of June-August. Most of the extreme events of high-streamflows were related to La Niña conditions of tropical Pacific. A few of them were also associated with the negative phases of IOD and the newly identified El Niño Modoki. Unlike the cases of extreme high streamflows, extreme low streamflow events are seen to be associated with the positive IODs. Nevertheless, it was also found that the low-stream-flow events related to positive IOD events were also associated with El Niño events except for one independent event of 1977. Because the occurrence season coincides the peak season of IOD, not only the picked extreme events are seen to fall under the IOD seasons but also there exists a statistically significant correlation of 0.51 between the seasonal IOD index and the seasonal streamflows. There also exists a significant lag correlation when IOD of June-August season leads the streamflows of September-November. A significant but lower correlation coefficient (0.39) is also found between the seasonal streamflow and El Niño for September-November season only.
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Effects of Urbanization on the Flow Regimes of Semi-Arid Southern California Streams
Hawley, R. J.; Bledsoe, B. P.; Stein, E. D.
2010-12-01
Stream channel erosion and associated habitat degradation are pervasive in streams draining urban areas in the southwestern US. The prevalence of these impacts results from the inherent sensitivity of streams in semi-arid climates to changes in flow and sediment regimes, and past inattention to management of geomorphically effective flows. Addressing this issue is difficult due to the lack of data linking ranges of flow (from small to large runoff events) to geomorphic channel response. Forty-three U. S. Geological Survey gages with record lengths greater than ~15 yrs and watershed areas less than ~250 square kilometers were used to empirically model the effects of urbanization on streams in southern California. The watersheds spanned a gradient of urban development and ranged from 0 to 23% total impervious area in 2001. With little flow control at the subdivision scale to date, most impervious area in the region is relatively well-connected to surface-drainage networks. Consequently, total impervious area was an effective surrogate for urbanization, and emerged as a significant (p approach expands on previous scaling procedures to produce histogram-style cumulative flow duration graphs for ungaged sites based on urbanization extent and other watershed descriptors. Urbanization resulted in proportionally-longer durations of all geomorphically-effective flows, with a more pronounced effect on the durations of moderate flows. For example, an average watershed from the study domain with ~20% imperviousness could experience five times as many days of mean daily flows on the order of 100 cfs (3 cubic meters per second) and approximately three times as many days on the order of 1,000 cfs (30 cubic meters per second) relative to the undeveloped setting. Increased duration of sediment-transporting flows is a primary driver of accelerated changes in channel form that are often concurrent with urbanization throughout southern California, particularly in unconfined, fine
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Directory of Open Access Journals (Sweden)
Islam S.M. Khalil
2016-06-01
Full Text Available Targeted therapy using magnetic microparticles and nanoparticles has the potential to mitigate the negative side-effects associated with conventional medical treatment. Major technological challenges still need to be addressed in order to translate these particles into in vivo applications. For example, magnetic particles need to be navigated controllably in vessels against flowing streams of body fluid. This paper describes the motion control of paramagnetic microparticles in the flowing streams of fluidic channels with time-varying flow rates (maximum flow is 35 ml.hr−1. This control is designed using a magnetic-based proportional-derivative (PD control system to compensate for the time-varying flow inside the channels (with width and depth of 2 mm and 1.5 mm, respectively. First, we achieve point-to-point motion control against and along flow rates of 4 ml.hr−1, 6 ml.hr−1, 17 ml.hr−1, and 35 ml.hr−1. The average speeds of single microparticle (with average diameter of 100 μm against flow rates of 6 ml.hr−1 and 30 ml.hr−1 are calculated to be 45 μm.s−1 and 15 μm.s−1, respectively. Second, we implement PD control with disturbance estimation and compensation. This control decreases the steady-state error by 50%, 70%, 73%, and 78% at flow rates of 4 ml.hr−1, 6 ml.hr−1, 17 ml.hr−1, and 35 ml.hr−1, respectively. Finally, we consider the problem of finding the optimal path (minimal kinetic energy between two points using calculus of variation, against the mentioned flow rates. Not only do we find that an optimal path between two collinear points with the direction of maximum flow (middle of the fluidic channel decreases the rise time of the microparticles, but we also decrease the input current that is supplied to the electromagnetic coils by minimizing the kinetic energy of the microparticles, compared to a PD control with disturbance compensation.
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Daya Sagar, B. S.
2005-01-01
Spatio-temporal patterns of small water bodies (SWBs) under the influence of temporally varied stream flow discharge are simulated in discrete space by employing geomorphologically realistic expansion and contraction transformations. Cascades of expansion-contraction are systematically performed by synchronizing them with stream flow discharge simulated via the logistic map. Templates with definite characteristic information are defined from stream flow discharge pattern as the basis to model the spatio-temporal organization of randomly situated surface water bodies of various sizes and shapes. These spatio-temporal patterns under varied parameters (λs) controlling stream flow discharge patterns are characterized by estimating their fractal dimensions. At various λs, nonlinear control parameters, we show the union of boundaries of water bodies that traverse the water body and non-water body spaces as geomorphic attractors. The computed fractal dimensions of these attractors are 1.58, 1.53, 1.78, 1.76, 1.84, and 1.90, respectively, at λs of 1, 2, 3, 3.46, 3.57, and 3.99. These values are in line with general visual observations.
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Directory of Open Access Journals (Sweden)
B. S. Daya Sagar
2005-01-01
Full Text Available Spatio-temporal patterns of small water bodies (SWBs under the influence of temporally varied stream flow discharge are simulated in discrete space by employing geomorphologically realistic expansion and contraction transformations. Cascades of expansion-contraction are systematically performed by synchronizing them with stream flow discharge simulated via the logistic map. Templates with definite characteristic information are defined from stream flow discharge pattern as the basis to model the spatio-temporal organization of randomly situated surface water bodies of various sizes and shapes. These spatio-temporal patterns under varied parameters (λs controlling stream flow discharge patterns are characterized by estimating their fractal dimensions. At various λs, nonlinear control parameters, we show the union of boundaries of water bodies that traverse the water body and non-water body spaces as geomorphic attractors. The computed fractal dimensions of these attractors are 1.58, 1.53, 1.78, 1.76, 1.84, and 1.90, respectively, at λs of 1, 2, 3, 3.46, 3.57, and 3.99. These values are in line with general visual observations.
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Hydraulic Properties related to Stream Reaeration
Energy Technology Data Exchange (ETDEWEB)
Tsivoglou, E. C.; Wallace, J. R. [School of Civil Engineering, Georgia Institute of Technology, Atlanta, GA (United States)
1970-09-15
The paper reports the results of recent and current field tracer experiments designed to investigate the relationships between the reaeration capacity of a flowing stream and the stream's hydraulic properties. The purpose of the studies is to develop models for the accurate prediction of stream reaeration capacity on the basis of observation of the associated hydraulic properties. The ability of a flowing stream to absorb oxygen from the overlying atmosphere is the principal process by which the stream is able to recover its dissolved oxygen resources once they have been depleted by bacterial degradation of organic wastes. Accurate knowledge of stream reaeration capacity is therefore a necessity in determining the required degree of waste treatment, and the associated costs, in any specific case. Oxygen absorption can only occur at the air-water interface, hence reaeration is a direct function of the rate of surface water replacement due to turbulent mixing. The latter is not directly observable, and so reaeration capacity has not been observable before the quite recent development of a gaseous radiotracer technique for field measurement of reaeration. This procedure involves the simultaneous use of three tracers, namely a fluorescent dye for time of flow, tritiated water for accurate dispersion measurement, and dissolved krypton-85 for measurement of gas transfer. Field results obtained by this technique are highly reproducible. Field tracer studies of the reaeration capacities of three medium-sized streams have been conducted over a total of about fifty river miles. Associated hydraulic properties such as stream flow, cross-sectional area, depth, velocity, hydraulic gradient and dispersion have also been measured. Features such as waterfalls, rapids and pools are included, and more than eighty observations of the reaeration capacities of individual stream reaches have been made. The paper reports the observed relationships between stream reaeration capacity and
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Hydraulic properties related to stream reaeration
Energy Technology Data Exchange (ETDEWEB)
Tsivoglou, E C; Wallace, J R [School of Civil Engineering, Georgia Institute of Technology, Atlanta, GA (United States)
1970-09-15
The paper reports the results of recent and current field tracer experiments designed to investigate the relationships between the reaeration capacity of a flowing stream and the stream's hydraulic properties. The purpose of the studies is to develop models for the accurate prediction of stream reaeration capacity on the basis of observation of the associated hydraulic properties. The ability of a flowing stream to absorb oxygen from the overlying atmosphere is the principal process by which the stream is able to recover its dissolved oxygen resources once they have been depleted by bacterial degradation of organic wastes. Accurate knowledge of stream reaeration capacity is therefore a necessity in determining the required degree of waste treatment, and the associated costs, in any specific case. Oxygen absorption can only occur at the air-water interface, hence reaeration is a direct function of the rate of surface water replacement due to turbulent mixing. The latter is not directly observable, and so reaeration capacity has not been observable before the quite recent development of a gaseous radiotracer technique for field measurement of reaeration. This procedure involves the simultaneous use of three tracers, namely a fluorescent dye for time of flow, tritiated water for accurate dispersion measurement, and dissolved krypton-85 for measurement of gas transfer. Field results obtained by this technique are highly reproducible. Field tracer studies of the reaeration capacities of three medium-sized streams have been conducted over a total of about fifty river miles. Associated hydraulic properties such as stream flow, cross-sectional area, depth, velocity, hydraulic gradient and dispersion have also been measured. Features such as waterfalls, rapids and pools are included, and more than eighty observations of the reaeration capacities of individual stream reaches have been made. The paper reports the observed relationships between stream reaeration capacity and
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Robert Progar; Andrew R. Moldenke
2009-01-01
We examined the effect of canopy cover on adult aquatic insect emergence by collecting bi-weekly samples from twelve headwater stream reaches flowing either under a mature conifer canopy or streams flowing through ten-year-old regeneration in western Oregon from February to November 1997. Density and biomass generally followed a bimodal curve with peaks during early...
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Energy Technology Data Exchange (ETDEWEB)
Cid, N., E-mail: ncid@ub.edu [Grup de Recerca “Freshwater Ecology and Management (FEM)”, Departament d' Ecologia, Universitat de Barcelona, Catalonia (Spain); Verkaik, I. [Grup de Recerca “Freshwater Ecology and Management (FEM)”, Departament d' Ecologia, Universitat de Barcelona, Catalonia (Spain); García-Roger, E.M. [Grup de Recerca “Freshwater Ecology and Management (FEM)”, Departament d' Ecologia, Universitat de Barcelona, Catalonia (Spain); Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de València (Spain); Rieradevall, M.; Bonada, N. [Grup de Recerca “Freshwater Ecology and Management (FEM)”, Departament d' Ecologia, Universitat de Barcelona, Catalonia (Spain); Sánchez-Montoya, M.M. [Department of Ecology and Hydrology, Regional Campus of International Excellence “Campus Mare Nostrum”—University of Murcia (Spain); Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin (Germany); Gómez, R.; Suárez, M.L.; Vidal-Abarca, M.R. [Department of Ecology and Hydrology, Regional Campus of International Excellence “Campus Mare Nostrum”—University of Murcia (Spain); Demartini, D.; Buffagni, A.; Erba, S. [Instituto di Ricerca Sulle Acque (CNR-IRSA) (Italy); Karaouzas, I.; Skoulikidis, N. [Hellenic Center for Marine Research (HCMR) (Greece); Prat, N. [Grup de Recerca “Freshwater Ecology and Management (FEM)”, Departament d' Ecologia, Universitat de Barcelona, Catalonia (Spain)
2016-01-01
Many streams in the Mediterranean Basin have temporary flow regimes. While timing for seasonal drought is predictable, they undergo strong inter-annual variability in flow intensity. This high hydrological variability and associated ecological responses challenge the ecological status assessment of temporary streams, particularly when setting reference conditions. This study examined the effects of flow connectivity in aquatic macroinvertebrates from seven reference temporary streams across the Mediterranean Basin where hydrological variability and flow conditions are well studied. We tested for the effect of flow cessation on two streamflow indices and on community composition, and, by performing random forest and classification tree analyses we identified important biological predictors for classifying the aquatic state either as flowing or disconnected pools. Flow cessation was critical for one of the streamflow indices studied and for community composition. Macroinvertebrate families found to be important for classifying the aquatic state were Hydrophilidae, Simuliidae, Hydropsychidae, Planorbiidae, Heptageniidae and Gerridae. For biological traits, trait categories associated to feeding habits, food, locomotion and substrate relation were the most important and provided more accurate predictions compared to taxonomy. A combination of selected metrics and associated thresholds based on the most important biological predictors (i.e. Bio-AS Tool) were proposed in order to assess the aquatic state in reference temporary streams, especially in the absence of hydrological data. Although further development is needed, the tool can be of particular interest for monitoring, restoration, and conservation purposes, representing an important step towards an adequate management of temporary rivers not only in the Mediterranean Basin but also in other regions vulnerable to the effects of climate change. - Highlights: • The effect of flow connectivity on macroinvertebrate
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International Nuclear Information System (INIS)
Wilcock, Robert J.; Scarsbrook, Mike R.; Cooke, James G.; Costley, Kerry J.; Nagels, John W.
2004-01-01
Controlled releases of NH 4 -N and conservative tracers (Br - and Cl - ) to five reaches of four streams with contrasting macrophyte communities have shown differing retentions, largely as a result of the way plants interact with stream flow and velocity. First-order constants (k) were 1.0-4.8 d -1 and retention of NH 4 -N was 6-71% of amounts added to each reach. Distance travelled before a 50% reduction in concentration was achieved were 40-450 m in three streams under low-flow conditions, and 2400-3800 m at higher flows. Retention (%) of NH 4 -N can be approximated by a simple function of travel time and k, highlighting the importance of the relationship between macrophytes and stream velocity on nutrient processing. This finding has significant management implications, particularly with respect to restoration of riparian shade. Small streams with predominantly marginal emergent plants are likely to have improved retention of NH 4 -N as a result of shading or other means of reducing plant biomass. Streams dominated by submerged macrophytes will have impaired NH 4 -N retention if plant biomass is reduced because of reduced contact times between NH 4 -N molecules and reactive sites. In these conditions water resource managers should utilise riparian shading in concert with unshaded vegetated reaches to achieve a balance between enhanced in-stream habitat and nutrient processing capacity
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Analysis of groundwater flow and stream depletion in L-shaped fluvial aquifers
Lin, Chao-Chih; Chang, Ya-Chi; Yeh, Hund-Der
2018-04-01
Understanding the head distribution in aquifers is crucial for the evaluation of groundwater resources. This article develops a model for describing flow induced by pumping in an L-shaped fluvial aquifer bounded by impermeable bedrocks and two nearly fully penetrating streams. A similar scenario for numerical studies was reported in Kihm et al. (2007). The water level of the streams is assumed to be linearly varying with distance. The aquifer is divided into two subregions and the continuity conditions of the hydraulic head and flux are imposed at the interface of the subregions. The steady-state solution describing the head distribution for the model without pumping is first developed by the method of separation of variables. The transient solution for the head distribution induced by pumping is then derived based on the steady-state solution as initial condition and the methods of finite Fourier transform and Laplace transform. Moreover, the solution for stream depletion rate (SDR) from each of the two streams is also developed based on the head solution and Darcy's law. Both head and SDR solutions in the real time domain are obtained by a numerical inversion scheme called the Stehfest algorithm. The software MODFLOW is chosen to compare with the proposed head solution for the L-shaped aquifer. The steady-state and transient head distributions within the L-shaped aquifer predicted by the present solution are compared with the numerical simulations and measurement data presented in Kihm et al. (2007).
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Free-stream turbulence effects on the flow around an S809 wind turbine airfoil
Energy Technology Data Exchange (ETDEWEB)
Torres-Nieves, Sheilla; Maldonado, Victor; Lebron, Jose [Rensselaer Polytechnic Institute, Troy, NY (United States); Kang, Hyung-Suk [United States Naval Academy, Annapolis, MD (United States); Meneveau, Charles [Johns Hopkins Univ., Baltimore, MD (United States); Castillo, Luciano [Texas Tech Univ., Lubbock, TX (United States)
2012-07-01
Two-dimensional Particle Image Velocimetry (2-D PIV) measurements were performed to study the effect of free-stream turbulence on the flow around a smooth and rough surface airfoil, specifically under stall conditions. A 0.25-m chord model with an S809 profile, common for horizontal-axis wind turbine applications, was tested at a wind tunnel speed of 10 m/s, resulting in Reynolds numbers based on the chord of Re{sub c} {approx} 182,000 and turbulence intensity levels of up to 6.14%. Results indicate that when the flow is fully attached, turbulence significantly decreases aerodynamic efficiency (from L/D {approx} 4.894 to L/D {approx} 0.908). On the contrary, when the flow is mostly stalled, the effect is reversed and aerodynamic performance is slightly improved (from L/D {approx} 1.696 to L/D {approx} 1.787). Analysis of the mean flow over the suction surface shows that, contrary to what is expected, free-stream turbulence is actually advancing separation, particularly when the turbulent scales in the free-stream are of the same order as the chord. This is a result of the complex dynamics between the boundary layer scales and the free-stream turbulence length scales when relatively high levels of active-grid generated turbulence are present. (orig.)
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Quantifying in-stream nitrate reaction rates using continuously-collected water quality data
Matthew Miller; Anthony Tesoriero; Paul Capel
2016-01-01
High frequency in situ nitrate data from three streams of varying hydrologic condition, land use, and watershed size were used to quantify the mass loading of nitrate to streams from two sources â groundwater discharge and event flow â at a daily time step for one year. These estimated loadings were used to quantify temporally-variable in-stream nitrate processing ...
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Flow-Through Stream Modeling with MODFLOW and MT3D: Certainties and Limitations.
Ben Simon, Rose; Bernard, Stéphane; Meurville, Charles; Rebour, Vincent
2015-01-01
This paper aims to assess MODFLOW and MT3D capabilities for simulating the spread of contaminants from a river exhibiting an unusual relationship with an alluvial aquifer, with the groundwater head higher than the river head on one side and lower on the other (flow-through stream). A series of simulation tests is conducted using a simple hypothetical model so as to characterize and quantify these limitations. Simulation results show that the expected contaminant spread could be achieved with a specific configuration composed of two sets of parameters: (1) modeled object parameters (hydraulic groundwater gradient, hydraulic conductivity values of aquifer and streambed), and (2) modeling parameters (vertical discretization of aquifer, horizontal refinement of stream modeled with River [RIV] package). The influence of these various parameters on simulation results is investigated, and potential complications and errors are identified. Contaminant spread from stream to aquifer is not always reproduced by MT3D due to the RIV package's inability to simulate lateral exchange fluxes between stream and aquifer. This paper identifies the need for a MODFLOW streamflow package allowing lateral stream-aquifer interactions and streamflow routine calculations. Such developments could be of particular interest for modeling contaminated flow-through streams. © 2015, National Ground Water Association.
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Layer-based buffer aware rate adaptation design for SHVC video streaming
Gudumasu, Srinivas; Hamza, Ahmed; Asbun, Eduardo; He, Yong; Ye, Yan
2016-09-01
This paper proposes a layer based buffer aware rate adaptation design which is able to avoid abrupt video quality fluctuation, reduce re-buffering latency and improve bandwidth utilization when compared to a conventional simulcast based adaptive streaming system. The proposed adaptation design schedules DASH segment requests based on the estimated bandwidth, dependencies among video layers and layer buffer fullness. Scalable HEVC video coding is the latest state-of-art video coding technique that can alleviate various issues caused by simulcast based adaptive video streaming. With scalable coded video streams, the video is encoded once into a number of layers representing different qualities and/or resolutions: a base layer (BL) and one or more enhancement layers (EL), each incrementally enhancing the quality of the lower layers. Such layer based coding structure allows fine granularity rate adaptation for the video streaming applications. Two video streaming use cases are presented in this paper. The first use case is to stream HD SHVC video over a wireless network where available bandwidth varies, and the performance comparison between proposed layer-based streaming approach and conventional simulcast streaming approach is provided. The second use case is to stream 4K/UHD SHVC video over a hybrid access network that consists of a 5G millimeter wave high-speed wireless link and a conventional wired or WiFi network. The simulation results verify that the proposed layer based rate adaptation approach is able to utilize the bandwidth more efficiently. As a result, a more consistent viewing experience with higher quality video content and minimal video quality fluctuations can be presented to the user.
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Determination of the self purification of streams using tracers
International Nuclear Information System (INIS)
Salviano, J.S.
1982-04-01
A methodology for the 'in situ' evaluation of the self purification of streams is discussed. It consists of the simultaneous injection of two tracers into the stream. One of the tracers is oxidized by biochemical processes. It can be either artificially supplied to the stream or a naturally present component can be used. This tracer is used for the determination of the self purification parameters. The other tracer is conservative and allows for the hydrodynamic effects. Tests have been carried out in two streams with quite different hydrodynamic and physicochemical conditions. In the first stream, with a flow-rate of about 0.9 m 3 /s, urea was used as the nonconservative tracer. In the other stream, which had a flow-rate of about 5 m 3 /s, only a radioactive tracer has been used, and the rate of biochemical oxidation has been determined from BOD measurements. Calculations have been implemented on a digital computer. In both cases it was found that the reoxygenation rate is more conveniently determined by empirical formulas. Results from both tests have been deemed realistic by comparison with similar experiments. (Author) [pt
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Maruyama, Kazunori; Nikaido, Mitsuru; Hara, Yoshinori; Tanizaki, Yoshie
2012-01-01
Both streaming potential and accumulated charge of water flowed out were measured simultaneously using a sandwich-type cell. The voltages generated in divided sections along flow direction satisfied additivity. The sign of streaming potential agreed with that of streaming electrification. The relation between streaming potential and streaming electrification was explained from a viewpoint of electrical double layer in glass-water interface.
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Interaction of counter-streaming plasma flows in dipole magnetic field
Shaikhislamov, I F; Posukh, V G; Melekhov, A V; Prokopov, P A; Boyarintsev, E L; Zakharov, Yu P; Ponomarenko, A G
2017-01-01
Transient interaction of counter-streaming super-sonic plasma flows in dipole magnetic dipole is studied in laboratory experiment. First quasi-stationary flow is produced by teta-pinch and forms a magnetosphere around the magnetic dipole while laser beams focused at the surface of the dipole cover launch second explosive plasma expanding from inner dipole region outward. Laser plasma is energetic enough to disrupt magnetic field and to sweep through the background plasma for large distances. ...
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Streaming potential of superhydrophobic microchannels.
Park, Hung Mok; Kim, Damoa; Kim, Se Young
2017-03-01
For the purpose of gaining larger streaming potential, it has been suggested to employ superhydrophobic microchannels with a large velocity slip. There are two kinds of superhydrophobic surfaces, one having a smooth wall with a large Navier slip coefficient caused by the hydrophobicity of the wall material, and the other having a periodic array of no- shear slots of air pockets embedded in a nonslip wall. The electrokinetic flows over these two superhydrophobic surfaces are modelled using the Navier-Stokes equation and convection-diffusion equations of the ionic species. The Navier slip coefficient of the first kind surfaces and the no-shear slot ratio of the second kind surfaces are similar in the sense that the volumetric flow rate increases as these parameter values increase. However, although the streaming potential increases monotonically with respect to the Navier slip coefficient, it reaches a maximum and afterward decreases as the no-shear ratio increases. The results of the present investigation imply that the characterization of superhydrophobic surfaces employing only the measurement of volumetric flow rate against pressure drop is not appropriate and the fine structure of the superhydrophobic surfaces must be verified before predicting the streaming potential and electrokinetic flows accurately. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Gotch, Frank A; Panlilio, Froilan; Sergeyeva, Olga; Rosales, Laura; Folden, Tom; Kaysen, George; Levin, Nathan
2003-01-01
In vivo solute clearances can be estimated from dialyzer blood (Qb) and dialysate (Qd) flow rates and a solute- and dialyzer-specific overall permeability membrane area product (KoA). However, these calculations require knowledge of the flow rate of the effective solute distribution volume in the flowing bloodstream (Qe) in order to calculate in vivo clearances and KoAs. We have determined Qe for urea, creatinine, and inorganic phosphorus from changes in concentrations across the blood compartment and mass balance between the blood and dialysate streams. We made four serial measurements over one dialysis in 23 patients and found that Qeu equals the total blood water flow rate, Qecr equals the plasma water flow rate plus 61% of red cell water flow rate, and QeiP is limited to the plasma water flow rate. Equations are derived to calculate Qe for each of these solutes from Qb and hematocrit and in vivo KoAs for each solute were calculated.
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Wagner, Brian J.; Harvey, Judson W.
1997-01-01
Tracer experiments are valuable tools for analyzing the transport characteristics of streams and their interactions with shallow groundwater. The focus of this work is the design of tracer studies in high-gradient stream systems subject to advection, dispersion, groundwater inflow, and exchange between the active channel and zones in surface or subsurface water where flow is stagnant or slow moving. We present a methodology for (1) evaluating and comparing alternative stream tracer experiment designs and (2) identifying those combinations of stream transport properties that pose limitations to parameter estimation and therefore a challenge to tracer test design. The methodology uses the concept of global parameter uncertainty analysis, which couples solute transport simulation with parameter uncertainty analysis in a Monte Carlo framework. Two general conclusions resulted from this work. First, the solute injection and sampling strategy has an important effect on the reliability of transport parameter estimates. We found that constant injection with sampling through concentration rise, plateau, and fall provided considerably more reliable parameter estimates than a pulse injection across the spectrum of transport scenarios likely encountered in high-gradient streams. Second, for a given tracer test design, the uncertainties in mass transfer and storage-zone parameter estimates are strongly dependent on the experimental Damkohler number, DaI, which is a dimensionless combination of the rates of exchange between the stream and storage zones, the stream-water velocity, and the stream reach length of the experiment. Parameter uncertainties are lowest at DaI values on the order of 1.0. When DaI values are much less than 1.0 (owing to high velocity, long exchange timescale, and/or short reach length), parameter uncertainties are high because only a small amount of tracer interacts with storage zones in the reach. For the opposite conditions (DaI ≫ 1.0), solute
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Dating base flow in streams using dissolved gases and diurnal temperature changes
Sanford, Ward E.; Casile, Gerolamo C.; Haase, Karl B.
2015-01-01
A method is presented for using dissolved CFCs or SF6 to estimate the apparent age of stream base flow by indirectly estimating the mean concentration of the tracer in the inflowing groundwater. The mean value is estimated simultaneously with the mean residence times of the gas and water in the stream by sampling the stream for one or both age tracers, along with dissolved nitrogen and argon at a single location over a period of approximately 12–14 h. The data are fitted to an equation representing the temporal in-stream gas exchange as it responds to the diurnal temperature fluctuation. The efficacy of the method is demonstrated by collecting and analyzing samples at six different stream locations across parts of northern Virginia, USA. The studied streams drain watersheds with areas of between 2 and 122 km2 during periods when the diurnal stream temperature ranged between 2 and 5°C. The method has the advantage of estimating the mean groundwater residence time of discharge from the watershed to the stream without the need for the collection of groundwater infiltrating to streambeds or local groundwater sampled from shallow observation wells near the stream.
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Analysis of groundwater flow and stream depletion in L-shaped fluvial aquifers
Directory of Open Access Journals (Sweden)
C.-C. Lin
2018-04-01
Full Text Available Understanding the head distribution in aquifers is crucial for the evaluation of groundwater resources. This article develops a model for describing flow induced by pumping in an L-shaped fluvial aquifer bounded by impermeable bedrocks and two nearly fully penetrating streams. A similar scenario for numerical studies was reported in Kihm et al. (2007. The water level of the streams is assumed to be linearly varying with distance. The aquifer is divided into two subregions and the continuity conditions of the hydraulic head and flux are imposed at the interface of the subregions. The steady-state solution describing the head distribution for the model without pumping is first developed by the method of separation of variables. The transient solution for the head distribution induced by pumping is then derived based on the steady-state solution as initial condition and the methods of finite Fourier transform and Laplace transform. Moreover, the solution for stream depletion rate (SDR from each of the two streams is also developed based on the head solution and Darcy's law. Both head and SDR solutions in the real time domain are obtained by a numerical inversion scheme called the Stehfest algorithm. The software MODFLOW is chosen to compare with the proposed head solution for the L-shaped aquifer. The steady-state and transient head distributions within the L-shaped aquifer predicted by the present solution are compared with the numerical simulations and measurement data presented in Kihm et al. (2007.
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Comparative Measurement of Stream Flow in the Ethiope River for ...
African Journals Online (AJOL)
This study investigates comparative measurement of stream flow in the Ethiope River for small hydropower development. Two methods – the Float and Current Meter or Bridge Broom Methods were investigated and values compared to determine best method for optimal power generation. Depth and width measurements ...
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Llorens, Pilar; Gallart, Francesc; Latron, Jérôme; Cid, Núria; Rieradevall, Maria; Prat, Narcís
2016-04-01
Aquatic life in temporary streams is strongly conditioned by the temporal variability of the hydrological conditions that control the occurrence and connectivity of diverse mesohabitats. In this context, the software TREHS (Temporary Rivers' Ecological and Hydrological Status) has been developed, in the framework of the LIFE Trivers project, to help managers for adequately implement the Water Framework Directive in this type of water bodies. TREHS, using the methodology described in Gallart et al (2012), defines six temporal 'aquatic states', based on the hydrological conditions representing different mesohabitats, for a given reach at a particular moment. Nevertheless, hydrological data for assessing the regime of temporary streams are often non-existent or scarce. The scarcity of flow data makes frequently impossible the characterization of temporary streams hydrological regimes and, as a consequence, the selection of the correct periods and methods to determine their ecological status. Because of its qualitative nature, the TREHS approach allows the use of alternative methodologies to assess the regime of temporary streams in the lack of observed flow data. However, to adapt the TREHS to this qualitative data both the temporal scheme (from monthly to seasonal) as well as the number of aquatic states (from 6 to 3) have been modified. Two alternatives complementary methodologies were tested within the TREHS framework to assess the regime of temporary streams: interviews and aerial photographs. All the gauging stations (13) belonging to the Catalan Internal Catchments (NE, Spain) with recurrent zero flows periods were selected to validate both methodologies. On one hand, non-structured interviews were carried out to inhabitants of villages and small towns near the gauging stations. Flow permanence metrics for input into TREHS were drawn from the notes taken during the interviews. On the other hand, the historical series of available aerial photographs (typically 10
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Stochastic Modelling of Shiroro River Stream flow Process
Musa, J. J
2013-01-01
Economists, social scientists and engineers provide insights into the drivers of anthropogenic climate change and the options for adaptation and mitigation, and yet other scientists, including geographers and biologists, study the impacts of climate change. This project concentrates mainly on the discharge from the Shiroro River. A stochastic approach is presented for modeling a time series by an Autoregressive Moving Average model (ARMA). The development and use of a stochastic stream flow m...
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The Advent of Streaming Television in Denmark - Ratings Revisited
DEFF Research Database (Denmark)
Lai, Signe Sophus
Digital media convergence is turning television practices upside down, including advertising, the motives for political and administrative decisions, and also extends to planning, producing, distributing, and programming content (Buzzard 2012; Cunningham and Silver 2013; Havens 2014; Ihlebæk, Syv......-demand. It discusses the potential impact of declining accuracy of audience measurement on market actors’ decisions concerning streaming, as well as potential strategies for improving audience measurement.......Digital media convergence is turning television practices upside down, including advertising, the motives for political and administrative decisions, and also extends to planning, producing, distributing, and programming content (Buzzard 2012; Cunningham and Silver 2013; Havens 2014; Ihlebæk....... It is noteworthy that although the shift towards online television distribution entails that viewing become measurable by the existing system for online audience tracking (Gemius), market actors have so far failed in their attempt to consolidate online measurements of viewing time with audience ratings of flow...
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Böhm, E.; Hopkins, T. S.; Pietrafesa, L. J.; Churchill, J. H.
2006-08-01
As described by [Csanady, G.T., Hamilton, P., 1988. Circulation of slope water. Continental Shelf Research 8, 565-624], the flow regime over the slope of the southern Middle Atlantic Bight (MAB) includes a current reversal in which southwestward flow over the upper and middle slope becomes entrained in the northeastward current adjacent to the Gulf Stream. In this paper we use satellite-derived data to quantify how lateral motions of the Gulf Stream impact this current system. In our analysis, the Gulf Stream’s thermal front is delineated using a two-year time series of sea surface temperature derived from NOAA/AVHRR satellite data. Lateral motions of the Gulf Stream are represented in terms of temporal variations of the area, east of 73°W, between the Gulf Stream thermal front and the shelf edge. Variations of slope water flow within this area are represented by anomalies of geostrophic velocity as derived from the time series of the sea level anomaly determined from TOPEX/POSEIDON satellite altimeter data. A strong statistical relationship is found between Gulf Stream displacements and parabathic flow over the continental slope. It is such that the southwestward flow over the slope is accelerated when the Gulf Stream is relatively far from the shelf edge, and is decelerated (and perhaps even reversed) when the Gulf Stream is close to the shelf edge. This relationship between Gulf Stream displacements and parabathic flow is also observed in numerical simulations produced by the Miami Isopycnic Coordinate Model. In qualitative terms, it is consistent with the notion that when the Gulf Stream is closer to the 200-m isobath, it is capable of entraining a larger fraction of shelf water masses. Alternatively, when the Gulf Stream is far from the shelf-break, more water is advected into the MAB slope region from the northeast. Analysis of the diabathic flow indicates that much of the cross-slope transport by which the southwestward flow entering the study region is
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Cid, N; Verkaik, I; García-Roger, E M; Rieradevall, M; Bonada, N; Sánchez-Montoya, M M; Gómez, R; Suárez, M L; Vidal-Abarca, M R; Demartini, D; Buffagni, A; Erba, S; Karaouzas, I; Skoulikidis, N; Prat, N
2016-01-01
Many streams in the Mediterranean Basin have temporary flow regimes. While timing for seasonal drought is predictable, they undergo strong inter-annual variability in flow intensity. This high hydrological variability and associated ecological responses challenge the ecological status assessment of temporary streams, particularly when setting reference conditions. This study examined the effects of flow connectivity in aquatic macroinvertebrates from seven reference temporary streams across the Mediterranean Basin where hydrological variability and flow conditions are well studied. We tested for the effect of flow cessation on two streamflow indices and on community composition, and, by performing random forest and classification tree analyses we identified important biological predictors for classifying the aquatic state either as flowing or disconnected pools. Flow cessation was critical for one of the streamflow indices studied and for community composition. Macroinvertebrate families found to be important for classifying the aquatic state were Hydrophilidae, Simuliidae, Hydropsychidae, Planorbiidae, Heptageniidae and Gerridae. For biological traits, trait categories associated to feeding habits, food, locomotion and substrate relation were the most important and provided more accurate predictions compared to taxonomy. A combination of selected metrics and associated thresholds based on the most important biological predictors (i.e. Bio-AS Tool) were proposed in order to assess the aquatic state in reference temporary streams, especially in the absence of hydrological data. Although further development is needed, the tool can be of particular interest for monitoring, restoration, and conservation purposes, representing an important step towards an adequate management of temporary rivers not only in the Mediterranean Basin but also in other regions vulnerable to the effects of climate change. Copyright © 2015 Elsevier B.V. All rights reserved.
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Ryan A. McManamay; Donald J. Orth; Charles A. Dolloff; Emmaneul A. Firmpong
2012-01-01
River regulation has resulted in substantial losses in habitat connectivity, biodiversity and ecosystem services. River managers are faced with a growing need to protect the key aspects of the natural flow regime. A practical approach to providing environmental flow standards is to create a regional framework by classifying unregulated streams into groups of similar...
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Streaming flow from ultrasound contrast agents by acoustic waves in a blood vessel model.
Cho, Eunjin; Chung, Sang Kug; Rhee, Kyehan
2015-09-01
To elucidate the effects of streaming flow on ultrasound contrast agent (UCA)-assisted drug delivery, streaming velocity fields from sonicated UCA microbubbles were measured using particle image velocimetry (PIV) in a blood vessel model. At the beginning of ultrasound sonication, the UCA bubbles formed clusters and translated in the direction of the ultrasound field. Bubble cluster formation and translation were faster with 2.25MHz sonication, a frequency close to the resonance frequency of the UCA. Translation of bubble clusters induced streaming jet flow that impinged on the vessel wall, forming symmetric vortices. The maximum streaming velocity was about 60mm/s at 2.25MHz and decreased to 15mm/s at 1.0MHz for the same acoustic pressure amplitude. The effect of the ultrasound frequency on wall shear stress was more noticeable. Maximum wall shear stress decreased from 0.84 to 0.1Pa as the ultrasound frequency decreased from 2.25 to 1.0MHz. The maximum spatial gradient of the wall shear stress also decreased from 1.0 to 0.1Pa/mm. This study showed that streaming flow was induced by bubble cluster formation and translation and was stronger upon sonication by an acoustic wave with a frequency near the UCA resonance frequency. Therefore, the secondary radiant force, which is much stronger at the resonance frequency, should play an important role in UCA-assisted drug delivery. Copyright © 2015 Elsevier B.V. All rights reserved.
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Analysis of hydraulic characteristics for stream diversion in small stream
Energy Technology Data Exchange (ETDEWEB)
Ahn, Sang-Jin; Jun, Kye-Won [Chungbuk National University, Cheongju(Korea)
2001-10-31
This study is the analysis of hydraulic characteristics for stream diversion reach by numerical model test. Through it we can provide the basis data in flood, and in grasping stream flow characteristics. Analysis of hydraulic characteristics in Seoknam stream were implemented by using computer model HEC-RAS(one-dimensional model) and RMA2(two-dimensional finite element model). As a result we became to know that RMA2 to simulate left, main channel, right in stream is more effective method in analysing flow in channel bends, steep slope, complex bed form effect stream flow characteristics, than HEC-RAS. (author). 13 refs., 3 tabs., 5 figs.
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Beyond Rating Curves: Time Series Models for in-Stream Turbidity Prediction
Wang, L.; Mukundan, R.; Zion, M.; Pierson, D. C.
2012-12-01
The New York City Department of Environmental Protection (DEP) manages New York City's water supply, which is comprised of over 20 reservoirs and supplies over 1 billion gallons of water per day to more than 9 million customers. DEP's "West of Hudson" reservoirs located in the Catskill Mountains are unfiltered per a renewable filtration avoidance determination granted by the EPA. While water quality is usually pristine, high volume storm events occasionally cause the reservoirs to become highly turbid. A logical strategy for turbidity control is to temporarily remove the turbid reservoirs from service. While effective in limiting delivery of turbid water and reducing the need for in-reservoir alum flocculation, this strategy runs the risk of negatively impacting water supply reliability. Thus, it is advantageous for DEP to understand how long a particular turbidity event will affect their system. In order to understand the duration, intensity and total load of a turbidity event, predictions of future in-stream turbidity values are important. Traditionally, turbidity predictions have been carried out by applying streamflow observations/forecasts to a flow-turbidity rating curve. However, predictions from rating curves are often inaccurate due to inter- and intra-event variability in flow-turbidity relationships. Predictions can be improved by applying an autoregressive moving average (ARMA) time series model in combination with a traditional rating curve. Since 2003, DEP and the Upstate Freshwater Institute have compiled a relatively consistent set of 15-minute turbidity observations at various locations on Esopus Creek above Ashokan Reservoir. Using daily averages of this data and streamflow observations at nearby USGS gauges, flow-turbidity rating curves were developed via linear regression. Time series analysis revealed that the linear regression residuals may be represented using an ARMA(1,2) process. Based on this information, flow-turbidity regressions with
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Directory of Open Access Journals (Sweden)
B. Zhang
2011-10-01
Full Text Available Subsurface lateral flow from agricultural hillslopes is often overlooked compared with overland flow and tile drain flow, partly due to the difficulties in monitoring and quantifying. The objectives of this study were to examine how subsurface lateral flow generated through soil pedons from cropped hillslopes and to quantify its contribution to nitrate loading in the streams through an agricultural catchment in the subtropical region of China. Profiles of soil water potential along hillslopes and stream hydro-chemographs in a trenched stream below a cropped hillslope and at the catchment outlet were simultaneously recorded during two rainstorm events. The dynamics of soil water potential showed positive matrix soil water potential over impermeable soil layer at 0.6 to 1.50 m depths during and after the storms, indicating soil water saturation and drainage processes along the hillslopes irrespective of land uses. The hydro-chemographs in the streams, one trenched below a cropped hillslope and one at the catchment outlet, showed that the concentrations of particulate nitrogen and phosphorus corresponded well to stream flow during the storm, while the nitrate concentration increased on the recession limbs of the hydrographs after the end of the storm. All the synchronous data revealed that nitrate was delivered from the cropped hillslope through subsurface lateral flow to the streams during and after the end of the rainstorms. A chemical mixing model based on electricity conductivity (EC and H+ concentration was successfully established, particularly for the trenched stream. The results showed that the subsurface lateral flow accounted for 29% to 45% of total stream flow in the trenched stream, responsible for 86% of total NO3−-N loss (or 26% of total N loss, and for 5.7% to 7.3% of total stream flow at the catchment outlet, responsible for about 69% of total NO3−-N loss (or 28% of total N
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Z. Zhou; Y. Ouyang; Z. Qiu; G. Zhou; M. Lin; Y. Li
2017-01-01
Stream low flow estimates are central to assessing climate change impact, water resource management, and ecosystem restoration. This study investigated the impacts of climate change upon stream low flows from a rainforest watershed in Jianfengling (JFL) Mountain, Hainan Island, China, using the low flow selection method as well as the frequency and probability analysis...
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Juvonen, Piia
2012-01-01
ABSTRACT Juvonen, Piia Suvi Päivikki 2012. Effective information flow through efficient supply chain management -Value stream mapping approach - Case Outokumpu Tornio Works. Master`s Thesis. Kemi-Tornio University of Applied Sciences. Business and Culture. Pages 63. Appendices 2. The general aim of this thesis is to explore effective information flow through efficient supply chain management by following one of the lean management principles, value stream mapping. The specific research...
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Directory of Open Access Journals (Sweden)
Cheyenne Lei
Full Text Available We investigated possible influences of land use/land cover change (LULCC and precipitation on spatiotemporal changes in extreme stream flows within the watershed of the Huron River Basin during the summer seasons from 1992 to 2011. Within the basin, the urban landscape increased from 8% to 16% during the study period, while forest and agricultural lands declined by 7%. There was an increase in landscape heterogeneity within the watershed that varied from 1.21% in 1992 to 1.34% in 2011, with agricultural practices and forest regions competing due to the expansion of varying intensities of urban development. Normalized stream discharge from multiple subwatersheds increased over time, with an average increase from 0.21 m3 s−1 m to 1.64 m3 s−1 m over the study period. Land use and precipitation affected stream discharge, with increasing urban development exhibiting a 37% chance of affecting extreme stream flows within the watershed. More importantly, much of the precipitation observed within the watershed temporally affected stream discharge based on expansion of urban settlement within the basin. This caused a higher likelihood of flashiness, as runoff is more concentrated and stream flow became more variable. We concluded that, within the watersheds of the Huron River, LULCC is the major determinant of increased stream flow and potential flooding. Keywords: Urbanization, Land use, Land cover, Climate, Hydrology, ArcGIS, FRAGSTATS
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Instream flow assessment of streams draining the Arbuckle-Simpson Aquifer
Seilheimer, Titus S.; Fisher, William L.
2008-01-01
The availability of high quality water is critical to both humans and ecosystems. A recent proposal was made by rapidly expanding municipalities in central Oklahoma to begin transferring groundwater from the Arbuckle-Simpson aquifer, a sensitive sole-source aquifer in south-central Oklahoma. Concerned citizens and municipalities living on and getting their drinking water from the Arbuckle-Simpson lobbied the legislature to pass a temporary moratorium on groundwater transfer to allow for a comprehensive study of the aquifer and its ecosystems. We conducted an instream flow assessment using Physical Habitat Simulation (PHABSIM) on springs and streams with four spring-dependent species: two minnows, southern redbelly dace (Phoxinus erthyrogaster) and redspot chub (Nocomis asper); and two darters, least darter (Etheostoma microperca) and orangethroat darter (Etheostoma spectabile). Spring habitats are unique compared to other river habitats because they have constant flow and temperature, small and isolated habitat patches, and a general lack of predators. Our study sites included two spring-fed streams, one larger stream with high groundwater inputs, and a river with both groundwater and surface water inputs that is adjacent to the small spring-fed streams. These habitats meet the criteria for groundwater dependent ecosystems because they would not exist without the surface expression of groundwater. A total of 99 transects in all four sites were surveyed for channel elevation, and three sets of water surface elevation and water velocity were measured. Habitat suitability criteria were derived for the species at each site using nonparametric confidence limits based on underwater observations made by snorkelers. Simulations of flow were focused on declines in discharge, which is the expected effect of the proposed groundwater diversion. Our results show that only a small proportion of the total available area in each habitat is considered to be preferred habitat
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Letcher, Benjamin H.; Schueller, Paul; Bassar, Ronald D.; Nislow, Keith H.; Coombs, Jason A.; Sakrejda, Krzysztof; Morrissey, Michael; Sigourney, Douglas B.; Whiteley, Andrew R.; O'Donnell, Matthew J.; Dubreuil, Todd L.
2015-01-01
Modelling the effects of environmental change on populations is a key challenge for ecologists, particularly as the pace of change increases. Currently, modelling efforts are limited by difficulties in establishing robust relationships between environmental drivers and population responses.We developed an integrated capture–recapture state-space model to estimate the effects of two key environmental drivers (stream flow and temperature) on demographic rates (body growth, movement and survival) using a long-term (11 years), high-resolution (individually tagged, sampled seasonally) data set of brook trout (Salvelinus fontinalis) from four sites in a stream network. Our integrated model provides an effective context within which to estimate environmental driver effects because it takes full advantage of data by estimating (latent) state values for missing observations, because it propagates uncertainty among model components and because it accounts for the major demographic rates and interactions that contribute to annual survival.We found that stream flow and temperature had strong effects on brook trout demography. Some effects, such as reduction in survival associated with low stream flow and high temperature during the summer season, were consistent across sites and age classes, suggesting that they may serve as robust indicators of vulnerability to environmental change. Other survival effects varied across ages, sites and seasons, indicating that flow and temperature may not be the primary drivers of survival in those cases. Flow and temperature also affected body growth rates; these responses were consistent across sites but differed dramatically between age classes and seasons. Finally, we found that tributary and mainstem sites responded differently to variation in flow and temperature.Annual survival (combination of survival and body growth across seasons) was insensitive to body growth and was most sensitive to flow (positive) and temperature (negative
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HANARO core channel flow-rate measurement
Energy Technology Data Exchange (ETDEWEB)
Kim, Heon Il; Chae, Hee Tae; Im, Don Soon; Kim, Seon Duk [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)
1996-06-01
HANARO core consists of 23 hexagonal flow tubes and 16 cylindrical flow tubes. To get the core flow distribution, we used 6 flow-rate measuring dummy fuel assemblies (instrumented dummy fuel assemblies). The differential pressures were measured and converted to flow-rates using the predetermined relationship between AP and flow-rate for each instrumented dummy fuel assemblies. The flow-rate for the cylindrical flow channels shows +-7% relative errors and that for the hexagonal flow channels shows +-3.5% relative errors. Generally the flow-rates of outer core channels show smaller values compared to those of inner core. The channels near to the core inlet pipe and outlet pipes also show somewhat lower flow-rates. For the lower flow channels, the thermal margin was checked by considering complete linear power histories. From the experimental results, the gap flow-rate was estimated to be 49.4 kg/s (cf. design flow of 50 kg/s). 15 tabs., 9 figs., 10 refs. (Author) .new.
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Ouyang, Ying; Parajuli, Prem B; Li, Yide; Leininger, Theodor D; Feng, Gary
2017-08-01
Characterization of stream flow is essential to water resource management, water supply planning, environmental protection, and ecological restoration; while air temperature variation due to climate change can exacerbate stream flow and add instability to the flow. In this study, the wavelet analysis technique was employed to identify temporal trend of air temperature and its impact upon forest stream flows in Lower Mississippi River Alluvial Valley (LMRAV). Four surface water monitoring stations, which locate near the headwater areas with very few land use disturbances and the long-term data records (60-90 years) in the LMRAV, were selected to obtain stream discharge and air temperature data. The wavelet analysis showed that air temperature had an increasing temporal trend around its mean value during the past several decades in the LMRAV, whereas stream flow had a decreasing temporal trend around its average value at the same time period in the same region. Results of this study demonstrated that the climate in the LMRAV did get warmer as time elapsed and the streams were drier as a result of warmer air temperature. This study further revealed that the best way to estimate the temporal trends of air temperature and stream flow was to perform the wavelet transformation around their mean values. Published by Elsevier Ltd.
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Directory of Open Access Journals (Sweden)
T. H. M. Rientjes
2011-06-01
Full Text Available In this study we evaluated changes in land cover and rainfall in the Upper Gilgel Abbay catchment in the Upper Blue Nile basin and how changes affected stream flow in terms of annual flow, high flows and low flows. Land cover change assessment was through classification analysis of remote sensing based land cover data while assessments on rainfall and stream flow data are by statistical analysis. Results of the supervised land cover classification analysis indicated that 50.9 % and 16.7 % of the catchment area was covered by forest in 1973 and 2001, respectively. This significant decrease in forest cover is mainly due to expansion of agricultural land.
By use of a change detection procedure, three periods were identified for which changes in rainfall and stream flow were analyzed. Rainfall was analyzed at monthly base by use of the Mann-Kendall test statistic and results indicated a statistically significant, decreasing trend for most months of the year. However, for the wet season months of June, July and August rainfall has increased. In the period 1973–2005, the annual flow of the catchment decreased by 12.1 %. Low flow and high flow at daily base were analyzed by a low flow and a high flow index that is based on a 95 % and 5 % exceedance probability. Results of the low flow index indicated decreases of 18.1 % and 66.6 % for the periods 1982–2000 and 2001–2005 respectively. Results of high flows indicated an increase of 7.6 % and 46.6 % for the same periods. In this study it is concluded that over the period 1973–2005 stream flow has changed in the Gilgel Abbay catchment by changes in land cover and changes in rainfall. -
Linking stream flow and groundwater to avian habitat in a desert riparian system.
Merritt, David M; Bateman, Heather L
2012-10-01
Increasing human populations have resulted in aggressive water development in arid regions. This development typically results in altered stream flow regimes, reduced annual flow volumes, changes in fluvial disturbance regimes, changes in groundwater levels, and subsequent shifts in ecological patterns and processes. Balancing human demands for water with environmental requirements to maintain functioning ecosystems requires quantitative linkages between water in streams and ecosystem attributes. Streams in the Sonoran Desert provide important habitat for vertebrate species, including resident and migratory birds. Habitat structure, food, and nest-building materials, which are concentrated in riparian areas, are provided directly or indirectly by vegetation. We measured riparian vegetation, groundwater and surface water, habitat structure, and bird occurrence along Cherry Creek, a perennial tributary of the Salt River in central Arizona, USA. The purpose of this work was to develop an integrated model of groundwater-vegetation-habitat structure and bird occurrence by: (1) characterizing structural and provisioning attributes of riparian vegetation through developing a bird habitat index (BHI), (2) validating the utility of our BHI through relating it to measured bird community composition, (3) determining the riparian plant species that best explain the variability in BHI, (4) developing predictive models that link important riparian species to fluvial disturbance and groundwater availability along an arid-land stream, and (5) simulating the effects of changes in flow regime and groundwater levels and determining their consequences for riparian bird communities. Riparian forest and shrubland vegetation cover types were correctly classified in 83% of observations as a function of fluvial disturbance and depth to water table. Groundwater decline and decreased magnitude of fluvial disturbance caused significant shifts in riparian cover types from riparian forest to
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Stream II-V5: Revision Of Stream II-V4 To Account For The Effects Of Rainfall Events
International Nuclear Information System (INIS)
Chen, K.
2010-01-01
STREAM II-V4 is the aqueous transport module currently used by the Savannah River Site emergency response Weather Information Display (WIND) system. The transport model of the Water Quality Analysis Simulation Program (WASP) was used by STREAM II to perform contaminant transport calculations. WASP5 is a US Environmental Protection Agency (EPA) water quality analysis program that simulates contaminant transport and fate through surface water. STREAM II-V4 predicts peak concentration and peak concentration arrival time at downstream locations for releases from the SRS facilities to the Savannah River. The input flows for STREAM II-V4 are derived from the historical flow records measured by the United States Geological Survey (USGS). The stream flow for STREAM II-V4 is fixed and the flow only varies with the month in which the releases are taking place. Therefore, the effects of flow surge due to a severe storm are not accounted for by STREAM II-V4. STREAM II-V4 has been revised to account for the effects of a storm event. The steps used in this method are: (1) generate rainfall hyetographs as a function of total rainfall in inches (or millimeters) and rainfall duration in hours; (2) generate watershed runoff flow based on the rainfall hyetographs from step 1; (3) calculate the variation of stream segment volume (cross section) as a function of flow from step 2; (4) implement the results from steps 2 and 3 into the STREAM II model. The revised model (STREAM II-V5) will find the proper stream inlet flow based on the total rainfall and rainfall duration as input by the user. STREAM II-V5 adjusts the stream segment volumes (cross sections) based on the stream inlet flow. The rainfall based stream flow and the adjusted stream segment volumes are then used for contaminant transport calculations.
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Survival and growth rates of juvenile salmonids reared in lowland streams
Directory of Open Access Journals (Sweden)
Golski Janusz
2016-12-01
Full Text Available The aim of this study was to assess the efficiency of propagating juvenile trout, Salmo trutta L. in small lowland streams and to evaluate the impact of the environmental conditions in the streams on the juvenile fish. Brown trout (Salmo trutta fario and sea trout (Salmo trutta trutta early fry fed under controlled conditions were used to stock third-order lowland streams. During summer, fall, and spring catches, fry were counted, measured, and weighed. The following parameters were calculated using the data collected: fry stocking density (ind. m-2; survival; specific mortality rate (SMR; length range; mean specimen length; body weight; mean body weight; specific growth rate (SGR; body condition (Fulton’s index. The ichthyological studies were accompanied by simultaneous analyses of environmental conditions that were performed monthly, and benthic macroinvertebrates were sampled in spring and fall. No differences were observed in the biological parameters analyzed between sea trout and brown trout. Variability in environmental parameters such as temperature, oxygenation, conductivity, and stream width and depth were associated with differentiation in the biological parameters of the fry. The results clearly indicate that the considerable potential of small lowland streams for the propagation of salmonid juvenile stages is currently underexploited.
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Messinger, Terence; Wiley, Jeffrey B.
2004-01-01
Three bankfull channel characteristics?cross-sectional area, width, and depth?were significantly correlated with drainage area in regression equations developed for two regions in West Virginia. Channel characteristics were determined from analysis of flow measurements made at 74 U.S. Geological Survey stream-gaging stations at flows between 0.5 and 5.0 times bankfull flow between 1911 and 2002. Graphical and regression analysis were used to delineate an 'Eastern Region' and a 'Western Region,' which were separated by the boundary between the Appalachian Plateaus and Valley and Ridge Physiographic Provinces. Streams that drained parts of both provinces had channel characteristics typical of the Eastern Region, and were grouped with it. Standard error for the six regression equations, three for each region, ranged between 8.7 and 16 percent. Cross-sectional area and depth were greater relative to drainage area for the Western Region than they were for the Eastern Region. Regression equations were defined for streams draining between 46.5 and 1,619 square miles for the Eastern Region, and between 2.78 and 1,354 square miles for the Western Region. Stream-gaging stations with two or more cross sections where flow had been measured at flows between 0.5 and 5.0 times the 1.5-year flow showed poor replication of channel characteristics compared to the 95-percent confidence intervals of the regression, suggesting that within-reach variability for the stream-gaging stations may be substantial. A disproportionate number of the selected stream-gaging stations were on large (drainage area greater than 100 square miles) streams in the central highlands of West Virginia, and only one stream-gaging station that met data-quality criteria was available to represent the region within about 50 miles of the Ohio River north of Parkersburg, West Virginia. Many of the cross sections were at bridges, which can change channel shape. Although the data discussed in this report may not be
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R.A. Payn; M.N. Gooseff; B.L. McGlynn; K.E. Bencala; S.M. Wondzell
2009-01-01
Channel water balances of contiguous reaches along streams represent a poorly understood scale of stream-subsurface interaction. We measured reach water balances along a headwater stream in Montana, United States, during summer base flow recessions. Reach water balances were estimated from series of tracer tests in 13 consecutive reaches delineated evenly along a 2.6-...
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Mas-Pla, Josep; Font, Eva; Astui, Oihane; Menció, Anna; Rodríguez-Florit, Agustí; Folch, Albert; Brusi, David; Pérez-Paricio, Alfredo
2012-12-01
Stream flow, as a part of a basin hydrological cycle, will be sensible to water scarcity as a result of climate change. Stream vulnerability should then be evaluated as a key component of the basin water budget. Numerical flow modeling has been applied to an alluvial formation in a small mountain basin to evaluate the stream-aquifer relationship under these future scenarios. The Arbúcies River basin (116 km(2)) is located in the Catalan Inner Basins (NE Spain) and its lower reach, which is related to an alluvial aquifer, usually becomes dry during the summer period. This study seeks to determine the origin of such discharge losses whether from natural stream leakage and/or induced capture due to groundwater withdrawal. Our goal is also investigating how discharge variations from the basin headwaters, representing potential effects of climate change, may affect stream flow, aquifer recharge, and finally environmental preservation and human supply. A numerical flow model of the alluvial aquifer, based on MODFLOW and especially in the STREAM routine, reproduced the flow system after the usual calibration. Results indicate that, in the average, stream flow provides more than 50% of the water inputs to the alluvial aquifer, being responsible for the amount of stored water resources and for satisfying groundwater exploitation for human needs. Detailed simulations using daily time-steps permit setting threshold values for the stream flow entering at the beginning of the studied area so surface discharge is maintained along the whole watercourse and ecological flow requirements are satisfied as well. The effects of predicted rainfall and temperature variations on the Arbúcies River alluvial aquifer water balance are also discussed from the outcomes of the simulations. Finally, model results indicate the relevance of headwater discharge management under future climate scenarios to preserve downstream hydrological processes. They also point out that small mountain basins
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International Nuclear Information System (INIS)
Aoki, Shigehisa; Ikeda, Satoshi; Takezawa, Toshiaki; Kishi, Tomoya; Makino, Junichi; Uchihashi, Kazuyoshi; Matsunobu, Aki; Noguchi, Mitsuru; Sugihara, Hajime; Toda, Shuji
2011-01-01
Highlights: ► Late-onset peritoneal fibrosis leading to EPS remains to be elucidated. ► Fluid streaming is a potent factor for peritoneal fibrosis in PD. ► We focused on the prolonged effect of fluid streaming on mesothelial cell kinetics. ► A history of fluid streaming exposure promoted mesothelial proliferative activity. ► We have thus identified a potent new factor for late-onset peritoneal fibrosis. -- Abstract: Encapsulating peritoneal sclerosis (EPS) often develops after transfer to hemodialysis and transplantation. Both termination of peritoneal dialysis (PD) and transplantation-related factors are risks implicated in post-PD development of EPS, but the precise mechanism of this late-onset peritoneal fibrosis remains to be elucidated. We previously demonstrated that fluid flow stress induced mesothelial proliferation and epithelial–mesenchymal transition via mitogen-activated protein kinase (MAPK) signaling. Therefore, we speculated that the prolonged bioactive effect of fluid flow stress may affect mesothelial cell kinetics after cessation of fluid streaming. To investigate how long mesothelial cells stay under the bioactive effect brought on by fluid flow stress after removal of the stress, we initially cultured mesothelial cells under fluid flow stress and then cultured the cells under static conditions. Mesothelial cells exposed to fluid flow stress for a certain time showed significantly high proliferative activity compared with static conditions after stoppage of fluid streaming. The expression levels of protein phosphatase 2A, which dephosphorylates MAPK, in mesothelial cells changed with time and showed a biphasic pattern that was dependent on the duration of exposure to fluid flow stress. There were no differences in the fluid flow stress-related bioactive effects on mesothelial cells once a certain time had passed. The present findings show that fluid flow stress exerts a prolonged bioactive effect on mesothelial cells after termination
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Removal of Contaminants from Waste Streams at Gas Evolving Flow-Through Porous Electrodes
International Nuclear Information System (INIS)
Mahmoud Saleh, M.
1999-01-01
Electrochemical techniques have been used for the removal of inorganic and organic toxic materials from industrial waste streams. One of the most important branch of these electrochemical techniques is the flow-through porous electrode. Such systems allow for the continuous operation and hence continuous removal of the contaminants from waste streams at high rates and high efficiency. However, when there is an evolution of gas bubbles with the removal process, the treatment process needs a much different treatment of both the design and the mathematical treatment of the such these systems. The evolving gas bubbles within the electrode decrease the pore electrolyte conductivity of the porous electrodes, decrease the efficiency and make the current more non-uniform. This cause the under utilization of the reaction area and finally make the electrode inoperable. In this work the harmful effects of the gas bubbles on the performance of the porous electrode will be modeled. The model accounts for the effects of kinetic, mass transfer and gas bubbles resistance on the overall performance of the electrode. This will help in optimizing the operating conditions and the cell design
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Directory of Open Access Journals (Sweden)
Magdalena TUTAK
2014-04-01
Full Text Available Flow of ventilation air stream through the dog heading with a fire centre is the flow with complex character, during which as a result of emission of fire gases into the mining atmosphere, there occur to disturbances of its flow. In the paper there is presented a numerical analysis of an influence of exogenous fire in a dog heading, on the parameters of the ventilation air stream flowing through this heading. Modeling tests were carried out with a use of ANSYS software, basing on the Finite Volume Method. For the made assumptions, there were determined physical parameters of air stream flowing through the heading with a fire centre, and also changes in mass fraction of gases in this stream during its flow through the analyzed heading: oxygen, carbon monoxide and carbon dioxide. As a result of performed analysis over the fire centre, the local increase of velocity and temperature and violent decrease of static pressure were recorded. Model of heading presented in the paper gives possibilities for development, and then the analysis of more complicated problems in a range of ventilation of mining headings.
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Tesoriero, Anthony J.; Liebscher, Hugh; Cox, Stephen E.
2000-01-01
The rate and mechanism of nitrate removal along and between groundwater flow paths were investigated using a series of well nests screened in an unconfined sand and gravel aquifer. Intensive agricultural activity in this area has resulted in nitrate concentrations in groundwater often exceeding drinking water standards. Both the extent and rate of denitrification varied depending on the groundwater flow path. While little or no denitrification occurred in much of the upland portions of the aquifer, a gradual redox gradient is observed as aerobic upland groundwater moves deeper in the aquifer. In contrast, a sharp shallow redox gradient is observed adjacent to a third‐order stream as aerobic groundwater enters reduced sediments. An essentially complete loss of nitrate concurrent with increases in excess N2 provide evidence that denitrification occurs as groundwater enters this zone. Electron and mass balance calculations suggest that iron sulfide (e.g., pyrite) oxidation is the primary source of electrons for denitrification. Denitrification rate estimates were based on mass balance calculations using nitrate and excess N2 coupled with groundwater travel times. Travel times were determined using a groundwater flow model and were constrained by chlorofluorocarbon‐based age dates. Denitrification rates were found to vary considerably between the two areas where denitrification occurs. Denitrification rates in the deep, upland portions of the aquifer were found to range from from 1.0 to 2.7 mM of N per year. Potential denitrification rates in groundwater adjacent to the stream may be much faster, with rates up to 140 mM per year based on an in situ experiment conducted in this zone.
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Drainage basins, channels, and flow characteristics of selected streams in central Pennsylvania
Brush, Lucien M.
1961-01-01
The hydraulic, basin, and geologic characteristics of 16 selected streams in central Pennsylvania were measured for the purpose of studying the relations among these general characteristics and their process of development. The basic parameters which were measured include bankfull width and depth, channel slope, bed material size and shape, length of stream from drainage divide, and size of drainage area. The kinds of bedrock over which the streams flow were noted. In these streams the bankfull channel is filled by flows approximating the 2.3-year flood. By measuring the breadth and mean depth of the channel, it was possible to compute the bankfull mean velocity for each of the 119 sampling stations. These data were then used to compute the downstream changes in hydraulic geometry of the streams studied. This method has been called an indirect computation of the hydraulic geometry. The results obtained by the indirect method are similar to those of the direct method of other workers. The basins were studied by examining the relations of drainage area, discharge, and length of stream from drainage divide. For the streams investigated, excellent correlations were found to exist between drainage area and the 2.3-year flood, as well as between length of stream from the basin divide and drainage area. From these correlations it is possible to predict the discharge for the 2.3-year flood at any arbitrary point along the length of the stream. The long, intermediate, and short axes of pebbles sampled from the bed of the stream were recorded to study both size and sphericity changes along individual streams and among the streams studied. No systematic downstream changes in sphericity were found. Particle size changes are erratic and show no consistent relation to channel slope. Particle size decreases downstream in many streams but remains constant or increases in others. Addition of material by tributaries is one factor affecting particle size and another is the parent
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Evaluation of stream flow effects on smolt survival in the Yakima River Basin, Washington, 2012-2014
Courter, Ian; Garrison, Tommy; Kock, Tobias J.; Perry, Russell W.
2015-01-01
The influence of stream flow on survival of emigrating juvenile (smolts) Pacific salmon Oncorhynchus spp. and steelhead trout O. mykiss is of key management interest. However, few studies have quantified flow effects on smolt migration survival, and available information does not indicate a consistent flow-survival relationship within the typical range of flows under management control. It is hypothesized that smolt migration and dam passage survival are positively correlated with stream flow because higher flows increase migration rates, potentially reducing exposure to predation, and reduce delays in reservoirs. However, available empirical data are somewhat equivocal concerning the influence of flow on smolt survival and the underlying mechanisms driving this relationship. Stream flow effects on survival of emigrating anadromous salmonids in the Yakima Basin have concerned water users and fisheries managers for over 20 years, and previous studies do not provide sufficient information at the resolution necessary to inform water operations, which typically occur on a small spatiotemporal scale. Using a series of controlled flow releases from 2012-2014, combined with radio telemetry, we quantified the relationship between flow and smolt survival from Roza Dam 208 km downstream to the Yakima River mouth, as well as for specific routes of passage at Roza Dam. A novel multistate mark-recapture model accounted for weekly variation in flow conditions experienced by radio-tagged fish. Groups of fish were captured and radio-tagged at Roza Dam and released at two locations, upstream at the Big Pines Campground (river kilometer [rkm] 211) and downstream in the Roza Dam tailrace (rkm 208). A total of 904 hatchery-origin yearling Chinook salmon O. tshawytscha were captured in the Roza Dam fish bypass, radio-tagged and released upstream of Roza Dam. Two hundred thirty seven fish were released in the tailrace of Roza Dam. Fish released in the tailrace of Roza Dam were tagged
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Optimum solar collector fluid flow rates
DEFF Research Database (Denmark)
Furbo, Simon; Shah, Louise Jivan
1996-01-01
Experiments showed that by means of a standard electronically controlled pump, type UPE 2000 from Grundfos it is possible to control the flow rate in a solar collector loop in such a way that the flow rate is strongly influenced by the temperature of the solar collector fluid passing the pump....... The flow rate is increasing for increasing temperature.The flow rate at the high temperature level is typically 70 % greater than the flow rate at the low temperature level.Further, the energy consumption for the electronically controlled pump in a solar heating system will be somewhat smaller than...... the energy consumption of a normal ciculation pump in the solar heating system.Calculations showed that the highest thermal performances for small SDHW systems based on mantle tanks with constant volume flow rates in the solar collector loops are achieved if the flow rate is situated in the interval from 0...
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Joule heating induced stream broadening in free-flow zone electrophoresis.
Dutta, Debashis
2018-03-01
The use of an electric field in free-flow zone electrophoresis (FFZE) automatically leads to Joule heating yielding a higher temperature at the center of the separation chamber relative to that around the channel walls. For small amounts of heat generated, this thermal effect introduces a variation in the equilibrium position of the analyte molecules due to the dependence of liquid viscosity and analyte diffusivity on temperature leading to a modification in the position of the analyte stream as well as the zone width. In this article, an analytic theory is presented to quantitate such effects of Joule heating on FFZE assays in the limit of small temperature differentials across the channel gap yielding a closed form expression for the stream position and zone variance under equilibrium conditions. A method-of-moments approach is employed to develop this analytic theory, which is further validated with numerical solutions of the governing equations. Interestingly, the noted analyses predict that Joule heating can drift the location of the analyte stream either way of its equilibrium position realized in the absence of any temperature rise in the system, and also tends to reduce zone dispersion. The extent of these modifications, however, is governed by the electric field induced temperature rise and three Péclet numbers evaluated based on the axial pressure-driven flow, transverse electroosmotic and electrophoretic solute velocities in the separation chamber. Monte Carlo simulations of the FFZE system further establish a time and a length scale over which the results from the analytic theory are valid. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Measuring in-stream retention of copper by means of constant-rate additions.
Serra, A; Guasch, H; Martí, E; Geiszinger, A
2009-06-01
Human practices entail inputs of nutrients and toxicants such as heavy metals to the fluvial ecosystems. While nutrient dynamics in fluvial ecosystems have been widely studied for over three decades, dynamics of toxicants still remain unclear. In this investigation, the nutrient spiraling concept and associated methodologies to quantify nutrient retention in streams were applied to study copper (Cu) dynamics in streams. The present study aimed to quantify total dissolved Cu retention using a simplified system of indoor channels colonized with fluvial biofilms. Cu retention was studied at sub-toxic concentrations to avoid negative/lethal effects on biota. In addition, Cu retention was compared with retention estimates of a macronutrient, phosphate (PO(4)(3-)), which has been widely studied within the context of the nutrient spiraling concept. The methodology used allowed a successful quantification of Cu and PO(4)(3-) retention. The results showed higher retention efficiency for PO(4)(3-) than for Cu. The biofilm played a key role in retaining both solutes. Although retention efficiency for both solutes was higher in the experiments with colonized substrata compared to uncolonized substrata, we found a positive relationship between uptake rate and chlorophyll-a only for PO(4)(3-). Finally, retention efficiency for both solutes was influenced by water discharge, showing lower retention efficiencies under higher flow conditions. These results suggest that the fate and toxic effects of copper on stream biota may be strongly influenced by the prevailing environmental conditions. Our results indicate that the experimental approach considered can provide new insights into the investigation of retention of toxic compounds in fluvial systems and their controlling mechanisms.
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Stang, Christoph; Wieczorek, Matthias Valentin; Noss, Christian; Lorke, Andreas; Scherr, Frank; Goerlitz, Gerhard; Schulz, Ralf
2014-07-01
Quantitative information on the processes leading to the retention of plant protection products (PPPs) in surface waters is not available, particularly for flow-through systems. The influence of aquatic vegetation on the hydraulic- and sorption-mediated mitigation processes of three PPPs (triflumuron, pencycuron, and penflufen; logKOW 3.3-4.9) in 45-m slow-flowing stream mesocosms was investigated. Peak reductions were 35-38% in an unvegetated stream mesocosm, 60-62% in a sparsely vegetated stream mesocosm (13% coverage with Elodea nuttallii), and in a similar range of 57-69% in a densely vegetated stream mesocosm (100% coverage). Between 89% and 93% of the measured total peak reductions in the sparsely vegetated stream can be explained by an increase of vegetation-induced dispersion (estimated with the one-dimensional solute transport model OTIS), while 7-11% of the peak reduction can be attributed to sorption processes. However, dispersion contributed only 59-71% of the peak reductions in the densely vegetated stream mesocosm, where 29% to 41% of the total peak reductions can be attributed to sorption processes. In the densely vegetated stream, 8-27% of the applied PPPs, depending on the logKOW values of the compounds, were temporarily retained by macrophytes. Increasing PPP recoveries in the aqueous phase were accompanied by a decrease of PPP concentrations in macrophytes indicating kinetic desorption over time. This is the first study to provide quantitative data on how the interaction of dispersion and sorption, driven by aquatic macrophytes, influences the mitigation of PPP concentrations in flowing vegetated stream systems. Copyright © 2014 Elsevier Ltd. All rights reserved.
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Stick-slip Cycles and Tidal Modulation of Ice Stream Flow
Lipovsky, B.; Dunham, E. M.
2016-12-01
The reactivation of a single dormant Antarctic ice stream would double the continent's mass imbalance. Despite importance of understanding the likelihood of such an event, direct observation of the basal processes that lead to the activation and stagnation of streaming ice are minimal. As the only ice stream undergoing stagnation, the Whillans Ice Plain (WIP) occupies a central role in our understanding of these subglacial processes. Complicating matters is the observation, from GPS records, that the WIP experiences most of its motion during episodes of rapid sliding. These sliding events are tidally modulated and separated by 12 hour periods of quiescence. We conduct numerical simulations of ice stream stick-slip cycles. Our simulations include rate- and state-dependent frictional sliding, tidal forcing, inertia, upstream loading in a cross-stream, thickness-averaged formulation. Our principal finding is that ice stream motion may respond to ocean tidal forcing with one of two end member behaviors. In one limit, tidally modulated slip events have rupture velocities that approach the shear wave speed and slip events have a duration that scales with the ice stream width divided by the shear wave speed. In the other limit, tidal modulation results in ice stream sliding velocities with lower amplitude variation but at much longer timescales, i.e. semi-diurnal and longer. This latter behavior more closely mimics the behavior of several active ice streams (Bindschadler, Rutford). We find that WIP slip events exist between these two end member behaviors: rupture velocities are far below the inertial limit yet sliding occurs only episodically. The continuum of sliding behaviors is governed by a critical ice stream width over which slip event nucleate. When the critical width is much longer than the ice stream width, slip events are unable to nucleate. The critical width depends on the subglacial effective pressure, ice thickness, and frictional and elastic constitutive
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Shakespeare, B.; Gooseff, M. N.
2005-12-01
Understanding what role particular catchment attributes (slope, aspect, landcover, and contributing area) play in the contribution of stream flow is important for land management decisions, especially in the semi-arid western areas of the United States. Our study site is paired small catchments (approximately 9 and 11 km2) in the headwaters of the Weber drainage basin in Northern Utah. These catchments are surrounded by Wasatch formation with loamy textured soils. One catchment is predominantly underlain by quartzite while the other catchment is mostly underlain by limestone. We measured lateral flow gains every 200 to 400 meters using salt dilution gauging techniques throughout the ~5 km long streams. These measurements were taken synoptically 3 times during the seasonal discharge recession (summer 2005). The flows ranged spatially from 4 L s-1 to 55 L s-1 and varied temporally by as much as 50% when comparing the same reaches. Using GIS software, landscape analysis of slope, aspect, contributing area, topographic convergence, riparian and hillslope area, and landcover was performed for each of the delineated stream reach contributing areas. The results were tested for correlations between lateral flow gains measured in the field and different landscape characteristics. Each of the synoptic events was compared with each other to explore effects of seasonal recession on the relationships between flow gain and landscape characteristics.
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Prediction of the impacts of climate changes on the stream flow of ...
African Journals Online (AJOL)
Abstract. Soil and Water Assessment Tool, (SWAT) model was used to predict the impacts of Climate Change on Ajali River watershed, Aguobu-Umumba, Ezeagu, Enugu State, Nigeria. The model was first used to simulate stream flow using observed data. After model run, parameterization, sensitivity analysis, the monthly ...
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Regional Comparison of Nitrogen Export to Japanese Forest Streams
Directory of Open Access Journals (Sweden)
Hideaki Shibata
2001-01-01
Full Text Available Nitrogen (N emissions in Asian countries are predicted to increase over the next several decades. An understanding of the mechanisms that control temporal and spatial fluctuation of N export to forest streams is important not only to quantify critical loads of N, N saturation status, and soil acidification N dynamics and budgets in Japanese forested watersheds is not clear due to the lack of regional comparative studies on stream N chemistry. To address the lack of comparative studies, we measured inorganic N (nitrate and ammonium concentrations from June 2000 to May 2001 in streams in 18 experimental forests located throughout the Japanese archipelago and belonging to the Japanese Union of University Forests. N concentrations in stream water during base flow and high flow periods were monitored, and N mineralization potential in soil was measured using batch incubation experiments. Higher nitrate concentrations in stream water were present in central Japan, an area that receives high rates of atmospheric N deposition. In northern Japan, snowmelt resulted in increased nitrate concentrations in stream water. The potential net N mineralization rate was higher in surface soil than in subsurface soil, and the high potential for N mineralization in the surface soil partly contributed to the increase in nitrate concentration in stream water during a storm event. Regional differences in the atmospheric N deposition and seasonality of precipitation and high discharge are principal controls on the concentrations and variations of nitrates in stream water in forested watersheds of Japan.
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Directory of Open Access Journals (Sweden)
G. Vijay Chakaravarthy
2012-11-01
Full Text Available Lot streaming is a technique used to split the processing of lots into several sublots (transfer batches to allow the overlapping of operations in a multistage manufacturing systems thereby shortening the production time (makespan. The objective of this paper is to minimize the makespan and total flow time of -job, -machine lot streaming problem in a flow shop with equal and variable size sublots and also to determine the optimal sublot size. In recent times researchers are concentrating and applying intelligent heuristics to solve flow shop problems with lot streaming. In this research, Firefly Algorithm (FA and Artificial Immune System (AIS algorithms are used to solve the problem. The results obtained by the proposed algorithms are also compared with the performance of other worked out traditional heuristics. The computational results shows that the identified algorithms are more efficient, effective and better than the algorithms already tested for this problem.
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Stream biofilm responses to flow intermittency: from cells to ecosystems
Directory of Open Access Journals (Sweden)
Sergi eSabater
2016-03-01
Full Text Available Temporary streams are characterized by the alternation of dry and wet hydrological phases, creating both a harsh environment for the biota as well as a high diversity of opportunities for adaptation. These systems are eminently microbial-based during several of these hydrological phases, and those growing on all solid substrata (biofilms accordingly change their physical structure and community composition. Biofilms experience large decreases on cell densities and biomass, both of bacteria and algae, during dryness. Algal and bacterial communities show remarkable decreases in their diversity, at least locally (at the habitat scale. Biofilms also respond with significant physiological plasticity to each of the hydrological changes. The decreasing humidity of the substrata through the drying process, and the changing quantity and quality of organic matter and nutrients available in the stream during that process, causes unequal responses on the biofilm bacteria and algae. Biofilm algae are affected faster than bacteria by the hydric stress, and as a result the ecosystem respiration resists longer than gross primary production to the increasing duration of flow intermittency. This response implies enhancing ecosystem heterotrophy, a pattern that can be exacerbated in temporary streams suffering of longer dry periods under global change.
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Modeling the time--varying subjective quality of HTTP video streams with rate adaptations.
Chen, Chao; Choi, Lark Kwon; de Veciana, Gustavo; Caramanis, Constantine; Heath, Robert W; Bovik, Alan C
2014-05-01
Newly developed hypertext transfer protocol (HTTP)-based video streaming technologies enable flexible rate-adaptation under varying channel conditions. Accurately predicting the users' quality of experience (QoE) for rate-adaptive HTTP video streams is thus critical to achieve efficiency. An important aspect of understanding and modeling QoE is predicting the up-to-the-moment subjective quality of a video as it is played, which is difficult due to hysteresis effects and nonlinearities in human behavioral responses. This paper presents a Hammerstein-Wiener model for predicting the time-varying subjective quality (TVSQ) of rate-adaptive videos. To collect data for model parameterization and validation, a database of longer duration videos with time-varying distortions was built and the TVSQs of the videos were measured in a large-scale subjective study. The proposed method is able to reliably predict the TVSQ of rate adaptive videos. Since the Hammerstein-Wiener model has a very simple structure, the proposed method is suitable for online TVSQ prediction in HTTP-based streaming.
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2010-07-19
... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER10-1750-000] Stream Energy Pennsylvania, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket... of Stream Energy Pennsylvania, LLC's application for market-based rate authority, with an...
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Justin K. Anderson; Steven M. Wondzell; Michael N. Gooseff; Roy. Haggerty
2005-01-01
There is a need to identify measurable characteristics of stream channel morphology that vary predictably throughout stream networks and that influence patterns of hyporheic exchange flow in mountain streams. In this paper we characterize stream longitudinal profiles according to channel unit spacing and the concavity of the water surface profile. We demonstrate that...
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A numeric investigation of co-flowing liquid streams using the Lattice Boltzmann Method
Somogyi, Andy; Tagg, Randall
2007-11-01
We present a numerical investigation of co-flowing immiscible liquid streams using the Lattice Boltzmann Method (LBM) for multi component, dissimilar viscosity, immiscible fluid flow. When a liquid is injected into another immiscible liquid, the flow will eventually transition from jetting to dripping due to interfacial tension. Our implementation of LBM models the interfacial tension through a variety of techniques. Parallelization is also straightforward for both single and multi component models as only near local interaction is required. We compare the results of our numerical investigation using LBM to several recent physical experiments.
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Methods for estimating low-flow statistics for Massachusetts streams
Ries, Kernell G.; Friesz, Paul J.
2000-01-01
Methods and computer software are described in this report for determining flow duration, low-flow frequency statistics, and August median flows. These low-flow statistics can be estimated for unregulated streams in Massachusetts using different methods depending on whether the location of interest is at a streamgaging station, a low-flow partial-record station, or an ungaged site where no data are available. Low-flow statistics for streamgaging stations can be estimated using standard U.S. Geological Survey methods described in the report. The MOVE.1 mathematical method and a graphical correlation method can be used to estimate low-flow statistics for low-flow partial-record stations. The MOVE.1 method is recommended when the relation between measured flows at a partial-record station and daily mean flows at a nearby, hydrologically similar streamgaging station is linear, and the graphical method is recommended when the relation is curved. Equations are presented for computing the variance and equivalent years of record for estimates of low-flow statistics for low-flow partial-record stations when either a single or multiple index stations are used to determine the estimates. The drainage-area ratio method or regression equations can be used to estimate low-flow statistics for ungaged sites where no data are available. The drainage-area ratio method is generally as accurate as or more accurate than regression estimates when the drainage-area ratio for an ungaged site is between 0.3 and 1.5 times the drainage area of the index data-collection site. Regression equations were developed to estimate the natural, long-term 99-, 98-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, and 50-percent duration flows; the 7-day, 2-year and the 7-day, 10-year low flows; and the August median flow for ungaged sites in Massachusetts. Streamflow statistics and basin characteristics for 87 to 133 streamgaging stations and low-flow partial-record stations were used to develop the equations. The
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Directory of Open Access Journals (Sweden)
Nikić Zoran
2006-01-01
Full Text Available During the long rainless spells of the dry season, flows in medium and small streams get reduced to what is generally known as "low flow". For ungauged streams, the controlling "low flows" are determined using the regional analysis method. In the presently described exploration, the method applied was based on the assumption that dry weather discharges in medium and small rivers depended on the hydrogeological conditions. The controlling effect of hydrogeology on the natural low flow in medium and small streams of the hilly and mountainous part of Serbia was analyzed applying the theory of multiple linear regression. The thirty-day minimum mean 80 and 95 per cent exceedance flows were taken for dependent variables, and quantified hydrogeological elements as independent variables. The analysis covered streams that had small or medium size catchment areas. The treated example encompassed sixty-one gauged catchments. The resulting regional relations for the thirty day minimum mean 80 and 95 per cent exceedance flows are presented in this paper. The quality of the established relation was controlled by relevant statistic tests.
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Groundwater flow and mixing in a wetland–stream system
DEFF Research Database (Denmark)
Karan, Sachin; Engesgaard, Peter Knudegaard; Zibar, Majken Caroline Looms
2013-01-01
steady-state groundwater model that was calibrated against average head observations. The model results were tested against groundwater fluxes determined from streambed temperature measurements. Discharge varied up to one order of magnitude across the stream and the model was successful in capturing...... in the top of the aquifer and immediately underneath the streambed no NO3- was detected deeper within the aquifer. An inverse relationship between NO3- and SO42- suggests that pyrite oxidation takes place in the deeper parts of the aquifer. Simulated flow path lines showed very different origins for deeper...
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A review of lot streaming in a flow shop environment with makespan criteria
Directory of Open Access Journals (Sweden)
Pedro Gómez-Gasquet
2013-07-01
Full Text Available Purpose: This paper reviews current literature and contributes a set of findings that capture the current state-of-the-art of the topic of lot streaming in a flow-shop. Design/methodology/approach: A literature review to capture, classify and summarize the main body of knowledge on lot streaming in a flow-shop with makespan criteria and, translate this into a form that is readily accessible to researchers and practitioners in the more mainstream production scheduling community. Findings and Originality/value: The existing knowledge base is somewhat fragmented. This is a relatively unexplored topic within mainstream operations management research and one which could provide rich opportunities for further exploration. Originality/value: This paper sets out to review current literature, from an advanced production scheduling perspective, and contributes a set of findings that capture the current state-of-the-art of this topic.
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Hysteretic behavior of stage-discharge relationships in urban streams
Miller, A. J.; Lindner, G. A.
2009-12-01
Reliable stage-discharge relationships or rating curves are of critical importance for accurate calculation of streamflow and maintenance of long-term flow records. Urban streams offer particular challenges for the maintenance of accurate rating curves. It is often difficult or impossible to collect direct discharge measurements at high flows, many of which are generated by short-duration high-intensity summer thunderstorms, both because of dangerous conditions in the channel and also because the stream rises and falls so rapidly that field crews cannot reach sites in time and sometimes cannot make measurements rapidly enough to keep pace with changing water levels even when they are on site during a storm. Work in urban streams in the Baltimore metropolitan area has shown that projection of rating curves beyond the range of measured flows can lead to overestimation of flood peaks by as much as 100%, and these can only be corrected when adequate field data are available to support modeling efforts. Even moderate flows that are above safe wading depth and velocity may best be estimated using hydraulic models. Current research for NSF CNH project 0709659 includes the application of 2-d depth-averaged hydraulic models to match existing rating curves over a range of low to moderate flows and to extend rating curves for higher flows, based on field collection of high-water marks. Although it is generally assumed that stage-discharge relationships are single-valued, we find that modeling results in small urban streams often generate hysteretic relationships, with higher discharges on the rising limb of the hydrograph than on the falling limb. The difference between discharges for the same stage on the rising and falling limb can be on the order of 20-30% even for in-channel flows that are less than 1 m deep. As safety considerations dictate that it is preferable to make direct discharge measurements on the falling limb of the hydrograph, the higher direct measurements
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Short-term stream flow forecasting at Australian river sites using data-driven regression techniques
CSIR Research Space (South Africa)
Steyn, Melise
2017-09-01
Full Text Available This study proposes a computationally efficient solution to stream flow forecasting for river basins where historical time series data are available. Two data-driven modeling techniques are investigated, namely support vector regression...
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StreamMap: Smooth Dynamic Visualization of High-Density Streaming Points.
Li, Chenhui; Baciu, George; Han, Yu
2018-03-01
Interactive visualization of streaming points for real-time scatterplots and linear blending of correlation patterns is increasingly becoming the dominant mode of visual analytics for both big data and streaming data from active sensors and broadcasting media. To better visualize and interact with inter-stream patterns, it is generally necessary to smooth out gaps or distortions in the streaming data. Previous approaches either animate the points directly or present a sampled static heat-map. We propose a new approach, called StreamMap, to smoothly blend high-density streaming points and create a visual flow that emphasizes the density pattern distributions. In essence, we present three new contributions for the visualization of high-density streaming points. The first contribution is a density-based method called super kernel density estimation that aggregates streaming points using an adaptive kernel to solve the overlapping problem. The second contribution is a robust density morphing algorithm that generates several smooth intermediate frames for a given pair of frames. The third contribution is a trend representation design that can help convey the flow directions of the streaming points. The experimental results on three datasets demonstrate the effectiveness of StreamMap when dynamic visualization and visual analysis of trend patterns on streaming points are required.
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Coriolis mass flow rate meters for low flows
Mehendale, A.
2008-01-01
The accurate and quick measurement of small mass flow rates (~10 mg/s) of fluids is considered an “enabling technology��? in semiconductor, fine-chemical, and food & drugs industries. Flowmeters based on the Coriolis effect offer the most direct sensing of the mass flow rate, and for this reason do
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Stewart-Maddox, N. S.; Tysor, E. H.; Swanson, J.; Degon, A.; Howard, J.; Tsinnajinnie, L.; Frisbee, M. D.; Wilson, J. L.; Newman, B. D.
2014-12-01
A community well is the primary water supply to the town of El Rito. This small rural town in is located in a semi-arid, mountainous portion of northern New Mexico where water is scarce. The well is 72 meters from a nearby intermittent stream. Initial tritium sampling suggests a groundwater connection between the stream and well. The community is concerned with the sustainability and future quality of the well water. If this well is as tightly connected to the stream as the tritium data suggests, then the well is potentially at risk due to upstream contamination and the impacts of extended drought. To examine this, we observed the well over a two-week period performing pump and recovery tests, electrical resistivity surveys, and physical observations of the nearby stream. We also collected general chemistry, stable isotope and radon samples from the well and stream. Despite the large well diameter, our pump test data exhibited behavior similar to a Theis curve, but the rate of drawdown decreased below the Theis curve late in the test. This decrease suggests that the aquifer is being recharged, possibly through delayed yield, upwelling of groundwater, or from the stream. The delayed yield hypothesis is supported by our electrical resistivity surveys, which shows very little change in the saturated zone over the course of the pump test, and by low values of pump-test estimated aquifer storativity. Observations of the nearby stream showed no change in stream-water level throughout the pump test. Together this data suggests that the interaction between the stream and the well is low, but recharge could be occurring through other mechanisms such as delayed yield. Additional pump tests of longer duration are required to determine the exact nature of the aquifer and its communication with the well.
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Ptaquiloside from bracken in stream water at base flow and during storm events
DEFF Research Database (Denmark)
Clauson-Kaas, Frederik; Ramwell, Carmel; Hansen, Hans Chr. Bruun
2016-01-01
not decrease over the course of the event. In the stream, the throughfall contribution to PTA cannot be separated from a possible below-ground input from litter, rhizomes and soil. Catchment-specific factors such as the soil pH, topography, hydrology, and bracken coverage will evidently affect the level of PTA...... rainfall and PTA concentration in the stream, with a reproducible time lag of approx. 1 h from onset of rain to elevated concentrations, and returning rather quickly (about 2 h) to base flow concentration levels. The concentration of PTA behaved similar to an inert tracer (Cl(-)) in the pulse experiment...
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Flow Rate Measurement in Multiphase Flow Rig: Radiotracer and Conventional
International Nuclear Information System (INIS)
Nazrul Hizam Yusoff; Noraishah Othman; Nurliyana Abdullah; Amirul Syafiq Mohd Yunos; Rasif Mohd Zain; Roslan Yahya
2015-01-01
Applications of radiotracer technology are prevalent throughout oil refineries worldwide, and this industry is one of the main users and beneficiaries of the technology. Radioactive tracers have been used to a great extent in many applications i.e. flow rate measurement, RTD, plant integrity evaluation and enhancing oil production in oil fields. Chemical and petrochemical plants are generally continuously operating and technically complex where the radiotracer techniques are very competitive and largely applied for troubleshooting inspection and process analysis. Flow rate measurement is a typical application of radiotracers. For flow measurements, tracer data are important, rather than the RTD models. Research is going on in refining the existing methods for single phase flow measurement, and in developing new methods for multiphase flow without sampling. The tracer techniques for single phase flow measurements are recognized as ISO standards. This paper presents technical aspect of laboratory experiments, which have been carried out using Molybdenum-99 - Mo99 (radiotracer) to study and determine the flow rate of liquid in multiphase flow rig. The multiphase flow rig consists of 58.7 m long and 20 cm diameter pipeline that can accommodate about 0.296 m 3 of liquid. Tap water was used as liquid flow in pipeline and conventional flow meters were also installed at the flow rig. The flow rate results; radiotracer and conventional flow meter were compared. The total count method was applied for radiotracer technique and showed the comparable results with conventional flow meter. (author)
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Flow characterization temporary streams : using the model SIMGRO for the Evrotas basin, Greece
Vernooij, M.G.M.; Querner, E.P.; Jacobs, C.; Froebrich, J.
2011-01-01
Tools were developed to quantify space–time development of different flow phases on a river basin scale. Such information is needed for the WFD. The spatial development of temporary streams was investigated in the Evrotas basin, Greece. We used the regional hydrological model SIMGRO in a GIS
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Soil Microbial Community Contribution to Small Headwater Stream Metabolism.
Clapcott, J. E.; Gooderham, J. P.; Barmuta, L. A.; Davies, P. E.
2005-05-01
The temporal dynamics of sediment respiration were examined in seven small headwater streams in forested catchments in 2004. A strong seasonal response was observed with higher respiration rates in depositional zones than in gravel runs. The data were also examined in the context of proportional habitat distributions that highlighted the importance of high flow events in shaping whole stream metabolic budgets. This study specifically examines the question of terrestrial soil respiration contribution to whole stream metabolism by the controlled inundation of terrestrial soils. The experiment included six experimentally inundated terrestrial zones, six terrestrial controls, and six in-stream depositional zones. Sediment bacterial respiration was measured using 14C leucine incorporation and cotton strip bioassays were also employed to provide an indicative measure of sediment microbial activity. Despite high variability and exhibiting significantly lower bacterial activity than in-stream sediments, modelling using flow data and habitat mapping illustrated the important contribution of terrestrial soil respiration to the whole stream metabolic budgets of small headwater streams. In addition, microbial community composition examined using phospholipid fatty acid analysis clearly differentiated between terrestrial and aquatic communities. Freshly inundated terrestrial communities remained similar to un-inundated controls after 28 days.
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PIV pictures of stream field predict haemolysis index of centrifugal pump with streamlined impeller.
Qian, K X; Feng, Z G; Ru, W M; Zeng, P; Yuan, H Y
2007-01-01
Previously it has been found by pump haemolysis testing that the flow rate has a remarkable effect on index of haemolysis (IH), while pressure head does not affect IH. Recent investigation with particle image velocimetry (PIV) technology has demonstrated that IH is directly related to the flow pattern of stream field in impeller vane channels. PIV is a visible approach showing the real flow status in the pump. The different positions of a tracer particle in two PIV pictures taken at 20 micros intervals decide the velocity value and direction. The velocity vectors of many particles draw the flow pattern of the stream field. The same pictures are taken at 2, 4 and 6 l min(-1) flow rates while the pressure head is kept unchanged at 100 mmHg; then the pictures are taken at 4 l min(-1) flow with different pressure heads of 80, 100 and 120 mmHg. Results reveal that the flow rate of 4 l min(-1) (IH = 0.030) has the best stream field, and neither turbulence nor separation can be seen. In other flow rates (IH: 0.048 - 0.082), there is obviously second flow. Meanwhile, no significant difference can be seen among the PIV pictures of different pressure heads pumped, which agrees with the results of haemolysis testing showing that pressure has no effect on pump haemolysis. It may be concluded that the haemolysis property of a centrifugal pump can be assessed approximately by PIV pictures, which are much easier to take than haemolysis tests.
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Influence of liquid and gas flow rates on sulfuric acid mist removal from air by packed bed tower
Directory of Open Access Journals (Sweden)
Jafari Mohammad Javad
2012-12-01
Full Text Available Abstract The possible emission of sulfuric acid mists from a laboratory scale, counter-current packed bed tower operated with a caustic scrubbing solution was studied. Acid mists were applied through a local exhaust hood. The emissions from the packed bed tower were monitored in three different categories of gas flow rate as well as three liquid flow rates, while other influencing parameters were kept almost constant. Air sampling and sulfuric acid measurement were carried out iso-kinetically using USEPA method 8. The acid mists were measured by the barium-thorin titration method. According to the results when the gas flow rate increased from 10 L/s to 30 L/s, the average removal efficiency increased significantly (p 3, respectively. L/G of 2–3 was recommended for designing purposes of a packed tower for sulfuric acid mists and vapors removal from contaminated air stream.
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Christensen, H.; Wooten, J. P.; Swanson, E.; Senison, J. J.; Myers, K. D.; Befus, K. M.; Warden, J.; Zamora, P. B.; Gomez, J. D.; Wilson, J. L.; Groffman, A.; Rearick, M. S.; Cardenas, M. B.
2012-12-01
A study by the 2012 Hydrogeology Field Methods class of the University of Texas at Austin implemented multiple approaches to evaluate and characterize local hyporheic zone flow and biogeochemical trends in a highly meandering reach of the of the East Fork of the Jemez River, a fourth order stream in northwestern New Mexico. This section of the Jemez River is strongly meandering and exhibits distinct riffle-pool morphology. The high stream sinuosity creates inter-meander hyporheic flow that is also largely influenced by local groundwater gradients. In this study, dozens of piezometers were used to map the water table and flow vectors were then calculated. Surface water and ground water samples were collected and preserved for later geochemical analysis by ICPMS and HPLC, and unstable parameters and alkalinity were measured on-site. Additionally, information was collected from thermal monitoring of the streambed, stream gauging, and from a series of electrical resistivity surveys forming a network across the site. Hyporheic flow paths are suggested by alternating gaining and losing sections of the stream as determined by stream gauging at multiple locations along the reach. Water table maps and calculated fluxes across the sediment-water interface also indicate hyporheic flow paths. We find variability in the distribution of biogeochemical constituents (oxidation-reduction potential, nitrate, ammonium, and phosphate) along interpreted flow paths which is partly consistent with hyporheic exchange. The variability and heterogeneity of reducing and oxidizing conditions is interpreted to be a result of groundwater-surface water interaction. Two-dimensional mapping of biogeochemical parameters show redox transitions along interpreted flow paths. Further analysis of various measured unstable chemical parameters results in observable trends strongly delineated along these preferential flow paths that are consistent with the direction of groundwater flow and the assumed
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Energy Technology Data Exchange (ETDEWEB)
Wan Mohamad Tahir, Wan Zakaria; Mohamad, Daud; Hamzah, Abdul Razak; Yusuf, Johari Mohamad; Aziz Wan Mohamad, Wan Abdul
1986-06-01
A radiotracer technique using Tc-99 to measure flows of small rivers was introduced in Malaysia. Three rivers in the Ulu Langat District were selected for a comparative study on flow rate determination by conventional and radioisotope methods. Radioisotopic approach, comprising injection procedures, calibration, mixing length and safety aspects are discussed. The results measured by radioisotope method are compared to the Drainage and Irrigation Department's (DID's) discharge curves data collected from 1980 to 1982 which is calibrated using a current meter. The results are comparable and fall within the range obtained by conventional method. Related to this study, a comprehensive work on stream gauging of moderate and high flow rates using both methods is proposed to be carried out directly.
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Type and timing of stream flow changes in urbanizing watersheds in the Eastern U.S.
Directory of Open Access Journals (Sweden)
Kristina G. Hopkins
2015-06-01
Full Text Available Abstract Linking the type and timing of hydrologic changes with patterns of urban growth is essential to identifying the underlying mechanisms that drive declines in urban aquatic ecosystems. In six urbanizing watersheds surrounding three U.S. cities (Baltimore, MD, Boston, MA, and Pittsburgh, PA, we reconstructed the history of development patterns since 1900 and assessed the magnitude and timing of stream flow changes during watershed development. Development reconstructions indicated that the majority of watershed development occurred during a period of peak population growth, typically between 1950 and 1970. Stream flow records indicated significant increases in annual frequency of high-flow events in all six watersheds and increases in annual runoff efficiency in five watersheds. Annual development intensity during the peak growth period had the strongest association with the magnitude of changes in high-flow frequency from the pre- to post-development periods. Results suggest the timing of the peak growth period is particularly important to understanding hydrologic changes, because it can set the type of stormwater infrastructure installed within a watershed. In three watersheds there was a rapid (∼10-15 years shift toward more frequent high-flow events, and in four watersheds there was a shift toward higher runoff efficiency. Breakpoint analyses indicated these shifts occurred between 1969 and 1976 for high-flow frequency and between 1962 and 1984 for runoff efficiency. Results indicated that the timing of high-flow changes were mainly driven by the development trajectory of each watershed, whereas the timing of runoff-efficiency changes were driven by a combination of development trajectories and extreme weather events. Our results underscore the need to refine the causes of urban stream degradation to incorporate the impact of gradual versus rapid urbanization on hydrologic changes and aquatic ecosystem function, as well as to
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Stochastic ice stream dynamics.
Mantelli, Elisa; Bertagni, Matteo Bernard; Ridolfi, Luca
2016-08-09
Ice streams are narrow corridors of fast-flowing ice that constitute the arterial drainage network of ice sheets. Therefore, changes in ice stream flow are key to understanding paleoclimate, sea level changes, and rapid disintegration of ice sheets during deglaciation. The dynamics of ice flow are tightly coupled to the climate system through atmospheric temperature and snow recharge, which are known exhibit stochastic variability. Here we focus on the interplay between stochastic climate forcing and ice stream temporal dynamics. Our work demonstrates that realistic climate fluctuations are able to (i) induce the coexistence of dynamic behaviors that would be incompatible in a purely deterministic system and (ii) drive ice stream flow away from the regime expected in a steady climate. We conclude that environmental noise appears to be crucial to interpreting the past behavior of ice sheets, as well as to predicting their future evolution.
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Directory of Open Access Journals (Sweden)
M. Moravej
2016-02-01
Full Text Available Introduction: Studying the hydrological cycle, especially in large scales such as water catchments, is difficult and complicated despite the fact that the numbers of hydrological components are limited. This complexity rises from complex interactions between hydrological components and environment. Recognition, determination and modeling of all interactive processes are needed to address this issue, but it's not feasible for dealing with practical engineering problems. So, it is more convenient to consider hydrological components as stochastic phenomenon, and use stochastic models for modeling them. Stochastic simulation of time series models related to water resources, particularly hydrologic time series, have been widely used in recent decades in order to solve issues pertaining planning and management of water resource systems. In this study time series models fitted to the precipitation, evaporation and stream flow series separately and the relationships between stream flow and precipitation processes are investigated. In fact, the three mentioned processes should be modeled in parallel to each other in order to acquire a comprehensive vision of hydrological conditions in the region. Moreover, the relationship between the hydrologic processes has been mostly studied with respect to their trends. It is desirable to investigate the relationship between trends of hydrological processes and climate change, while the relationship of the models has not been taken into consideration. The main objective of this study is to investigate the relationship between hydrological processes and their effects on each other and the selected models. Material and Method: In the current study, the four sub-basins of Lake Urmia Basin namely Zolachay (A, Nazloochay (B, Shahrchay (C and Barandoozchay (D were considered. Precipitation, evaporation and stream flow time series were modeled by linear time series. Fundamental assumptions of time series analysis namely
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2011-11-08
... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER12-225-000] Stream Energy New Jersey, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for... Stream Energy New Jersey, LLC's application for market-based rate authority, with an accompanying rate...
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Gordon, R.; Lautz, L. K.; McKenzie, J. M.; Mark, B. G.; Chavez, D.
2013-12-01
Melting tropical glaciers supply approximately half of dry season stream discharge in glacierized valleys of the Cordillera Blanca, Peru. The remainder of streamflow originates as groundwater stored in alpine meadows, moraines and talus slopes. A better understanding of the dynamics of alpine groundwater, including sources and contributions to streamflow, is important for making accurate estimates of glacial inputs to the hydrologic budget, and for our ability to make predictions about future water resources as glaciers retreat. Our field study, conducted during the dry season in the Llanganuco valley, focused on a 0.5-km2 alpine meadow complex at 4400 m elevation, which includes talus slopes, terminal moraines, and a debris fan. Two glacial lakes and springs throughout the complex feed a network of stream channels that flow across the meadow (~2 km total length). We combined tracer measurements of stream and spring discharge and groundwater-surface water exchange with synoptic sampling of water isotopic and geochemical composition, in order to characterize and quantify contributions to streamflow from different geomorphic features. Surface water inputs to the stream channels totaled 58 l/s, while the stream gained an additional 57 l/s from groundwater inputs. Water chemistry is primarily controlled by flowpath type (surface/subsurface) and length, as well as bedrock lithology, while stable water isotopic composition appears to be controlled by water source (glacial lake, meadow or deep groundwater). Stream water chemistry is most similar to meadow groundwater springs, but isotopic composition suggests that the majority of stream water, which issues from springs at the meadow/fan interface, is from the same glacial source as the up-gradient lake. Groundwater sampled from piezometers in confined meadow aquifers is unique in both chemistry and isotopic composition, but does not contribute a large percentage of stream water exiting this small meadow, as quantified by
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Effect of Free Stream Turbulence on the Flow-Induced Background Noise of In-Flow Microphones
Allen, Christopher S.; Olson, Lawrence E. (Technical Monitor)
1998-01-01
When making noise measurements of sound sources in flow using microphones immersed in an air stream or wind tunnel, the factor limiting the dynamic range of the measurement is, in many cases, the noise caused by the flow over the microphone. To lower this self-noise, and to protect the microphone diaphragm, an aerodynamic microphone forebody is usually mounted on the tip of the omnidirectional microphone. The microphone probe is then pointed into the wind stream. Even with a microphone forebody, however, the self-noise persists, prompting further research in the area of microphone forebody design for flow-induced self-noise reduction. The magnitude and frequency characteristics of in-flow microphone probe self-noise is dependent upon the exterior shape of the probe and on the level of turbulence in the onset flow, among other things. Several recent studies present new designs for microphone forebodies, some showing the forbodies' self-noise characteristics when used in a given facility. However, these self-noise characteristics may change when the probes are used in different facilities. The present paper will present results of an experimental investigation to determine an empirical relationship between flow turbulence and self-noise levels for several microphone forebody shapes as a function of frequency. As a result, the microphone probe self-noise for these probes will be known as a function of freestream turbulence, and knowing the freestream turbulence spectra for a given facility, the probe self-noise can be predicted. Flow-induced microphone self-noise is believed to be related to the freestream. turbulence by three separate mechanisms. The first mechanism is produced by large scale, as compared to the probe size, turbulence which appears to the probe as a variation in the angle of attack of the freestream. flow. This apparent angle of attack variation causes the pressure along the probe surface to fluctuate, and at the location of the sensor orifice this
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Determining hyporheic storage using the rSAS model in urban restored streams.
Stoll, E.; Putnam, S. M.; Cosans, C.; Harman, C. J.
2017-12-01
One aim of stream restoration is to increase the connectivity of the stream with the hyporheic zone, which is important for processes like denitrification. This study analyzed transects of different restoration techniques in an urban stream, Stony Run in Baltimore, Maryland. The extent of the hyporheic zone was determined using a combination of salt slug injection tracer studies to determine the breakthrough curves and the rank StorAge Selection (rSAS) model. Previous studies using salt tracer injections have often focused on the shape of the breakthrough curve and the transit time distributions of streams to infer indicies correlated with hyporheic zone storage. This study uses the rSAS model to determine the volume of storage that must be turning over to produce the breakthrough curve. This study looked at transects of two different restoration techniques, one with floodplain rehabilitation and one without. Both transects had cross vanes and pool and riffle systems and only differed in the steepness of the banks surrounding the stream. The utility and accuracy of rSAS method was found to be heavily dependent on accurate flow rates. To avoid potential skew in the results, normalized, relatively flow rate-independent metric of storage were compared among transects to reduce error resulting from the flow rate. The results suggested that stream water was retained for longer in a larger storage volume in the transect that did not have floodplain rehabilitation. When compared to the storage of a natural stream with similar geomorphologic characteristics, the restored transect without floodplain rehabilitation had a larger storage volume than the natural stream. The restored transect with floodplain rehabilitation not only had a smaller storage volume than the restored section without rehabilitation, but also had a smaller storage volume than the natural stream with similar bank slopes. This suggests that the floodplain restoration does not significantly contribute to
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A novel concept of measuring mass flow rates using flow induced ...
Indian Academy of Sciences (India)
Measurement of mass flow rate is important for automatic control of the mass flow rate in .... mass flow rate. The details are as follows. ... Assuming a symmetry plane passing through the thickness of the plate, at the symmetry plane δu∗n,B = 0.
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Directory of Open Access Journals (Sweden)
Komlavi Akpoti
2016-07-01
Full Text Available Potential implications of rainfall variability along with Land Use and Land Cover Change (LULC on stream flow have been assessed in the Black Volta basin using the SWAT model. The spatio-temporal variability of rainfall over the Black Volta was assessed using the Mann-Kendall monotonic trend test and the Sen’s slope for the period 1976–2011. The statistics of the trend test showed that 61.4% of the rain gauges presented an increased precipitation trend whereas the rest of the stations showed a decreased trend. However, the test performed at the 95% confidence interval level showed that the detected trends in the rainfall data were not statistically significant. Land use trends between the year 2000 and 2013 show that within thirteen years, land use classes like bare land, urban areas, water bodies, agricultural lands, deciduous forests and evergreen forests have increased respectively by 67.06%, 33.22%, 7.62%, 29.66%, 60.18%, and 38.38%. Only grass land has decreased by 44.54% within this period. Changes in seasonal stream flow due to LULC were assessed by defining dry and wet seasons. The results showed that from year 2000 to year 2013, the dry season discharge has increased by 6% whereas the discharge of wet season has increased by 1%. The changes in stream flows components such us surface run-off (SURF_Q, lateral flow (LAT_Q and ground water contribution to stream flow (GW_Q and also on evapotranspiration (ET changes due to LULC was evaluated. The results showed that between the year 2000 and 2013, SURF_Q and LAT_Q have respectively increased by 27% and 19% while GW_Q has decreased by 6% while ET has increased by 4.59%. The resultant effects are that the water yield to stream flow has increased by 4%.
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Sengupta, Tapan K.; Gullapalli, Atchyut
2016-11-01
Spinning cylinder rotating about its axis experiences a transverse force/lift, an account of this basic aerodynamic phenomenon is known as the Robins-Magnus effect in text books. Prandtl studied this flow by an inviscid irrotational model and postulated an upper limit of the lift experienced by the cylinder for a critical rotation rate. This non-dimensional rate is the ratio of oncoming free stream speed and the surface speed due to rotation. Prandtl predicted a maximum lift coefficient as CLmax = 4π for the critical rotation rate of two. In recent times, evidences show the violation of this upper limit, as in the experiments of Tokumaru and Dimotakis ["The lift of a cylinder executing rotary motions in a uniform flow," J. Fluid Mech. 255, 1-10 (1993)] and in the computed solution in Sengupta et al. ["Temporal flow instability for Magnus-robins effect at high rotation rates," J. Fluids Struct. 17, 941-953 (2003)]. In the latter reference, this was explained as the temporal instability affecting the flow at higher Reynolds number and rotation rates (>2). Here, we analyze the flow past a rotating cylinder at a super-critical rotation rate (=2.5) by the enstrophy-based proper orthogonal decomposition (POD) of direct simulation results. POD identifies the most energetic modes and helps flow field reconstruction by reduced number of modes. One of the motivations for the present study is to explain the shedding of puffs of vortices at low Reynolds number (Re = 60), for the high rotation rate, due to an instability originating in the vicinity of the cylinder, using the computed Navier-Stokes equation (NSE) from t = 0 to t = 300 following an impulsive start. This instability is also explained through the disturbance mechanical energy equation, which has been established earlier in Sengupta et al. ["Temporal flow instability for Magnus-robins effect at high rotation rates," J. Fluids Struct. 17, 941-953 (2003)].
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Rosenberger, A.E.; Dunham, J.B.; Buffington, J.M.; Wipfli, M.S.
2011-01-01
Wildfire and debris flows are important physical and ecological drivers in headwater streams of western North America. Past research has primarily examined short-term effects of these disturbances; less is known about longer-term impacts. We investigated wildfire effects on the invertebrate prey base for drift-feeding rainbow trout (Oncorhynchus mykiss, Walbaum) in Idaho headwater streams a decade after wildfire. Three stream types with different disturbance histories were examined: 1) unburned, 2) burned, and 3) burned followed by debris flows that reset channel morphology and riparian vegetation. The quantity of macroinvertebrate drift (biomass density) was more variable within than among disturbance categories. Average body weight and taxonomic richness of drift were significantly related to water temperature and influenced by disturbance history. During the autumn sampling period, the amount of terrestrial insects in rainbow trout diets varied with disturbance history and the amount of overhead canopy along the stream banks. Results indicate that there are detectable changes to macroinvertebrate drift and trout diet a decade after wildfire, and that these responses are better correlated with specific characteristics of the stream (water temperature, canopy cover) than with broad disturbance classes.
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Energy Technology Data Exchange (ETDEWEB)
R. T. Jubin; D. M. Strachan; N. R. Soelberg
2013-09-01
Used nuclear fuel is currently being reprocessed in only a few countries, notably France, England, Japan, and Russia. The need to control emissions of the gaseous radionuclides to the air during nuclear fuel reprocessing has already been reported for the entire plant. But since the gaseous radionuclides can partition to various different reprocessing off-gas streams, for example, from the head end, dissolver, vessel, cell, and melter, an understanding of each of these streams is critical. These off-gas streams have different flow rates and compositions and could have different gaseous radionuclide control requirements, depending on how the gaseous radionuclides partition. This report reviews the available literature to summarize specific engineering data on the flow rates, forms of the volatile radionuclides in off-gas streams, distributions of these radionuclides in these streams, and temperatures of these streams. This document contains an extensive bibliography of the information contained in the open literature.
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Feinson, Lawrence S.; Gibs, Jacob; Imbrigiotta, Thomas E.; Garrett, Jessica D.
2016-01-01
The U.S. Geological Survey's New Jersey and Iowa Water Science Centers deployed ultraviolet-visible spectrophotometric sensors at water-quality monitoring sites on the Passaic and Pompton Rivers at Two Bridges, New Jersey, on Toms River at Toms River, New Jersey, and on the North Raccoon River near Jefferson, Iowa to continuously measure in-stream nitrate plus nitrite as nitrogen (NO3 + NO2) concentrations in conjunction with continuous stream flow measurements. Statistical analysis of NO3 + NO2 vs. stream discharge during storm events found statistically significant links between land use types and sampling site with the normalized area and rotational direction of NO3 + NO2-stream discharge (N-Q) hysteresis patterns. Statistically significant relations were also found between the normalized area of a hysteresis pattern and several flow parameters as well as the normalized area adjusted for rotational direction and minimum NO3 + NO2 concentrations. The mean normalized hysteresis area for forested land use was smaller than that of urban and agricultural land uses. The hysteresis rotational direction of the agricultural land use was opposite of that of the urban and undeveloped land uses. An r2 of 0.81 for the relation between the minimum normalized NO3 + NO2 concentration during a storm vs. the normalized NO3 + NO2 concentration at peak flow suggested that dilution was the dominant process controlling NO3 + NO2 concentrations over the course of most storm events.
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Measurements of flow-rate transients in one-phase liquid flow
International Nuclear Information System (INIS)
Mueller-Roos, J.
1975-01-01
A report is given on a method to determine flow-rate transients in a one-phase flow. Periodic temperature signals are superposed on the flow, from which flow times are calculated through correlation each over a half period. The evaluation is carried out according to the digitalization 'off-line' on a large computer. Rate peaks of over 100% within 1.9 s were qualitatively and quantitatively well represented. (orig./LH) [de
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Meshgi, A.; Babovic, V.; Chui, T. F. M.; Schmitter, P.
2014-12-01
Developing reliable methods to estimate stream flow has been a subject of interest due to its importance in planning, design and management of water resources within a basin. Machine learning tools such as Artificial Neural Network (ANN) and Genetic Programming (GP) have been widely applied for rainfall-runoff modeling as they require less computational time as compared to physically-based models. As GP is able to generate a function with understandable structure, it may offer advantages over other data driven techniques and therefore has been used in different studies to generate rainfall-runoff functions. However, to date, proposed formulations only contain rainfall and/or streamflow data and consequently are local and cannot be generalized and adopted in other catchments which have different physical characteristics. This study investigated the capability of GP in developing a physically interpretable model with understandable structure to simulate stream flow based on hydrological parameters (e.g. precipitation) and catchment conditions (e.g., initial groundwater table elevation and area of the catchment) by following a modular approach. The modular model resulted in two sub-models where the baseflow was first predicted and the direct runoff was then estimated for a semi-urban catchment in Singapore. The simulated results matched very well with observed data in both the training and the testing of data sets, giving NSEs of 0.97 and 0.96 respectively demonstrated the successful estimation of stream flow using the modular model derived in this study. The results of this study indicate that GP is an effective tool in developing a physically interpretable model with understandable structure to simulate stream flow that can be transferred to other catchments.
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Daniele Tonina; John M. Buffington
2011-01-01
Hyporheic flow results from the interaction between streamflow and channel morphology and is an important component of stream ecosystems because it enhances water and solute exchange between the river and its bed. Hyporheic flow in pool-riffle channels is particularly complex because of three-dimensional topography that spans a range of partially to fully submerged...
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Kang, Seokkoo; Borazjani, Iman; Sotiropoulos, Fotis
2008-11-01
Unsteady 3D simulations of flows in natural streams is a challenging task due to the complexity of the bathymetry, the shallowness of the flow, and the presence of multiple nature- and man-made obstacles. This work is motivated by the need to develop a powerful numerical method for simulating such flows using coherent-structure-resolving turbulence models. We employ the curvilinear immersed boundary method of Ge and Sotiropoulos (Journal of Computational Physics, 2007) and address the critical issue of numerical efficiency in large aspect ratio computational domains and grids such as those encountered in long and shallow open channels. We show that the matrix-free Newton-Krylov method for solving the momentum equations coupled with an algebraic multigrid method with incomplete LU preconditioner for solving the Poisson equation yield a robust and efficient procedure for obtaining time-accurate solutions in such problems. We demonstrate the potential of the numerical approach by carrying out a direct numerical simulation of flow in a long and shallow meandering stream with multiple hydraulic structures.
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Critical flow rate in a single phase flow. Blocking concept
International Nuclear Information System (INIS)
Giot, Michel
1978-01-01
After referring to the phenomena accompanying the appearance of a critical flow rate in a nozzle and presenting equations governing single phase flows, the critical condition is defined. Several particular cases are then examined; the horizontal and vertical isentropic flow, Fanno's flow and Raleigh's and the isothermal flow. The entropy deviation is calculated on either side of a normal impact. To conclude, the link existing between the concepts of critical flow and the propagation rate of small perturbations is demonstrated. To do so, the method of perturbations, that of Prandtl and that of characteristic directions are applied in turn [fr
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Climate and Land-Cover Change Impacts on Stream Flow in the Southwest U.S.
Vegetation change in arid and semi-arid climatic regions of the American West are a primary concern in sustaining key ecosystem services such as clean, reliable water sources for multiple uses. Land cover and climate change impacts on stream flow were investigated in a southeast ...
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P.B. Parajuli; P. Jayakody; G.F. Sassenrath; Y. Ouyang
2016-01-01
This study evaluated climate change impacts on stream flow, crop and sediment yields from three differ-ent tillage systems (conventional, reduced 1âclose to conservation, and reduced 2âclose to no-till), in theBig Sunflower River Watershed (BSRW) in Mississippi. The Soil and Water Assessment Tool (SWAT) modelwas applied to the BSRW using observed stream flow and crop...
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Lee, L. C.; Wang, S.; Wei, C. Q.; Tsurutani, B. T.
1988-01-01
This paper investigates the growth rates and eigenmode structures of the streaming sausage, kink, and tearing instabilities in a current sheet with a super-Alfvenic flow. The growth rates and eigenmode structures are first considered in the ideal incompressible limit by using a four-layer model, as well as a more realistic case in which all plasma parameters and the magnetic field vary continuously along the direction perpendicular to the magnetic field and plasma flow. An initial-value method is applied to obtain the growth rate and eigenmode profiles of the fastest growing mode, which is either the sausage mode or kink mode. It is shown that, in the earth's magnetotail, where super-Alfvenic plasma flows are observed in the plasma sheet and the ratio between the plasma and magnetic pressures far away from the current layer is about 0.1-0.3 in the lobes, the streaming sausage and streaming tearing instabilities, but not kink modes, are likely to occur.
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Izuka, Scot K.; Ewart, Charles J.
1995-01-01
A study of the geology, streamflow, and water chemistry of Talufofo Stream Basin, Saipan, Commonwealth of the Northern Mariana Islands, was undertaken to determine the flow characteristics of Talufofo Stream and the relation to the geology of the drainage basin. The Commonwealth government is exploring the feasibility of using water from Talufofo Stream to supplement Saipan's stressed municipal water supply. Streamflow records from gaging stations on the principal forks of Talufofo Stream indicate that peak streamflows and long-term average flow are higher at the South Fork gaging station than at the Middle Fork gaging station because the drainage area of the South Fork gaging station is larger, but persistent base flow from ground-water discharge during dry weather is greater in the Middle Fork gaging station. The sum of the average flows at the Middle Fork and South Fork gaging stations, plus an estimate of the average flow at a point in the lower reaches of the North Fork, is about 2.96 cubic feet per second or 1.91 million gallons per day. Although this average represents the theoretical maximum long-term draft rate possible from the Talufofo Stream Basin if an adequate reservoir can be built, the actual amount of surface water available will be less because of evaporation, leaks, induced infiltration, and reservoir-design constraints. Base-flow characteristics, such as stream seepage and spring discharge, are related to geology of the basin. Base flow in the Talufofo Stream Basin originates as discharge from springs near the base of limestones located in the headwaters of Talufofo Stream, flows over low-permeability volcanic rocks in the middle reaches, and seeps back into the high-permeability limestones in the lower reaches. Water sampled from Talufofo Stream during base flow had high dissolved-calcium concentrations (between 35 and 98 milligrams per liter), characteristic of water from a limestone aquifer. Concentrations of potassium, sodium, and chloride
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Free stream turbulence and density ratio effects on the interaction region of a jet in a cross flow
Wark, C. E.; Foss, J. F.
1984-01-01
Jets of low temperature air are introduced into the aft sections of gas turbine combustors for the purpose of cooling the high temperature gases and quenching the combustion reactions. Research studies, motivated by this complex flow field, have been executed by introducing a heated jet into the cross stream of a wind tunnel. The investigation by Kamotani and Greber stands as a prime example of such investigations and it serves as the principal reference for the present study. The low disturbance level of the cross stream, in their study and in similar research investigations, is compatible with an interest in identifying the basic features of this flow field. The influence of the prototypes' strongly disturbed cross flow is not, however, made apparent in these prior investigations.
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Cutting-edge analysis of extracellular microparticles using ImageStream(X) imaging flow cytometry.
Headland, Sarah E; Jones, Hefin R; D'Sa, Adelina S V; Perretti, Mauro; Norling, Lucy V
2014-06-10
Interest in extracellular vesicle biology has exploded in the past decade, since these microstructures seem endowed with multiple roles, from blood coagulation to inter-cellular communication in pathophysiology. In order for microparticle research to evolve as a preclinical and clinical tool, accurate quantification of microparticle levels is a fundamental requirement, but their size and the complexity of sample fluids present major technical challenges. Flow cytometry is commonly used, but suffers from low sensitivity and accuracy. Use of Amnis ImageStream(X) Mk II imaging flow cytometer afforded accurate analysis of calibration beads ranging from 1 μm to 20 nm; and microparticles, which could be observed and quantified in whole blood, platelet-rich and platelet-free plasma and in leukocyte supernatants. Another advantage was the minimal sample preparation and volume required. Use of this high throughput analyzer allowed simultaneous phenotypic definition of the parent cells and offspring microparticles along with real time microparticle generation kinetics. With the current paucity of reliable techniques for the analysis of microparticles, we propose that the ImageStream(X) could be used effectively to advance this scientific field.
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Study of stream flow effects on bubble motion
International Nuclear Information System (INIS)
Sami, S.S.
1983-01-01
The formation of air bubbles at constant-pressure by submerged orifices was investigated in both quiescent and moving streams inside a vertical tube. Parameters affecting the bubble rise velocity, such as bubble generating frequency and diameter, were studied and analyzed for bubbles rising in a chain and homogeneous mixture. A special technique for measuring bubble motion parameters has been developed, tested, and employed throughout the experimental investigation. The method is based on a water-air impedance variation. Results obtained in stagnant liquid show that increasing the bubble diameter serves to increase bubble rise velocity, while an opposite trend has been observed for stream liquid where the bubble diameter increase reduces the bubble rise velocity. The increase of bubble generation frequency generally increases the bubble rise velocity. Experimental data covered with bubble radial distribution showed symmetrical profiles of bubble velocity and frequency, and the radial distribution of the velocity profiles sometimes has two maxima and one minimum depending on the liquid velocity. Finally, in stagnant liquid, a normalized correlation has been developed to predict the terminal rise velocity in terms of bubble generating frequency, bubble diameter, single bubble rise velocity, and conduit dimensions. Another correlation is presented for forced bubbly flow, where the bubble rise velocity is expressed as a function of bubble generating frequency, bubble diameter, and water superficial velocity
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Carlson, Carl S.; Walter, Donald A.; Barbaro, Jeffrey R.
2015-12-21
Water use, such as withdrawals, wastewater return flows, and interbasin transfers, can alter streamflow regimes, water quality, and the integrity of aquatic habitat and affect the availability of water for human and ecosystem needs. To provide the information needed to determine alteration of streamflows and pond water levels in southeastern Massachusetts, existing groundwater models of the Plymouth-Carver region and western (Sagamore flow lens) and eastern (Monomoy flow lens) Cape Cod were used to delineate subbasins and simulate long-term average and average monthly streamflows and pond levels for a series of water-use conditions. Model simulations were used to determine the extent to which streamflows and pond levels were altered by comparing simulated streamflows and pond levels under predevelopment conditions with streamflows and pond levels under pumping only and pumping with wastewater return flow conditions. The pumping and wastewater return flow rates used in this study are the same as those used in previously published U.S. Geological Survey studies in southeastern Massachusetts and represent the period from 2000 to 2005. Streamflow alteration for the nontidal portions of streams in southeastern Massachusetts was evaluated within and at the downstream outlets of 78 groundwater subbasins delineated for this study. Evaluation of streamflow alteration at subbasin outlets is consistent with the approach used by the U.S. Geological Survey for the topographically derived subbasins in the rest of Massachusetts.
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A Smart Soft Sensor Predicting Feedwater Flow Rate
International Nuclear Information System (INIS)
Yang, Heon Young; Na, Man Gyun
2009-01-01
Since we evaluate thermal nuclear reactor power with secondary system calorimetric calculations based on feedwater flow rate measurements, we need to measure the feedwater flow rate accurately. The Venturi flow meters that are being used to measure the feedwater flow rate in most pressurized water reactors (PWRs) measure the flow rate by developing a differential pressure across a physical flow restriction. The differential pressure is then multiplied by a calibration factor that depends on various flow conditions in order to calculate the feedwater flow rate. The calibration factor is determined by the feedwater temperature and pressure. However, Venturi meters cause a buildup of corrosion products near the orifice of the meter. This fouling increases the measured pressure drop across the meter, thereby causing an overestimation of the feedwater flow rate
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Stoichiometry of excreta and excretion rates of a stream-dwelling plethodontid salamander
U.S. Environmental Protection Agency — Stoichiometry of excreta and excretion rates of a stream-dwelling plethodontid salamander in Cincinnati, OH, USA. This dataset is associated with the following...
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Directory of Open Access Journals (Sweden)
A. H. Haria
2004-01-01
Full Text Available Upland streamflow generation has traditionally been modelled as a simple rainfall-runoff mechanism. However, recent hydrochemical studies conducted in upland Wales have highlighted the potentially important role of bedrock groundwater in streamflow generation processes. To investigate these processes, a detailed and novel field study was established in the riparian zone and lower hillslopes of the Hafren catchment at Plynlimon, mid-Wales. Results from this study showed groundwater near the river behaving in a complex and most likely confined manner within depth-specific horizons. Rapid responses to rainfall in all boreholes at the study site indicated rapid recharge pathways further upslope. The different flow pathways and travel times influenced the chemical character of groundwaters with depth. Groundwaters were shown to discharge into the stream from the fractured bedrock. A lateral rapid flow horizon was also identified as a fast flow pathway immediately below the soils. This highlighted a mechanism whereby rising groundwater may pick up chemical constituents from the lower soils and transfer them quickly to the stream channel. Restrictions in this horizon resulted in groundwater upwelling into the soils at some locations indicating soil water to be sourced from both rising groundwater and rainfall. The role of bedrock groundwater in upland streamflow generation is far more complicated than previously considered, particularly with respect to residence times and flow pathways. Hence, water quality models in upland catchments that do not take account of the bedrock geology and the groundwater interactions therein will be seriously flawed. Keywords: bedrock, groundwater, Hafren, hillslope hydrology, Plynlimon, recharge, soil water, streamflow generation
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Streaming potential near a rotating porous disk.
Prieve, Dennis C; Sides, Paul J
2014-09-23
Theory and experimental results for the streaming potential measured in the vicinity of a rotating porous disk-shaped sample are described. Rotation of the sample on its axis draws liquid into its face and casts it from the periphery. Advection within the sample engenders streaming current and streaming potential that are proportional to the zeta potential and the disk's major dimensions. When Darcy's law applies, the streaming potential is proportional to the square of the rotation at low rate but becomes invariant with rotation at high rate. The streaming potential is invariant with the sample's permeability at low rate and is proportional to the inverse square of the permeability at high rate. These predictions were tested by determining the zeta potential and permeability of the loop side of Velcro, a sample otherwise difficult to characterize; reasonable values of -56 mV for zeta and 8.7 × 10(-9) m(2) for the permeability were obtained. This approach offers the ability to determine both the zeta potential and the permeability of materials having open structures. Compressing them into a porous plug is unnecessary. As part of the development of the theory, a convenient formula for a flow-weighted volume-averaged space-charge density of the porous medium, -εζ/k, was obtained, where ε is the permittivity, ζ is the zeta potential, and k is the Darcy permeability. The formula is correct when Smoluchowski's equation and Darcy's law are both valid.
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Directory of Open Access Journals (Sweden)
Sean Zeiger
2017-06-01
Full Text Available Accurate mean areal precipitation (MAP estimates are essential input forcings for hydrologic models. However, the selection of the most accurate method to estimate MAP can be daunting because there are numerous methods to choose from (e.g., proximate gauge, direct weighted average, surface-fitting, and remotely sensed methods. Multiple methods (n = 19 were used to estimate MAP with precipitation data from 11 distributed monitoring sites, and 4 remotely sensed data sets. Each method was validated against the hydrologic model simulated stream flow using the Soil and Water Assessment Tool (SWAT. SWAT was validated using a split-site method and the observed stream flow data from five nested-scale gauging sites in a mixed-land-use watershed of the central USA. Cross-validation results showed the error associated with surface-fitting and remotely sensed methods ranging from −4.5 to −5.1%, and −9.8 to −14.7%, respectively. Split-site validation results showed the percent bias (PBIAS values that ranged from −4.5 to −160%. Second order polynomial functions especially overestimated precipitation and subsequent stream flow simulations (PBIAS = −160 in the headwaters. The results indicated that using an inverse-distance weighted, linear polynomial interpolation or multiquadric function method to estimate MAP may improve SWAT model simulations. Collectively, the results highlight the importance of spatially distributed observed hydroclimate data for precipitation and subsequent steam flow estimations. The MAP methods demonstrated in the current work can be used to reduce hydrologic model uncertainty caused by watershed physiographic differences.
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Blaen, P.; Riml, J.; Khamis, K.; Krause, S.
2017-12-01
Within river catchments across the world, headwater streams represent important sites of nutrient transformation and uptake due to their high rates of microbial community processing and relative abundance in the landscape. However, separating the combined influence of in-stream transport and reaction processes from the overall catchment response can be difficult due to spatio-temporal variability in nutrient and organic matter inputs, flow regimes, and reaction rates. Recent developments in optical sensor technologies enable high-frequency, in situ nutrient measurements, and thus provide opportunities for greater insights into in-stream processes. Here, we use in-stream observations of hourly nitrate (NO3-N), dissolved organic carbon (DOC) and dissolved oxygen (DO) measurements from paired in situ sensors that bound a 1 km headwater stream reach in a mixed-use catchment in central England. We employ a spectral approach to decompose (1) variances in solute loading from the surrounding landscape, and (2) variances in reach-scale in-stream nutrient transport and reaction processes. In addition, we estimate continuous rates of reach-scale NO3-N and DOC assimilation/dissimilation, ecosystem respiration and primary production. Comparison of these results over a range of hydrological conditions (baseflow, variable storm events) and timescales (event-based, diel, seasonal) facilitates new insights into the physical and biogeochemical processes that drive in-stream nutrient dynamics in headwater streams.
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Flow shapes and higher harmonics in anisotropic transverse collective flow
Energy Technology Data Exchange (ETDEWEB)
Argintaru, Danut; Baban, Valerica [Constanta Maritime University, Faculty of Navigation and Naval Transport, Constanta (Romania); Besliu, Calin; Jipa, Alexandru; Grossu, Valeriu [University of Bucharest, Faculty of Physics, Bucharest (Romania); Esanu, Tiberiu; Cherciu, Madalin [Institute of Space Sciences Bucharest-Magurele, Bucharest (Romania)
2017-01-15
In this paper we show that by using a jet-finder algorithm (the Anti-k{sub T} one) on UrQMD/C simulated (Au+Au at 4, 10 and 15A GeV) collisions, we can identify different flow shape structures (single flow stream events, two flow streams events, three flow streams events, etc.) and order the bulk of events in equivalence flow shape classes. Considering these flow streams as the main directions of anisotropic transverse flow, we show that the Fourier coefficients v{sub n} of anisotropic flow are better emphasized when we analyze the different event flow shape classes than when the events are mixed. Also, if we do not know the real orientation of the reaction plane, we can use as reference the Flow stream 1 - the main particle flow stream - orientation (Ψ{sub Flowstream} {sub 1}) to highlight the initial shape of the participant nuclear matter in a central to peripheral collision, and the orientation of the participant plane of order n. (orig.)
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Maurice, L.; Rawlins, B. G.; Farr, G.; Bell, R.; Gooddy, D. C.
2017-11-01
The evasion of greenhouse gases (including CO2, CH4, and N2O) from streams and rivers to the atmosphere is an important process in global biogeochemical cycles, but our understanding of gas transfer in steep (>10%) streams, and under varying flows, is limited. We investigated gas transfer using combined tracer injections of SF6 and salt. We used a novel experimental design in which we compared four very steep (18.4-29.4%) and four moderately steep (3.7-7.6%) streams and conducted tests in each stream under low flow conditions and during a high-discharge event. Most dissolved gas evaded over short distances ( 100 and 200-400 m, respectively), so accurate estimates of evasion fluxes will require sampling of dissolved gases at these scales to account for local sources. We calculated CO2 gas transfer coefficients (KCO2) and found statistically significant differences between larger KCO2 values for steeper (mean 0.465 min-1) streams compared to those with shallower slopes (mean 0.109 min-1). Variations in flow had an even greater influence. KCO2 was substantially larger under high (mean 0.497 min-1) compared to low flow conditions (mean 0.077 min-1). We developed a statistical model to predict KCO2 using values of streambed slope × discharge which accounted for 94% of the variation. We show that two models using slope and velocity developed by Raymond et al. (2012) for streams and rivers with shallower slopes also provide reasonable estimates of our CO2 gas transfer velocities (kCO2; m d-1). We developed a robust field protocol which could be applied in future studies.
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International Nuclear Information System (INIS)
Fondeur, F; Michael Poirier, M; Samuel Fink, S
2007-01-01
Effluent streams from the Modular Caustic-Side Solvent Extraction Unit (MCU) will transfer to the tank farms and to the Defense Waste Processing Facility (DWPF). These streams will contain entrained solvent. A significant portion of the Strip Effluent (SE) pipeline (i.e., acid stream containing Isopar(reg s ign) L residues) length is within one inch of a sludge stream. Personnel envisioned the sludge stream temperature may reach 100 C during operation. The nearby SE stream may receive heat from the sludge stream and reach temperatures that may lead to flammability issues once the contents of the SE stream discharge into a larger reservoir. To this end, personnel used correlations from the literature to estimate the maximum temperature rise the SE stream may experience if the nearby sludge stream reaches boiling temperature. Several calculation methods were used to determine the temperature rise of the SE stream. One method considered a heat balance equation under steady state that employed correlation functions to estimate heat transfer rate. This method showed the maximum temperature of the acid stream (SE) may exceed 45 C when the nearby sludge stream is 80 C or higher. A second method used an effectiveness calculation used to predict the heat transfer rate in single pass heat exchanger. By envisioning the acid and sludge pipes as a parallel flow pipe-to-pipe heat exchanger, this method provides a conservative estimation of the maximum temperature rise. Assuming the contact area (i.e., the area over which the heat transfer occurs) is the whole pipe area, the results found by this method nearly matched the results found with the previous calculation method. It is recommended that the sludge stream be maintained below 80 C to minimize a flammable vapor hazard from occurring
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Application of the Hydroecological Integrity Assessment Process for Missouri Streams
Kennen, Jonathan G.; Henriksen, James A.; Heasley, John; Cade, Brian S.; Terrell, James W.
2009-01-01
Natural flow regime concepts and theories have established the justification for maintaining or restoring the range of natural hydrologic variability so that physiochemical processes, native biodiversity, and the evolutionary potential of aquatic and riparian assemblages can be sustained. A synthesis of recent research advances in hydroecology, coupled with stream classification using hydroecologically relevant indices, has produced the Hydroecological Integrity Assessment Process (HIP). HIP consists of (1) a regional classification of streams into hydrologic stream types based on flow data from long-term gaging-station records for relatively unmodified streams, (2) an identification of stream-type specific indices that address 11 subcomponents of the flow regime, (3) an ability to establish environmental flow standards, (4) an evaluation of hydrologic alteration, and (5) a capacity to conduct alternative analyses. The process starts with the identification of a hydrologic baseline (reference condition) for selected locations, uses flow data from a stream-gage network, and proceeds to classify streams into hydrologic stream types. Concurrently, the analysis identifies a set of non-redundant and ecologically relevant hydrologic indices for 11 subcomponents of flow for each stream type. Furthermore, regional hydrologic models for synthesizing flow conditions across a region and the development of flow-ecology response relations for each stream type can be added to further enhance the process. The application of HIP to Missouri streams identified five stream types ((1) intermittent, (2) perennial runoff-flashy, (3) perennial runoff-moderate baseflow, (4) perennial groundwater-stable, and (5) perennial groundwater-super stable). Two Missouri-specific computer software programs were developed: (1) a Missouri Hydrologic Assessment Tool (MOHAT) which is used to establish a hydrologic baseline, provide options for setting environmental flow standards, and compare past and
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Mittal, Sanjay; Kumar, Bhaskar
2003-02-01
Flow past a spinning circular cylinder placed in a uniform stream is investigated via two-dimensional computations. A stabilized finite element method is utilized to solve the incompressible Navier Stokes equations in the primitive variables formulation. The Reynolds number based on the cylinder diameter and free-stream speed of the flow is 200. The non-dimensional rotation rate, [alpha] (ratio of the surface speed and freestream speed), is varied between 0 and 5. The time integration of the flow equations is carried out for very large dimensionless time. Vortex shedding is observed for [alpha] cylinder. The results from the stability analysis for the rotating cylinder are in very good agreement with those from direct numerical simulations. For large rotation rates, very large lift coefficients can be obtained via the Magnus effect. However, the power requirement for rotating the cylinder increases rapidly with rotation rate.
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Conventional to Cloud: Detailed survey and comparative study of multimedia streaming rate Adaptation
Selvaraj Kesavan; Jayakumar J
2014-01-01
Infotainment and telecommunication industry is fast evolving towards personalized network connectivity and newer applications services ranging from music playback to ever changing telephony applications. Streaming is the key services which enables the users to view real time multimedia content on-the-go anywhere and everywhere. In streaming, quality of service is a major concern in the increasing network traffic and high user demand. Rate adaptation is crucial process to dynamically evaluate,...
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Hendrickson, P. J.; Gooseff, M. N.; Huryn, A. D.
2017-12-01
Aufeis (icings or naleds) are seasonal arctic and sub-arctic features that accumulate through repeated overflow and freeze events of river or spring discharge. Aufeis fields, defined as the substrate on which aufeis form and the overlaying ice, have been studied to mitigate impacts on engineering structures; however, ecological characteristics and functions of aufeis fields are poorly understood. The perennial springs that supply warm water to aufeis fields create unique fluvial habitats, and are thought to act as winter and summer oases for biota. To investigate ecosystem function, we measured whole-stream metabolism at the Kuparuk River Aufeis (North Slope, AK), a large ( 5 km2) field composed of cobble substrate and predominately subsurface flow dynamics. The single-station open channel diel oxygen method was utilized at several dissolved oxygen (DO) stations located within and downstream of the aufeis field. DO loggers were installed in August 2016, and data downloaded summer 2017. Daily ecosystem respiration (ER), gross primary production (GPP) and reaeration rates were modeled using BASE, a package freely available in the open-source software R. Preliminary results support net heterotrophy during a two-week period of DO measurements in the fall season when minimum ice extent is observed. GPP, ER, and net metabolism are greater at the upstream reach near the spring source (P/R = 0.53), and decrease as flow moves downstream. As flow exits the aufeis field, surface and subsurface flow are incorporated into the metabolism model, and indicate the stream system becomes dependent on autochthonous production (P/R = 0.91). Current work is directed towards spring and summer discharge and metabolic parameter estimation, which is associated with maximum ice extent and rapid melting of the aufeis feature.
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VEGETATION BEHAVIOR AND ITS HABITAT REGION AGAINST FLOOD FLOW IN URBAN STREAMS
Directory of Open Access Journals (Sweden)
IL-KI CHOI
2013-06-01
Full Text Available Hydraulic effects on the vegetation behavior and on its habitat region against flood flow in the urban streams were analysed in this paper. Vegetation behavior was classified into stable, recovered, damaged and swept away stages. Criteria between recovered and damaged status were determined by the bending angle of the aquatic plants. Aquatic plants whose bending angle is lower than 30~50 degree is recovered, but they were damaged and cannot be recovered when the bending angle is higher than 30~50 degree. Phragmites japonica was inhabited in the hydraulic condition of high Froude number which shows that it was inhabited in the upstream reaches. Phragmites communis was inhabited in the relatively low Froude number compared with Phragmites japonica. This shows that it was inhabited in the downstream reaches. Persicaria blumei was found in the relatively wide range of flow velocity and flow depth, which shows that it was inhabited in the middle and downstream reaches. Criterion on the vegetation behavior of Persicaria thunbergii was not clear, which implies that it may be affected by the flow turbulence rather than flow velocity and flow depth.
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Semiempirical method of determining flow coefficients for pitot rake mass flow rate measurements
Trefny, C. J.
1985-01-01
Flow coefficients applicable to area-weighted pitot rake mass flow rate measurements are presented for fully developed, turbulent flow in an annulus. A turbulent velocity profile is generated semiempirically for a given annulus hub-to-tip radius ratio and integrated numerically to determine the ideal mass flow rate. The calculated velocities at each probe location are then summed, and the flow rate as indicated by the rake is obtained. The flow coefficient to be used with the particular rake geometry is subsequently obtained by dividing the ideal flow rate by the rake-indicated flow rate. Flow coefficients ranged from 0.903 for one probe placed at a radius dividing two equal areas to 0.984 for a 10-probe area-weighted rake. Flow coefficients were not a strong function of annulus hub-to-tip radius ratio for rakes with three or more probes. The semiempirical method used to generate the turbulent velocity profiles is described in detail.
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ENVIRONMENTAL FACTORS INFLUENCING THE VEGETATION IN MIDDLE-SIZED STREAMS IN LATVIA
Directory of Open Access Journals (Sweden)
L. GRINBERGA
2011-04-01
Full Text Available In this study the species diversity and distribution of macrophytes in 131 surveyed sites of middle-sized streams of Latvia were investigated. The aim of the study was to determine the composition of macrophyte vegetation in Latvian streams in relation to the environmental factors (stream width, water depth, substrate type, shading and flow velocity. On the basis of these factors, five major groups of streams were distinguished representing mutually different typical macrophyte communities – (1 fast flowing streams on gravelly and stony substrate, (2 slow flowing streams on gravelly and stony substrate, (3 fast flowing streams on sandy substrate, (4 slow flowing streams on sandy substrate, and (5 streams with soft, silty substrate. Totally, 47 macrophyte taxa were found in the streams. The most common macrophyte species were Nuphar lutea found in 65% of all sites, followed by Sparganium emersum (64%, S. erectum s.l. (48%, Phalaris arundinacea (50%, Alisma plantago-aquatica (54% and Lemna minor (41%. The highest species richness (22 was found in slow flowing streams with gravelly substrate. Species-poor macrophyte communities were characteristic for fast flowing streams on sandy substrate.
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ENVIRONMENTAL FACTORS INFLUENCING THE VEGETATION IN MIDDLE-SIZED STREAMS IN LATVIA
Directory of Open Access Journals (Sweden)
L. GRINBERGA
2011-01-01
Full Text Available In this study the species diversity and distribution of macrophytes in 131 surveyed sites of middle-sized streams of Latvia were investigated. The aim of the study was to determine the composition of macrophyte vegetation in Latvian streams in relation to the environmental factors (stream width, water depth, substrate type, shading and flow velocity. On the basis of these factors, five major groups of streams were distinguished representing mutually different typical macrophyte communities – (1 fast flowing streams on gravelly and stony substrate, (2 slow flowing streams on gravelly and stony substrate, (3 fast flowing streams on sandy substrate, (4 slow flowing streams on sandy substrate, and (5 streams with soft, silty substrate. Totally, 47 macrophyte taxa were found in the streams. The most common macrophyte species were Nuphar lutea found in 65% of all sites, followed by Sparganium emersum (64%, S. erectum s.l. (48%, Phalaris arundinacea (50%, Alisma plantago-aquatica (54% and Lemna minor (41%. The highest species richness (22 was found in slow flowing streams with gravelly substrate. Species-poor macrophyte communities were characteristic for fast flowing streams on sandy substrate.
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FINE MAGNETIC STRUCTURE AND ORIGIN OF COUNTER-STREAMING MASS FLOWS IN A QUIESCENT SOLAR PROMINENCE
International Nuclear Information System (INIS)
Shen, Yuandeng; Liu, Yu; Xu, Zhi; Liu, Zhong; Liu, Ying D.; Chen, P. F.; Su, Jiangtao
2015-01-01
We present high-resolution observations of a quiescent solar prominence that consists of a vertical and a horizontal foot encircled by an overlying spine and has ubiquitous counter-streaming mass flows. While the horizontal foot and the spine were connected to the solar surface, the vertical foot was suspended above the solar surface and was supported by a semicircular bubble structure. The bubble first collapsed, then reformed at a similar height, and finally started to oscillate for a long time. We find that the collapse and oscillation of the bubble boundary were tightly associated with a flare-like feature located at the bottom of the bubble. Based on the observational results, we propose that the prominence should be composed of an overlying horizontal spine encircling a low-lying horizontal and vertical foot, in which the horizontal foot consists of shorter field lines running partially along the spine and has ends connected to the solar surface, while the vertical foot consists of piling-up dips due to the sagging of the spine fields and is supported by a bipolar magnetic system formed by parasitic polarities (i.e., the bubble). The upflows in the vertical foot were possibly caused by the magnetic reconnection at the separator between the bubble and the overlying dips, which intruded into the persistent downflow field and formed the picture of counter-streaming mass flows. In addition, the counter-streaming flows in the horizontal foot were possibly caused by the imbalanced pressure at the both ends
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InSTREAM: the individual-based stream trout research and environmental assessment model
Steven F. Railsback; Bret C. Harvey; Stephen K. Jackson; Roland H. Lamberson
2009-01-01
This report documents Version 4.2 of InSTREAM, including its formulation, software, and application to research and management problems. InSTREAM is a simulation model designed to understand how stream and river salmonid populations respond to habitat alteration, including altered flow, temperature, and turbidity regimes and changes in channel morphology. The model...
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DYNAMICAL EVOLUTION OF AGN HOST GALAXIES-GAS IN/OUT-FLOW RATES IN SEVEN NUGA GALAXIES
International Nuclear Information System (INIS)
Haan, Sebastian; Schinnerer, Eva; Rix, Hans-Walter; Emsellem, Eric; GarcIa-Burillo, Santiago; Combes, Francoise; Mundell, Carole G.
2009-01-01
To examine the role of the host galaxy structure in fueling nuclear activity, we estimated gas flow rates from several kpc down to the inner few 10 pc for seven nearby spiral galaxies, selected from the NUclei of GAlaxies sample. We calculated gravitational torques from near-infrared images and determined gas in/out-flow rates as a function of radius and location within the galactic disks, based on high angular resolution interferometric observations of molecular (CO using Plateau de Bure interferometer) and atomic (H I using the Very Large Array) gas. The results are compared with kinematic evidence for radial gas flows and the dynamical state of the galaxies (via resonances) derived from several different methods. We show that gravitational torques are very efficient at transporting gas from the outer disk all the way into the galaxies centers at ∼100 pc; previously assumed dynamical barriers to gas transport, such as the corotation resonance of stellar bars, seem to be overcome by gravitational torque induced gas flows from other nonaxisymmetric structures. The resulting rates of gas mass inflow range from 0.01 to 50 M sun yr -1 and are larger for the galaxy center than for the outer disk. Our gas flow maps show the action of nested bars within larger bars for three galaxies. Noncircular streaming motions found in the kinematic maps are larger in the center than in the outer disk and appear to correlate only loosely with the in/out-flow rates as a function of radius. We demonstrate that spiral gas disks are very dynamic systems that undergo strong radial evolution on timescales of a few rotation periods (e.g., 5 x 10 8 yrs at a radius of 5 kpc), due to the effectiveness of gravitational torques in redistributing the cold galactic gas.
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Drummond, J. D.; Bernal, S.; Meredith, W.; Schumer, R.; Martí Roca, E.
2017-12-01
Waste water treatment plant (WWTP) effluents constitute point source inputs of fine sediment, nutrients, carbon, and microbes to stream ecosystems. A range of responses to these inputs may be observed in recipient streams, including increases in respiration rates, which augment CO2 emissions to the atmosphere. Yet, little is known about which fractions of organic carbon (OC) contribute the most to stream metabolism in WWTP-influenced streams. Fine particulate OC (POC) represents ca. 40% of the total mass of OC in river networks, and is generally more labile than dissolved OC. Therefore, POC inputs from WWTPs could contribute disproportionately to higher rates of heterotrophic metabolism by stream microbial communities. The aim of this study was to investigate the influence of POC inputs from a WWTP effluent on the metabolism of a Mediterranean stream over a wide range of hydrologic conditions. We hypothesized that POC inputs would have a positive effect on respiration rates, and that the response to POC availability would be larger during low flows when the dilution capacity of the recipient stream is negligible. We focused on the easily resuspended fine sediment near the sediment-water interface (top 3 cm), as this region is a known hot spot for biogeochemical processes. For one year, samples of resuspended sediment were collected bimonthly at 7 sites from 0 to 800 m downstream of the WWTP point source. We measured total POC, organic matter (OM) content (%), and the associated metabolic activity of the resuspended sediment using the resazurin-resorufin smart tracer system as a proxy for aerobic ecosystem respiration. Resuspended sediment showed no difference in total POC over the year, while the OM content increased with decreasing discharge. This result together with the decreasing trend of total POC observed downstream of the point source during autumn after a long dry period, suggests that the WWTP effluent was the main contributor to stream POC. Furthermore
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Stressig, R; Fimmers, R; Schaible, T; Degenhardt, J; Axt-Fliedner, R; Gembruch, U; Kohl, T
2013-12-01
Preferential streaming of the ductus venosus (DV) toward the right atrium has been observed in fetuses with left diaphragmatic hernia (LDH). The purpose of this retrospective study was to compare survival rates to discharge between a group with preferential streaming of the DV toward the right heart and a group in which this abnormal flow pattern was not present. We retrospectively searched our patient records for fetuses with LDH in whom liver position, DV streaming and postnatal outcome information was available. 55 cases were found and divided into two groups: Group I fetuses exhibited abnormal DV streaming toward the right side of the heart; group II fetuses did not. Various prognostic and outcome parameters were compared. 62 % of group I fetuses and 88 % of group II fetuses survived to discharge (p = 0.032). Fetoscopic tracheal balloon occlusion (FETO) was performed in 66 % of group I fetuses and 23 % of group II fetuses (p = 0.003). Postnatal ECMO therapy was performed in 55 % of group I fetuses and 23 % of group II infants (p = 0.025). Moderate to severe chronic lung disease in survivors was observed in 56 % of the survivors of group I and 9 % of the survivors of group II (p = 0.002). Preferential streaming of the DV toward the right heart in human fetuses with left-sided diaphragmatic hernia was associated with a poorer postnatal outcome despite a higher rate of invasive pre- and postnatal procedures compared to fetuses without this flow abnormality. Specifically, abnormal DV streaming was found to be an independent predictor for FETO. © Georg Thieme Verlag KG Stuttgart · New York.
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Streaming Pool: reuse, combine and create reactive streams with pleasure
CERN. Geneva
2017-01-01
When connecting together heterogeneous and complex systems, it is not easy to exchange data between components. Streams of data are successfully used in industry in order to overcome this problem, especially in the case of "live" data. Streams are a specialization of the Observer design pattern and they provide asynchronous and non-blocking data flow. The ongoing effort of the ReactiveX initiative is one example that demonstrates how demanding this technology is even for big companies. Bridging the discrepancies of different technologies with common interfaces is already done by the Reactive Streams initiative and, in the JVM world, via reactive-streams-jvm interfaces. Streaming Pool is a framework for providing and discovering reactive streams. Through the mechanism of dependency injection provided by the Spring Framework, Streaming Pool provides a so called Discovery Service. This object can discover and chain streams of data that are technologically agnostic, through the use of Stream IDs. The stream to ...
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Estimated Perennial Streams of Idaho and Related Geospatial Datasets
Rea, Alan; Skinner, Kenneth D.
2009-01-01
The perennial or intermittent status of a stream has bearing on many regulatory requirements. Because of changing technologies over time, cartographic representation of perennial/intermittent status of streams on U.S. Geological Survey (USGS) topographic maps is not always accurate and (or) consistent from one map sheet to another. Idaho Administrative Code defines an intermittent stream as one having a 7-day, 2-year low flow (7Q2) less than 0.1 cubic feet per second. To establish consistency with the Idaho Administrative Code, the USGS developed regional regression equations for Idaho streams for several low-flow statistics, including 7Q2. Using these regression equations, the 7Q2 streamflow may be estimated for naturally flowing streams anywhere in Idaho to help determine perennial/intermittent status of streams. Using these equations in conjunction with a Geographic Information System (GIS) technique known as weighted flow accumulation allows for an automated and continuous estimation of 7Q2 streamflow at all points along a stream, which in turn can be used to determine if a stream is intermittent or perennial according to the Idaho Administrative Code operational definition. The selected regression equations were applied to create continuous grids of 7Q2 estimates for the eight low-flow regression regions of Idaho. By applying the 0.1 ft3/s criterion, the perennial streams have been estimated in each low-flow region. Uncertainty in the estimates is shown by identifying a 'transitional' zone, corresponding to flow estimates of 0.1 ft3/s plus and minus one standard error. Considerable additional uncertainty exists in the model of perennial streams presented in this report. The regression models provide overall estimates based on general trends within each regression region. These models do not include local factors such as a large spring or a losing reach that may greatly affect flows at any given point. Site-specific flow data, assuming a sufficient period of
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Cytoplasmic Streaming in the Drosophila Oocyte.
Quinlan, Margot E
2016-10-06
Objects are commonly moved within the cell by either passive diffusion or active directed transport. A third possibility is advection, in which objects within the cytoplasm are moved with the flow of the cytoplasm. Bulk movement of the cytoplasm, or streaming, as required for advection, is more common in large cells than in small cells. For example, streaming is observed in elongated plant cells and the oocytes of several species. In the Drosophila oocyte, two stages of streaming are observed: relatively slow streaming during mid-oogenesis and streaming that is approximately ten times faster during late oogenesis. These flows are implicated in two processes: polarity establishment and mixing. In this review, I discuss the underlying mechanism of streaming, how slow and fast streaming are differentiated, and what we know about the physiological roles of the two types of streaming.
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Predicting the natural flow regime: Models for assessing hydrological alteration in streams
Carlisle, D.M.; Falcone, J.; Wolock, D.M.; Meador, M.R.; Norris, R.H.
2009-01-01
Understanding the extent to which natural streamflow characteristics have been altered is an important consideration for ecological assessments of streams. Assessing hydrologic condition requires that we quantify the attributes of the flow regime that would be expected in the absence of anthropogenic modifications. The objective of this study was to evaluate whether selected streamflow characteristics could be predicted at regional and national scales using geospatial data. Long-term, gaged river basins distributed throughout the contiguous US that had streamflow characteristics representing least disturbed or near pristine conditions were identified. Thirteen metrics of the magnitude, frequency, duration, timing and rate of change of streamflow were calculated using a 20-50 year period of record for each site. We used random forests (RF), a robust statistical modelling approach, to develop models that predicted the value for each streamflow metric using natural watershed characteristics. We compared the performance (i.e. bias and precision) of national- and regional-scale predictive models to that of models based on landscape classifications, including major river basins, ecoregions and hydrologic landscape regions (HLR). For all hydrologic metrics, landscape stratification models produced estimates that were less biased and more precise than a null model that accounted for no natural variability. Predictive models at the national and regional scale performed equally well, and substantially improved predictions of all hydrologic metrics relative to landscape stratification models. Prediction error rates ranged from 15 to 40%, but were 25% for most metrics. We selected three gaged, non-reference sites to illustrate how predictive models could be used to assess hydrologic condition. These examples show how the models accurately estimate predisturbance conditions and are sensitive to changes in streamflow variability associated with long-term land-use change. We also
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Jamieson, E. C.; Rennie, C. D.; Townsend, R. D.
2009-05-01
Stream barbs (a type of submerged groyne or spur dike) are low-profile linear rock structures that prevent the erosion of stream banks by redirecting high velocity flow away from the bank. Stream barbs are becoming a popular method for stream bank protection as they can be built at a relatively low cost and provide added ecological benefit. The design and construction of stream barbs in Sawmill Creek, a small urban stream in the city of Ottawa, Canada, will serve as a demonstration project for the use of barbs as a bank stabilization technique that will contribute to the rehabilitation of urban creeks while reducing erosion threats to property and infrastructure. As well as providing bank protection, these structures promote vegetated stream banks, create resting pools and scour holes for fish habitat, and increase bio-diversity for aquatic species. Despite these benefits, stream barbs are not a common means of stream bank protection in Canada, due largely to a lack of suitable design guidelines. The overall goal of stream habitat restoration in incising channel systems should be to accelerate natural processes of channel equilibrium recovery, riparian re-vegetation, and stream-floodplain interaction. Incorporating stream barbs, instead of traditional bank protection measures, attempts to achieve these goals. A three-dimensional numerical model: 'Simulation in Intakes with Multiblock option' (SSIIM), was used to model the effects of placing a series of stream barbs along an unstable section of Sawmill Creek. The average bankfull depth, width, and discharge of the creek are 1.2 m, 7.5 m, and 9 m3/s respectively. The model was used to assess various design alternatives for a series of seven stream barbs at two consecutive channel bends requiring stabilization measures along their outer banks. Design criteria were principally based on the reduction of velocity, shear stress and subsequent erosion at the outside bank of each bend, and on the relocation of a new thalweg
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Investigation of the mixture flow rates of oil-water two-phase flow using the turbine flow meter
International Nuclear Information System (INIS)
Li Donghui; Feng Feifei; Wu Yingxiang; Xu Jingyu
2009-01-01
In this work, the mixture flow rate of oil-water flows was studied using the turbine flow-meter. The research emphasis focuses on the effect of oil viscosity and input fluids flow rates on the precision of the meter. Experiments were conducted to measure the in-situ mixture flow rate in a horizontal pipe with 0.05m diameter using seven different viscosities of white oil and tap water as liquid phases. Results showed that both oil viscosity and input oil fraction exert a remarkable effect on measured results, especially when the viscosity of oil phase remained in the area of high value. In addition, for metering mixture flow rate using turbine flow-meter, the results are not sensitive to two-phase flow pattern according to the experimental data.
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Jet stream wind power as a renewable energy resource: little power, big impacts
Directory of Open Access Journals (Sweden)
L. M. Miller
2011-11-01
Full Text Available Jet streams are regions of sustained high wind speeds in the upper atmosphere and are seen by some as a substantial renewable energy resource. However, jet streams are nearly geostrophic flow, that is, they result from the balance between the pressure gradient and Coriolis force in the near absence of friction. Therefore, jet stream motion is associated with very small generation rates of kinetic energy to maintain the high wind velocities, and it is this generation rate that will ultimately limit the potential use of jet streams as a renewable energy resource. Here we estimate the maximum limit of jet stream wind power by considering extraction of kinetic energy as a term in the free energy balance of kinetic energy that describes the generation, depletion, and extraction of kinetic energy. We use this balance as the basis to quantify the maximum limit of how much kinetic energy can be extracted sustainably from the jet streams of the global atmosphere as well as the potential climatic impacts of its use. We first use a simple thought experiment of geostrophic flow to demonstrate why the high wind velocities of the jet streams are not associated with a high potential for renewable energy generation. We then use an atmospheric general circulation model to estimate that the maximum sustainable extraction from jet streams of the global atmosphere is about 7.5 TW. This estimate is about 200-times less than previous estimates and is due to the fact that the common expression for instantaneous wind power 12 ρv3 merely characterizes the transport of kinetic energy by the flow, but not the generation rate of kinetic energy. We also find that when maximum wind power is extracted from the jet streams, it results in significant
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Patterned basal seismicity shows sub-ice stream bedforms
Barcheck, C. G.; Tulaczyk, S. M.; Schwartz, S. Y.
2017-12-01
Patterns in seismicity emanating from the bottom of fast-moving ice streams and glaciers may indicate localized patches of higher basal resistance— sometimes called 'sticky spots', or otherwise varying basal properties. These seismogenic basal areas resist an unknown portion of the total driving stress of the Whillans Ice Plain (WIP), in West Antarctica, but may play an important role in the WIP stick-slip cycle and ice stream slowdown. To better understand the mechanism and importance of basal seismicity beneath the WIP, we analyze seismic data collected by a small aperture (micro-earthquakes in Dec 2014, and we compare the resulting map of seismicity to ice bottom depth measured by airborne radar. The number of basal earthquakes per area within the network is spatially heterogeneous, but a pattern of two 400m wide streaks of high seismicity rates is evident, with >50-500 earthquakes detected per 50x50m grid cell in 2 weeks. These seismically active streaks are elongated approximately in the ice flow direction with a spacing of 750m. Independent airborne radar measurements of ice bottom depth from Jan 2013 show a low-amplitude ( 5m) undulation in the basal topography superposed on a regional gradient in ice bottom depth. The flow-perpendicular wavelength of these low-amplitude undulations is comparable to the spacing of the high seismicity bands, and the streaks of high seismicity intersect local lows in the undulating basal topography. We interpret these seismic and radar observations as showing seismically active sub-ice stream bedforms that are low amplitude and elongated in the direction of ice flow, comparable to the morphology of mega scale glacial lineations (MSGLs), with high basal seismicity rates observed in the MSGL troughs. These results have implications for understanding the formation mechanism of MSGLS and well as understanding the interplay between basal topographic roughness, spatially varying basal till and hydrologic properties, basal
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Ultrasound-driven Viscous Streaming, Modelled via Momentum Injection
Directory of Open Access Journals (Sweden)
James PACKER
2008-12-01
Full Text Available Microfluidic devices can use steady streaming caused by the ultrasonic oscillation of one or many gas bubbles in a liquid to drive small scale flow. Such streaming flows are difficult to evaluate, as analytic solutions are not available for any but the simplest cases, and direct computational fluid dynamics models are unsatisfactory due to the large difference in flow velocity between the steady streaming and the leading order oscillatory motion. We develop a numerical technique which uses a two-stage multiscale computational fluid dynamics approach to find the streaming flow as a steady problem, and validate this model against experimental results.
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Wheeler, Kit; Wengerd, Seth J.; Walsh, Stephen J.; Martin, Zachary P.; Jelks, Howard L.; Freeman, Mary C.
2018-01-01
Many species have distributions that span distinctly different physiographic regions, and effective conservation of such taxa will require a full accounting of all factors that potentially influence populations. Ecologists recognize effects of physiographic differences in topography, geology and climate on local habitat configurations, and thus the relevance of landscape heterogeneity to species distributions and abundances. However, research is lacking that examines how physiography affects the processes underlying metapopulation dynamics. We used data describing occupancy dynamics of stream fishes to evaluate evidence that physiography influences rates at which individual taxa persist in or colonize stream reaches under different flow conditions. Using periodic survey data from a stream fish assemblage in a large river basin that encompasses multiple physiographic regions, we fit multi-species dynamic occupancy models. Our modeling results suggested that stream fish colonization but not persistence was strongly governed by physiography, with estimated colonization rates considerably higher in Coastal Plain streams than in Piedmont and Blue Ridge systems. Like colonization, persistence was positively related to an index of stream flow magnitude, but the relationship between flow and persistence did not depend on physiography. Understanding the relative importance of colonization and persistence, and how one or both processes may change across the landscape, is critical information for the conservation of broadly distributed taxa, and conservation strategies explicitly accounting for spatial variation in these processes are likely to be more successful for such taxa.
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Heat transfer by liquids in suspension in a turbulent gas stream (1960)
International Nuclear Information System (INIS)
Grison, E.; Commissariat a l'Energie Atomique, Saclay
1960-01-01
The introduction of a small volume of liquid into a turbulent gas stream used as cooling agent improves considerably the heat transfer coefficient of the gas. When the turbulent regime is established, one observes in a cylindrical tube two types of flow whether the liquid wets or does not wet the wall. In the first case, one gets on the wall an annular liquid film and droplets in suspension are in the gas stream. In the second case, a fog of droplets is formed without any liquid film on the wall. Experiments were performed with the following mixtures: water-hydrogen, water-nitrogen, ethanol-nitrogen (wetting liquids) introduced into a stainless steel tube of 4 mm ID, electrically heated on 320 mm of length. We varied the gas flow rate (Reynolds until 50000), the rate of the liquid flow rate to gas flow rate (until 15), the pressure (until 10 kg/cm 2 ), the temperature (until the boiling point) and the heat flux (until 250 W/cm 2 ). Two types of burnout were observed. A formula of correlation of the burnout heat flux is given. Making use of the analogy between mass transfer and heat transfer, a dimensionless formula of correlation of the local heat transfer coefficients is established. (author) [fr
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Steven M. Wondzell
2006-01-01
Stream-tracer injections were used to examine the effect of channel morphology and changing stream discharge on hyporheic exchange flows. Direct observations were made from well networks to follow tracer movement through the hyporheic zone. The reach-integrated influence of hyporheic exchange was evaluated using the transient storage model (TSM) OTIS-P. Transient...
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Hierarchical programming language for modal multi-rate real-time stream processing applications
Geuns, S.J.; Hausmans, J.P.H.M.; Bekooij, Marco Jan Gerrit
2014-01-01
Modal multi-rate stream processing applications with real-time constraints which are executed on multi-core embedded systems often cannot be conveniently specified using current programming languages. An important issue is that sequential programming languages do not allow for convenient programming
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Fitzpatrick, Faith A.; Peppler, Marie C.; Saad, David A.; Pratt, Dennis M.; Lenz, Bernard N.
2015-01-01
In 2002–03, the U.S. Geological Survey conducted a study of the geomorphic, flood, and groundwater-flow characteristics of five Bayfield Peninsula streams, Wisconsin (Cranberry River, Bark River, Raspberry River, Sioux River, and Whittlesey Creek) to determine the physical limitations for brook-trout habitat. The goals of the study were threefold: (1) to describe geomorphic characteristics and processes, (2) to determine how land-cover characteristics affect flood peaks, and (3) to determine how regional groundwater flow patterns affect base flow.
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International Nuclear Information System (INIS)
Kotoh, Kenji; Miura, Katsuya; Kashio, Yousuke; Nishikawa, Masabumi
1991-01-01
A method was proposed previously for collection and measurement of tritiated moisture in gas stream using P 2 O 5 -desiccant. Influences of the gas humidity, the gas flow rate and the distance between gas nozzle and P 2 O 5 -desiccant layer surface on the moisture collection efficiency have been examined through experiments, and the isotope effect on the collection has been investigated. The collection efficiency is the ratio of collected to supplied moisture, and the moisture supplying rate is in proportion to the humidity and flow rate of feed gas. The experiments show that; the collection efficiency dose not depend on the gas humidity, but is affected by the gas flow rate and by the nozzle-layer distance. The effects of the flow rate and the nozzle position are related to the mass transfer distance from the bulk of gas stream to the desiccant layer surface in the collection cell. The moisture collecting rate is promoted by the approach of the gas stream to the layer surface. An expression of effective separation factor has been derived to explain the isotope effect on the moisture collection. Experimental data distribution of the separation factor have been reasonably simulated by the analysis. (author)
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Cross-Layer Design of Source Rate Control and Congestion Control for Wireless Video Streaming
Directory of Open Access Journals (Sweden)
Peng Zhu
2007-01-01
Full Text Available Cross-layer design has been used in streaming video over the wireless channels to optimize the overall system performance. In this paper, we extend our previous work on joint design of source rate control and congestion control for video streaming over the wired channel, and propose a cross-layer design approach for wireless video streaming. First, we extend the QoS-aware congestion control mechanism (TFRCC proposed in our previous work to the wireless scenario, and provide a detailed discussion about how to enhance the overall performance in terms of rate smoothness and responsiveness of the transport protocol. Then, we extend our previous joint design work to the wireless scenario, and a thorough performance evaluation is conducted to investigate its performance. Simulation results show that by cross-layer design of source rate control at application layer and congestion control at transport layer, and by taking advantage of the MAC layer information, our approach can avoid the throughput degradation caused by wireless link error, and better support the QoS requirements of the application. Thus, the playback quality is significantly improved, while good performance of the transport protocol is still preserved.
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Cellular Subcompartments through Cytoplasmic Streaming.
Pieuchot, Laurent; Lai, Julian; Loh, Rachel Ann; Leong, Fong Yew; Chiam, Keng-Hwee; Stajich, Jason; Jedd, Gregory
2015-08-24
Cytoplasmic streaming occurs in diverse cell types, where it generally serves a transport function. Here, we examine streaming in multicellular fungal hyphae and identify an additional function wherein regimented streaming forms distinct cytoplasmic subcompartments. In the hypha, cytoplasm flows directionally from cell to cell through septal pores. Using live-cell imaging and computer simulations, we identify a flow pattern that produces vortices (eddies) on the upstream side of the septum. Nuclei can be immobilized in these microfluidic eddies, where they form multinucleate aggregates and accumulate foci of the HDA-2 histone deacetylase-associated factor, SPA-19. Pores experiencing flow degenerate in the absence of SPA-19, suggesting that eddy-trapped nuclei function to reinforce the septum. Together, our data show that eddies comprise a subcellular niche favoring nuclear differentiation and that subcompartments can be self-organized as a consequence of regimented cytoplasmic streaming. Copyright © 2015 Elsevier Inc. All rights reserved.
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2011-04-07
... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER11-3188-000] Stream Energy Maryland, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket Section 204 Authorization This is a supplemental notice in the above-referenced proceeding Stream Energy...
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2011-11-08
... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [ Docket No. ER12-224-000] Stream Energy Columbia, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket Section 204 Authorization This is a supplemental notice in the above-referenced proceeding of Stream...
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Liquid metal coolant flow rate regulation
International Nuclear Information System (INIS)
Vitkovskij, I.V.; Glukhikh, V.A.; Kirillov, I.R.; Smirnov, A.M.
1981-01-01
Some aspects of fast reactor and experimental bench operation related to liquid metal flow rate regulation are considered. Requirements to the devices for the flow rate regulation are formulated. A new type of these devices namely magnetohydrodynamic (MHD) throttles is described. Structural peculiarities of MHD throttles of different types are described as well. It is noted that the MHD throttles with a screw channel have the best energy mass indices. On the basis of the comparison of the MHD throttles with mechanical valves it is concluded that the MHD throttles described are useful for regulating the flow rates of any working media. Smoothness and accuracy of the flow rate regulation by the throttles are determined by the electric control circuit and may be practically anyone. The total coefficient of hydraulic losses in the throttle channel in the absence of a magnetic field is ten and more times lesser than in completely open mechanical valve. Electromagnetic time constant of the MHD throttles does not exceed several tenths of a second [ru
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Mason, M. L.; Putnam, L. E.
1979-01-01
The flow field behind a circular arc nozzle with exhaust jet was studied at subsonic free stream Mach numbers. A conical probe was used to measure the pitot pressure in the jet and free stream regions. Pressure data were recorded for two nozzle configurations at nozzle pressure ratios of 2.0, 2.9, and 5.0. At each set of test conditions, the probe was traversed from the jet center line into the free stream region at seven data acquisition stations. The survey began at the nozzle exit and extended downstream at intervals. The pitot pressure data may be applied to the evaluation of computational flow field models, as illustrated by a comparison of the flow field data with results of inviscid jet plume theory.
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McKnight, Diane M.; Tate, C.M.; Andrews, E.D.; Niyogi, D.K.; Cozzetto, K.; Welch, K.; Lyons, W.B.; Capone, D.G.
2007-01-01
The McMurdo Dry Valleys of Antarctica contain many glacial meltwater streams that flow for 6 to 12??weeks during the austral summer and link the glaciers to the lakes on the valley floors. Dry valley streams gain solutes longitudinally through weathering reactions and microbial processes occurring in the hyporheic zone. Some streams have thriving cyanobacterial mats. In streams with regular summer flow, the mats are freeze-dried through the winter and begin photosynthesizing with the onset of flow. To evaluate the longer term persistence of cyanobacterial mats, we diverted flow to an abandoned channel, which had not received substantial flow for approximately two decades. Monitoring of specific conductance showed that for the first 3??years after the diversion, the solute concentrations were greater in the reactivated channel than in most other dry valley streams. We observed that cyanobacterial mats became abundant in the reactivated channel within a week, indicating that the mats had been preserved in a cryptobiotic state in the channel. Over the next several years, these mats had high rates of productivity and nitrogen fixation compared to mats from other streams. Experiments in which mats from the reactivated channel and another stream were incubated in water from both of the streams indicated that the greater solute concentrations in the reactivated channel stimulated net primary productivity of mats from both streams. These stream-scale experimental results indicate that the cryptobiotic preservation of cyanobacterial mats in abandoned channels in the dry valleys allows for rapid response of these stream ecosystems to climatic and geomorphological change, similar to other arid zone stream ecosystems. ?? 2006 Elsevier B.V. All rights reserved.
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Williams, P Stephen
2016-05-01
Asymmetrical flow field-flow fractionation (As-FlFFF) has become the most commonly used of the field-flow fractionation techniques. However, because of the interdependence of the channel flow and the cross flow through the accumulation wall, it is the most difficult of the techniques to optimize, particularly for programmed cross flow operation. For the analysis of polydisperse samples, the optimization should ideally be guided by the predicted fractionating power. Many experimentalists, however, neglect fractionating power and rely on light scattering detection simply to confirm apparent selectivity across the breadth of the eluted peak. The size information returned by the light scattering software is assumed to dispense with any reliance on theory to predict retention, and any departure of theoretical predictions from experimental observations is therefore considered of no importance. Separation depends on efficiency as well as selectivity, however, and efficiency can be a strong function of retention. The fractionation of a polydisperse sample by field-flow fractionation never provides a perfectly separated series of monodisperse fractions at the channel outlet. The outlet stream has some residual polydispersity, and it will be shown in this manuscript that the residual polydispersity is inversely related to the fractionating power. Due to the strong dependence of light scattering intensity and its angular distribution on the size of the scattering species, the outlet polydispersity must be minimized if reliable size data are to be obtained from the light scattering detector signal. It is shown that light scattering detection should be used with careful control of fractionating power to obtain optimized analysis of polydisperse samples. Part I is concerned with isocratic operation of As-FlFFF, and part II with programmed operation.
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Numerical Model of Streaming DEP for Stem Cell Sorting
Directory of Open Access Journals (Sweden)
Rucha Natu
2016-11-01
Full Text Available Neural stem cells are of special interest due to their potential in neurogenesis to treat spinal cord injuries and other nervous disorders. Flow cytometry, a common technique used for cell sorting, is limited due to the lack of antigens and labels that are specific enough to stem cells of interest. Dielectrophoresis (DEP is a label-free separation technique that has been recently demonstrated for the enrichment of neural stem/progenitor cells. Here we use numerical simulation to investigate the use of streaming DEP for the continuous sorting of neural stem/progenitor cells. Streaming DEP refers to the focusing of cells into streams by equilibrating the dielectrophoresis and drag forces acting on them. The width of the stream should be maximized to increase throughput while the separation between streams must be widened to increase efficiency during retrieval. The aim is to understand how device geometry and experimental variables affect the throughput and efficiency of continuous sorting of SC27 stem cells, a neurogenic progenitor, from SC23 cells, an astrogenic progenitor. We define efficiency as the ratio between the number of SC27 cells over total number of cells retrieved in the streams, and throughput as the number of SC27 cells retrieved in the streams compared to their total number introduced to the device. The use of cylindrical electrodes as tall as the channel yields streams featuring >98% of SC27 cells and width up to 80 µm when using a flow rate of 10 µL/min and sample cell concentration up to 105 cells/mL.
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Reaeration of oxygen in shallow, macrophyte rich streams. 1
International Nuclear Information System (INIS)
Thyssen, N.; Erlandsen, M.; Jeppesen, E.
1987-01-01
The rate coefficient K 2 for the exchange of oxygen between flowing water and the atmosphere (reaeration) has been studied in six Danish streams covering a relatively wide range of hydraulic conditions, pollutional loading, and macrophyte abundance. 103 K 2 measurements were performed in 1978-85. 82 measurements were obtained applying 5 different indirect methods all balancing the sources and sinks of stream dissolved oxygen under conditions of normal operation of the system (3 methods) and under artificial depletion of the oxygen concentration of the stream water by addition of sodium sulfite (2 methods). 21 K 2 values were determined directly applying the gaseous tracer 85 Kr for reaeration. Guidelines for selecting a proper method to determine K 2 knowing macrophyte biomass and loading characteristics of the particular stream are provided. (author)
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International Nuclear Information System (INIS)
Wissink, Jan G.; Rodi, Wolfgang
2009-01-01
Direct numerical simulations (DNS) of flow over and heat transfer from a flat plate affected by free-stream fluctuations were performed. A contoured upper wall was employed to generate a favourable streamwise pressure gradient along a large portion of the flat plate. The free-stream fluctuations originated from a separate LES of isotropic turbulence in a box. In the laminar portions of the accelerating boundary layer flow the formation of streaks was observed to induce an increase in heat transfer by the exchange of hot fluid near the surface of the plate and cold fluid from the free-stream. In the regions where the streamwise pressure gradient was only mildly favourable, intermittent turbulent spots were detected which relaminarised downstream as the streamwise pressure gradient became stronger. The relaminarisation of the turbulent spots was reflected by a slight decrease in the friction coefficient, which converged to its laminar value in the region where the streamwise pressure gradient was strongest.
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Ries, Kernell G.; Newson, Jeremy K.; Smith, Martyn J.; Guthrie, John D.; Steeves, Peter A.; Haluska, Tana L.; Kolb, Katharine R.; Thompson, Ryan F.; Santoro, Richard D.; Vraga, Hans W.
2017-10-30
IntroductionStreamStats version 4, available at https://streamstats.usgs.gov, is a map-based web application that provides an assortment of analytical tools that are useful for water-resources planning and management, and engineering purposes. Developed by the U.S. Geological Survey (USGS), the primary purpose of StreamStats is to provide estimates of streamflow statistics for user-selected ungaged sites on streams and for USGS streamgages, which are locations where streamflow data are collected.Streamflow statistics, such as the 1-percent flood, the mean flow, and the 7-day 10-year low flow, are used by engineers, land managers, biologists, and many others to help guide decisions in their everyday work. For example, estimates of the 1-percent flood (which is exceeded, on average, once in 100 years and has a 1-percent chance of exceedance in any year) are used to create flood-plain maps that form the basis for setting insurance rates and land-use zoning. This and other streamflow statistics also are used for dam, bridge, and culvert design; water-supply planning and management; permitting of water withdrawals and wastewater and industrial discharges; hydropower facility design and regulation; and setting of minimum allowed streamflows to protect freshwater ecosystems. Streamflow statistics can be computed from available data at USGS streamgages depending on the type of data collected at the stations. Most often, however, streamflow statistics are needed at ungaged sites, where no streamflow data are available to determine the statistics.
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Reactor core flow rate control system
International Nuclear Information System (INIS)
Sakuma, Hitoshi; Tanikawa, Naoshi; Takahashi, Toshiyuki; Miyakawa, Tetsuya.
1996-01-01
When an internal pump is started by a variable frequency power source device, if magnetic fields of an AC generator are introduced after the rated speed is reached, neutron flux high scram occurs by abrupt increase of a reactor core flow rate. Then, in the present invention, magnetic fields for the AC generator are introduced at a speed previously set at which the fluctuation range of the reactor core flow rate (neutron flux) by the start up of the internal pump is within an allowable value. Since increase of the speed of the internal pump upon its start up is suppressed to determine the change of the reactor core flow rate within an allowable range, increase of neutron fluxes is suppressed to enable stable start up. Then, since transition boiling of fuels caused by abrupt decrease of the reactor core flow rate upon occurrence of abnormality in an external electric power system is prevented, and the magnetic fields for the AC generator are introduced in such a manner to put the speed increase fluctuation range of the internal pump upon start up within an allowable value, neutron flux high scram is not caused to enable stable start-up. (N.H.)
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Directory of Open Access Journals (Sweden)
Mukesh Kumar Awasthi
2013-01-01
Full Text Available The instability of a thin sheet of viscous and dielectric liquid moving in the same direction as an air stream in the presence of a uniform horizontal electric field has been carried out using viscous potential flow theory. It is observed that aerodynamic-enhanced instability occurs if the Weber number is much less than a critical value related to the ratio of the air and liquid stream velocities, viscosity ratio of two fluids, the electric field, and the dielectric constant values. Liquid viscosity has stabilizing effect in the stability analysis, while air viscosity has destabilizing effect.
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Directory of Open Access Journals (Sweden)
Christina Rahayuningtyas
2014-01-01
Full Text Available The upstream Lesti watershed is one of the major watersheds of East Java in Indonesia, covering about 38093 hectares. Although there are enough water resources to meet current demands in the basin, many challenges including high spatial and temporal variability in precipitation from year to year exist. It is essential to understand how the climatic condition affects Lesti River stream flow in each sub basin. This study investigated the applicability of using the Soil and Water Assessment Tool (SWAT with the incorporation of groundwater recharge prediction in stream flow simulation in the upstream Lesti watershed. Four observation wells in the upstream Lesti watershed were used to evaluate the seasonal and annual variations in the water level and estimate the groundwater recharge in the deep aquifer. The results show that annual water level rise was within the 2800 - 5700 mm range in 2007, 3900 - 4700 mm in 2008, 3200 - 5100 mm in 2009, and 2800 - 4600 mm in 2010. Based on the specific yield and the measured water level rise, the area-weighted groundwater predictions at the watershed outlet are 736, 820.9, 786.7, 306.4 mm in 2007, 2008, 2009, and 2010, respectively. The consistency test reveals that the R-square statistical value is greater than 0.7, and the DV (% ranged from 32 - 55.3% in 2007 - 2010. Overall, the SWAT model performs better in the wet season flow simulation than the dry season. It is suggested that the SWAT model needs to be improved for stream flow simulation in tropical regions.
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Vitreous flow rates through dual pneumatic cutters: effects of duty cycle and cut rate
Directory of Open Access Journals (Sweden)
Abulon DJK
2015-02-01
Full Text Available Dina Joy K Abulon Medical Affairs, Alcon Research, Ltd, Lake Forest, CA, USA Purpose: We aimed to investigate effects of instrument settings on porcine vitreous flow rates through dual pneumatic high-speed vitrectomy probes. Methods: The CONSTELLATION® Vision System was tested with 250, 450, and 650 mmHg of vacuum using six ULTRAVIT® vitrectomy probes of each diameter (25+®, 25, 23, and 20 gauge operated from 500 cuts per minute (cpm up to 5,000 cpm. Duty cycle modes tested included biased open, 50/50, and biased closed. Flow rates were calculated by assessing the change in weight of porcine eyes during vitreous aspiration. Volumetric flow rate was measured with a computer-connected electronic scale. Results: At lower cut rates, the biased open mode produced higher flow than did the 50/50 mode, which produced higher flow than did the biased closed mode. In the biased closed and 50/50 modes, vitreous flow rates tended to increase with increasing cut rate. Vitreous flow rates in the biased open duty cycle mode remained relatively constant across cut rates. Conclusion: Vitreous flow rates through dual pneumatic vitrectomy probes could be manipulated by changing the duty cycle modes on the vitrectomy system. Differences in duty cycle behavior suggest that high-speed cut rates of 5,000 cpm may optimize vitreous aspiration. Keywords: enhanced 25-gauge vitrectomy, 25-gauge vitrectomy, 20-gauge vitrectomy, 23-gauge vitrectomy, aspiration, Constellation Vision System
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Method for Modeling High-Temporal-Resolution Stream Inflows in a Long-Term ParFlow.CLM Simulation
Miller, G. R.; Merket, C.
2017-12-01
Traditional hydrologic modeling has compartmentalized the water cycle into distinct components (e.g. rainfall-runoff, river routing, or groundwater flow models). An integrated, process-based modeling framework assesses two or more of these components simultaneously, reducing the error associated with approximated boundary conditions. One integrated model, ParFlow.CLM, offers the advantage of parallel computing, but it lacks any mechanism for incorporating time-varying streamflow as an upstream boundary condition. Here, we present a generalized method for applying transient streamflow at an upstream boundary in ParFlow.CLM. Downstream flow values are compared to predictions by traditional runoff and routing methods as implemented in HEC-HMS. Additionally, we define a model spin-up process which includes initialization of steady-state streamflow. The upstream inflow method was successfully tested on two domains - one synthetic tilted V catchment and an idealized small stream catchment in the Brazos River Basin. The stream in the idealized domain is gaged at the upstream and downstream boundaries. Both tests assumed a homogeneous subsurface so that the efficacy of the transient streamflow method could be evaluated with minimal complications by groundwater interactions. In the tilted V catchment, spin-up criteria were achieved within 6 model years. A 25 x 25 x 66 cell model grid was run at a computational efficiency of values early in the simulation.
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Estimation of flow rates through intergranular stress corrosion cracks
International Nuclear Information System (INIS)
Collier, R.P.; Norris, D.M.
1984-01-01
Experimental studies of critical two-phase water flow, through simulated and actual intergranular stress corrosion cracks, were performed to obtain data to evaluate a leak flow rate model and investigate acoustic transducer effectiveness in detecting and sizing leaks. The experimental program included a parametric study of the effects of crack geometry, fluid stagnation pressure and temperature, and crack surface roughness on leak flow rate. In addition, leak detection, location, and leak size estimation capabilities of several different acoustic transducers were evaluated as functions of leak rate and transducer position. This paper presents flow rate data for several different cracks and fluid conditions. It also presents the minimum flow rate detected with the acoustic sensors and a relationship between acoustic signal strength and leak flow rate
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Hall, J. L.
1974-01-01
A study of the effect of free-stream thermal-energy release from shock-induced exothermic reactions on boundary-layer development and transition is presented. The flow model is that of a boundary layer developing behind a moving shock wave in two-dimensional unsteady flow over a shock-tube wall. Matched sets of combustible hydrogen-oxygen-nitrogen mixtures and inert hydrogen-nitrogen mixtures were used to obtain transition data over a range of transition Reynolds numbers from 1,100,000 to 21,300,000. The heat-energy is shown to significantly stabilize the boundary layer without changing its development character. A method for application of this data to flat-plate steady flows is included.
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ADAPTIVE STREAMING OVER HTTP (DASH UNTUK APLIKASI VIDEO STREAMING
Directory of Open Access Journals (Sweden)
I Made Oka Widyantara
2015-12-01
Full Text Available This paper aims to analyze Internet-based streaming video service in the communication media with variable bit rates. The proposed scheme on Dynamic Adaptive Streaming over HTTP (DASH using the internet network that adapts to the protocol Hyper Text Transfer Protocol (HTTP. DASH technology allows a video in the video segmentation into several packages that will distreamingkan. DASH initial stage is to compress the video source to lower the bit rate video codec uses H.26. Video compressed further in the segmentation using MP4Box generates streaming packets with the specified duration. These packages are assembled into packets in a streaming media format Presentation Description (MPD or known as MPEG-DASH. Streaming video format MPEG-DASH run on a platform with the player bitdash teritegrasi bitcoin. With this scheme, the video will have several variants of the bit rates that gave rise to the concept of scalability of streaming video services on the client side. The main target of the mechanism is smooth the MPEG-DASH streaming video display on the client. The simulation results show that the scheme based scalable video streaming MPEG-DASH able to improve the quality of image display on the client side, where the procedure bufering videos can be made constant and fine for the duration of video views
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Physical stream habitat dynamics in Lower Bear Creek, northern Arkansas
Reuter, Joanna M.; Jacobson, Robert B.; Elliott, Caroline M.
2003-01-01
We evaluated the roles of geomorphic and hydrologic dynamics in determining physical stream habitat in Bear Creek, a stream with a 239 km2 drainage basin in the Ozark Plateaus (Ozarks) in northern Arkansas. During a relatively wet 12-month monitoring period, the geomorphology of Bear Creek was altered by a series of floods, including at least four floods with peak discharges exceeding a 1-year recurrence interval and another flood with an estimated 2- to 4-year recurrence interval. These floods resulted in a net erosion of sediment from the study reach at Crane Bottom at rates far in excess of other sites previously studied in the Ozarks. The riffle-pool framework of the study reach at Crane Bottom was not substantially altered by these floods, but volumes of habitat in riffles and pools changed. The 2- to 4-year flood scoured gravel from pools and deposited it in riffles, increasing the diversity of available stream habitat. In contract, the smaller floods eroded gravel from the riffles and deposited it in pools, possibly flushing fine sediment from the substrate but also decreasing habitat diversity. Channel geometry measured at the beginning of the study was use to develop a two-dimensional, finite-element hydraulic model at assess how habitat varies with hydrologic dynamics. Distributions of depth and velocity simulated over the range of discharges observed during the study (0.1 to 556 cubic meters per second, cms) were classified into habitat units based on limiting depths and Froude number criteria. The results indicate that the areas of habitats are especially sensitive to change to low to medium flows. Races (areas of swift, relatively deep water downstream from riffles) disappear completely at the lowest flows, and riffles (areas of swift, relatively shallow water) contract substantially in area. Pools also contract in area during low flow, but deep scours associated with bedrock outcrops sustain some pool area even at the lowest modeled flows. Modeled
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Watson, Kara M.; McHugh, Amy R.
2014-01-01
Regional regression equations were developed for estimating monthly flow-duration and monthly low-flow frequency statistics for ungaged streams in Coastal Plain and non-coastal regions of New Jersey for baseline and current land- and water-use conditions. The equations were developed to estimate 87 different streamflow statistics, which include the monthly 99-, 90-, 85-, 75-, 50-, and 25-percentile flow-durations of the minimum 1-day daily flow; the August–September 99-, 90-, and 75-percentile minimum 1-day daily flow; and the monthly 7-day, 10-year (M7D10Y) low-flow frequency. These 87 streamflow statistics were computed for 41 continuous-record streamflow-gaging stations (streamgages) with 20 or more years of record and 167 low-flow partial-record stations in New Jersey with 10 or more streamflow measurements. The regression analyses used to develop equations to estimate selected streamflow statistics were performed by testing the relation between flow-duration statistics and low-flow frequency statistics for 32 basin characteristics (physical characteristics, land use, surficial geology, and climate) at the 41 streamgages and 167 low-flow partial-record stations. The regression analyses determined drainage area, soil permeability, average April precipitation, average June precipitation, and percent storage (water bodies and wetlands) were the significant explanatory variables for estimating the selected flow-duration and low-flow frequency statistics. Streamflow estimates were computed for two land- and water-use conditions in New Jersey—land- and water-use during the baseline period of record (defined as the years a streamgage had little to no change in development and water use) and current land- and water-use conditions (1989–2008)—for each selected station using data collected through water year 2008. The baseline period of record is representative of a period when the basin was unaffected by change in development. The current period is
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Energy Technology Data Exchange (ETDEWEB)
Rashidi, S. [Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad 91775-1111 (Iran, Islamic Republic of); Dehghan, M. [Department of Mechanical Engineering, Semnan University, P.O. Box: 35196-45399, Semnan (Iran, Islamic Republic of); Ellahi, R., E-mail: rellahi@engr.ucr.edu [Department of Mathematics and Statistics, FBAS, IIUI, 44000 Islamabad (Pakistan); Department of Mechanical Engineering, Bourns Hall, University of California, Riverside, CA 92521 (United States); Riaz, M. [Department of QEC, National Defense University, E-9 Sector, 44000 Islamabad (Pakistan); Jamal-Abad, M.T. [Department of Mechanical Engineering, Semnan University, P.O. Box: 35196-45399, Semnan (Iran, Islamic Republic of)
2015-03-15
A mathematical model for two-dimensional fluid flow under the influence of stream wise transverse magnetic fields in laminar regime is simulated in this study. Heat transfer past a square diamond shaped porous obstacle is also taken into account. The attention is focused to investigate the effects of intensity and direction of magnetic field, Darcy and Reynolds numbers on the mechanism of convective heat transfer and flow structures. The Darcy–Brinkman–Forchheimer model along with the Maxwell equations is used. The nonlinear coupled equations using a finite volume approach (FVA) are solved numerically. The calculations are performed for different governing parameters such as Reynolds number, Nusselt number, Stuart number and Prandtl Number. The physical interpretation of velocity and isothermal contours is assigned through graphs. It is shown that the effects of a transverse magnetic field on flow behavior and heat transfer mechanism are more than that of the stream wise magnetic field. The configuration of streamlines and vorticity contours phenomena are also presented for porous diamond obstacle. Comparison of the numerical solutions with existing literature is also made. - Highlights: • This paper analyses two-dimensional fluid flow under the influence of stream wise transverse magnetic field. • Heat transfer past a square diamond shaped porous obstacle is taken into account. • The Darcy–Brinkman–Forchheimer model is used. • Finite volume approach is used to find numerical solutions. • The configuration of streamlines and vorticity contours phenomena are presented through graphs.
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Leschik, S.; Musolff, A.; Reinstorf, F.; Strauch, G.; Schirmer, M.
2009-05-01
Urban streams receive effluents of wastewater treatment plants and untreated wastewater during combined sewer overflow events. In the case of losing streams substances, which originate from wastewater, can reach the groundwater and deteriorate its quality. The estimation of mass flow rates Mex from losing streams to the groundwater is important to support groundwater management strategies, but is a challenging task. Variable inflow of wastewater with time-dependent concentrations of wastewater constituents causes a variable water composition in urban streams. Heterogeneities in the structure of the streambed and the connected aquifer lead, in combination with this variable water composition, to heterogeneous concentration patterns of wastewater constituents in the vicinity of urban streams. Groundwater investigation methods based on conventional point sampling may yield unreliable results under these conditions. Integral Pumping Tests (IPT) can overcome the problem of heterogeneous concentrations in an aquifer by increasing the sampled volume. Long-time pumping (several days) and simultaneous sampling yields reliable average concentrations Cav and mass flow rates Mcp for virtual control planes perpendicular to the natural flow direction. We applied the IPT method in order to estimate Mex of a stream section in Leipzig (Germany). The investigated stream is strongly influenced by combined sewer overflow events. Four pumping wells were installed up- and downstream of the stream section and operated for a period of five days. The study was focused on four inorganic (potassium, chloride, nitrate and sulfate) and two organic (caffeine and technical-nonylphenol) wastewater constituents with different transport properties. The obtained concentration-time series were used in combination with a numerical flow model to estimate Mcp of the respective wells. The difference of the Mcp's between up- and downstream wells yields Mex of wastewater constituents that increase
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Numerical study on flow rate limitation of open capillary channel flow through a wedge
Directory of Open Access Journals (Sweden)
Ting-Ting Zhang
2016-04-01
Full Text Available The flow characteristics of slender-column flow in wedge-shaped channel under microgravity condition are investigated in this work. The one-dimensional theoretical model is applied to predict the critical flow rate and surface contour of stable flow. However, the one-dimensional model overestimates the critical flow rate for not considering the extra pressure loss. Then, we develop a three-dimensional simulation method with OpenFOAM, a computational fluid dynamics tool, to simulate various phenomena in wedge channels with different lengths. The numerical results are verified with the capillary channel flow experimental data on the International Space Station. We find that the three-dimensional simulation perfectly predicts the critical flow rates and surface contours under various flow conditions. Meanwhile, the general behaviors in subcritical, critical, and supercritical flow are studied in three-dimensional simulation considering variations of flow rate and open channel length. The numerical techniques for three-dimensional simulation is validated for a wide range of configurations and is hopeful to provide valuable guidance for capillary channel flow experiment and efficient liquid management in space.
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Jorgensen, Donald G.; Signor, Donald C.; Imes, Jeffrey L.
1989-01-01
Intracell flow is important in modeling cells that contain both sources and sinks. Special attention is needed if recharge through the water table is a source. One method of modeling multiple sources and sinks is to determine the net recharge per cell. For example, for a model cell containing both a sink and recharge through the water table, the amount of recharge should be reduced by the ratio of the area of influence of the sink within the cell to the area of the cell. The reduction is the intercepted portion of the recharge. In a multilayer model this amount is further reduced by a proportion factor, which is a function of the depth of the flow lines from the water table boundary to the internal sink. A gaining section of a stream is a typical sink. The aquifer contribution to a gaining stream can be conceptualized as having two parts; the first part is the intercepted lateral flow from the water table and the second is the flow across the streambed due to differences in head between the water level in the stream and the aquifer below. The amount intercepted is a function of the geometry of the cell, but the amount due to difference in head across the stream bed is largely independent of cell geometry. A discharging well can intercept recharge through the water table within a model cell. The net recharge to the cell would be reduced in proportion to the area of influence of the well within the cell. The area of influence generally changes with time. Thus the amount of intercepted recharge and net recharge may not be constant with time. During periods when the well is not discharging there will be no intercepted recharge even though the area of influence from previous pumping may still exist. The reduction of net recharge per cell due to internal interception of flow will result in a model-calculated mass balance less than the prototype. Additionally the “effective transmissivity” along the intercell flow paths may be altered when flow paths are occupied by
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Three-dimensional model of corotating streams in the solar wind 3. Magnetohydrodynamic streams
International Nuclear Information System (INIS)
Pizzo, V.J.
1982-01-01
The focus of this paper is two-fold: (1) to examine how the presence of the spiral magnetic field affects the evolution of interplanetary corotating solar wind streams, and (2) to ascertain the nature of secondary large-scale phenomena likely to be associated with streams having a pronounced three-dimensional (3-D) structure. The dynamics are presumed to be governed by the nonlinear polytropic, single-fluid, 3-D MHD equations. Solutions are obtained with an explicit, Eulerian, finite differences technique that makes use of a simple form of artificial diffusion for handling shocks. For smooth axisymmetric flows, the picture of magnetically induced meridional motions previously established by linear models requires only minor correction. In the case of broad 3-D streams input near the sun, inclusion of the magnetic field is found to retard the kinematic steepening at the stream front substantially but to produce little deviation from planar flow. For the more realistic case of initially sharply bounded streams, however, it becomes essential to account for magnetic effects in the formulation. Whether a full 3-D treatment is required depends upon the latitudinal geometry of the stream
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Bypass flow rate control method
International Nuclear Information System (INIS)
Kiyama, Yoichi.
1997-01-01
In a PWR type reactor, bypass flow rate is controlled by exchanging existent jetting hole plugs of a plurality of nozzles disposed to the upper end of incore structures in order to flow a portion of primary coolants as a bypass flow to the upper portion of the pressure vessel. Two kinds of exchange plugs, namely, a first plug and a second plug each having a jetting out hole of different diameter are used as exchange plugs. The first plug has the diameter as that of an existent plug and the second plug has a jetting out hole having larger diameter than that of the existent plug. Remained extent plugs are exchanged to a combination of the first and the second plugs without exchanging existent plugs having seizing with the nozzles, in which the number and the diameter of the jetting out holes of the second plugs are previously determined based on predetermined total bypass flow rate to be jetted from the entire plugs after exchange of plugs. (N.H.)
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Energy Technology Data Exchange (ETDEWEB)
Sato, H; Shima, H [Oyo Corp., Tokyo (Japan)
1997-05-27
To investigate a possibility of exploration of underground water flow as well as to grasp the underground fluid flow by measuring streaming potential at the ground surface, some experiments were conducted using a model unit by considering the difference of permeability. For this experimental unit, water is driven by adding head difference between the polyethylene vessel filled with water and the experimental water tank. The size of water tank is 350{times}160 mm with a height of 160 mm. Twenty platinum electrodes are set on the cover of water tank. Toyoura standard sand and Kanto loam were used for the experiments. For the experiments, fluid was injected in various combined models by considering the permeability, to measure the streaming potential. As a result, it was explained by the streaming potential that the fluid flows in a form of laminar flow in the experimental water tank, and that the movement of fluid in the Kanto loam is quite slow. It was also confirmed that the streaming potential method is an effective technique for grasping the movement of fluid. 3 refs., 8 figs.
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Internal Flow of Contra-Rotating Small Hydroturbine at Off- Design Flow Rates
SHIGEMITSU, Toru; TAKESHIMA, Yasutoshi; OGAWA, Yuya; FUKUTOMI, Junichiro
2016-11-01
Small hydropower generation is one of important alternative energy, and enormous potential lie in the small hydropower. However, efficiency of small hydroturbines is lower than that of large one. Then, there are demands for small hydroturbines to keep high performance in wide flow rate range. Therefore, we adopted contra-rotating rotors, which can be expected to achieve high performance. In this research, performance of the contra-rotating small hydroturbine with 60mm casing diameter was investigated by an experiment and numerical analysis. Efficiency of the contra-rotating small hydroturbine was high in pico-hydroturbine and high efficiency could be kept in wide flow rate range, however the performance of a rear rotor decreased significantly in partial flow rates. Then, internal flow condition, which was difficult to measure experimentally, was investigated by the numerical flow analysis. Then, a relation between the performance and internal flow condition was considered by the numerical analysis result.
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Cronenberger, M. S.; McMillan, S. K.
2011-12-01
Increasing urbanization and the subsequent disruption of floodplains has led to the need for implementing stormwater management strategies to mitigate the effects of urbanization, including soil and streambank erosion, increased export of nutrients and contaminants and decreased biotic richness. Excessive stormwater runoff due to the abundance of impervious surfaces associated with an urban landscape has led to the ubiquitous use of best management practices (BMPs) to attenuate runoff events and prevent the destructive delivery of large volumes of water to stream channels. As a result, effluent from BMPs (i.e. wetlands and wet ponds) has the potential to alter the character of the receiving stream channel and thus, key ecosystem processes such as denitrification. The purpose of this study was to determine the extent to which BMPs, in the form of constructed wetlands and wet ponds, influence in-stream denitrification rates in the urban landscape of Charlotte, NC. Four sites, two of each BMP type, were evaluated. Sediment samples were collected upstream and downstream of the BMP outflow from May-July 2011 to determine the effect of wetland discharge on in-stream nitrogen removal via denitrification. Denitrification rates were determined using the acetylene block method; water column nutrient and carbon concentrations and sediment organic matter content were also measured. Generally, wetland sites exhibited higher denitrification rates, nitrate concentrations and sediment organic matter content. Our work and others has demonstrated a significant positive correlation between nitrate concentration and denitrification rates, which is the likely driver of the higher observed rates at the wetland sites. Geomorphology was also found to be a key factor in elevated denitrification rates at sites with riffles and boulder jams. Sediment organic matter was found to be higher downstream of BMP outflows at all four sites, but demonstrated no significant relationship with
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The multi-stream flows and the dynamics of the cosmic web
International Nuclear Information System (INIS)
Shandarin, Sergei F.
2011-01-01
A new numerical technique to identify the cosmic web is proposed. It is based on locating multi-stream flows, i.e. the places where the velocity field is multi-valued. The method is local in Eulerian space, simple and computationally efficient. This technique uses the velocities of particles and thus takes into account the dynamical information. This is in contrast with the majority of standard methods that use the coordinates of particles only. Two quantities are computed in every mesh cell: the mean and variance of the velocity field. Ideally in the cells where the velocity is single-valued the variance must be equal to zero exactly, therefore the cells with non-zero variance are identified as multi-stream flows. The technique has been tested in the Zel'dovich approximation and in the N-body simulation of the ΛCDM model. The effect of numerical noise is discussed. The web identified by the new method has been compared with the web identified by the standard technique using only the particle coordinates. The comparison has shown overall similarity of two webs as expected, however they by no means are identical. For example, the isocontours of the corresponding fields have significantly different shapes and some density peaks of similar heights exhibit significant differences in the velocity variance and vice versa. This suggests that the density and velocity variance have a significant degree of independence. The shape of the two-dimensional pdf of density and velocity variance confirms this proposition. Thus, we conclude that the dynamical information probed by this technique introduces an additional dimension into analysis of the web
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The multi-stream flows and the dynamics of the cosmic web
Energy Technology Data Exchange (ETDEWEB)
Shandarin, Sergei F., E-mail: sergei@ku.edu [Department of Physics and Astronomy, University of Kansas, 10082 Malott Hall, 1251 Wescoe Hall Dr, Lawrence, Kansas, 66045 (United States)
2011-05-01
A new numerical technique to identify the cosmic web is proposed. It is based on locating multi-stream flows, i.e. the places where the velocity field is multi-valued. The method is local in Eulerian space, simple and computationally efficient. This technique uses the velocities of particles and thus takes into account the dynamical information. This is in contrast with the majority of standard methods that use the coordinates of particles only. Two quantities are computed in every mesh cell: the mean and variance of the velocity field. Ideally in the cells where the velocity is single-valued the variance must be equal to zero exactly, therefore the cells with non-zero variance are identified as multi-stream flows. The technique has been tested in the Zel'dovich approximation and in the N-body simulation of the ΛCDM model. The effect of numerical noise is discussed. The web identified by the new method has been compared with the web identified by the standard technique using only the particle coordinates. The comparison has shown overall similarity of two webs as expected, however they by no means are identical. For example, the isocontours of the corresponding fields have significantly different shapes and some density peaks of similar heights exhibit significant differences in the velocity variance and vice versa. This suggests that the density and velocity variance have a significant degree of independence. The shape of the two-dimensional pdf of density and velocity variance confirms this proposition. Thus, we conclude that the dynamical information probed by this technique introduces an additional dimension into analysis of the web.
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International Nuclear Information System (INIS)
Daud Mohammad; Abd Razak Hamzah; Wan Abd Aziz Wan Mohamad; Juhari Yusoff; Wan Zakaria Wan Mohd Tahir
1985-01-01
Measuring the flow rate of a water course is one of the basic operations in hydrology, being of general relevance to water problems and of particular importance in the planning of water control schemes. The techniques commonly used in streamflow gauging are either by a current meter of tracer dilution method. This paper describes the latter technique in which radioisotope Tc-99m was used as a tracer in streamflow measurements performed in 1983 in a few selected irrigation canals and pump house under the Kemubu Agriculture Development Authority (KADA), Kelantan. Total count technique and peak-to-peak method were adopted in this study. (author)
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Cherniuk, V. V.; Riabenko, O. A.; Ivaniv, V. V.
2017-12-01
The influence of transit flow rate of water upon operative of the equipped with nozzles pressure pipeline is experimentally investigated. External pressure, which varies in the range of 1465-2295 mm, acted upon the pipeline. The angle β between vectors of velocities of the stream in the pipeline and jets which branch off through nozzles were given the value: 0° ; 45° ; 90° ; 135° ; 180°. The diameter of the pipeline was of D=20.18 mm, the diameter of nozzles d=6.01 mm. The distances between the nozzles were 180 mm, and the number of them 11. The value of the transit flow rate at input into the pipeline varied from 4.05 to 130.20 cm3 / s. The increase in flow rate of the transit flux Qtr caused increase in non-uniformity of distribution of operating heads and increase in flow rate of water along the pipeline over the segment of its dispensation. On the segment of collecting of water, inverse tendency was observed. The number of nozzles through which water became to be dispensed increased with the increase in Qtr.
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Directory of Open Access Journals (Sweden)
Rameen S. AbdelHady
2011-10-01
Full Text Available The magnetic treatment of hard water is an alternative, simple approach by which the hard water that needs to be treated flows through a magnetic field. This field is created by inducing current in a coil wrapped around a pipe. Consequently some of its properties, such as total dissolved salts (TDS, conductivity (Ec and PH change. The primary purpose of hard water treatment is to decrease TDS in the incoming liquid stream. Using performance data from the application of different magnetic field densities on the different flow levels of water, empirical mathematical models were developed relating the salt removal percentage (SRP to operating flow rate and current of the coil. The obtained experimental results showed that the SRP increased with increasing the current at low flow rates (up to 0.75 ml/s.
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2012-07-31
... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER12-2301-000] Stream Energy New York, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket Section 204 Authorization This is a supplemental notice in the above-referenced proceeding, of Stream...
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The Influence of the Powder Stream on High-Deposition-Rate Laser Metal Deposition with Inconel 718
Directory of Open Access Journals (Sweden)
Chongliang Zhong
2017-10-01
Full Text Available For the purpose of improving the productivity of laser metal deposition (LMD, the focus of current research is set on increasing the deposition rate, in order to develop high-deposition-rate LMD (HDR-LMD. The presented work studies the effects of the powder stream on HDR-LMD with Inconel 718. Experiments have been designed and conducted by using different powder feeding nozzles—a three-jet and a coaxial powder feeding nozzle—since the powder stream is mainly determined by the geometry of the powder feeding nozzle. After the deposition trials, metallographic analysis of the samples has been performed. The laser intensity distribution (LID and the powder stream intensity distribution (PID have been characterized, based on which the processes have been simulated. Finally, for verifying and correcting the used models for the simulation, the simulated results have been compared with the experimental results. Through the conducted work, suitable boundary conditions for simulating the process with different powder streams has been determined, and the effects of the powder stream on the process have also been determined. For a LMD process with a three-jet nozzle a substantial part of the powder particles that hit the melt pool surface are rebounded; for a LMD process with a coaxial nozzle almost all the particles are caught in the melt pool. This is due to the different particle velocities achieved with the two different nozzles. Moreover, the powder stream affects the heat exchange between the heated particles and the melt pool: a surface boundary condition applies for a powder stream with lower particle velocities, in the experiment provided by a three-jet nozzle, and a volumetric boundary condition applies for a powder stream with higher particle velocities, provided by a coaxial nozzle.
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Gas flow rate and powder flow rate effect on properties of laser metal deposited Ti6Al4V
CSIR Research Space (South Africa)
Pityana, S
2013-03-01
Full Text Available . The powder flow rate and the gas flow rate were varied to study their effect on the physical, metallurgical and mechanical properties of the deposits. The physical properties studied are: the track width, the track height and the deposit weight...
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Javed, T.; Ghaffari, A.; Ahmad, H.
2016-05-01
The unsteady stagnation point flow impinging obliquely on a flat plate in presence of a uniform applied magnetic field due to an oscillating stream has been studied. The governing partial differential equations are transformed into dimensionless form and the stream function is expressed in terms of Hiemenz and tangential components. The dimensionless partial differential equations are solved numerically by using well-known implicit finite difference scheme named as Keller-box method. The obtained results are compared with those available in the literature. It is observed that the results are in excellent agreement with the previous studies. The effects of pertinent parameters involved in the problem namely magnetic parameter, Prandtl number and impinging angle on flow and heat transfer characteristics are illustrated through graphs. It is observed that the influence of magnetic field strength increases the fluid velocity and by the increase of obliqueness parameter, the skin friction increases.
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What Can Hierarchies Do for Data Streams?
DEFF Research Database (Denmark)
Yin, Xuepeng; Pedersen, Torben Bach
Much effort has been put into building data streams management systems for querying data streams. Here, data streams have been viewed as a flow of low-level data items, e.g., sensor readings or IP packet data. Stream query languages have mostly been SQL-based, with the STREAM and TelegraphCQ lang...
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Reconfigurable Multicore Architectures for Streaming Applications
Smit, Gerardus Johannes Maria; Kokkeler, Andre B.J.; Rauwerda, G.K.; Jacobs, J.W.M.; Nicolescu, G.; Mosterman, P.J.
2009-01-01
This chapter addresses reconfigurable heterogenous and homogeneous multicore system-on-chip (SoC) platforms for streaming digital signal processing applications, also called DSP applications. In streaming DSP applications, computations can be specified as a data flow graph with streams of data items
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River Stream-Flow and Zayanderoud Reservoir Operation Modeling Using the Fuzzy Inference System
Directory of Open Access Journals (Sweden)
Saeed Jamali
2007-12-01
Full Text Available The Zayanderoud basin is located in the central plateau of Iran. As a result of population increase and agricultural and industrial developments, water demand on this basin has increased extensively. Given the importance of reservoir operation in water resource and management studies, the performance of fuzzy inference system (FIS for Zayanderoud reservoir operation is investigated in this paper. The model of operation consists of two parts. In the first part, the seasonal river stream-flow is forecasted using the fuzzy rule-based system. The southern oscillated index, rain, snow, and discharge are inputs of the model and the seasonal river stream-flow its output. In the second part, the operation model is constructed. The amount of releases is first optimized by a nonlinear optimization model and then the rule curves are extracted using the fuzzy inference system. This model operates on an "if-then" principle, where the "if" is a vector of fuzzy permits and "then" is the fuzzy result. The reservoir storage capacity, inflow, demand, and year condition factor are used as permits. Monthly release is taken as the consequence. The Zayanderoud basin is investigated as a case study. Different performance indices such as reliability, resiliency, and vulnerability are calculated. According to results, FIS works more effectively than the traditional reservoir operation methods such as standard operation policy (SOP or linear regression.
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Turbulent Mixing of Primary and Secondary Flow Streams in a Rocket-Based Combined Cycle Engine
Cramer, J. M.; Greene, M. U.; Pal, S.; Santoro, R. J.; Turner, Jim (Technical Monitor)
2002-01-01
This viewgraph presentation gives an overview of the turbulent mixing of primary and secondary flow streams in a rocket-based combined cycle (RBCC) engine. A significant RBCC ejector mode database has been generated, detailing single and twin thruster configurations and global and local measurements. On-going analysis and correlation efforts include Marshall Space Flight Center computational fluid dynamics modeling and turbulent shear layer analysis. Potential follow-on activities include detailed measurements of air flow static pressure and velocity profiles, investigations into other thruster spacing configurations, performing a fundamental shear layer mixing study, and demonstrating single-shot Raman measurements.
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Environmental risk of climate change and groundwater abstraction on stream ecological conditions
DEFF Research Database (Denmark)
Seaby, Lauren Paige; Bøgh, Eva; Jensen, Niels H.
with DAISY, a one dimensional crop model describing soil water dynamics in the root zone, and MIKE SHE, a distributed groundwater-surface water model. The relative and combined impacts on low flows, groundwater levels, and nitrate leaching are quantified and compared to assess the water resource sensitivity...... and risk to stream ecological conditions. We find low flow and annual discharge to be most impacted by scenarios of climate change, with high variation across climate models (+/- 40% change). Doubling of current groundwater abstraction rates reduces annual discharge by approximately 20%, with higher...... flows and groundwater levels are of interest, as they relate to aquatic habitat and nitrate leaching, respectively. This study evaluates the risk to stream ecological conditions for a lowland Danish catchment under multiple scenarios of climate change and groundwater abstraction. Projections of future...
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Wang, Chi R.; Yeh, Frederick C.
1987-01-01
A theoretical analysis and numerical calculations for the turbulent flow field and for the effect of free-stream turbulence on the surface heat transfer rate of a stagnation flow are presented. The emphasis is on the modeling of turbulence and its augmentation of surface heat transfer rate. The flow field considered is the region near the forward stagnation point of a circular cylinder in a uniform turbulent mean flow. The free stream is steady and incompressible with a Reynolds number of the order of 10 to the 5th power and turbulence intensity of less than 5 percent. For this analysis, the flow field is divided into three regions: (1) a uniform free-stream region where the turbulence is homogeneous and isotropic; (2) an external viscid flow region where the turbulence is distorted by the variation of the mean flow velocity; and, (3) an anisotropic turbulent boundary layer region over the cylinder surface. The turbulence modeling techniques used are the kappa-epsilon two-equation model in the external flow region and the time-averaged turbulence transport equation in the boundary layer region. The turbulence double correlations, the mean velocity, and the mean temperature within the boundary layer are solved numerically from the transport equations. The surface heat transfer rate is calculated as functions of the free-stream turbulence longitudinal microlength scale, the turbulence intensity, and the Reynolds number.
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Evaluation of IOM personal sampler at different flow rates.
Zhou, Yue; Cheng, Yung-Sung
2010-02-01
The Institute of Occupational Medicine (IOM) personal sampler is usually operated at a flow rate of 2.0 L/min, the rate at which it was designed and calibrated, for sampling the inhalable mass fraction of airborne particles in occupational environments. In an environment of low aerosol concentrations only small amounts of material are collected, and that may not be sufficient for analysis. Recently, a new sampling pump with a flow rate up to 15 L/min became available for personal samplers, with the potential of operating at higher flow rates. The flow rate of a Leland Legacy sampling pump, which operates at high flow rates, was evaluated and calibrated, and its maximum flow was found to be 10.6 L/min. IOM samplers were placed on a mannequin, and sampling was conducted in a large aerosol wind tunnel at wind speeds of 0.56 and 2.22 m/s. Monodisperse aerosols of oleic acid tagged with sodium fluorescein in the size range of 2 to 100 microm were used in the test. The IOM samplers were operated at flow rates of 2.0 and 10.6 L/min. Results showed that the IOM samplers mounted in the front of the mannequin had a higher sampling efficiency than those mounted at the side and back, regardless of the wind speed and flow rate. For the wind speed of 0.56 m/s, the direction-averaged (the average value of all orientations facing the wind direction) sampling efficiency of the samplers operated at 2.0 L/min was slightly higher than that of 10.6 L/min. For the wind speed of 2.22 m/s, the sampling efficiencies at both flow rates were similar for particles < 60 microm. The results also show that the IOM's sampling efficiency at these two different flow rates follows the inhalable mass curve for particles in the size range of 2 to 20 microm. The test results indicate that the IOM sampler can be used at higher flow rates.
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Nitrous oxide emission from denitrification in stream and river networks
Beaulieu, J.J.; Tank, J.L.; Hamilton, S.K.; Wollheim, W.M.; Hall, R.O.; Mulholland, P.J.; Peterson, B.J.; Ashkenas, L.R.; Cooper, L.W.; Dahm, Clifford N.; Dodds, W.K.; Grimm, N. B.; Johnson, S.L.; McDowell, W.H.; Poole, G.C.; Maurice, Valett H.; Arango, C.P.; Bernot, M.J.; Burgin, A.J.; Crenshaw, C.L.; Helton, A.M.; Johnson, L.T.; O'Brien, J. M.; Potter, J.D.; Sheibley, R.W.; Sobota, D.J.; Thomas, S.M.
2011-01-01
Nitrous oxide (N2O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N 2O via microbial denitrification that converts N to N2O and dinitrogen (N2). The fraction of denitrified N that escapes as N2O rather than N2 (i.e., the N2O yield) is an important determinant of how much N2O is produced by river networks, but little is known about the N2O yield in flowing waters. Here, we present the results of whole-stream 15N-tracer additions conducted in 72 headwater streams draining multiple land-use types across the United States. We found that stream denitrification produces N2O at rates that increase with stream water nitrate (NO3-) concentrations, but that production, but does not increase the N2O yield. In our study, most streams were sources of N2O to the atmosphere and the highest emission rates were observed in streams draining urban basins. Using a global river network model, we estimate that microbial N transformations (e.g., denitrification and nitrification) convert at least 0.68 Tg??y -1 of anthropogenic N inputs to N2O in river networks, equivalent to 10% of the global anthropogenic N2O emission rate. This estimate of stream and river N2O emissions is three times greater than estimated by the Intergovernmental Panel on Climate Change.
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Milk Flow Rates from bottle nipples used after hospital discharge.
Pados, Britt Frisk; Park, Jinhee; Thoyre, Suzanne M; Estrem, Hayley; Nix, W Brant
To test the milk flow rates and variability in flow rates of bottle nipples used after hospital discharge. Twenty-six nipple types that represented 15 common brands as well as variety in price per nipple and store location sold (e.g., Babies R' Us, Walmart, Dollar Store) were chosen for testing. Ten of each nipple type (n = 260 total) were tested by measuring the amount of infant formula expressed in 1 minute using a breast pump. Mean milk flow rate (mL/min) and coefficient of variation (CV) were calculated. Flow rates of nipples within brand were compared statistically. Milk flow rates varied from 1.68 mL/min for the Avent Natural Newborn Flow to 85.34 mL/min for the Dr. Brown's Standard Y-cut. Variability between nipple types also varied widely, from .03 for the Dr. Brown's Standard Level 3 to .37 for MAM Nipple 1 Slow Flow. The extreme range of milk flow rates found may be significant for medically fragile infants being discharged home who are continuing to develop oral feeding skills. The name of the nipple does not provide clear information about the flow rate to guide parents in decision making. Variability in flow rates within nipples of the same type may complicate oral feeding for the medically fragile infant who may not be able to adapt easily to change in flow rates. Both flow rate and variability should be considered when guiding parents to a nipple choice.
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Morphology of a Wetland Stream
Jurmu; Andrle
1997-11-01
/ Little attention has been paid to wetland stream morphology in the geomorphological and environmental literature, and in the recently expanding wetland reconstruction field, stream design has been based primarily on stream morphologies typical of nonwetland alluvial environments. Field investigation of a wetland reach of Roaring Brook, Stafford, Connecticut, USA, revealed several significant differences between the morphology of this stream and the typical morphology of nonwetland alluvial streams. Six morphological features of the study reach were examined: bankfull flow, meanders, pools and riffles, thalweg location, straight reaches, and cross-sectional shape. It was found that bankfull flow definitions originating from streams in nonwetland environments did not apply. Unusual features observed in the wetland reach include tight bends and a large axial wavelength to width ratio. A lengthy straight reach exists that exceeds what is typically found in nonwetland alluvial streams. The lack of convex bank point bars in the bends, a greater channel width at riffle locations, an unusual thalweg location, and small form ratios (a deep and narrow channel) were also differences identified. Further study is needed on wetland streams of various regions to determine if differences in morphology between alluvial and wetland environments can be applied in order to improve future designs of wetland channels.KEY WORDS: Stream morphology; Wetland restoration; Wetland creation; Bankfull; Pools and riffles; Meanders; Thalweg
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Stretch-minimising stream surfaces
Barton, Michael; Kosinka, Jin; Calo, Victor M.
2015-01-01
We study the problem of finding stretch-minimising stream surfaces in a divergence-free vector field. These surfaces are generated by motions of seed curves that propagate through the field in a stretch minimising manner, i.e., they move without stretching or shrinking, preserving the length of their arbitrary arc. In general fields, such curves may not exist. How-ever, the divergence-free constraint gives rise to these 'stretch-free' curves that are locally arc-length preserving when infinitesimally propagated. Several families of stretch-free curves are identified and used as initial guesses for stream surface generation. These surfaces are subsequently globally optimised to obtain the best stretch-minimising stream surfaces in a given divergence-free vector field. Our algorithm was tested on benchmark datasets, proving its applicability to incompressible fluid flow simulations, where our stretch-minimising stream surfaces realistically reflect the flow of a flexible univariate object. © 2015 Elsevier Inc. All rights reserved.
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Stretch-minimising stream surfaces
Barton, Michael
2015-05-01
We study the problem of finding stretch-minimising stream surfaces in a divergence-free vector field. These surfaces are generated by motions of seed curves that propagate through the field in a stretch minimising manner, i.e., they move without stretching or shrinking, preserving the length of their arbitrary arc. In general fields, such curves may not exist. How-ever, the divergence-free constraint gives rise to these \\'stretch-free\\' curves that are locally arc-length preserving when infinitesimally propagated. Several families of stretch-free curves are identified and used as initial guesses for stream surface generation. These surfaces are subsequently globally optimised to obtain the best stretch-minimising stream surfaces in a given divergence-free vector field. Our algorithm was tested on benchmark datasets, proving its applicability to incompressible fluid flow simulations, where our stretch-minimising stream surfaces realistically reflect the flow of a flexible univariate object. © 2015 Elsevier Inc. All rights reserved.
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Lipovsky, Bradley Paul; Dunham, Eric M.
2017-04-01
The Whillans Ice Plain (WIP), Antarctica, experiences twice daily tidally modulated stick-slip cycles. Slip events last about 30 min, have sliding velocities as high as ˜0.5 mm/s (15 km/yr), and have total slip ˜0.5 m. Slip events tend to occur during falling ocean tide: just after high tide and just before low tide. To reproduce these characteristics, we use rate-and-state friction, which is commonly used to simulate tectonic faulting, as an ice stream sliding law. This framework describes the evolving strength of the ice-bed interface throughout stick-slip cycles. We present simulations that resolve the cross-stream dimension using a depth-integrated treatment of an elastic ice layer loaded by tides and steady ice inflow. Steady sliding with rate-weakening friction is conditionally stable with steady sliding occurring for sufficiently narrow ice streams relative to a nucleation length. Stick-slip cycles occur when the ice stream is wider than the nucleation length or, equivalently, when effective pressures exceed a critical value. Ice streams barely wider than the nucleation length experience slow-slip events, and our simulations suggest that the WIP is in this slow-slip regime. Slip events on the WIP show a sense of propagation, and we reproduce this behavior by introducing a rate-strengthening region in the center of the otherwise rate-weakening ice stream. If pore pressures are raised above a critical value, our simulations predict that the WIP would exhibit quasi-steady tidally modulated sliding as observed on other ice streams. This study validates rate-and-state friction as a sliding law to describe ice stream sliding styles.
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Stream pH as an abiotic gradient influencing distributions of trout in Pennsylvania streams
Kocovsky, P.M.; Carline, R.F.
2005-01-01
Elevation and stream slope are abiotic gradients that limit upstream distributions of brook trout Salvelinus fontinalis and brown trout Salmo trutta in streams. We sought to determine whether another abiotic gradient, base-flow pH, may also affect distributions of these two species in eastern North America streams. We used historical data from the Pennsylvania Fish and Boat Commission's fisheries management database to explore the effects of reach elevation, slope, and base-flow pH on distributional limits to brook trout and brown trout in Pennsylvania streams in the Appalachian Plateaus and Ridge and Valley physiographic provinces. Discriminant function analysis (DFA) was used to calculate a canonical axis that separated allopatric brook trout populations from allopatric brown trout populations and allowed us to assess which of the three independent variables were important gradients along which communities graded from allopatric brook trout to allopatric brown trout. Canonical structure coefficients from DFA indicated that in both physiographic provinces, stream base-flow pH and slope were important factors in distributional limits; elevation was also an important factor in the Ridge and Valley Province but not the Appalachian Plateaus Province. Graphs of each variable against the proportion of brook trout in a community also identified apparent zones of allopatry for both species on the basis of pH and stream slope. We hypothesize that pH-mediated interspecific competition that favors brook trout in competition with brown trout at lower pH is the most plausible mechanism for segregation of these two species along pH gradients. Our discovery that trout distributions in Pennsylvania are related to stream base-flow pH has important implications for brook trout conservation in acidified regions. Carefully designed laboratory and field studies will be required to test our hypothesis and elucidate the mechanisms responsible for the partitioning of brook trout and
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Reverse stream flow routing by using Muskingum models
Indian Academy of Sciences (India)
Reverse stream flow routing is a procedure that determines the upstream hydrograph given the downstream hydrograph. This paper presents the development of methodology for Muskingum models parameter estimation for reverse stream flow routing. The standard application of the Muskingum models involves calibration ...
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Stream Response to an Extreme Defoliation Event
Gold, A.; Loffredo, J.; Addy, K.; Bernhardt, E. S.; Berdanier, A. B.; Schroth, A. W.; Inamdar, S. P.; Bowden, W. B.
2017-12-01
Extreme climatic events are known to profoundly impact stream flow and stream fluxes. These events can also exert controls on insect outbreaks, which may create marked changes in stream characteristics. The invasive Gypsy Moth (Lymantria dispar dispar) experiences episodic infestations based on extreme climatic conditions within the northeastern U.S. In most years, gypsy moth populations are kept in check by diseases. In 2016 - after successive years of unusually warm, dry spring and summer weather -gypsy moth caterpillars defoliated over half of Rhode Island's 160,000 forested ha. No defoliation of this magnitude had occurred for more than 30 years. We examined one RI headwater stream's response to the defoliation event in 2016 compared with comparable data in 2014 and 2015. Stream temperature and flow was gauged continuously by USGS and dissolved oxygen (DO) was measured with a YSI EXO2 sonde every 30 minutes during a series of deployments in the spring, summer and fall from 2014-2016. We used the single station, open channel method to estimate stream metabolism metrics. We also assessed local climate and stream temperature data from 2009-2016. We observed changes in stream responses during the defoliation event that suggest changes in ET, solar radiation and heat flux. Although the summer of 2016 had more drought stress (PDSI) than previous years, stream flow occurred throughout the summer, in contrast to several years with lower drought stress when stream flow ceased. Air temperature in 2016 was similar to prior years, but stream temperature was substantially higher than the prior seven years, likely due to the loss of canopy shading. DO declined dramatically in 2016 compared to prior years - more than the rising stream temperatures would indicate. Gross Primary Productivity was significantly higher during the year of the defoliation, indicating more total fixation of inorganic carbon from photo-autotrophs. In 2016, Ecosystem Respiration was also higher and Net
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Katie Price; C. Jackson; Albert Parker; Trond Reitan; John Dowd; Mike Cyterski
2011-01-01
Land use and physiographic variability influence stream low flows, yet their interactions and relative influence remain unresolved. Our objective was to assess the influence of land use and watershed geomorphic characteristics on low-flow variability in the southern Blue Ridge Mountains of North Carolina and Georgia. Ten minute interval discharge data for 35 streams (...
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Energy from streaming current and potential
Olthuis, Wouter; Schippers, Bob; Eijkel, Jan C.T.; van den Berg, Albert
2005-01-01
It is investigated how much energy can be delivered by a streaming current source. A streaming current and subsequent streaming potential originate when double layer charge is transported by hydrodynamic flow. Theory and a network model of such a source is presented and initial experimental results
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Analyzing indicators of stream health for Minnesota streams
Singh, U.; Kocian, M.; Wilson, B.; Bolton, A.; Nieber, J.; Vondracek, B.; Perry, J.; Magner, J.
2005-01-01
Recent research has emphasized the importance of using physical, chemical, and biological indicators of stream health for diagnosing impaired watersheds and their receiving water bodies. A multidisciplinary team at the University of Minnesota is carrying out research to develop a stream classification system for Total Maximum Daily Load (TMDL) assessment. Funding for this research is provided by the United States Environmental Protection Agency and the Minnesota Pollution Control Agency. One objective of the research study involves investigating the relationships between indicators of stream health and localized stream characteristics. Measured data from Minnesota streams collected by various government and non-government agencies and research institutions have been obtained for the research study. Innovative Geographic Information Systems tools developed by the Environmental Science Research Institute and the University of Texas are being utilized to combine and organize the data. Simple linear relationships between index of biological integrity (IBI) and channel slope, two-year stream flow, and drainage area are presented for the Redwood River and the Snake River Basins. Results suggest that more rigorous techniques are needed to successfully capture trends in IBI scores. Additional analyses will be done using multiple regression, principal component analysis, and clustering techniques. Uncovering key independent variables and understanding how they fit together to influence stream health are critical in the development of a stream classification for TMDL assessment.
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Vermont Center for Geographic Information — Physical measurements and attributes of stream crossing structures and adjacent stream reaches which are used to provide a relative rating of aquatic organism...
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Evaluation of stream crossing methods prior to gas pipeline construction
International Nuclear Information System (INIS)
Murphy, M.H.; Rogers, J.S.; Ricca, A.
1995-01-01
Stream surveys are conducted along proposed gas pipeline routes prior to construction to assess potential impacts to stream ecosystems and to recommend preferred crossing methods. Recently, there has been a high level of scrutiny from the Public Service Commission (PSC) to conduct these stream crossings with minimal effects to the aquatic community. PSC's main concern is the effect of sediment on aquatic biota. Smaller, low flowing or intermittent streams are generally crossed using a wet crossing technique. This technique involves digging a trench for the pipeline while the stream is flowing. Sediment control measures are used to reduce sediment loads downstream. Wider, faster flowing, or protected streams are typically crossed with a dry crossing technique. A dry crossing involves placing a barrier upstream of the crossing and diverting the water around the crossing location. The pipeline trench is then dug in the dry area. O'Brien and Gere and NYSEG have jointly designed a modified wet crossing for crossing streams that exceed maximum flows for a dry crossing, and are too wide for a typical wet crossing. This method diverts water around the crossing using a pumping system, instead of constructing a dam. The trench is similar to a wet crossing, with sediment control devices in place upstream and downstream. If streams are crossed during low flow periods, the pumping system will be able to reduce the majority of water flow and volume form the crossing area, thereby reducing ecological impacts. Evaluation of effects of this crossing type on the stream biota are currently proposed and may proceed when construction begins
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Schelker, J.; Grabs, T.; Bishop, K.; Laudon, H.
2013-12-01
disturbance such as clear-cutting has been identified as an important factor for increasing dissolved organic carbon (DOC) concentrations in boreal streams. We used a long-term data set of soil temperature, soil moisture, shallow groundwater (GW) levels, and stream DOC concentrations from three boreal first-order streams to investigate mechanisms causing these increases. Clear-cutting was found to alter soil conditions with warmer and wetter soils during summer. The application of a riparian flow concentration integration model (RIM) explained a major part of variation in stream [DOC] arising from changing flow pathways in riparian soils during the pretreatment period (r2 = 0.4-0.7), but less well after the harvest. Model residuals were sensitive to changes in soil temperature. The linear regression models for the temperature dependence of [DOC] in soils were not different in the disturbed and undisturbed catchments, whereas a nonlinear response to soil moisture was found. Overall these results suggest that the increased DOC mobilization after forest disturbance is caused by (i) increased GW levels leading to increased water fluxes in shallow flow path in riparian soils and (ii) increased soil temperature increasing the DOC availability in soils during summer. These relationships indicate that the mechanisms of DOC mobilization after forest disturbance are not different to those of undisturbed catchments, but that catchment soils respond to the higher hydro-climatic variation observed after clear-cutting. This highlights the sensitivity of boreal streams to changes in the energy and water balance, which may be altered as a result of both land management and climate change.
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Effects of Gravel Bars on Nutrient Spiraling in Bedrock-Alluvium Streams
Iobst, B. R.; Carroll, E. P.; Furbish, D. J.
2007-05-01
The importance of the connection between nutrient transport and local stream geomorphology is becoming increasingly important. Studies have shown that the interconnectivity of nutrient cycles in the downstream direction is in part controlled by the distribution and size of gravel bars in low order streams, as hyporheic flow occurs dominantly through alternate and mid-channel gravel bars. For this investigation multiple gravel bars in a 3rd order bedrock-alluvium stream were studied to determine general relationships between nutrient spiraling and hyporheic flow. The first goal was to understand (1) the extent to which water moves through hyporheic zones and (2) the basic chemistry of the hyporheic water. The second part of the study was to understand how nutrients, notably nitrogen, are affected in their cycling by the relatively long residence times encountered in gravel bars during hyporheic flow. Wells were installed along a 600 m reach of Panther Creek, KY in selected bars, as well as in a secondary location involving a grid installation pattern in one large bar. Results have shown that hyporheic flow through gravel bars is an important factor in influencing stream chemistry. Background water chemistry surveys have shown that certain parameters, specifically ammonium and nitrogen concentrations vary downstream, and that the dominant control over these changes is gravel bar location. Rhodamine WT was used in field tracer tests to track the travel times of water through bars as well as partitioning of water between the open channel and hyporheic flows. Further tests will be conducted utilizing a stable isotope study to determine how nitrogen is affected by hyporheic flow, and what implications this has for nutrient transport. We expect results to show that the spacing and size of gravel bars is a dominant control in key nutrient spiraling parameters, namely uptake lengths and overall nitrogen cycling rates. This has implications for how natural systems will
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Streaming reversal of energetic particles in the magnetotail during a substorm
Lui, A. T. Y.; Williams, D. J.; Eastman, T. E.; Frank, L. A.; Akasofu, S.-I.
1984-01-01
A case of reversal in the streaming anisotropy of energetic ions and in the plasma flow observed from the IMP 8 spacecraft during a substorm on February 8, 1978 is studied in detail using measurements of energetic particles, plasma, and magnetic field. Four new features emerge when high time resolution data are examined in detail. The times of streaming reversal of energetic particles in different energy ranges do not coincide with the time of plasma flow reversal. Qualitatively different velocity distributions are observed in earthward and tailward plasma flows during the observed flow reversal intervals. Strong tailward streaming of energetic particles can be detected during northward magnetic field environments and, conversely, earthward streaming in southward field environments. During the period of tailward streaming of energetic particles, earthward streaming fluxes are occasionally detected.
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International Nuclear Information System (INIS)
Gosling, J.T.; Asbridge, J.R.; Bame, S.J.; Feldman, W.C.
1978-01-01
Measurements aboard Imp 6, 7, and 8 reveal that approximately one third of all high-speed solar wind streams observed at 1 AU contain a sharp boundary (of thickness less than approx.4 x 10 4 km) near their leading edge, called a stream interface, which separates plasma of distinctly different properties and origins. Identified as discontinuities across which the density drops abruptly, the proton temperature increases abruptly, and the speed rises, stream interfaces are remarkably similar in character from one stream to the next. A superposed epoch analysis of plasma data has been performed for 23 discontinuous stream interfaces observed during the interval March 1971 through August 1974. Among the results of this analysis are the following: (1) a stream interface separates what was originally thick (i.e., dense) slow gas from what was originally thin (i.e., rare) fast gas; (2) the interface is the site of a discontinuous shear in the solar wind flow in a frame of reference corotating with the sun; (3) stream interfaces occur at speeds less than 450 km s - 1 and close to or at the maximum of the pressure ridge at the leading edges of high-speed streams; (4) a discontinuous rise by approx.40% in electron temperature occurs at the interface; and (5) discontinuous changes (usually rises) in alpha particle abundance and flow speed relative to the protons occur at the interface. Stream interfaces do not generally recur on successive solar rotations, even though the streams in which they are embedded often do. At distances beyond several astronomical units, stream interfaces should be bounded by forward-reverse shock pairs; three of four reverse shocks observed at 1 AU during 1971--1974 were preceded within approx.1 day by stream interfaces. Our observations suggest that many streams close to the sun are bounded on all sides by large radial velocity shears separating rapidly expanding plasma from more slowly expanding plasma
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Effect of gas temperature on flow rate characteristics of an averaging pitot tube type flow meter
Energy Technology Data Exchange (ETDEWEB)
Yeo, Seung Hwa; Lee, Su Ryong; Lee, Choong Hoon [Seoul National University of Science and Technology, Seoul (Korea, Republic of)
2015-01-15
The flow rate characteristics passing through an averaging Pitot tube (APT) while constantly controlling the flow temperature were studied through experiments and CFD simulations. At controlled temperatures of 25, 50, 75, and 100 .deg .C, the flow characteristics, in this case the upstream, downstream and static pressure at the APT flow meter probe, were measured as the flow rate was increased. The flow rate through the APT flow meter was represented using the H-parameter (hydraulic height) obtained by a combination of the differential pressure and the air density measured at the APT flow meter probe. Four types of H-parameters were defined depending on the specific combination. The flow rate and the upstream, downstream and static pressures measured at the APT flow meter while changing the H-parameters were simulated by means of CFD. The flow rate curves showed different features depending on which type of H-parameter was used. When using the constant air density value in a standard state to calculate the H-parameters, the flow rate increased linearly with the H-parameter and the slope of the flow rate curve according to the H-parameter increased as the controlled target air temperature was increased. When using different air density levels corresponding to each target air temperature to calculate the H-parameter, the slope of the flow rate curve according to the H-parameter was constant and the flow rate curve could be represented by a single line. The CFD simulation results were in good agreement with the experimental results. The CFD simulations were performed while increasing the air temperature to 1200 K. The CFD simulation results for high air temperatures were similar to those at the low temperature ranging from 25 to 100 .deg. C.
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Effect of gas temperature on flow rate characteristics of an averaging pitot tube type flow meter
International Nuclear Information System (INIS)
Yeo, Seung Hwa; Lee, Su Ryong; Lee, Choong Hoon
2015-01-01
The flow rate characteristics passing through an averaging Pitot tube (APT) while constantly controlling the flow temperature were studied through experiments and CFD simulations. At controlled temperatures of 25, 50, 75, and 100 .deg .C, the flow characteristics, in this case the upstream, downstream and static pressure at the APT flow meter probe, were measured as the flow rate was increased. The flow rate through the APT flow meter was represented using the H-parameter (hydraulic height) obtained by a combination of the differential pressure and the air density measured at the APT flow meter probe. Four types of H-parameters were defined depending on the specific combination. The flow rate and the upstream, downstream and static pressures measured at the APT flow meter while changing the H-parameters were simulated by means of CFD. The flow rate curves showed different features depending on which type of H-parameter was used. When using the constant air density value in a standard state to calculate the H-parameters, the flow rate increased linearly with the H-parameter and the slope of the flow rate curve according to the H-parameter increased as the controlled target air temperature was increased. When using different air density levels corresponding to each target air temperature to calculate the H-parameter, the slope of the flow rate curve according to the H-parameter was constant and the flow rate curve could be represented by a single line. The CFD simulation results were in good agreement with the experimental results. The CFD simulations were performed while increasing the air temperature to 1200 K. The CFD simulation results for high air temperatures were similar to those at the low temperature ranging from 25 to 100 .deg. C.
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Innovative model-based flow rate optimization for vanadium redox flow batteries
König, S.; Suriyah, M. R.; Leibfried, T.
2016-11-01
In this paper, an innovative approach is presented to optimize the flow rate of a 6-kW vanadium redox flow battery with realistic stack dimensions. Efficiency is derived using a multi-physics battery model and a newly proposed instantaneous efficiency determination technique. An optimization algorithm is applied to identify optimal flow rates for operation points defined by state-of-charge (SoC) and current. The proposed method is evaluated against the conventional approach of applying Faraday's first law of electrolysis, scaled to the so-called flow factor. To make a fair comparison, the flow factor is also optimized by simulating cycles with different charging/discharging currents. It is shown through the obtained results that the efficiency is increased by up to 1.2% points; in addition, discharge capacity is also increased by up to 1.0 kWh or 5.4%. Detailed loss analysis is carried out for the cycles with maximum and minimum charging/discharging currents. It is shown that the proposed method minimizes the sum of losses caused by concentration over-potential, pumping and diffusion. Furthermore, for the deployed Nafion 115 membrane, it is observed that diffusion losses increase with stack SoC. Therefore, to decrease stack SoC and lower diffusion losses, a higher flow rate during charging than during discharging is reasonable.
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Trail Creek II: Modeling Flow and E. Coli Concentrations in a Small Urban Stream using SWAT
Radcliffe, D. E.; Saintil, T.
2017-12-01
Pathogens are one of the leading causes of stream and river impairment in the State of Georgia. The common presence of fecal bacteria is driven by several factors including rapid population growth stressing pre-existing and ageing infrastructure, urbanization and poor planning, increase percent imperviousness, urban runoff, municipal discharges, sewage, pet/wildlife waste and leaky septic tanks. The Trail Creek watershed, located in Athens-Clarke County, Georgia covers about 33 km2. Stream segments within Trail Creek violate the GA standard due to high levels of fecal coliform bacteria. In this study, the Soil and Water Assessment Tool (SWAT) modeling software was used to predict E. coli bacteria concentrations during baseflow and stormflow. Census data from the county was used for human and animal population estimates and the Fecal Indicator Tool to generate the number of colony forming units of E. Coli for each source. The model was calibrated at a daily time step with one year of monitored streamflow and E. coli bacteria data using SWAT-CUP and the SUFI2 algorithm. To simulate leaking sewer lines, we added point sources in the five subbasins in the SWAT model with the greatest length of sewer line within 50 m of the stream. The flow in the point sources were set to 5% of the stream flow and the bacteria count set to that of raw sewage (30,000 cfu/100 mL). The calibrated model showed that the average load during 2003-2013 at the watershed outlet was 13 million cfu per month. Using the calibrated model, we simulated scenarios that assumed leaking sewers were repaired in one of the five subbasins with point sources. The reduction ranged from 10 to 46%, with the largest reduction in subbasin in the downtown area. Future modeling work will focus on the use of green infrastructure to address sources of bacteria.
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Shigeta, M.; Sato, T.; Dasgupta, B.
1985-01-01
The magnetohydrodynamic stability of streaming tearing mode is investigated numerically. A bulk plasma flow parallel to the antiparallel magnetic field lines and localized in the neutral sheet excites a streaming tearing mode more strongly than the usual tearing mode, particularly for the wavelength of the order of the neutral sheet width (or smaller), which is stable for the usual tearing mode. Interestingly, examination of the eigenfunctions of the velocity perturbation and the magnetic field perturbation indicates that the streaming tearing mode carries more energy in terms of the kinetic energy rather than the magnetic energy. This suggests that the streaming tearing mode instability can be a more feasible mechanism of plasma acceleration than the usual tearing mode instability.
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Electromagnetic application device for flow rate/flow speed control
International Nuclear Information System (INIS)
Yoshioka, Senji.
1994-01-01
Electric current and magnetic field are at first generated in a direction perpendicular to a flow channel of a fluid, and forces generated by electromagnetic interaction of the current and the magnetic field are combined and exerted on the fluid, to control the flow rate and the flow speed thereby decreasing flowing pressure loss. In addition, an electric current generation means and a magnetic field generation means integrated together are disposed to a structural component constituting the flow channel, and they are combined to attain the aimed effect. The current generating means forms a potential difference by supplying electric power to a pair of electrodes as a cathode and an anode by using structures disposed along the channel, to generate an electric field or electric current in a direction perpendicular to the flow channel. The magnetic field generating means forms a counter current (reciprocal current) by using structures disposed along the flow channel, to generate synthesized or emphasized magnetic field. The fluid can be applied with a force in the direction of the flowing direction by the electromagnetic interaction of the electric current and the magnetic field, thereby capable of propelling the fluid. Accordingly, the flowrate/flowing speed can be controlled inside of the flow channel and flowing pressure loss can be decreased. (N.H.)
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Quantification of Groundwater Discharge in a Subalpine Stream Using Radon-222
Directory of Open Access Journals (Sweden)
Elizabeth Avery
2018-01-01
Full Text Available During the dry months of the water year in Mediterranean climates, groundwater influx is essential to perennial streams for sustaining ecosystem health and regulating water temperature. Predicted earlier peak flow due to climate change may result in decreased baseflow and the transformation of perennial streams to intermittent streams. In this study, naturally occurring radon-222 (222Rn was used as a tracer of groundwater influx to Martis Creek, a subalpine stream near Lake Tahoe, CA. Groundwater 222Rn is estimated based on measurements of 222Rn activity in nearby deep wells and springs. To determine the degassing constant (needed for quantification of water and gas flux, an extrinsic tracer, xenon (Xe, was introduced to the stream and monitored at eight downstream locations. The degassing constant for 222Rn is based on the degassing constant for Xe, and was determined to be 1.9–9.0 m/day. Applying a simple model in which stream 222Rn activity is a balance between the main 222Rn source (groundwater and sink (volatilization, the influx in reaches of the upstream portion of Martis Creek was calculated to be <1 to 15 m3/day/m, which cumulatively constitutes a significant portion of the stream discharge. Experiments constraining 222Rn emanation from hyporheic zone sediments suggest that this should be considered a maximum rate of influx. Groundwater influx is typically difficult to identify and quantify, and the method employed here is useful for identifying locations for focused stream flow measurements, for formulating a water budget, and for quantifying streamwater–groundwater interaction.
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Sudo, S.; Ito, M.; Ishimoto, Y.; Nix, S.
2017-04-01
This paper describes microstreaming flows generated by oscillating interface of magnetic fluid adsorbed on a circular cylindrical permanent magnet in alternating magnetic field. The interface of magnetic fluid adsorbed on the NdFeB magnet responds to the external alternating magnetic flied as harmonic oscillation. The directions of alternating magnetic field are parallel and antiparallel to the magnetic field of permanent magnet. The oscillation of magnetic fluid interface generates streaming flow around the magnet-magnetic fluid element in water. Microstreaming flows are observed with a high-speed video camera analysis system. The flow pattern generated by magnetic fluid motion depends on the Keulegan-Carpenter number and the Reynolds number.
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Collisional effects in the ion Weibel instability for two counter-propagating plasma streams
Energy Technology Data Exchange (ETDEWEB)
Ryutov, D. D.; Fiuza, F.; Huntington, C. M.; Ross, J. S.; Park, H.-S. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2014-03-15
Experiments directed towards the study of the collisionless interaction between two counter-streaming plasma flows generated by high-power lasers are designed in such a way as to make collisions between the ions of the two flows negligibly rare. This is reached by making flow velocities v as high as possible and thereby exploiting the 1/v{sup 4} dependence of the Rutherford cross-section. At the same time, the plasma temperature of each flow may be relatively low so that collisional mean-free paths for the intra-stream particle collisions may be much smaller than the characteristic spatial scale of the unstable modes required for the shock formation. The corresponding effects are studied in this paper for the case of the ion Weibel (filamentation) instability. Dispersion relations for the case of strong intra-stream collisions are derived. It is shown that the growth-rates become significantly smaller than those stemming from a collisionless model. The underlying physics is mostly related to the increase of the electron stabilizing term. Additional effects are an increased “stiffness” of the collisional ion gas and the ion viscous dissipation. A parameter domain where collisions are important is identified.
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Cross-layer optimized rate adaptation and scheduling for multiple-user wireless video streaming
Ozcelebi, T.; Sunay, M.O.; Tekalp, A.M.; Civanlar, M.R.
2007-01-01
We present a cross-layer optimized video rate adaptation and user scheduling scheme for multi-user wireless video streaming aiming for maximum quality of service (QoS) for each user,, maximum system video throughput, and QoS fairness among users. These objectives are jointly optimized using a
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Nitrate Removal Rates in Denitrifying Bioreactors During Storm Flows
Pluer, W.; Walter, T.
2017-12-01
Field denitrifying bioreactors are designed to reduce excess nitrate (NO3-) pollution in runoff from agricultural fields. Field bioreactors saturate organic matter to create conditions that facilitate microbial denitrification. Prior studies using steady flow in lab-scale bioreactors showed that a hydraulic retention time (HRT) between 4 and 10 hours was optimal for reducing NO3- loads. However, during storm-induced events, flow rate and actual HRT fluctuate. These fluctuations have the potential to disrupt the system in significant ways that are not captured by the idealized steady-flow HRT models. The goal of this study was to investigate removal rate during dynamic storm flows of variable rates and durations. Our results indicate that storm peak flow and duration were not significant controlling variables. Instead, we found high correlations (p=0.004) in average removal rates between bioreactors displaying a predominantly uniform flow pattern compared with bioreactors that exhibited preferential flow (24.4 and 21.4 g N m-3 d-1, respectively). This suggests that the internal flow patterns are a more significant driver of removal rate than external factors of the storm hydrograph. Designing for flow patterns in addition to theoretical HRT will facilitate complete mixing within the bioreactors. This will help maximize excess NO3- removal during large storm-induced runoff events.
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Effects of soil data resolution on SWAT model stream flow and water quality predictions.
Geza, Mengistu; McCray, John E
2008-08-01
The prediction accuracy of agricultural nonpoint source pollution models such as Soil and Water Assessment Tool (SWAT) depends on how well model input spatial parameters describe the characteristics of the watershed. The objective of this study was to assess the effects of different soil data resolutions on stream flow, sediment and nutrient predictions when used as input for SWAT. SWAT model predictions were compared for the two US Department of Agriculture soil databases with different resolution, namely the State Soil Geographic database (STATSGO) and the Soil Survey Geographic database (SSURGO). Same number of sub-basins was used in the watershed delineation. However, the number of HRUs generated when STATSGO and SSURGO soil data were used is 261 and 1301, respectively. SSURGO, with the highest spatial resolution, has 51 unique soil types in the watershed distributed in 1301 HRUs, while STATSGO has only three distributed in 261 HRUS. As a result of low resolution STATSGO assigns a single classification to areas that may have different soil types if SSURGO were used. SSURGO included Hydrologic Response Units (HRUs) with soil types that were generalized to one soil group in STATSGO. The difference in the number and size of HRUs also has an effect on sediment yield parameters (slope and slope length). Thus, as a result of the discrepancies in soil type and size of HRUs stream flow predicted was higher when SSURGO was used compared to STATSGO. SSURGO predicted less stream loading than STATSGO in terms of sediment and sediment-attached nutrients components, and vice versa for dissolved nutrients. When compared to mean daily measured flow, STATSGO performed better relative to SSURGO before calibration. SSURGO provided better results after calibration as evaluated by R(2) value (0.74 compared to 0.61 for STATSGO) and the Nash-Sutcliffe coefficient of Efficiency (NSE) values (0.70 and 0.61 for SSURGO and STATSGO, respectively) although both are in the same satisfactory
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Flow Regime Classification and Hydrological Characterization: A Case Study of Ethiopian Rivers
Directory of Open Access Journals (Sweden)
Belete Berhanu
2015-06-01
Full Text Available The spatiotemporal variability of a stream flow due to the complex interaction of catchment attributes and rainfall induce complexity in hydrology. Researchers have been trying to address this complexity with a number of approaches; river flow regime is one of them. The flow regime can be quantified by means of hydrological indices characterizing five components: magnitude, frequency, duration, timing, and rate of change of flow. Similarly, this study aimed to understand the flow variability of Ethiopian Rivers using the observed daily flow data from 208 gauging stations in the country. With this process, the Hierarchical Ward Clustering method was implemented to group the streams into three flow regimes (1 ephemeral, (2 intermittent, and (3 perennial. Principal component analysis (PCA is also applied as the second multivariate analysis tool to identify dominant hydrological indices that cause the variability in the streams. The mean flow per unit catchment area (QmAR and Base flow index (BFI show an incremental trend with ephemeral, intermittent and perennial streams. Whereas the number of mean zero flow days ratio (ZFI and coefficient of variation (CV show a decreasing trend with ephemeral to perennial flow regimes. Finally, the streams in the three flow regimes were characterized with the mean and standard deviation of the hydrological variables and the shape, slope, and scale of the flow duration curve. Results of this study are the basis for further understanding of the ecohydrological processes of the river basins in Ethiopia.
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Directory of Open Access Journals (Sweden)
Norfifah Bachok
2012-01-01
Full Text Available The steady boundary layer flow and heat transfer of a viscous fluid on a moving flat plate in a parallel free stream with variable fluid properties are studied. Two special cases, namely, constant fluid properties and variable fluid viscosity, are considered. The transformed boundary layer equations are solved numerically by a finite-difference scheme known as Keller-box method. Numerical results for the flow and the thermal fields for both cases are obtained for various values of the free stream parameter and the Prandtl number. It is found that dual solutions exist for both cases when the fluid and the plate move in the opposite directions. Moreover, fluid with constant properties shows drag reduction characteristics compared to fluid with variable viscosity.
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DEFF Research Database (Denmark)
Powell, Daryl; Olesen, Peter Bjerg
2013-01-01
Companies use value stream mapping to identify waste, often in the early stages of a lean implementation. Though the tool helps users to visualize material and information flows and to identify improvement opportunities, a limitation of this approach is the lack of an integrated method...... for analysing and re-designing the MPC system in order to support lean improvement. We reflect on the current literature regarding value stream mapping, and use practical insights in order to develop and propose a two-dimensional value stream mapping tool that integrates the design of the MPC system within...... the material and information flow map....
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Two-stream instability in pulsar magnetospheres
International Nuclear Information System (INIS)
Usov, V.V.
1987-01-01
If the electron-positron plasma flow from the pulsar environment is stationary, the two-stream instability does not have enough time to develop in the pulsar magnetosphere. In that case the outflowing electron-positron plasma gathers into separate clouds. The clouds move along magnetic field lines and disperse as they go farther from the pulsar. At a distance of about 10 to the 8th cm from the pulsar surface, the high-energy particles of a given cloud catch up with the low-energy particles that belong to the cloud going ahead of it. In this region of a pulsar magnetosphere, the energy distribution of plasma particles is two-humped, and a two-stream instability may develop. The growth rate of the instability is quite sufficient for its development. 17 references
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Retention/Diffusivity Studies in Free-Surface Flowing Liquid Lithium
International Nuclear Information System (INIS)
R.A. Stubbers; G.H. Miley; M. Nieto; W. Olczak; D.N. Ruzic; A. Hassanein
2004-01-01
FLIRE was designed to measure the hydrogen and helium retention and diffusivity in a flowing stream of liquid lithium, and it has accomplished these goals. Retention coefficients for helium in the flowing liquid stream were 0.1-2% for flow speeds of 44 cm/s and implantation energies between 500 and 2000 eV. The energy dependence of retention is linear for the energy range considered, as expected, and the dependence of retention on flow velocity fits the expected square-root of flow speed dependence. Estimates of the helium diffusion coefficient in the flowing lithium stream were ∼ 4 x 10 -7 cm 2 /s, and are independent of implantation energy. This value is much lower than expected, which could be due to several factors, such as mixing, bubble formation or surface film formation. In the case of hydrogen, long term retention and release mechanisms are of greatest importance, since this relates to tritium inventory in flowing lithium PFCs for fusion applications. The amount of hydride formation was measured for flowing lithium exposed to neutral deuterium gas. Thermal desorption spectroscopy (TDS) measurements indicate that the hydride concentration was between 0.1 and 0.2% over a wide range of pressures (6.5 x 10 -5 to 1 Torr). This result implies that the deuterium absorption rate is limited by the surface dissociation rate, since deuterium (hydrogen/tritium) is absorbed in its atomic form, not its molecular form
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Retention/Diffusivity Studies in Free-Surface Flowing Liquid Lithium
Energy Technology Data Exchange (ETDEWEB)
R.A. Stubbers; G.H. Miley; M. Nieto; W. Olczak; D.N. Ruzic; A. Hassanein
2004-12-14
FLIRE was designed to measure the hydrogen and helium retention and diffusivity in a flowing stream of liquid lithium, and it has accomplished these goals. Retention coefficients for helium in the flowing liquid stream were 0.1-2% for flow speeds of 44 cm/s and implantation energies between 500 and 2000 eV. The energy dependence of retention is linear for the energy range considered, as expected, and the dependence of retention on flow velocity fits the expected square-root of flow speed dependence. Estimates of the helium diffusion coefficient in the flowing lithium stream were {approx} 4 x 10{sup -7} cm{sup 2}/s, and are independent of implantation energy. This value is much lower than expected, which could be due to several factors, such as mixing, bubble formation or surface film formation. In the case of hydrogen, long term retention and release mechanisms are of greatest importance, since this relates to tritium inventory in flowing lithium PFCs for fusion applications. The amount of hydride formation was measured for flowing lithium exposed to neutral deuterium gas. Thermal desorption spectroscopy (TDS) measurements indicate that the hydride concentration was between 0.1 and 0.2% over a wide range of pressures (6.5 x 10{sup -5} to 1 Torr). This result implies that the deuterium absorption rate is limited by the surface dissociation rate, since deuterium (hydrogen/tritium) is absorbed in its atomic form, not its molecular form.
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GROWTH RATE DISTRIBUTION OF BORAX SINGLE CRYSTALS ON THE (001 FACE UNDER VARIOUS FLOW RATES
Directory of Open Access Journals (Sweden)
Suharso Suharso
2010-06-01
Full Text Available The growth rates of borax single crystals from aqueous solutions at various flow rates in the (001 direction were measured using in situ cell method. From the growth rate data obtained, the growth rate distribution of borax crystals was investigated using Minitab Software and SPSS Software at relative supersaturation of 0807 and temperature of 25 °C. The result shows that normal, gamma, and log-normal distribution give a reasonably good fit to GRD. However, there is no correlation between growth rate distribution and flow rate of solution. Keywords: growth rate dispersion (GRD, borax, flow rate
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Ciparis, Serena; Iwanowicz, Deborah D.; Voshell, J. Reese
2013-01-01
Summary 1. Nutrient enrichment is a widespread environmental problem in freshwater ecosystems. Eutrophic conditions caused by nutrient enrichment may result in a higher prevalence of infection by trematode parasites in host populations, due to greater resource availability for the molluscan first intermediate hosts. 2. This study examined relationships among land use, environmental variables indicating eutrophication, population density of the pleurocerid snail, Leptoxis carinata, and trematode infections. Fifteen study sites were located in streams within the Shenandoah River catchment (Virginia, U.S.A.), where widespread nutrient enrichment has occurred. 3. Snail population density had a weak positive relationship with stream water nutrient concentration. Snail population density also increased as human activities within stream catchments increased, but density did not continue to increase in catchments where anthropogenic disturbance was greatest. 4. Cercariae from five families of trematodes were identified in L. carinata, and infection rate was generally low (<10%). Neither total infection rate nor the infection rate of individual trematode types showed a positive relationship with snail population density, nutrients or land use. 5. There were statistically significant but weak relationships between the prevalence of infection by two trematode families and physical and biological variables. The prevalence of Notocotylidae was positively related to water depth, which may be related to habitat use by definitive hosts. Prevalence of Opecoelidae had a negative relationship with orthophosphate concentration and a polynomial relationship with chlorophyll a concentration. Transmission of Opecoelid trematodes between hosts may be inhibited by eutrophic conditions. 6. Leptoxis carinata appears to be a useful species for monitoring the biological effects of eutrophication and investigating trematode transmission dynamics in lotic systems.
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U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted August stream/river temperature maximum negative rate of change in New England based on a...
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Physics design of fissile mass-flow monitoring system
International Nuclear Information System (INIS)
Mattingly, J.K.; March-Leuba, J.; Valentine, T.E.; Mihalczo, J.T.; Uckan, T.
1997-01-01
The system measures the flow rate and uranium-235 content in liquid or gas streams; it does not penetrate the process piping. A moderated fission neutron source is used to periodicially introduce a burst of thermal neutrons into the fluid stream to induce fission; delayed gamma emissions from the resulting fission fragments are detected by high-efficiency scintillators downstream of the neutron source. The fluid flow rate is measure from the time between initiation of the thermal neutron burst and detection of the fission product gamma emissions, and the U-235 content is inferred from the intensity of the gamma burst detected. Design of the fissile mass flow monitor requires satisfaction of several competing constraints. Efficient operation of the monitor requires that source-induced fission rate and detection efficiency be maximized while the source-induced background rate is simultaneoulsy minimized. Near optical nuclear design of the system was achieved using numerous Monte Carlo calculations and measurements. This paper addresses calculational aspects of the physics design for the system applied to UF 6 gas
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Bowles, C. J.; Lawrence, R. L.; Noll, C.; Hancock, G. S.
2005-12-01
Channel incision is a widely observed response to increased flow in urbanized watersheds, but the effects of channel lowering on riparian water tables is not well documented. In a rapidly incising suburban stream in the Virginia Coastal Plain, we hypothesize that stream incision has lowered floodplain water tables and decreased the overbank flow frequency. The monitored stream is a tributary to the James River draining 1.3 km2 of which 15% is impervious cover. Incision has occurred largely through upstream migration of a one meter high knickpoint at a rate of ~1.5 m/yr, primarily during high flow events. We installed 63 wells in six stream-perpendicular transects as well as a cluster of wells around the knickpoint to assess water table elevations beneath the floodplain adjacent to the incising stream. Two transects are located 30 and 50 m upstream of the knickpoint in the unincised floodplain, and the remainder are 5, 30, 70, and 100 m downstream in the incised floodplain. In one transect above and two below, pressure transducers attached to dataloggers provide a high-resolution record of water table changes. Erosion pins were installed and channel cross-sections surveyed to determine streambed stability. Significant differences are observed in bank morphology and groundwater flow above vs. below the knickpoint. Above the knickpoint, the banks are stable, ~3 m wide, and ~0.3 m deep, and widen and deepen slightly toward the knickpoint. The water table is relatively flat and is 0.2-0.4 m below the floodplain surface, and groundwater contours suggest flow is parallel to the stream direction. The water table responds immediately to precipitation events, and rises to the floodplain surface in significant rainfall events. Immediately downstream of the knickpoint, channel width increases by about a meter, and stream depth increases to ~1.5 meters. The water table immediately below the knickpoint possesses a steep gradient, and is up to one meter below the floodplain
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Influence of diurnal variations in stream temperature on streamflow loss and groundwater recharge
Constantz, Jim; Thomas, Carole L.; Zellweger, Gary W.
1994-01-01
We demonstrate that for losing reaches with significant diurnal variations in stream temperature, the effect of stream temperature on streambed seepage is a major factor contributing to reduced afternoon streamflows. An explanation is based on the effect of stream temperature on the hydraulic conductivity of the streambed, which can be expected to double in the 0° to 25°C temperature range. Results are presented for field experiments in which stream discharge and temperature were continuously measured for several days over losing reaches at St. Kevin Gulch, Colorado, and Tijeras Arroyo, New Mexico. At St. Kevin Gulch in July 1991, the diurnal stream temperature in the 160-m study reach ranged from about 4° to 18°C, discharges ranged from 10 to 18 L/s, and streamflow loss in the study reach ranged from 2.7 to 3.7 L/s. On the basis of measured stream temperature variations, the predicted change in conductivity was about 38%; the measured change in stream loss was about 26%, suggesting that streambed temperature varied less than the stream temperature. At Tijeras Arroyo in May 1992, diurnal stream temperature in the 655-m study reach ranged from about 10° to 25°C and discharge ranged from 25 to 55 L/s. Streamflow loss was converted to infiltration rates by factoring in the changing stream reach surface area and streamflow losses due to evaporation rates as measured in a hemispherical evaporation chamber. Infiltration rates ranged from about 0.7 to 2.0 m/d, depending on time and location. Based on measured stream temperature variations, the predicted change in conductivity was 29%; the measured change in infiltration was also about 27%. This suggests that high infiltration rates cause rapid convection of heat to the streambed. Evapotranspiration losses were estimated for the reach and adjacent flood plain within the arroyo. On the basis of these estimates, only about 5% of flow loss was consumed via stream evaporation and stream-side evapotranspiration
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Nitrogen concentrations in a small Mediterranean stream: 1. Nitrate 2. Ammonium
Directory of Open Access Journals (Sweden)
A. Butturini
2002-01-01
Full Text Available The importance of storm frequency as well as the groundwater and hyporheic inputs on nitrate (NO3-N and ammonium (NH4-N levels in stream water were studied in a small perennial Mediterranean catchment, Riera Major, in northeast Spain. NO3-N concentrations ranged from 0.15 to 1.9 mg l-1. Discharge explained 47% of the annual NO3-N concentration variance, but this percentage increased to 97% when single floods were analysed. The rate of change in nitrate concentration with respect to flow, ΔNO3-N/ΔQ, ranged widely from 0 to 20 μg NO3-N s l-2. The ΔNO3-N/ΔQ values fitted to a non linear model with respect to the storm flow magnitude (ΔQ (r2=0.48, d.f.=22, P3-N/ΔQ occurred at intermediate ΔQ values, whereas low ΔNO3-N/ΔQ values occurred during severe storms (ΔQ > 400 l s-1. N3-N concentrations exhibit anticlockwise hysteresis patterns with changing flow and the patterns observed for autumnal and winter storms indicated that groundwater was the main N3-N source for stream and hyporheic water. At baseflow, NO3-N concentration in groundwater was higher (t=4.75, d.f.=29, P>0.001 and co-varied with concentrations in the stream (r=0.91, d.f.=28, P3-N concentration in hyporheic water was identical to that in stream water. The role of the hyporheic zone as source or sink for ammonium was studied hyporheic was studied comparing its concentrations in stream and hyporheic zone before and after a major storm occurred in October 1994 that removed particulate organic matter stored in sediments. Results showed high ammonium concentrations (75±28 s.d. μg NH4-N l-1 before the storm flow in the hyporheic zone. After the storm, the ammonium concentration in the hyporheic dropped by 80% (13.6±8 μg N4-N l-1 and approached to the level found in stream water (11±8 μg NH4-N l-1 indicating that indisturbed hyporheic sediments act as a source for ammonium. After the storm, the ammonium concentrations in the stream, hyporheic and groundwater zones were very
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The Relationship between High Flow Nasal Cannula Flow Rate and Effort of Breathing in Children.
Weiler, Thomas; Kamerkar, Asavari; Hotz, Justin; Ross, Patrick A; Newth, Christopher J L; Khemani, Robinder G
2017-10-01
To use an objective metric of effort of breathing to determine optimal high flow nasal cannula (HFNC) flow rates in children flow rates of 0.5, 1.0, 1.5, and 2.0 L/kg/minute. For a subgroup of patients, 2 different HFNC delivery systems (Fisher & Paykel [Auckland, New Zealand] and Vapotherm [Exeter, New Hampshire]) were compared. Twenty-one patients (49 titration episodes) were studied. The most common diagnoses were bronchiolitis and pneumonia. Overall, there was a significant difference in the percent change in PRP from baseline (of 0.5 L/kg/minute) with increasing flow rates for the entire cohort (P flow rates were increased (P = .001) than patients >8 kg. The optimal HFNC flow rate to reduce effort of breathing in infants and young children is approximately 1.5-2.0 L/kg/minute with more benefit seen in children ≤8 kg. Copyright © 2017 Elsevier Inc. All rights reserved.
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Gursoy, Kadir Ali; Yavuz, Mehmet Metin
2014-11-01
In continuous casting operation of steel, the flow through tundish to the mold can be controlled by different flow rate control systems including stopper rod and slide-gate. Ladle changes in continuous casting machines result in liquid steel level changes in tundishes. During this transient event of production, the flow rate controller opening is increased to reduce the pressure drop across the opening which helps to keep the mass flow rate at the desired level for the reduced liquid steel level in tundish. In the present study, computational fluid dynamic (CFD) models are developed to investigate the effect of flow rate controller on mold flow structure, and particularly to understand the effect of flow controller opening on meniscus flow. First, a detailed validation of the CFD models is conducted using available experimental data and the performances of different turbulence models are compared. Then, the constant throughput casting operations for different flow rate controller openings are simulated to quantify the opening effect on meniscus region. The results indicate that the meniscus velocities are significantly affected by the flow rate controller and its opening level. The steady state operations, specified as constant throughput casting, do not provide the same mold flow if the controller opening is altered. Thus, for quality and castability purposes, adjusting the flow controller opening to obtain the fixed mold flow structure is proposed. Supported by Middle East Technical University (METU) BAP (Scientific Research Projects) Coordination.
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Stream-Groundwater Interaction Buffers Seasonal Changes in Urban Stream Water Quality
Ledford, S. H.; Lautz, L. K.
2013-12-01
Urban streams in the northeastern United States have large road salt inputs during winter, increased nonpoint sources of inorganic nitrogen, and decreased short-term and permanent storage of nutrients. Meadowbrook Creek, a first order stream in Syracuse, New York, flows along a negative urbanization gradient, from a channelized and armored stream running through the middle of a roadway to a pool-riffle stream meandering through a broad, vegetated floodplain with a riparian aquifer. In this study we investigated how reconnection to groundwater and introduction of riparian vegetation impacted surface water chemistry by making bi-weekly longitudinal surveys of stream water chemistry in the creek from May 2012 until June 2013. Chloride concentrations in the upstream, urban reach of Meadowbrook Creek were strongly influenced by discharge of road salt to the creek during snow melt events in winter and by the chemistry of water draining an upstream retention basin in summer. Chloride concentrations ranged from 161.2 mg/L in August to 2172 mg/L in February. Chloride concentrations in the downstream, 'connected' reach had less temporal variation, ranging from 252.0 mg/L in August to 1049 mg/L in January, and were buffered by groundwater discharge, as the groundwater chloride concentrations during the sampling period ranged from 84.0 to 655.4 mg/L. Groundwater discharge resulted in higher chloride concentrations in summer and lower concentrations in winter in the connected reach relative to the urban reach, minimizing annual variation. In summer, there was little-to-no nitrate in the urban reach due to a combination of limited sources and high primary productivity. In contrast, during the summer, nitrate concentrations reached over 1 mg N/L in the connected reach due to the presence of riparian vegetation and lower nitrate uptake due to cooler temperatures and shading. During the winter, when temperatures fell below freezing, nitrate concentrations in the urban reach
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Investigation of technology for the monitoring of UF6 mass flow in UF6 streams diluted with H2
International Nuclear Information System (INIS)
Baker, O.J.; Cooley, J.N.; Hewgley, W.A.; Moran, B.W.; Swindle, D.W. Jr.
1986-12-01
The applicability, availability, and effectiveness of gas flow meters are assessed as a means for verifying the mass flows of pure UF 6 streams diluted with a carrier gas. The initial survey identified the orifice, pitot tube, thermal, vortex shedding, and vortex precession (swirl) meters as promising for the intended use. Subsequent assessments of these flow meters revealed that two - the orifice meter and the pitot tube meter - are the best choices for the proposed applications: the first is recommended for low velocity gas, small diameter piping; the latter, for high velocity gas, large diameter piping. Final selection of the gas flow meters should be based on test loop evaluations in which the proposed meters are subjected to gas flows, temperatures, and pressures representative of those expected in service. Known instruments are evaluated that may be applicable to the measurement of uranium or UF 6 concentration in a UF 6 - H 2 process stream at an aerodynamic enrichment plant. Of the six procedures evaluated, four have been used for process monitoring in a UF 6 environment: gas mass spectrometry, infrared-ultraviolet-visible spectrophotometry, gas chromatography, and acoustic gas analysis. The remaining two procedures, laser fluorimetry and atomic absorption spectroscopy, would require significant development work before they could be used for process monitoring. Infrared-ultravioloet-visible spectrophotometry is judged to be the best procedure currently available to perform the required measurement
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On-stream chemical element monitor
International Nuclear Information System (INIS)
Averitt, O.R.; Dorsch, R.R.
1979-01-01
An apparatus and method for on-stream chemical element monitoring are described wherein a multiplicity of sample streams are flowed continuously through individual analytical cells and fluorescence analyses are performed on the sample streams in sequence, together with a method of controlling the time duration of each analysis as a function of the concomitant radiation exposure of a preselected perforate reference material interposed in the sample-radiation source path
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Krimmer, A N; Paul, A J; Hontela, A; Rasmussen, J B
2011-09-01
This study presents an experimental analysis of the effects of midwinter flow reduction (50-75%, reduction in discharge in 4 h daily pulses) on the physical habitat and on behaviour and physiology of overwintering brook trout Salvelinus fontinalis in a small mountain stream. Flow reduction did not result in significant lowering of temperature or formation of surface or subsurface ice. The main findings were (1) daily movement by S. fontinalis increased (c. 2·5-fold) during flow reduction, but was limited to small-scale relocations (reduced during flow reduction. (3) Although both experimental and reference fish did lose mass and condition during the experiment, no effects of flow reduction on stress indicators (blood cortisol or glucose) or bioenergetics (total body fat, water content or mass loss) were detected, probably because access to the preferred type of cover remained available. Like other salmonids, S. fontinalis moves little and seeks physical cover during winter. Unlike many of the more studied salmonids, however, this species overwinters successfully in small groundwater-rich streams that often remain ice-free, and this study identifies undercut banks as the critical winter habitat rather than substratum cover. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.
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StreamStats: A water resources web application
Ries, Kernell G.; Guthrie, John G.; Rea, Alan H.; Steeves, Peter A.; Stewart, David W.
2008-01-01
Streamflow statistics, such as the 1-percent flood, the mean flow, and the 7-day 10-year low flow, are used by engineers, land managers, biologists, and many others to help guide decisions in their everyday work. For example, estimates of the 1-percent flood (the flow that is exceeded, on average, once in 100 years and has a 1-percent chance of being exceeded in any year, sometimes referred to as the 100-year flood) are used to create flood-plain maps that form the basis for setting insurance rates and land-use zoning. This and other streamflow statistics also are used for dam, bridge, and culvert design; water-supply planning and management; water-use appropriations and permitting; wastewater and industrial discharge permitting; hydropower facility design and regulation; and the setting of minimum required streamflows to protect freshwater ecosystems. In addition, researchers, planners, regulators, and others often need to know the physical and climatic characteristics of the drainage basins (basin characteristics) and the influence of human activities, such as dams and water withdrawals, on streamflow upstream from locations of interest to understand the mechanisms that control water availability and quality at those locations. Knowledge of the streamflow network and downstream human activities also is necessary to adequately determine whether an upstream activity, such as a water withdrawal, can be allowed without adversely affecting downstream activities.Streamflow statistics could be needed at any location along a stream. Most often, streamflow statistics are needed at ungaged sites, where no streamflow data are available to compute the statistics. At U.S. Geological Survey (USGS) streamflow data-collection stations, which include streamgaging stations, partial-record stations, and miscellaneous-measurement stations, streamflow statistics can be computed from available data for the stations. Streamflow data are collected continuously at streamgaging stations
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Coupled Spatio-Temporal Patterns of Solute Transport, Metabolism and Nutrient Uptake in Streams
Kurz, M. J.; Schmidt, C.
2017-12-01
Slower flow velocities and longer residence times within stream transient storage (TS) zones facilitate interaction between solutes and microbial communities, potentially increasing local rates of metabolic activity. Multiple factors, including channel morphology and substrate, variable hydrology, and seasonal changes in biological and physical parameters, result in changes in the solute transport dynamics and reactivity of TS zones over time and space. These changes would be expected to, in turn, influence rates of whole-stream ecosystem functions such as metabolism and nutrient uptake. However, the linkages between solute transport and ecosystem functioning within TS zones, and the contribution of TS zones to whole-stream functioning, are not always so straight forward. This may be due, in part, to methodological challenges. In this study we investigated the influence of stream channel hydro-morphology and substrate type on reach (103 m) and sub-reach (102 m) scale TS and ecosystem functioning. Patterns in solute transport, metabolism and nitrate uptake were tracked from April through October in two contrasting upland streams using several methods. The two streams, located in the Harz Mountains, Germany, are characterized by differing size (0.02 vs. 0.3 m3/s), dominant stream channel substrate (bedrock vs. alluvium) and sub-reach morphology (predominance of pools, riffles and glides). Solute transport parameters and respiration rates at the reach and sub-reach scale were estimated monthly from coupled pulse injections of the reactive tracer resazurin (Raz) and conservative tracers uranine and salt. Raz, a weakly fluorescent dye, irreversibly transforms to resorufin (Rru) under mildly reducing conditions, providing a proxy for aerobic respiration. Daily rates of primary productivity, respiration and nitrate retention at the reach scale were estimated using the diel cycles in dissolved oxygen and nitrate concentrations measured by in-situ sensors. Preliminary
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Evaluating Use of Environmental Flows to Aerate Streams by Modelling the Counterfactual Case
Stewardson, Michael J.; Skinner, Dominic
2018-03-01
This paper evaluates an experimental environmental flow manipulation by modeling the counterfactual case that no environmental flow was applied. This is an alternate approach to evaluating the effect of an environmental flow intervention when a before-after or control-impact comparison is not possible. In this case, the flow manipulation is a minimum flow designed to prevent hypoxia in a weir on the low-gradient Broken Creek in south-eastern Australia. At low flows, low reaeration rates and high respiration rates associated with elevated organic matter loading in the weir pool can lead to a decline in dissolved oxygen concentrations with adverse consequences both for water chemistry and aquatic biota. Using a one dimensional oxygen balance model fitted to field measurements, this paper demonstrates that increased flow leads to increases in reaeration rates, presumably because of enhanced turbulence and hence mixing in the surface layers. By comparing the observed dissolved oxygen levels with the modeled counterfactual case, we show that the environmental flow was effective in preventing hypoxia.
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StreamExplorer: A Multi-Stage System for Visually Exploring Events in Social Streams.
Wu, Yingcai; Chen, Zhutian; Sun, Guodao; Xie, Xiao; Cao, Nan; Liu, Shixia; Cui, Weiwei
2017-10-18
Analyzing social streams is important for many applications, such as crisis management. However, the considerable diversity, increasing volume, and high dynamics of social streams of large events continue to be significant challenges that must be overcome to ensure effective exploration. We propose a novel framework by which to handle complex social streams on a budget PC. This framework features two components: 1) an online method to detect important time periods (i.e., subevents), and 2) a tailored GPU-assisted Self-Organizing Map (SOM) method, which clusters the tweets of subevents stably and efficiently. Based on the framework, we present StreamExplorer to facilitate the visual analysis, tracking, and comparison of a social stream at three levels. At a macroscopic level, StreamExplorer uses a new glyph-based timeline visualization, which presents a quick multi-faceted overview of the ebb and flow of a social stream. At a mesoscopic level, a map visualization is employed to visually summarize the social stream from either a topical or geographical aspect. At a microscopic level, users can employ interactive lenses to visually examine and explore the social stream from different perspectives. Two case studies and a task-based evaluation are used to demonstrate the effectiveness and usefulness of StreamExplorer.Analyzing social streams is important for many applications, such as crisis management. However, the considerable diversity, increasing volume, and high dynamics of social streams of large events continue to be significant challenges that must be overcome to ensure effective exploration. We propose a novel framework by which to handle complex social streams on a budget PC. This framework features two components: 1) an online method to detect important time periods (i.e., subevents), and 2) a tailored GPU-assisted Self-Organizing Map (SOM) method, which clusters the tweets of subevents stably and efficiently. Based on the framework, we present Stream
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Martins, António A.; Cabral, João; Cunha, Pedro P.; Stokes, Martin; Borges, José; Caldeira, Bento; Martins, A. Cardoso
2017-01-01
This study examines the long profiles of tributaries of the Tagus and Zêzere rivers in Portugal (West Iberia) in order to provide new insights into patterns, timing, and controls on drainage development during the Quaternary incision stage. The studied streams are incised into a relict culminant fluvial surface, abandoned at the beginning of the incision stage. The streams flow through a landscape with bedrock variations in lithology (mainly granites and metasediments) and faulted blocks with distinct uplift rates. The long profiles of the analyzed streams record an older transitory knickpoint/knickzone separating (1) an upstream relict graded profile, with lower steepness and higher concavity, that reflects a long period of quasi-equilibrium conditions reached after the beginning of the incision stage, and (2) a downstream rejuvenated long profile, with steeper gradient and lower concavity, particularly for the final reach, which is often convex. The rejuvenated reaches testify to the upstream propagation of several incision waves, interpreted as the response of each stream to increasing crustal uplift and prolonged periods of base-level lowering by the trunk drainages, coeval with low sea level conditions. The morphological configurations of the long profiles enabled spatial and relative temporal patterns of incisions to be quantified. The incision values of streams flowing on the Portuguese Central Range (PCR; ca. 380-150 m) are variable but generally higher than the incision values of streams flowing on the adjacent South Portugal Planation Surface (SPPS; ca. 220-110 m), corroborating differential uplift of the PCR relative to the SPPS. Owing to the fact that the relict graded profiles can be correlated with the Tagus River T1 terrace (1.1-0.9 My) present in the study area, incision rates can be estimated (1) for the streams located in the PCR, 0.38-0.15 m/ky and (2) for the streams flowing on the SPPS, 0.22-0.12 m/ky. The differential uplift inferred in the
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Miller, Matthew P.; McKnight, Diane M.; Cory, R.M.; Williams, Mark W.; Runkel, Robert L.
2006-01-01
The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport model showed that rates of exchange between the stream and hyporheic zone were rapid (?? ??? 10-3 s -1). Parallel factor analysis of fluorescence spectra was used to quantify the redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (?? = 6.5 ?? 10-3 s -1) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (?? = 1.2 ?? 10-3 s-1) and production of nitrate (?? = -1.0 ?? 10-3 s-1) were opposite in sign but almost equal in magnitude. Our results suggest that fulvic acids are involved in rapid electron-transfer processes in and near the stream channel and may be important in determining ecological energy flow at the catchment scale. ?? 2006 American Chemical Society.
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Evans, C.; Davies, T.D.; Murdoch, Peter S.
1999-01-01
Plots of solute concentration against discharge have been used to relate stream hydrochemical variations to processes of flow generation, using data collected at four streams in the Catskill Mountains, New York, during the Episodic Response Project of the US Environmental Protection Agency. Results suggest that a two-component system of shallow and deep saturated subsurface flow, in which the two components respond simultaneously during hydrologic events, may be applicable to the study basins. Using a large natural sea-salt sodium input as a tracer for precipitation, it is argued that an additional distinction can be made between pre-event and event water travelling along the shallow subsurface flow path. Pre-event water is thought to be displaced by infiltrating event water, which becomes dominant on the falling limb of the hydrograph. Where, as appears to be the case for sulfate, a solute equilibrates rapidly within the soil, the pre-event-event water distinction is unimportant. However, for some solutes there are clear and consistent compositional differences between water from the two sources, evident as a hysteresis loop in concentration-discharge plots. Nitrate and acidity, in particular, appear to be elevated in event water following percolation through the organic horizon. Consequently, the most acidic, high nitrate conditions during an episode generally occur after peak discharge. A simple conceptual model of episode runoff generation is presented on the basis of these results.Plots of solute concentration against discharge have been used to relate stream hydrochemical variations to processes of flow generation, using data collected at four streams in the Catskill Mountains, New York, during the Episodic Response Project of the US Environmental Protection Agency. Results suggest that a two-component system of shallow and deep saturated subsurface flow, in which the two components respond simultaneously during hydrologic events, may be applicable to the
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Instantaneous aerosol dynamics in a turbulent flow
Zhou, Kun
2012-01-01
Dibutyl phthalate aerosol particles evolution dynamics in a turbulent mixing layer is simulated by means of direct numerical simulation for the flow field and the direct quadrature method of moments for the aerosol evolution. Most par-ticles are nucleated in a thin layer region corresponding to a specific narrow temperature range near the cool stream side. However, particles undergo high growth rate on the hot stream side due to condensation. Coagulation decreases the total particle number density at a rate which is highly correlated to the in-stantaneous number density.
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Falcone, James A.; Carlisle, Daren M.; Wolock, David M.; Meador, Michael R.
2010-01-01
Stream flow is a controlling element in the ecology of rivers and streams. Knowledge of the natural flow regime facilitates the assessment of whether specific hydrologic attributes have been altered by humans in a particular stream and the establishment of specific goals for stream-flow restoration. Because most streams are ungaged or have been altered by human influences, characterizing the natural flow regime is often only possible by estimating flow characteristics based on nearby stream gages of reference quality, i.e., gaged locations that are least disturbed by human influences. The ability to evaluate natural stream flow, that which is not altered by human activities, would be enhanced by the existence of a nationally consistent and up-to-date database of gages in relatively undisturbed watersheds.
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How and Why Does Stream Water Temperature Vary at Small Spatial Scales in a Headwater Stream?
Morgan, J. C.; Gannon, J. P.; Kelleher, C.
2017-12-01
The temperature of stream water is controlled by climatic variables, runoff/baseflow generation, and hyporheic exchange. Hydrologic conditions such as gaining/losing reaches and sources of inflow can vary dramatically along a stream on a small spatial scale. In this work, we attempt to discern the extent that the factors of air temperature, groundwater inflow, and precipitation influence stream temperature at small spatial scales along the length of a stream. To address this question, we measured stream temperature along the perennial stream network in a 43 ha catchment with a complex land use history in Cullowhee, NC. Two water temperature sensors were placed along the stream network on opposite sides of the stream at 100-meter intervals and at several locations of interest (i.e. stream junctions). The forty total sensors recorded the temperature every 10 minutes for one month in the spring and one month in the summer. A subset of sampling locations where stream temperature was consistent or varied from one side of the stream to the other were explored with a thermal imaging camera to obtain a more detailed representation of the spatial variation in temperature at those sites. These thermal surveys were compared with descriptions of the contributing area at the sample sites in an effort to discern specific causes of differing flow paths. Preliminary results suggest that on some branches of the stream stormflow has less influence than regular hyporheic exchange, while other tributaries can change dramatically with stormflow conditions. We anticipate this work will lead to a better understanding of temperature patterns in stream water networks. A better understanding of the importance of small-scale differences in flow paths to water temperature may be able to inform watershed management decisions in the future.
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Sando, Roy; Sando, Steven K.; McCarthy, Peter M.; Dutton, DeAnn M.
2016-04-05
The U.S. Geological Survey (USGS), in cooperation with the Montana Department of Natural Resources and Conservation, completed a study to update methods for estimating peak-flow frequencies at ungaged sites in Montana based on peak-flow data at streamflow-gaging stations through water year 2011. The methods allow estimation of peak-flow frequencies (that is, peak-flow magnitudes, in cubic feet per second, associated with annual exceedance probabilities of 66.7, 50, 42.9, 20, 10, 4, 2, 1, 0.5, and 0.2 percent) at ungaged sites. The annual exceedance probabilities correspond to 1.5-, 2-, 2.33-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence intervals, respectively.Regional regression analysis is a primary focus of Chapter F of this Scientific Investigations Report, and regression equations for estimating peak-flow frequencies at ungaged sites in eight hydrologic regions in Montana are presented. The regression equations are based on analysis of peak-flow frequencies and basin characteristics at 537 streamflow-gaging stations in or near Montana and were developed using generalized least squares regression or weighted least squares regression.All of the data used in calculating basin characteristics that were included as explanatory variables in the regression equations were developed for and are available through the USGS StreamStats application (http://water.usgs.gov/osw/streamstats/) for Montana. StreamStats is a Web-based geographic information system application that was created by the USGS to provide users with access to an assortment of analytical tools that are useful for water-resource planning and management. The primary purpose of the Montana StreamStats application is to provide estimates of basin characteristics and streamflow characteristics for user-selected ungaged sites on Montana streams. The regional regression equations presented in this report chapter can be conveniently solved using the Montana StreamStats application.Selected results from
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Simulation and comparison of stream power in-channel and on the floodplain in a German lowland area
Directory of Open Access Journals (Sweden)
Song Song
2014-06-01
Full Text Available Extensive lowland floodplains cover substantial parts of the glacially formed landscape of Northern Germany. Stream power is recognized as a force of formation and development of the river morphology and an interaction system between channel and floodplain. In order to understand the effects of the river power and flood power, HEC-RAS models were set up for ten river sections in the Upper Stör catchment, based on a 1 m digital elevation model and field data, sampled during a moderate water level period (September, 2011, flood season (January, 2012 and dry season (April, 2012. The models were proven to be highly efficient and accurate through the seasonal roughness modification. The coefficients of determination (R2 of the calibrated models were 0.90, 0.90, 0.93 and 0.95 respectively. Combined with the continuous and long-term data support from SWAT model, the stream power both in-channel and on the floodplain was analysed. Results show that the 10-year-averaged discharge and unit stream power were around 1/3 of bankfull discharge and unit power, and the 10-year-peak discharge and unit stream power were nearly 1.6 times the bankfull conditions. Unit stream power was proportional to the increase of stream discharge, while the increase rate of unit in-channel stream power was 3 times higher than that of unit stream power on the floodplain. Finally, the distribution of the hydraulic parameters under 10-years-peak discharge conditions was shown, indicating that only 1-10% of flow stream was generated by floodplain flow, but 40-75% volume of water was located on the floodplain. The variation of the increasing rate of the stream power was dominated by the local roughness height, while the stream power distributed on the floodplain mainly depended on the local slope of the sub-catchment.
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Influence of Gas Flow Rate on the Deposition Rate on Stainless Steel 202 Substrates
Directory of Open Access Journals (Sweden)
M.A. Chowdhury
2012-12-01
Full Text Available Solid thin films have been deposited on stainless steel 202 (SS 202 substrates at different flow rates of natural gas using a hot filament thermal chemical vapor deposition (CVD reactor. In the experiments, the variations of thin film deposition rate with the variation of gas flow rate have been investigated. The effects of gap between activation heater and substrate on the deposition rate have also been observed. Results show that deposition rate on SS 202 increases with the increase in gas flow rate within the observed range. It is also found that deposition rate increases with the decrease in gap between activation heater and substrate. In addition, friction coefficient and wear rate of SS 202 sliding against SS 304 under different sliding velocities are also investigated before and after deposition. The experimental results reveal that improved friction coefficient and wear rate is obtained after deposition than that of before deposition.
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A new flow focusing technique to produce very thin jets
International Nuclear Information System (INIS)
Acero, A J; Rebollo-Muñoz, N; Montanero, J M; Gañán-Calvo, A M; Vega, E J
2013-01-01
A new technique is proposed in this paper to produce jets, droplets, and emulsions with sizes ranging from tens of microns down to the submicrometer scale. Liquid is injected at a constant flow rate through a hypodermic needle to form a film over the needle's outer surface. This film flows toward the needle tip until a liquid ligament is steadily ejected. Both the film motion and the liquid ejection are driven by the viscous and pressure forces exerted by a coflowing fluid stream. If this stream is a high-speed gas current, the outcome is a capillary jet which breaks up into droplets due to the Rayleigh instability. Micrometer emulsions are also produced by this instability mechanism when the injected liquid is focused by a viscous liquid stream. The minimum flow rates reached with the proposed technique are two orders of magnitude lower than those of the standard flow focusing configuration. This sharp reduction of the minimum flow rate allows one to form steady jets with radii down to the submicrometer scale. The stability of this new configuration is analyzed experimentally for both gas–liquid and liquid–liquid systems. In most of the cases, the loss of stability must be attributed to the liquid source because the critical Weber (capillary) number for the gas–liquid (liquid–liquid) case was significantly greater than the value corresponding to the convective/absolute instability transition in the jet. (paper)
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Stream Width Dynamics in a Small Headwater Catchment
Barefoot, E. A.; Pavelsky, T.; Allen, G. H.; Zimmer, M. A.; McGlynn, B. L.
2016-12-01
Changing streamflow conditions cause small, ephemeral and intermittent stream networks to expand and contract, while simultaneously driving widening and narrowing of streams. The resulting dynamic surface area of ephemeral streams impacts critical hydrological and biogeochemical processes, including air-water gas exchange, solute transport, and sediment transport. Despite the importance of these dynamics, to our knowledge there exists no complete study of how stream widths vary throughout an entire catchment in response to changing streamflow conditions. Here we present the first characterization of how variable hydrologic conditions impact the distribution of stream widths in a 48 ha headwater catchment in the Stony Creek Research Watershed, NC, USA. We surveyed stream widths longitudinally every 5 m on 12 occasions over a range of stream discharge from 7 L/s to 128 L/s at the catchment outlet. We hypothesize that the shape and location of the stream width distribution are driven by the action of two interrelated mechanisms, network extension and at-a-station widening, both of which increase with discharge. We observe that during very low flow conditions, network extension more significantly influences distribution location, and during high flow conditions stream widening is the dominant driver. During moderate flows, we observe an approximately 1 cm rightward shift in the distribution peak with every additional 10 L/s of increased discharge, which we attribute to a greater impact of at-a-station widening on distribution location. Aside from this small shift, the qualitative location and shape of the stream width distribution are largely invariant with changing streamflow. We suggest that the basic characteristics of stream width distributions constitute an equilibrium between the two described mechanisms across variable hydrologic conditions.
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Characterization and monitoring of 300 Area Facility liquid waste streams: Status report
International Nuclear Information System (INIS)
Manke, K.L.; Riley, R.G.; Ballinger, M.Y.; Damberg, E.G.; Evans, J.C.; Ikenberry, A.S.; Olsen, K.B.; Ozanich, R.M.; Thompson, C.J.
1994-09-01
This report summarizes the results of characterizing and monitoring the following sources during a portion of this year: liquid waste streams from Buildings 331, 320, and 3720; treated and untreated Columbia River water; and water at the confluence of the waste streams (that is, end-of-pipe). Characterization and monitoring data were evaluated for samples collected between March 22 and June 21, 1994, and subsequently analyzed for hazardous chemicals, radioactivity, and general parameters. Except for bis(2-ethylhexyl)phthalate, concentrations of chemicals detected and parameters measured at end-of-pipe were below the US Environmental Protection Agency existing and proposed drinking water standards. The source of the chemicals, except bis(2-ethylhexyl)phthalate, is not currently known. The bis(2-ethylhexyl)phthalate is probably an artifact of the plastic tubing used in the early stages of the sampling program. This practice was stopped. Concentrations and clearance times for contaminants at end-of-pipe depended strongly on source concentration at the facility release point, waste stream flow rates, dispersion, and the mechanical action of sumps. When present, the action of sumps had the greatest impact on contaminant clearance times. In the absence of sump activity, dispersion and flow rate were the controlling factors
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International Nuclear Information System (INIS)
Han Yan
1997-01-01
The heavy water loop (i,e, RCS) for ARR-2 in Algeria is a complex loop. Flow regulating means are not provided by the design in order to operate the reactor safely and simplify operating processes. How to determine precisely the orifice diameters of resistance parts for the loop is a key point for decreasing deviation between practical and design flow rates. Commissioning tests shall ensure that under every one of combined operating modes for the pumps, total coolant flow rate is about the same (the number of pumps operating in parallel is the same) and is consistent with design requirement, as well as the distribution of coolant flow rate to every branch is uniform. The flow Determination is divided into two steps. First and foremost, corresponding resistance part at each pump outlet is determined in commissioning test of shorted heavy water loop with light water, so that the problem about uniform distribution of the flow rate to each branch is solved, Secondly, resistance part at the reactor inlet is determined in commissioning test of heavy water loop connected with the vessel, so that the problem about that total heavy water flow rate is within optimal range is solved. According to practical requirements of the project, a computer program of hydraulic calculation and analysis for heavy water loop has been developed, and hydraulic characteristics test for a part of loop has been conducted in order to correct calculation error. By means of program calculation combining with tests in site, orifice diameters of 9 resistance parts has been determined rapidly and precisely and requirements of design and operation has been met adequately
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Supraorbital cutaneous blood flow rate during carotid endarterectomy
DEFF Research Database (Denmark)
Hove, Jens D; Rosenberg, Iben; Sejrsen, Per
2006-01-01
: The supraorbital cutaneous blood flow rate was measured by the application of heat to the skin and following the subsequent dissipation of the heat in seven patients undergoing carotid endarterectomy. At the same time, the oxygenation in the right and left frontal region was monitored by near-infrared spectroscopy......BACKGROUND: The supraorbital skin region is supplied by the supraorbital artery, which is a branch of the internal carotid artery. The supraorbital cutaneous blood flow rate may therefore be influenced by changes in the internal carotid artery flow during carotid endarterectomy. METHODS...... (NIRS). RESULTS: During cross-clamping of the carotid artery, the ipsilateral NIRS-determined frontal oxygenation tended to decrease [67 +/- 13% to 61 +/- 11% (P = 0.06); contralateral 68 +/- 11% to 66 +/- 8%] as did the supraorbital cutaneous blood flow rate from 56 +/- 23 to 44 +/- 7 ml 100 g(-1) min...
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Sensitivity of intermittent streams to climate variations in the United States
Eng, K.
2015-12-01
There is growing interest in the effects of climate change on streamflows because of the potential negative effects on aquatic biota and water supplies. Previous studies of climate controls on flows have primarily focused on perennial streams, and few studies have examined the effect of climate variability on intermittent streams. Our objectives in this study were to (1) identify regions showing similar patterns of intermittency, and (2) evaluate the sensitivity of intermittent streams to historical variability in climate in the United States. This study was carried out at 265 intermittent streams by evaluating: (1) correlations among time series of flow metrics (number of zero-flow events, the average of the central 50% and largest 10% of flows) with precipitation (magnitudes, durations and intensity) and temperature, and (2) decadal changes in the seasonality and long-term trends of these flow metrics. Results identified five distinct seasonal patterns of flow intermittency: fall, fall-to-winter, non-seasonal, summer, and summer-to-winter intermittent streams. In addition, strong associations between the low-flow metrics and historical climate variability were found. However, the lack of trends in historical variations in precipitation results in no significant seasonal shifts or decade-to-decade trends in the low-flow metrics over the period of record (1950 to 2013).
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Fluid Flow Behaviour under Different Gases and Flow Rate during Gas Metal Arc Welding
Jaison Peter
2013-01-01
Gas metal arc welding (GMAW) is a highly efficient and fast process for fabricating high quality weld. High quality welds are fabricated by proper selection of consumable includes gas and filler metals. The optimum flow rate of gas will ensure the proper quality of weld. In this project, a fluid flow behavior of different flow rate is modeled and the change quality will be studied.
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Clarke, John S.; Painter, Jaime A.
2014-01-01
Septic systems were identified at 241,733 locations in a 2,539-square-mile (mi2) study area that includes all or parts of 12 counties in the Metropolitan Atlanta, Georgia, area. Septic system percolation may locally be an important component of streamflow in small drainage basins where it augments natural groundwater recharge, especially during extreme low-flow conditions. The amount of groundwater reaching streams depends on how much is intercepted by plants or infiltrates to deeper parts of the groundwater system that flows beyond a basin divide and does not discharge into streams within a basin. The potential maximum percolation from septic systems in the study area is 62 cubic feet per second (ft3/s), of which 52 ft3/s is in the Chattahoochee River Basin and 10 ft3/s is in the Flint River Basin. These maximum percolation rates represent 0.4 to 5.7 percent of daily mean streamflow during the 2011–12 period at the farthest downstream gaging site (station 02338000) on the Chattahoochee River, and 0.5 to 179 percent of daily mean streamflow at the farthest downstream gaging site on the Flint River (02344350). To determine the difference in base flow between basins having different septic system densities, hydrograph separation analysis was completed using daily mean streamflow data at streamgaging stations at Level Creek (site 02334578), with a drainage basin having relatively high septic system density of 101 systems per square mile, and Woodall Creek (site 02336313), with a drainage basin having relatively low septic system density of 18 systems per square mile. Results indicated that base-flow yield during 2011–12 was higher at the Level Creek site, with a median of 0.47 cubic feet per second per square mile ([ft3/s]/mi2), compared to a median of 0.16 (ft3/s)/mi2, at the Woodall Creek site. At the less urbanized Level Creek site, there are 515 septic systems with a daily maximum percolation rate of 0.14 ft3/s, accounting for 11 percent of the base flow in
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Source modulation-correlation measurement for fissile mass flow in gas or liquid fissile streams
International Nuclear Information System (INIS)
Mihalczo, J.T.; March-Leuba, J.A.; Valentine, T.E.; Abston, R.A.; Mattingly, J.K.; Mullens, J.A.
1996-01-01
The method of monitoring fissile mass flow on all three legs of a blending point, where the input is high-enriched uranium (HEU) and low-enriched uranium (LEU) and the product is PEU, can yield the fissile stream velocity and, with calibration, the [sup235]U content. The product of velocity and content integrated over the pipe gives the fissile mass flow in each leg. Also, the ratio of fissile contents in each pipe: HEU/LEU, HEU/PEU, and PEU/LEU, are obtained. By modulating the source on the input HEU pipe differently from that on the output pipe, the HEU gas can be tracked through the blend point. This method can be useful for monitoring flow velocity, fissile content, and fissile mass flow in HEU blenddown of UF[sub 6] if the pressures are high enough to contain some of the induced fission products. This method can also be used to monitor transfer of fissile liquids and other gases and liquids that emit radiation delayed from particle capture. These preliminary experiments with the Oak Ridge apparatus show that the method will work and the modeling is adequate
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Flow rate-pressure drop relation for deformable shallow microfluidic channels
Christov, Ivan C.; Cognet, Vincent; Shidhore, Tanmay C.; Stone, Howard A.
2018-04-01
Laminar flow in devices fabricated from soft materials causes deformation of the passage geometry, which affects the flow rate--pressure drop relation. For a given pressure drop, in channels with narrow rectangular cross-section, the flow rate varies as the cube of the channel height, so deformation can produce significant quantitative effects, including nonlinear dependence on the pressure drop [{Gervais, T., El-Ali, J., G\\"unther, A. \\& Jensen, K.\\ F.}\\ 2006 Flow-induced deformation of shallow microfluidic channels.\\ \\textit{Lab Chip} \\textbf{6}, 500--507]. Gervais et. al. proposed a successful model of the deformation-induced change in the flow rate by heuristically coupling a Hookean elastic response with the lubrication approximation for Stokes flow. However, their model contains a fitting parameter that must be found for each channel shape by performing an experiment. We present a perturbation approach for the flow rate--pressure drop relation in a shallow deformable microchannel using the theory of isotropic quasi-static plate bending and the Stokes equations under a lubrication approximation (specifically, the ratio of the channel's height to its width and of the channel's height to its length are both assumed small). Our result contains no free parameters and confirms Gervais et. al.'s observation that the flow rate is a quartic polynomial of the pressure drop. The derived flow rate--pressure drop relation compares favorably with experimental measurements.
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Establishing a Multi-scale Stream Gaging Network in the Whitewater River Basin, Kansas, USA
Clayton, J.A.; Kean, J.W.
2010-01-01
Investigating the routing of streamflow through a large drainage basin requires the determination of discharge at numerous locations in the channel network. Establishing a dense network of stream gages using conventional methods is both cost-prohibitive and functionally impractical for many research projects. We employ herein a previously tested, fluid-mechanically based model for generating rating curves to establish a stream gaging network in the Whitewater River basin in south-central Kansas. The model was developed for the type of channels typically found in this watershed, meaning that it is designed to handle deep, narrow geomorphically stable channels with irregular planforms, and can model overbank flow over a vegetated floodplain. We applied the model to ten previously ungaged stream reaches in the basin, ranging from third- to sixth-order channels. At each site, detailed field measurements of the channel and floodplain morphology, bed and bank roughness, and vegetation characteristics were used to quantify the roughness for a range of flow stages, from low flow to overbank flooding. Rating curves that relate stage to discharge were developed for all ten sites. Both fieldwork and modeling were completed in less than 2 years during an anomalously dry period in the region, which underscores an advantage of using theoretically based (as opposed to empirically based) discharge estimation techniques. ?? 2010 Springer Science+Business Media B.V.
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Xin, Zhuohang; Kinouchi, Tsuyoshi
2013-05-01
Stream temperature variations of the Tama River, which runs through highly urbanized areas of Tokyo, were studied in relation to anthropogenic impacts, including wastewater effluents, dam release and water withdrawal. Both long-term and longitudinal changes in stream temperature were identified and the influences of stream flow rate, temperature and volume of wastewater effluents and air temperature were investigated. Water and heat budget analyses were also conducted for several segments of the mainstream to clarify the relative impacts from natural and anthropogenic factors. Stream temperatures in the winter season significantly increased over the past 20 years at sites affected by intensive and warm effluents from wastewater treatment plants (WWTPs) located along the mainstream. In the summer season, a larger stream temperature increase was identified in the upstream reaches, which was attributable to the decreased flow rate due to water withdrawal. The relationship between air and stream temperatures indicated that stream temperatures at the upstream site were likely to be affected by a dam release, while temperatures in the downstream reaches have deviated more from air temperatures in recent years, probably due to the increased impacts of effluents from WWTPs. Results of the water and heat budget analyses indicated that the largest contributions to water and heat gains were attributable to wastewater effluents, while other factors such as groundwater recharge and water withdrawal were found to behave as energy sinks, especially in summer. The inflow from tributaries worked to reduce the impacts of dam release and the heat exchanges at the air-water interface contributed less to heat budgets in both winter and summer seasons for all river segments.
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Directory of Open Access Journals (Sweden)
Milica Stankovic
2013-12-01
Full Text Available The species composition and structure of the plant communities along and in the fast-flowing streams on different bedrock types of the tropical mainland South-East Asia were investigated. The study was carried out in Peninsular Thailand, on the Nakhon Si Thammarat mountain range. A total number of 14 plots were placed within the five selected streams where vascular plants species had been collected, starting from November 2010 until July 2012. The estimation of the species was calculated by computer program EstimateS, and in order to distinguish plant communities, a cluster analysis was performed. A total number of 109 species of vascular plants has been recorded, with 59 species in the granite and 60 in the calcareous bedrock streams. There were four types of plant communities that had were categorized; of which three types occurred in the granitic bedrock streams and the other could be seen exclusively in the calcareous bedrock. It is convinced that the types of the bedrock as well as the topographic features of the streams might have major impact on the characterization of the plant communities.
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Flow rates through earthen, geomembrane ampersand composite cut-off walls
International Nuclear Information System (INIS)
Tachavises, C.; Benson, C.H.
1997-01-01
Flow rates through soil-bentonite (SIB), geomembrane (GM), and composite geomembrane-soil (CGS) cut-off walls were determined using a numerical model of ground water flow. Various geological and wall conditions were simulated. Results of the simulations show that flow rates past all wall types are affected by hydraulic conductivities of the aquifer and underlying confining layer. Flow rates past GM walls with perfect joints are very low, provided the confining layer has low hydraulic conductivity. However, if a small fraction of the joints are defective, GM walls can be ineffective in blocking flow. CGS walls with a low hydraulic conductivity shell are less sensitive to joint defects. CGS walls with good shells typically have lower flow rates than SB and GM walls, even if the CGS wall contains defective joints
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Influence of Gas Flow Rate on the Deposition Rate on Stainless Steel 202 Substrates
M.A. Chowdhury; D.M. Nuruzzaman
2012-01-01
Solid thin films have been deposited on stainless steel 202 (SS 202) substrates at different flow rates of natural gas using a hot filament thermal chemical vapor deposition (CVD) reactor. In the experiments, the variations of thin film deposition rate with the variation of gas flow rate have been investigated. The effects of gap between activation heater and substrate on the deposition rate have also been observed. Results show that deposition rate on SS 202 increases with the increase in g...
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Modelling of a vanishing Hawaiin stream with DHSVM
Verger, R.P.; Augustijn, Dionysius C.M.; Booij, Martijn J.; Fares, A.; Erdbrink, C.D.; van Os, A.G.
2008-01-01
Several Hawaiian streams show downward trends in stream flow. In this study Makaha Stream is investigated as an example. Three possible reasons are commonly mentioned for the discharge reduction: groundwater pumping, decreasing rainfall, and changes in vegetation. The effect of these factors on
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Flow rate dependency of critical wall shear stress in a radial-flow cell
DEFF Research Database (Denmark)
Detry, J.G.; Jensen, Bo Boye Busk; Sindic, M.
2009-01-01
In the present work, a radial-flow cell was used to study the removal of starch particle aggregates from several solid substrates (glass, stainless steel, polystyrene and PTFE) in order to determine the critical wall shear stress value for each case. The particle aggregates were formed by aspersion...... of a water or ethanol suspension of starch granules on the surfaces. Depending on the substrate and on the suspending liquid, the aggregates differed in size and shape. Aggregate removal was studied at two flow rates. At the lower flow rate (Re-inlet = 955), the values of critical wall shear stress...... for the different surfaces suggested that capillary forces were, for all of them, playing an important role in aggregate adhesion since aqueous based aggregates were always more difficult to remove. At the higher flow rate (Re-inlet = 2016) the critical wall shear stress increased as a result of the change...
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Holmquist, Jeffrey G.; Waddle, Terry J.
2013-01-01
We used two-dimensional hydrodynamic models for the assessment of water diversion effects on benthic macroinvertebrates and associated habitat in a montane stream in Yosemite National Park, Sierra Nevada Mountains, CA, USA. We sampled the macroinvertebrate assemblage via Surber sampling, recorded detailed measurements of bed topography and flow, and coupled a two-dimensional hydrodynamic model with macroinvertebrate indicators to assess habitat across a range of low flows in 2010 and representative past years. We also made zero flow approximations to assess response of fauna to extreme conditions. The fauna of this montane reach had a higher percentage of Ephemeroptera, Plecoptera, and Trichoptera (%EPT) than might be expected given the relatively low faunal diversity of the study reach. The modeled responses of wetted area and area-weighted macroinvertebrate metrics to decreasing discharge indicated precipitous declines in metrics as flows approached zero. Changes in area-weighted metrics closely approximated patterns observed for wetted area, i.e., area-weighted invertebrate metrics contributed relatively little additional information above that yielded by wetted area alone. Loss of habitat area in this montane stream appears to be a greater threat than reductions in velocity and depth or changes in substrate, and the modeled patterns observed across years support this conclusion. Our models suggest that step function losses of wetted area may begin when discharge in the Merced falls to 0.02 m3/s; proportionally reducing diversions when this threshold is reached will likely reduce impacts in low flow years.
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Removal of radioiodine species from gaseous stream on inorganic absorbents
International Nuclear Information System (INIS)
Vujisic, L.
1978-11-01
As a contribution to the development of an impregnated absorbent for the removal of airborne iodine species in the off-gas streams of nuclear facilities the adsorption of 131 l-labelled methyl iodide on impregnated alumina was investigated. Alcoa alumina H-151 was impregnated with metal nitrates (Ag, Ag+Cd, Ag+Pb) and with triethylenediamine (TEDA). The removal efficiency of CH 3 l was experimentally evaluated, as functions of relative humidity of air-stream, its temperature and flow rate and of the amount of impregnated materials. Under constant temperature, relative humidity and face velocity, the retention of CH 3 l increases as the total amount of Ag impregnation increases. In a wet air-stream the only efficient impregnation was found to be with silver nitrate. At constant temperature the CH 3 l retention decreases with increasing relative humidity or face velocity of the stream. An increase of temperature favours the CH 3 l retention. Very low retention of CH 3 l was found on TEDA impregnated alumina
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Investigation of the specific mass flow rate distribution in pipes supplied with a pulsating flow
Energy Technology Data Exchange (ETDEWEB)
Olczyk, Aleksander [Institute of Turbomachinery, Technical University of Lodz, Wolczanska 219/223, 90-924 Lodz (Poland)], E-mail: aolczyk@p.lodz.pl
2009-08-15
A pulsating flow is typical of inlet and exhaust pipes of internal combustion engines and piston compressors. Unsteady flow phenomena are especially important in the case of turbocharged engines, because dynamic effects occurring in the exhaust pipe can affect turbine operation conditions and performance. One of the basic parameters describing the unsteady flow is a transient mass flow rate related to the instantaneous flow velocity, which is usually measured by means of hot-wire anemometers. For the flowing gas, it is more appropriate to analyze the specific mass flow rate {phi}{sub m} = {rho}v, which takes into account also variations in the gas density. In order to minimize the volume occupied by measuring devices in the control section, special double-wire sensors for the specific mass flow rate (CTA) and temperature (CCT) measurement were applied. The article describes procedures of their calibration and measurement. Different forms of calibration curves are analyzed as well in order to match the approximation function to calibration points. Special attention is paid to dynamic phenomena related to the resonance occurring in a pipe for characteristic frequencies depending on the pipe length. One of these phenomena is a reverse flow, which makes it difficult to interpret properly the recorded CTA signal. Procedures of signal correction are described in detail. To verify the measurements, a flow field investigation was carried out by displacing probes radially and determining the profiles of the specific mass flow rate under the conditions of a steady and pulsating flow. The presence and general features of a reverse flow, which was identified experimentally, were confirmed by 1-D unsteady flow calculations.
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Investigation of the specific mass flow rate distribution in pipes supplied with a pulsating flow
International Nuclear Information System (INIS)
Olczyk, Aleksander
2009-01-01
A pulsating flow is typical of inlet and exhaust pipes of internal combustion engines and piston compressors. Unsteady flow phenomena are especially important in the case of turbocharged engines, because dynamic effects occurring in the exhaust pipe can affect turbine operation conditions and performance. One of the basic parameters describing the unsteady flow is a transient mass flow rate related to the instantaneous flow velocity, which is usually measured by means of hot-wire anemometers. For the flowing gas, it is more appropriate to analyze the specific mass flow rate φ m = ρv, which takes into account also variations in the gas density. In order to minimize the volume occupied by measuring devices in the control section, special double-wire sensors for the specific mass flow rate (CTA) and temperature (CCT) measurement were applied. The article describes procedures of their calibration and measurement. Different forms of calibration curves are analyzed as well in order to match the approximation function to calibration points. Special attention is paid to dynamic phenomena related to the resonance occurring in a pipe for characteristic frequencies depending on the pipe length. One of these phenomena is a reverse flow, which makes it difficult to interpret properly the recorded CTA signal. Procedures of signal correction are described in detail. To verify the measurements, a flow field investigation was carried out by displacing probes radially and determining the profiles of the specific mass flow rate under the conditions of a steady and pulsating flow. The presence and general features of a reverse flow, which was identified experimentally, were confirmed by 1-D unsteady flow calculations.
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Position paper -- Tank ventilation system design air flow rates
International Nuclear Information System (INIS)
Goolsby, G.K.
1995-01-01
The purpose of this paper is to document a project position on required ventilation system design air flow rates for the waste storage tanks currently being designed by project W-236A, the Multi-Function Waste Tank Facility (MWTF). The Title 1 design primary tank heat removal system consists of two systems: a primary tank vapor space ventilation system; and an annulus ventilation system. At the conclusion of Title 1 design, air flow rates for the primary and annulus ventilation systems were 960 scfm and 4,400 scfm, respectively, per tank. These design flow rates were capable of removing 1,250,000 Btu/hr from each tank. However, recently completed and ongoing studies have resulted in a design change to reduce the extreme case heat load to 700,000 Btu/hr. This revision of the extreme case heat load, coupled with results of scale model evaporative testing performed by WHC Thermal Hydraulics, allow for a reduction of the design air flow rates for both primary and annulus ventilation systems. Based on the preceding discussion, ICF Kaiser Hanford Co. concludes that the design should incorporate the following design air flow rates: Primary ventilation system--500 scfm maximum and Annulus ventilation system--1,100 scfm maximum. In addition, the minimum air flow rates in the primary and annulus ventilation systems will be investigated during Title 2 design. The results of the Title 2 investigation will determine the range of available temperature control using variable air flows to both ventilation systems
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U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted August stream/river temperature maximum positive daily rate of change in New England based on a...
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U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted July stream/river temperature maximum positive daily rate of change in New England based on a...
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U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted July stream/river temperature maximum negative daily rate of change in New England based on a...
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Streaming reversal of energetic particles in the magnetetail during a substorm
International Nuclear Information System (INIS)
Lui, A.T.Y.; Williams, D.J.; Eastman, T.E.; Frank, L.A.; Akasofu, S.
1984-01-01
Reversal from tailward streaming to earthward streaming of energetic ions at 0.29--0.50 MeV during a substorm on February 3, 1978, is studied with measurements of energetic particles, plasma, and magnetic field from that IMP 8 spacecraft near the dusk flank of the magnetotail. Four new features emerge when high time resolution data are examined in detail. The times of reversal from tailward to earthward streaming of energetic ions and from tailward to earthward plasma flow do not coincide. Second, the velocity distribution in the tailward flowing plasma has a cresent shape, whereas the velocity distribution in the earthward flowing plasma has a crescent shape, whereas the velocity distribution in the earthward flowing plasma resembles a convecting Maxwellian. Third, tailward streaming of energetic ions is sometime detected in northward magnetic field regions and conversely, earthward streaming in southward field environments. Fourth, energetic ions scattering earthward are occasionally present in conjunction with a strong tailward streaming population in the same energy range. These new features suggest that the streaming reversal of energetic ions and the plasma flow reversal in this event are due to the spacecraft traversing different plasma regions during the substorm-associated configurational change of the plasma sheet and the magnetotail and is unrelated to the motion of an acceleration region such as an X type neutral line moving past the spacecraft
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Fluid-flow-rate metrology: laboratory uncertainties and traceabilities
Mattingly, G. E.
1991-03-01
Increased concerns for improved fluid flowrate measurement are driving the fluid metering community-meter manufacturers and users alike-to search for better verification and documentation for their fluid measurements. These concerns affect both our domestic and international market places they permeate our technologies - aerospace chemical processes automotive bioengineering etc. They involve public health and safety and they impact our national defense. These concerns are based upon the rising value of fluid resources and products and the importance of critical material accountability. These values directly impact the accuracy needs of fluid buyers and sellers in custody transfers. These concerns impact the designers and operators of chemical process systems where control and productivity optimization depend critically upon measurement precision. Public health and safety depend upon the quality of numerous pollutant measurements - both liquid and gaseous. The performance testing of engines - both automotive and aircraft are critically based upon accurate fuel measurements - both liquid and oxidizer streams. Fluid flowrate measurements are established differently from counterparts in length and mass measurement systems because these have the benefits of " identity" standards. For rate measurement systems the metrology is based upon " derived standards" . These use facilities and transfer standards which are designed built characterized and used to constitute basic measurement capabilities and quantify performance - accuracy and precision. Because " identity standards" do not exist for flow measurements facsimiles or equivalents must
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Rao, S. T.; Krishnaswamy, J.; Bhalla, R. S.
2017-12-01
Alteration of natural flow regimes is considered as a major threat to freshwater fish assemblages as it disturbs the water quality and micro-habitat features of rivers. Small hydro-power (SHP), which is being promoted as a clean and green substitute for large hydro-power generation, alters the natural flow regime of head-water streams by flow diversion and regulation. The effects of altered flow regime on tropical stream fish assemblages, driven by seasonality induced perturbations to water quality and microhabitat parameters are largely understudied. My study examined the potential consequences of flow alteration by SHPs on fish assemblages in two tributaries of the west-flowing Yettinahole River which flows through the reserved forests of Sakleshpur in the Western Ghats of Karnataka. The flow in one of the tributaries followed natural flow regime while the other comprised three regimes: a near-natural flow regime above the dam, rapidly varying discharge below the dam and a dewatered regime caused by flow diversion. The study found that the altered flow regime differed from natural flow regime in terms of water quality, microhabitat heterogeneity and fish assemblage response, each indicative of the type of flow alteration. Fish assemblage in the natural flow regime was characterized by a higher catch per site, a strong association of endemic and trophic specialist species. The flow regime above the dam was found to mimic some components of the natural flow regime, both ecological and environmental. Non endemic, generalist and pool tolerant species were associated with the dewatered regime. There was a lack of strong species-regime association and an overall low catch per site for the flow regulated regime below the dam. This study highlights the consequences of altered flows on the composition of freshwater fish assemblages and portrays the potential of freshwater fish as indicators of the degree and extent of flow alteration. The study recommends the need for
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Extreme Changes in Stream Geomorphic Conditions induced by Fluvial Scour in Bridges
Özcan, O.; Ozcan, O.
2016-12-01
The numerous complexities associated with bridge scour have caused scour to be one of the most active topics of stream geomorphic research. The assessment of local scouring mechanism around bridge piers provides information for decision-making regarding the pile footing design, predicting the safety of bridges under critical scoured conditions, and as a result, may help prevent unnecessary loses. In the study, bridge design plans and HEC-RAS modeling were used for the assessment of changes in stream geomorphic conditions. The derived fluvial scour depths were compared with the field measurements and the empirical formula which is based on stream flow discharge rate, streambed condition and shape of river. Preliminary results revealed that bridge damage resulting from the flood event in 2003 induced substantial scour around bridge piles. Afterwards, significant stream bed change was observed under the influence of fluvial scour in another flood occurred in 2009. Consequently, geomorphic conditions of the stream bed should be considered in the structural design of the bridges.
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Device accurately measures and records low gas-flow rates
Branum, L. W.
1966-01-01
Free-floating piston in a vertical column accurately measures and records low gas-flow rates. The system may be calibrated, using an adjustable flow-rate gas supply, a low pressure gage, and a sequence recorder. From the calibration rates, a nomograph may be made for easy reduction. Temperature correction may be added for further accuracy.
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The role of geology in sediment supply and bedload transport patterns in coarse-grained streams
Sandra E. Ryan
2007-01-01
This paper compares gross differences in rates of bedload sediment moved at bankfull discharges in 19 channels on national forests in the Middle and Southern Rocky Mountains. Each stream has its own "bedload signal," in that the rate and size of materials transported at bankfull discharge largely reflect the nature of flow and sediment particular to that...
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A constant flow filter air sampler for workplace environments
International Nuclear Information System (INIS)
Parulian, A.; Rodgers, J.C.; McFarland, A.R.
1996-01-01
A filter air sampler has been developed for sampling radionuclide aerosol particles form the workplace environment. It provides easy filter changing, constant flow sampling, and a visual display to indicate proper operation. An experimental study was conducted to characterize the collection efficiency of the sampler as affected by variations in room air velocity, particle size, sampling flow rate, inlet geometry, and inlet orientation to the free stream. Tests were carried out in a wing tunnel at velocities between 0.3 m s -1 and 2.0 m s -1 , which is a range that covers anticipated velocities in the typical highly ventilated workplace environment of a nuclear facility. Nearly monodisperse aerosols with sizes between 5 and 20 μm aerodynamic diameter were sampled at flow rates between 28.3 and 84.9 L min -1 . Inlet orientations of 0 degree, 90 degree, and 180 degree from the horizontal were selected for evaluation. When the sampler was oriented at 0 degree over various ranges of free stream velocities, sampling flow rates and particle sizes, the transmission efficiency of aerosol was typically greater than 95%. The transmission efficiencies varied form 80% to 106% for 10-μm aerodynamic diameter particles over the previously noted range of free stream velocities and inlet orientations. Uniformity of deposits of 10 μm aerodynamic diameter particles on collection filters was examined for a sampling rate of 57 L min -1 , a sampler orientation of 90 degree into the wind and wind speeds of 0.3-2 m s -1 . The coefficients of variation for the areal density of the deposits ranged from 6.1% to 37.2%. A miniature critical flow venturi with a constant sampling flow rate of 57 L min -1 was developed for application to the new filter air sampler. It was demonstrated that the performance of the new filter air sampler is quite acceptable over a wide range of conditions. 31 refs., 8 figs., 1 tab
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Michael N. Gooseff; Justin K. Anderson; Steven M. Wondzell; Justin LaNier; Roy. Haggerty
2005-01-01
Studies of hyporheic exchange flows have identified physical features of channels that control exchange flow at the channel unit scale, namely slope breaks in the longitudinal profile of streams that generate subsurface head distributions. We recently completed a field study that suggested channel unit spacing in stream longitudinal profiles can be used to predict the...
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Streaming gravity mode instability
International Nuclear Information System (INIS)
Wang Shui.
1989-05-01
In this paper, we study the stability of a current sheet with a sheared flow in a gravitational field which is perpendicular to the magnetic field and plasma flow. This mixing mode caused by a combined role of the sheared flow and gravity is named the streaming gravity mode instability. The conditions of this mode instability are discussed for an ideal four-layer model in the incompressible limit. (author). 5 refs
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Lorah, Michelle M.; Herman, Janet S.
1988-01-01
This field study focuses on quantitatively defining the chemical changes occurring in Falling Spring Creek, a travertine-depositing stream located in Alleghany County, Virginia. The processes of CO2outgassing and calcite precipitation or dissolution control the chemical evolution of the stream. The observed chemical composition of the water was used with the computerized geochemical model WATEQF to calculate aqueous speciation, saturation indices, and CO2 partial pressure values. Mass balance calculations were performed to obtain mass transfers of CO2 and calcite. Reaction times, estimated from stream discharge, were used with the mass transfer results to calculate rates of CO2, outgassing and calcite precipitation between consecutive sampling points. The stream, which is fed by a carbonate spring, is supersaturated with respect to CO2 along the entire 5.2-km flow path. Outgassing of CO2 drives the solution to high degrees of supersaturation with respect to calcite. Metabolic uptake of CO2 by photosynthetic plants is insignificant, because the high supply rate of dissolved carbon dioxide and the extreme agitation of the stream at waterfalls and rapids causes a much greater amount of inorganic CO2 outgassing to occur. Calcite precipitation is kinetically inhibited until near the crest of a 20-m vertical waterfall. Calcite precipitation rates then reach a maximum at the waterfall where greater water turbulence allows the most rapid escape of CO2. Physical evidence for calcite precipitation exists in the travertine deposits which are first observed immediately above the waterfall and extend for at least 1.0 km below the falls. Net calcite precipitation occurs at all times of the year but is greatest during low-flow conditions in the summer and early fall.
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Sensitivity of intermittent streams to climate variations in the USA
Eng, Kenny; Wolock, David M.; Dettinger, Mike
2015-01-01
There is a great deal of interest in the literature on streamflow changes caused by climate change because of the potential negative effects on aquatic biota and water supplies. Most previous studies have primarily focused on perennial streams, and there have been only a few studies examining the effect of climate variability on intermittent streams. Our objectives in this study were to (1) identify regions of similar zero-flow behavior, and (2) evaluate the sensitivity of intermittent streams to historical variability in climate in the United States. This study was carried out at 265 intermittent streams by evaluating: (1) correlations among time series of flow metrics (number of zero-flow events, the average of the central 50% and largest 10% of flows) with climate (magnitudes, durations and intensity), and (2) decadal changes in the seasonality and long-term trends of these flow metrics. Results identified five distinct seasonality patterns in the zero-flow events. In addition, strong associations between the low-flow metrics and historical changes in climate were found. The decadal analysis suggested no significant seasonal shifts or decade-to-decade trends in the low-flow metrics. The lack of trends or changes in seasonality is likely due to unchanged long-term patterns in precipitation over the time period examined.
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Sodium flow rate measurement method of annular linear induction pump
International Nuclear Information System (INIS)
Araseki, Hideo
2011-01-01
This report describes a method for measuring sodium flow rate of annular linear induction pumps arranged in parallel and its verification result obtained through an experiment and a numerical analysis. In the method, the leaked magnetic field is measured with measuring coils at the stator end on the outlet side and is correlated with the sodium flow rate. The experimental data and the numerical result indicate that the leaked magnetic field at the stator edge keeps almost constant when the sodium flow rate changes and that the leaked magnetic field change arising from the flow rate change is small compared with the overall leaked magnetic field. It is shown that the correlation between the leaked magnetic field and the sodium flow rate is almost linear due to this feature of the leaked magnetic field, which indicates the applicability of the method to small-scale annular linear induction pumps. (author)
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Watershed land use and topographic variability influence stream low flows, yet their interactions and relative influence remain unresolved. Our objective was to assess the relative influences of land use and watershed geomorphic characteristics on low flow variability in the sour...
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Aeroacoustics of Three-Stream Jets
Henderson, Brenda S.
2012-01-01
Results from acoustic measurements of noise radiated from a heated, three-stream, co-annular exhaust system operated at subsonic conditions are presented. The experiments were conducted for a range of core, bypass, and tertiary stream temperatures and pressures. The nozzle system had a fan-to-core area ratio of 2.92 and a tertiary-to-core area ratio of 0.96. The impact of introducing a third stream on the radiated noise for third-stream velocities below that of the bypass stream was to reduce high frequency noise levels at broadside and peak jet-noise angles. Mid-frequency noise radiation at aft observation angles was impacted by the conditions of the third stream. The core velocity had the greatest impact on peak noise levels and the bypass-to-core mass flow ratio had a slight impact on levels in the peak jet-noise direction. The third-stream jet conditions had no impact on peak noise levels. Introduction of a third jet stream in the presence of a simulated forward-flight stream limits the impact of the third stream on radiated noise. For equivalent ideal thrust conditions, two-stream and three-stream jets can produce similar acoustic spectra although high-frequency noise levels tend to be lower for the three-stream jet.
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Hydrography - Streams and Shorelines
California Natural Resource Agency — The hydrography layer consists of flowing waters (rivers and streams), standing waters (lakes and ponds), and wetlands -- both natural and manmade. Two separate...
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Groundwater-derived contaminant fluxes along a channelized Coastal Plain stream
Energy Technology Data Exchange (ETDEWEB)
LaSage, Danita m [JL Sexton and Son; Fryar, Alan E [Dept of Earth and Geoligical Sciences, Univ of KY,; Mukherjee, Abhijit [Univ of Tx, Jackson School of Geosciences, Bur of Econ. Geology; Sturchio, Neil C [Dept of earth and Env. Sciences, Univ of Ill at Chicago; Heraty, Linnea J [Dept of earth and Env. Sciences, Univ of Ill at Chicago
2008-10-01
Recent studies in various settings across eastern North America have examined the movement of volatile organic compound (VOC) plumes from groundwater to streams, but few studies have addressed focused discharge of such plumes in unlithified sediments. From 1999 through 2002, we monitored concentrations of trichloroethene (TCE) and the non-volatile co-contaminant technetium-99 along Little Bayou Creek, a first -order perennial stream in the Coastal Plain of western Kentucky. Spring flow contributed TCE and technetium-99 to the creek, and TCE concentrations tended to vary with technetium-99 in springs. Contaminant concentrations in stream water fluctuated seasonally, but not always synchronously with stream flow. However, contaminant influxes varied seasonally with stream flow and were dominated by a few springs. Concentrations of O2, NO3⁻, and SO2-4, values of δ37CL in groundwater, and the lack of less-chlorinated ethenes in groundwater and stream water indicated that aerobic biodegradation of TCE was unlikely. Losses of TCE along Little Bayou Creek resulted mainly from volatilization, in contrast to streams receiving diffuse contaminated discharge, where intrinsic bioremediation of VOCs appears to be prevalent.
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Variation in summer nitrogen and phosphorus uptake among Siberian headwater streams
Directory of Open Access Journals (Sweden)
John D. Schade
2016-06-01
Full Text Available Arctic streams are likely to receive increased inputs of dissolved nutrients and organic matter from thawing permafrost as climate warms. Documenting how Arctic streams process inorganic nutrients is necessary to understand mechanisms that regulate watershed fluxes of permafrost-derived materials to downstream ecosystems. We report on summer nitrogen (N and phosphorus (P uptake in streams draining upland soils from the Pleistocene, and lowland floodplain soils from the Holocene, in Siberia's Kolyma River watershed. Uptake of N and P differed between upland and floodplain streams, suggesting topographic variation in nutrient limitation. In floodplain streams, P uptake rate and uptake velocity were higher than N, while upland streams had similar values for all N and P uptake metrics. Phosphorus uptake velocity and size of the transient hydrologic storage zone were negatively related across all study streams, indicating strong influence of hydrologic processes on nutrient fluxes. Physical sorption of P was higher in floodplain stream sediments relative to upland stream sediments, suggesting more physically driven uptake in floodplain streams and higher biological activity in upland streams. Overall, these results demonstrate that high-latitude headwater streams actively retain N and P during summer base flows; however, floodplain and upland streams varied substantially in N and P uptake and may respond differently to inorganic nutrient and organic matter inputs. Our results highlight the need for a comprehensive assessment of N and P uptake and retention in Arctic streams in order to fully understand the impact of permafrost-derived materials on ecosystem processes, and their fate in continental drainage networks.
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Analysis of the separation of protium from blanket tritium-product streams
International Nuclear Information System (INIS)
Misra, B.; Maroni, V.A.
1981-07-01
The case is considered in which the blanket product stream has been purified to the point where only protium, tritium, and a small quantity of deuterium remain. A cryogenic distillation cascade concept developed specifically to handle this enrichment problem is shown. The concept is based on a series of distillation columns and equilibrators capable of producing a protium-rich stream containing less than 1000 appm T and a tritium-rich stream containing less than 2000 appm H. It is envisioned that both of these streams could be blended with streams of comparable composition in the mainstream position of the fuel cycle without further processing. The computational analysis of the cascade was based on a fixed arrangement of columns and equilibrators and a fixed number of theoretical plates per columns, since these features are less easily varied in an actual system than reflux ratios and flow rates. In order to test the flexibility of this conceptual enruchment system to adjust to variations of the H/T ratio in the feed, H/T values of 0.333, 1.00, and 3.00 were investigated
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Flow rate measurement in a volume
Energy Technology Data Exchange (ETDEWEB)
Galvez, Cristhian
2018-04-17
A system for measuring flow rate within a volume includes one or more transmission devices that transmit one or more signals through fluid contained within the volume. The volume may be bounded, at least in part, by an outer structure and by an object at least partially contained within the outer structure. A transmission device located at a first location of the outer structure transmits a first signal to a second location of the outer structure. A second signal is transmitted through the fluid from the second location to a third location of the outer structure. The flow rate of the fluid within the volume may be determined based, at least in part, on the time of flight of both the first signal and the second signal.
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Solution and scope of utilization of the cross-stream cooling towers
International Nuclear Information System (INIS)
Zembaty, W.
1995-01-01
Technical solutions and operational properties of the cross-stream cooling towers as well as the scope of their utilization are presented. The differences within thermodynamic calculations of the cross-stream and counter-stream cooling towers due to the direction of the air flow as well as water flow in sprinkling system are discussed. The assessment of the capital and operational costs of the cross-stream cooling towers is given and compared with the cost of counter-stream cooling towers (utilizing as an example a calculation conducted for the cooling towers of the 720, 1100 and 1400 MW units). (author). 6 refs, 9 figs
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Evaluation of exhaled nitric oxide in schoolchildren at different exhalation flow rates.
Pedroletti, Christophe; Zetterquist, Wilhelm; Nordvall, Lennart; Alving, Kjell
2002-09-01
Nitric oxide (NO) in exhaled air is believed to reflect allergic inflammation in the airways. Measured levels of exhaled NO vary with the exhaled flow rate, which therefore must be standardized. The aim of this study was to estimate the optimal exhalation flow rate when measuring NO in exhaled air. We studied 15 asthmatic children (8-18 y) with elevated NO levels and 15 age-matched controls and focused on how the quality of the NO curve profile, the discriminatory power, and the reproducibility were influenced by the exhalation flow rate. We used an on-line system for NO measurements at six different exhalation flow rates in the interval of 11-382 mL/s. The fraction of exhaled nitric oxide (FENO) was highly flow-dependent as was expected. Intermediate flow rates yielded a flat and stable NO plateau and were considerably easier to interpret than those obtained at the highest and lowest flow rates. The ratio of FENO between asthmatics and controls was lower at higher flow rates and a considerable overlap in NO values was demonstrated at all flow rates except 50 mL/s. The reproducibility was much lower at more extreme flow rates and was best at 50 mL/s. We conclude that a target exhalation flow rate of approximately 50 mL/s is to be preferred using the single-breath method for on-line NO measurements in schoolchildren.
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Ferreira, Carla S. S.; Walsh, Rory P. D.; Ferreira, António J. D.; Steenhuis, Tammo S.; Coelho, Celeste A. O.
2015-04-01
control streamflow particularly during dry periods. Winter runoff was 2-4 times higher than total river flow in the summer dry season in highly urbanized areas, but was 21-fold higher in winter in the least urbanized sub-catchment, denoting greater flow connectivity enhanced by increased soil moisture. Although impermeable surfaces are prone to generate overland flow, the proximity to the stream network is an important parameter determining their hydrological impacts. During the monitoring period, the enlargement of 2% of the urban area at downslope locations in the Covões sub-catchment, led to a 6% increase in the runoff coefficient. In contrast, the urban area increase from 9 to 25% mainly in upslope parts of the Quinta sub-catchment did not increase the peak streamflow due to downslope infiltration and surface retention opportunities. Despite impermeable surfaces enhance overland flow, some urban features (e.g. walls and road embankments) promote surface water retention. The presence of artificial drainage systems, on the other hand, enhances flow connectivity, leading to increasing peak flow and quicker response times (~10 minutes versus 40-50 minutes) as in the Covões sub-catchment. Urbanization impact on streamflow responses may be minimized through planning the land-use mosaic so as to maximize infiltration opportunities. Knowledge of the influence of distinct urban mosaics on flow connectivity and stream discharge is therefore important to landscape managers and should guide urban planning in order to minimize flood hazards.
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Langland, Michael J.; Cinotto, Peter J.; Chichester, Douglas C.; Bilger, Michael D.; Brightbill, Robin A.
2010-01-01
Base-line and long-term monitoring of water resources of the National Guard Training Center at Fort Indiantown Gap in south-central Pennsylvania began in 2002. Results of continuous monitoring of streamflow and turbidity and monthly and stormflow water-quality samples from two continuous-record long-term stream sites, periodic collection of water-quality samples from five miscellaneous stream sites, and annual collection of biological data from 2002 to 2005 at 27 sites are discussed. In addition, results from a stream-geomorphic analysis and classification and a regional groundwater-flow model are included. Streamflow at the facility was above normal for the 2003 through 2005 water years and extremely high-flow events occurred in 2003 and in 2004. Water-quality samples were analyzed for nutrients, sediments, metals, major ions, pesticides, volatile and semi-volatile organic compounds, and explosives. Results indicated no exceedances for any constituent (except iron) above the primary and secondary drinking-water standards or health-advisory levels set by the U.S. Environmental Protection Agency. Iron concentrations were naturally elevated in the groundwater within the watershed because of bedrock lithology. The majority of the constituents were at or below the method detection limit. Sediment loads were dominated by precipitation due to the remnants of Hurricane Ivan in September 2004. More than 60 percent of the sediment load measured during the entire study was transported past the streamgage in just 2 days during that event. Habitat and aquatic-invertebrate data were collected in the summers of 2002-05, and fish data were collected in 2004. Although 2002 was a drought year, 2003-05 were above-normal flow years. Results indicated a wide diversity in invertebrates, good numbers of taxa (distinct organisms), and on the basis of a combination of metrics, the majority of the 27 sites indicated no or slight impairment. Fish-metric data from 25 sites indicated results
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Cytoplasmic streaming in plant cells emerges naturally by microfilament self-organization.
Woodhouse, Francis G; Goldstein, Raymond E
2013-08-27
Many cells exhibit large-scale active circulation of their entire fluid contents, a process termed cytoplasmic streaming. This phenomenon is particularly prevalent in plant cells, often presenting strikingly regimented flow patterns. The driving mechanism in such cells is known: myosin-coated organelles entrain cytoplasm as they process along actin filament bundles fixed at the periphery. Still unknown, however, is the developmental process that constructs the well-ordered actin configurations required for coherent cell-scale flow. Previous experimental works on streaming regeneration in cells of Characean algae, whose longitudinal flow is perhaps the most regimented of all, hint at an autonomous process of microfilament self-organization driving the formation of streaming patterns during morphogenesis. Working from first principles, we propose a robust model of streaming emergence that combines motor dynamics with both microscopic and macroscopic hydrodynamics to explain how several independent processes, each ineffectual on its own, can reinforce to ultimately develop the patterns of streaming observed in the Characeae and other streaming species.
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International Nuclear Information System (INIS)
Hsieh, C.; Bankoff, S.G.; Tankin, R.S.; Yuen, M.C.
1980-11-01
The perforated plate weeping phenomena have been studied in both air/water and steam/cold water systems. The air/water experiment is designed to investigate the effect of geometric factors of the perforated plate on the rate of weeping. A new dimensionless flow rate in the form of H star is suggested. The data obtained are successfully correlated by this H star scaling in the conventional flooding equation. The steam/cold water experiment is concentrated on locating the boundary between weeping and no weeping. The effects of water subcooling, water inlet flow rate, and position of water spray are investigated. Depending on the combination of these factors, several types of weeping were observed. The data obtained at high water spray position can be related to the air/water flooding correlation by replacing the stream flow rate to an effective stream flow rate, which is determined by the mixing efficiency above the plate
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Investigation of the liquid film flow rate in an annular two phase flow
International Nuclear Information System (INIS)
Chandraker, D.K.; Dasgupta, A.; Vijayan, P.K.; Aritomi, M.
2011-01-01
An accurate knowledge of the liquid film flow is essential in most thermal-hydraulic predictions, including the onset of dryout in boiling channels and post-dryout heat transfer during transient and accident scenarios. The determination of the film flow is an important aspect of the dryout analysis in the boiling channel. Dryout is caused due to the disappearance of the liquid film on the heated surface. Mechanistic prediction of dryout involves the modeling of the physical phenomenon of the processes like entrainment and deposition rate of droplets. In the nuclear reactor systems analytical prediction of the thermal hydraulic parameters is always desirable to avoid generation of exhaustive and expensive experimental data for optimizing the design parameters. Good constitutive models for entrainment and deposition are vital for an accurate prediction of the film flow rate and hence dryout in a fuel bundle. This paper attempts a comprehensive review of the dryout analysis involving application of the constitutive models for the film flow rate. Validation of these models against various experimental data has also been presented in this paper. (author)
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Heat transfer in a counterflow heat exchanger at low flow rates
International Nuclear Information System (INIS)
Hashimoto, A.; Hattori, N.; Naruke, K.
1995-01-01
A study was made of heat transfer in a double-tube heat exchanger at low flow rates of water. The temperatures of fluid and tube walls in the axial direction of tube were measured precisely at flow rate ratios of annulus to inner tube (or flow rate ratios of inner tube to annulus W i /W a , Re i approx. = 80 - 4000), W a /W i =0.1 - 1.1. In parallel with experiment, numerical calculation for forced-convection heat transfer was also carried out for laminar flows in the same tube configuration as experiment. Average over-all coefficients of heat transfer, obtained by experiments, indicate the same characteristics as numerical calculation in the examined range of flow rate ratio. Their experimental values, however, are somewhat larger than those of calculation at small values of flow rate ratio. (author)
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Type 1 diabetes mellitus, xerostomia, and salivary flow rates.
Moore, P A; Guggenheimer, J; Etzel, K R; Weyant, R J; Orchard, T
2001-09-01
The Oral Health Science Institute at the University of Pittsburgh has completed a cross-sectional epidemiologic study of 406 subjects with type 1 diabetes and 268 control subjects without diabetes that assessed the associations between oral health and diabetes. This report describes the prevalence of dry-mouth symptoms (xerostomia), the prevalence of hyposalivation in this population, and the possible interrelationships between salivary dysfunction and diabetic complications. The subjects with diabetes were participants in the Pittsburgh Epidemiology of Diabetes Complications study who were enrolled in an oral health substudy. Control subjects were spouses or best friends of participants or persons recruited from the community through advertisements in local newspapers. Assessments of salivary function included self-reported xerostomia measures and quantification of resting and stimulated whole saliva flow rates. Subjects with diabetes reported symptoms of dry mouth more frequently than did control subjects. Salivary flow rates were also impaired in the subjects with diabetes. Regression models of potential predictor variables were created for the 3 self-reported xerostomia measures and 4 salivary flow rate variables. Of the medical diabetic complications studied (ie, retinopathy, peripheral and autonomic neuropathy, nephropathy, and peripheral vascular disease), only neuropathy was found to be associated with xerostomia and decreased salivary flow measures. A report of dry-mouth symptoms was associated with current use of cigarettes, dysgeusia (report of a bad taste), and more frequent snacking behavior. Xerogenic medications and elevated fasting blood glucose concentrations were significantly associated with decreased salivary flow. Resting salivary flow rates less than 0.01 mL/min were associated with a slightly higher prevalence of dental caries. Subjects who reported higher levels of alcohol consumption were less likely to have lower rates of stimulated
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In-stream Physical Heterogeneity, Rainfall Aided Flushing, and Discharge on Stream Water Quality.
Gomes, Pattiyage I A; Wai, Onyx W H
2015-08-01
Implications of instream physical heterogeneity, rainfall-aided flushing, and stream discharge on water quality control have been investigated in a headwater stream of a climatic region that has contrasting dry and wet seasons. Dry (low flow) season's physical heterogeneity showed a positive correlation with good water quality. However, in the wet season, physical heterogeneity showed minor or no significance on water quality variations. Furthermore, physical heterogeneity appeared to be more complementary with good water quality subsequent to rainfall events. In many cases stream discharge was a reason for poor water quality. For the dry season, graywater inputs to the stream could be held responsible. In the wet season, it was probably the result of catchment level disturbances (e.g., regulation of ephemeral freshwater paths). Overall, this study revealed the importance of catchment-based approaches on water quality improvement in tandem with in-stream approaches framed on a temporal scale.
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International Nuclear Information System (INIS)
Agudo, E.G.; Duarte, V.; Ohara, T.; Sanches, W.
1973-01-01
Measurement of the sewage flow rate is a difficult problem in the field of sanitary engineering. A channel cross section calibration at a CHLORINE TREATMENT STATION was performed, in order to simplify the subsequent measurement of sewage flow, at a permanent stream-gauging station. The total count method was chosen because of its advantages over both the current instrument meter and the dilution technique of a radioactive or non-radioactive tracer (rodhamine and fluoresceine); the sewage transport materials might damage the current meter instruments and could also degrade chemical dyes because of the reduction properties of sewage. NH 4 Br labeled with 82 Br was used as radioactive tracer. The irradiated NH 4 Br was dissolved in a sodium thiosulphate solution. In spite of the presence of suspended materials in the sewage and the subsequent delicate operation of pumping out the flowing sewage through a by-pass where the measuring system was installed, accurate and reproducible field measurements were obtained [pt
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Mass transfer of a neutral solute in porous microchannel under streaming potential.
Mondal, Sourav; De, Sirshendu
2014-03-01
The mass transport of a neutral solute in a porous wall, under the influence of streaming field, has been analyzed in this study. The effect of the induced streaming field on the electroviscous effect of the fluid for different flow geometries has been suitably quantified. The overall electroosmotic velocity profile and expression for streaming field have been obtained analytically using the Debye-Huckel approximation, and subsequently used in the analysis for the mass transport. The analysis shows that as the solution Debye length increases, the strength of the streaming field and, consequently, the electroviscous effect diminishes. The species transport equation has been coupled with Darcy's law for quantification of the permeation rate across the porous wall. The concentration profile inside the mass transfer boundary layer has been solved using the similarity transformation, and the Sherwood number has been calculated from the definition. In this study, the variation of the permeation rate and solute permeate concentration has been with the surface potential, wall retention factor and osmotic pressure coefficient has been demonstrated for both the circular as well as rectangular channel cross-section. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Endoplasmic-reticulum-mediated microtubule alignment governs cytoplasmic streaming.
Kimura, Kenji; Mamane, Alexandre; Sasaki, Tohru; Sato, Kohta; Takagi, Jun; Niwayama, Ritsuya; Hufnagel, Lars; Shimamoto, Yuta; Joanny, Jean-François; Uchida, Seiichi; Kimura, Akatsuki
2017-04-01
Cytoplasmic streaming refers to a collective movement of cytoplasm observed in many cell types. The mechanism of meiotic cytoplasmic streaming (MeiCS) in Caenorhabditis elegans zygotes is puzzling as the direction of the flow is not predefined by cell polarity and occasionally reverses. Here, we demonstrate that the endoplasmic reticulum (ER) network structure is required for the collective flow. Using a combination of RNAi, microscopy and image processing of C. elegans zygotes, we devise a theoretical model, which reproduces and predicts the emergence and reversal of the flow. We propose a positive-feedback mechanism, where a local flow generated along a microtubule is transmitted to neighbouring regions through the ER. This, in turn, aligns microtubules over a broader area to self-organize the collective flow. The proposed model could be applicable to various cytoplasmic streaming phenomena in the absence of predefined polarity. The increased mobility of cortical granules by MeiCS correlates with the efficient exocytosis of the granules to protect the zygotes from osmotic and mechanical stresses.
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Yang, Michael Y; Chan, Hak-Kim
2017-06-01
The measurement of aerosol flow rates without obscuration of the flow is of particular concern with in vivo lung deposition studies, where precise knowledge of aerosol particle size distributions is a necessary requirement for the development of predictive correlations. This study examines the utility of an ultrasonic flow meter for such measurements and determines if a valved system can be attached to the flow meter for sampling exhaled aerosols. The flow rate across a D-30 flow meter was compared with and without nebulization of 0.9% saline aerosols from a PARI LC Sprint nebulizer. Particle size distributions of the nebulized aerosol before and after adding the D-30 flow meter and duckbill valve were measured using a Spraytec laser diffraction system. Finally, the ability of the Thor D-30 to capture a realistic breathing profile was assessed. The mean ± standard error flow rates measured by the D-30 flow meter with and without nebulization were 10.4 ± 0.1 versus 10.4 ± 0.1 L/min, 66.4 ± 0.1 versus 67.2 ± 0.1 L/min, and 89.9 ± 0.1 versus 91.4 ± 0.1 L/min. The D-30 flow meter did not considerably affect the volumetric median diameter (VMD) of the aerosols, while the VMD reduced slightly by 0.65 μm at 10 L/min and 0.69 μm at 72 L/min upon the inclusion of a duckbill valve. Time-weighted average inhalation flow rates measured by D-30 flow meters placed upstream and downstream of the one-way valve agreed well, 31.9 versus 32.6 L/min, respectively. The D-30 flow meter can be used to accurately measure inhalation flow rates of nebulized aerosols without significantly impacting particle size distributions, and one-way duckbill valves can be used to isolate the inhalation portion of a breathing pattern to facilitate collection of exhaled doses.
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A review on measuring methods of gas-liquid flow rates
International Nuclear Information System (INIS)
Minemura, Kiyoshi; Yamashita, Masato
2000-01-01
This paper presents a review on the state of current measuring techniques for gas-liquid multiphase flow rates. After briefly discussing the basic idea on measuring methods for single-phase and two-phase flows, existing methods for the two-phase flow rates are classified into several types, that is, with or without a homogenizing device, single or combined method of several techniques, with intrusive or non-intrusive sensors, and physical or software method. Each methods are comparatively reviewed in view of measuring accuracy and manageability. Its scope also contains the techniques developed for petroleum-gas-water flow rates. (author)
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Song, Hongjun; Wang, Yi; Pant, Kapil
2013-01-01
This paper presents an analytical study of the cross-stream diffusion of an analyte in a rectangular microchannel under combined electroosmotic flow (EOF) and pressure driven flow to investigate the heterogeneous transport behavior and spatially-dependent diffusion scaling law. An analytical model capable of accurately describing 3D steady-state convection-diffusion in microchannels with arbitrary aspect ratios is developed based on the assumption of the thin Electric Double Layer (EDL). The model is verified against high-fidelity numerical simulation in terms of flow velocity and analyte concentration profiles with excellent agreement (parametric analysis is then undertaken to interrogate the effect of the combined flow velocity field on the transport behavior in both the positive pressure gradient (PPG) and negative pressure gradient (NPG) cases. For the first time, the evolution from the spindle-shaped concentration profile in the PPG case, via the stripe-shaped profile (pure EOF), and finally to the butterfly-shaped profile in the PPG case is obtained using the analytical model along with a quantitative depiction of the spatially-dependent diffusion layer thickness and scaling law across a wide range of the parameter space.
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Knowledge discovery from data streams
Gama, Joao
2010-01-01
Since the beginning of the Internet age and the increased use of ubiquitous computing devices, the large volume and continuous flow of distributed data have imposed new constraints on the design of learning algorithms. Exploring how to extract knowledge structures from evolving and time-changing data, Knowledge Discovery from Data Streams presents a coherent overview of state-of-the-art research in learning from data streams.The book covers the fundamentals that are imperative to understanding data streams and describes important applications, such as TCP/IP traffic, GPS data, sensor networks,
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Ultrasonic 3-D Vector Flow Method for Quantitative In Vivo Peak Velocity and Flow Rate Estimation
DEFF Research Database (Denmark)
Holbek, Simon; Ewertsen, Caroline; Bouzari, Hamed
2017-01-01
Current clinical ultrasound (US) systems are limited to show blood flow movement in either 1-D or 2-D. In this paper, a method for estimating 3-D vector velocities in a plane using the transverse oscillation method, a 32×32 element matrix array, and the experimental US scanner SARUS is presented...... is validated in two phantom studies, where flow rates are measured in a flow-rig, providing a constant parabolic flow, and in a straight-vessel phantom ( ∅=8 mm) connected to a flow pump capable of generating time varying waveforms. Flow rates are estimated to be 82.1 ± 2.8 L/min in the flow-rig compared...
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Riparian zone controls on base cation concentrations in boreal streams
Ledesma, J. L. J.; Grabs, T.; Futter, M. N.; Bishop, K. H.; Laudon, H.; Köhler, S. J.
2013-01-01
Forest riparian zones are a major in control of surface water quality. Base cation (BC) concentrations, fluxes, and cycling in the riparian zone merit attention because of increasing concern of negative consequences for re-acidification of surface waters from future climate and forest harvesting scenarios. We present a two-year study of BC and silica (Si) flow-weighted concentrations from 13 riparian zones and 14 streams in a boreal catchment in northern Sweden. The Riparian Flow-Concentration Integration Model (RIM) was used to estimate riparian zone flow-weighted concentrations and tested to predict the stream flow-weighted concentrations. Spatial variation in BC and Si concentrations as well as in flow-weighted concentrations was related to differences in Quaternary deposits, with the largest contribution from lower lying silty sediments and the lowest contribution from wetland areas higher up in the catchment. Temporal stability in the concentrations of most elements, a remarkably stable Mg / Ca ratio in the soil water and a homogeneous mineralogy suggest that the stable patterns found in the riparian zones are a result of distinct mineralogical upslope groundwater signals integrating the chemical signals of biological and chemical weathering. Stream water Mg / Ca ratio indicates that the signal is subsequently maintained in the streams. RIM gave good predictions of Ca, Mg, and Na flow-weighted concentrations in headwater streams. The difficulty in modelling K and Si suggests a stronger biogeochemical influence on these elements. The observed chemical dilution effect with flow in the streams was related to variation in groundwater levels and element concentration profiles in the riparian zones. This study provides a first step toward specific investigations of the vulnerability of riparian zones to changes induced by forest management or climate change, with focus on BC or other compounds.
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Are international fund flows related to exchange rate dynamics?
Li, Suxiao; de Haan, Jakob; Scholtens, Bert
2018-01-01
Employing monthly data for 53 countries between 1996 and 2015, we investigate the relationship between international fund flows and exchange rate dynamics. We find strong co-movement between funds flows (as measured with the EPFR Global data base) and bilateral real exchange rates vis-à-vis the USD.
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STREAM II-V7: Revision for STREAM II-V6 to include outflow from all Savannah River Site tributaries
Energy Technology Data Exchange (ETDEWEB)
Maze, Grace M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2017-01-01
STREAM II is the aqueous transport model of the Weather Information Display (WIND) emergency response system at Savannah River Site. It is used to calculate transport in the event of a chemical or radiological spill into the waterways on the Savannah River Site. Improvements were made to the code (STREAM II V7) to include flow from all site tributaries to the Savannah River total flow and utilize a 4 digit year input. The predicted downstream concentrations using V7 were generally on the same order of magnitude as V6 with slightly lower concentrations and quicker arrival times when all onsite stream flows are contributing to the Savannah River flow. The downstream arrival time at the Savannah River Water Plant ranges from no change to an increase of 8.77%, with minimum changes typically in March/April and maximum changes typically in October/November. The downstream concentrations are generally no more than 15% lower using V7 with the maximum percent change in January through April and minimum changes in June/July.
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Assessing the Effects of Water Right Purchases on Stream Temperatures and Fish Habitat
Elmore, L.; Null, S. E.
2012-12-01
Warm stream temperature and low flow conditions are limiting factors for native trout species in Nevada's Walker River. Water rights purchases are being considered to increase instream flow and improve habitat conditions. However, the effect of water rights purchases on stream temperatures and fish habitat have yet to be assessed. Manipulating flow conditions affect stream temperatures by altering water depth, velocity, and thermal mass. This study uses the River Modeling System (RMSv4), an hourly, physically-based hydrodynamic and water quality model, to estimate flows and stream temperatures in the Walker River. The model is developed for two wet years (2010-2011). Study results highlight reaches with cold-water habitat that is suitable for native trout species. Previous research on the Walker River has evaluated instream flow changes with water rights purchases. This study incorporates stream temperatures as a proxy for trout habitat, and thus explicitly incorporates water quality and fish habitat into decision-making regarding water rights purchases. Walker River
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Didymosphenia geminata: Algal blooms in oligotrophic streams and rivers
Sundareshwar, P. V.; Upadhayay, S.; Abessa, M.; Honomichl, S.; Berdanier, B.; Spaulding, S. A.; Sandvik, C.; Trennepohl, A.
2011-05-01
In recent decades, the diatom Didymosphenia geminata has emerged as nuisance species in river systems around the world. This periphytic alga forms large “blooms” in temperate streams, presenting a counterintuitive result: the blooms occur primarily in oligotrophic streams and rivers, where phosphorus (P) availability typically limits primary production. The goal of this study is to examine how high algal biomass is formed under low P conditions. We reveal a biogeochemical process by which D. geminata mats concentrate P from flowing waters. First, the mucopolysaccaride stalks of D. geminata adsorb both iron (Fe) and P. Second, enzymatic and bacterial processes interact with Fe to increase the biological availability of P. We propose that a positive feedback between total stalk biomass and high growth rate is created, which results in abundant P for cell division. The affinity of stalks for Fe in association with iron-phosphorus biogeochemistry suggest a resolution to the paradox of algal blooms in oliogotrophic streams and rivers.
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A stream temperature model for the Peace-Athabasca River basin
Morales-Marin, L. A.; Rokaya, P.; Wheater, H. S.; Lindenschmidt, K. E.
2017-12-01
Water temperature plays a fundamental role in water ecosystem functioning. Because it regulates flow energy and metabolic rates in organism productivity over a broad spectrum of space and time scales, water temperature constitutes an important indicator of aquatic ecosystems health. In cold region basins, stream water temperature modelling is also fundamental to predict ice freeze-up and break-up events in order to improve flood management. Multiple model approaches such as linear and multivariable regression methods, neural network and thermal energy budged models have been developed and implemented to simulate stream water temperature. Most of these models have been applied to specific stream reaches and trained using observed data, but very little has been done to simulate water temperature in large catchment river networks. We present the coupling of RBM model, a semi-Lagrangian water temperature model for advection-dominated river system, and MESH, a semi-distributed hydrological model, to simulate stream water temperature in river catchments. The coupled models are implemented in the Peace-Athabasca River basin in order to analyze the variation in stream temperature regimes under changing hydrological and meteorological conditions. Uncertainty of stream temperature simulations is also assessed in order to determine the degree of reliability of the estimates.
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Assessing effects of water abstraction on fish assemblages in Mediterranean streams
Benejam, Lluis; Angermeier, Paul L.; Munne, Antoni; García-Berthou, Emili
2010-01-01
1. Water abstraction strongly affects streams in arid and semiarid ecosystems, particularly where there is a Mediterranean climate. Excessive abstraction reduces the availability of water for human uses downstream and impairs the capacity of streams to support native biota. 2. We investigated the flow regime and related variables in six river basins of the Iberian Peninsula and show that they have been strongly altered, with declining flows (autoregressive models) and groundwater levels during the 20th century. These streams had lower flows and more frequent droughts than predicted by the official hydrological model used in this region. Three of these rivers were sometimes dry, whereas there were predicted by the model to be permanently flowing. Meanwhile, there has been no decrease in annual precipitation. 3. We also investigated the fish assemblage of a stream in one of these river basins (Tordera) for 6 years and show that sites more affected by water abstraction display significant differences in four fish metrics (catch per unit effort, number of benthic species, number of intolerant species and proportional abundance of intolerant individuals) commonly used to assess the biotic condition of streams. 4. We discuss the utility of these metrics in assessing impacts of water abstraction and point out the need for detailed characterisation of the natural flow regime (and hence drought events) prior to the application of biotic indices in streams severely affected by water abstraction. In particular, in cases of artificially dry streams, it is more appropriate for regulatory agencies to assign index scores that reflect biotic degradation than to assign ‘missing’ scores, as is presently customary in assessments of Iberian streams.
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Instream flow characterization of upper Salmon River Basin streams, Central Idaho, 2003
Maret, Terry R.; Hortness, Jon E.; Ott, Douglas S.
2004-01-01
Anadromous fish populations in the Columbia River Basin have plummeted in the last 100 years. This severe decline led to Federal listing of chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss) stocks as endangered or threatened under the Endangered Species Act (ESA) in the 1990s. Historically, the upper Salmon River Basin (upstream from the confluence with the Pahsimeroi River) in Idaho provided migration corridors and significant habitat for these ESA-listed species, in addition to the federally listed bull trout (Salvelinus confluentus). Human development has modified the original streamflow conditions in many streams in the upper Salmon River Basin. Summer streamflow modifications, as a result of irrigation practices, have directly affected the quantity and quality of fish habitat and also have affected migration and (or) access to suitable spawning and rearing habitat for these fish. As a result of these ESA listings and Action 149 of the Federal Columbia River Power System Biological Opinion of 2000, the Bureau of Reclamation was tasked to conduct streamflow characterization studies in the upper Salmon River Basin to clearly define habitat requirements for effective species management and habitat restoration. These studies include the collection of habitat and streamflow information for the Physical Habitat Simulation (PHABSIM) model, a widely applied method to determine relations between habitat and discharge requirements for various fish species and life stages. Model results can be used by resource managers to guide habitat restoration efforts in the evaluation of potential fish habitat and passage improvements by increasing streamflow. Instream flow characterization studies were completed on Pole, Fourth of July, Elk, and Valley Creeks during 2003. Continuous streamflow data were collected upstream from all diversions on each stream. In addition, natural summer streamflows were estimated for each study site using regression
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Jobbagy, E. G.; Nosetto, M. D.; Pineiro, G.; Farley, K. A.; Palmer, S. M.; Jackson, R. B.
2005-12-01
Vegetation changes, particularly those involving transitions between tree- and grass-dominated systems, often modify evaporation as a result of plant-mediated shifts in moisture access and demand. The establishment of tree plantations (fast growing eucalypts and pines) on native grasslands is emerging as a major land-use change, particularly in the Southern Hemisphere, where cheap land and labor, public subsidies, and prospective C sequestration rewards provide converging incentives. What are the hydrological consequences of grassland afforestation? How are crucial ecosystem services such as fresh water supply and hydrological regulation being affected? We explore these questions focusing on a) evapotranspiration, b) stream flow, and c) groundwater recharge-discharge patterns across a network of paired stands and small watershed occupied by native grassland and tree plantation in Argentina and Uruguay. Radiometric information obtained from Landsat satellite images was used to estimate daily evapotranspiration in >100 tree plantations and grasslands stands in the humid plains of the Uruguay River (mean annual precipitation, MAP= 1350 mm). In spite of their lower albedo, tree plantations were 0.5 C° cooler than grasslands. Energy balance calculations suggested 80% higher evapotranspiration in afforested plots with relative differences becoming larger during dry periods. Seasonal stream flow measurements in twelve paired watershed (50-500 Ha) in the hills of Comechingones (MAP= 800 mm) and Minas (MAP= 1200 mm) showed declining water yields following afforestation. Preliminary data in Cordoba showed four-fold reductions of base flow in the dry season and two-fold reductions of peak flow after storms. A network of twenty paired grassland-plantation stands covering a broad range of sediment textures in the Pampas (MAP= 1000 mm, typical groundwater depth= 1-5 m) showed increased groundwater salinity in afforested stands (plantation:grassland salinity ratio = 1.2, 10, and
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Peak Expiratory Flow Rate In Cigarette Smokers | Ukoli | Highland ...
African Journals Online (AJOL)
Objective: To compare lung function between smokers and non-smokers using Peak Expiratory Flow Rate (PEFR). Methods: This study examines the peak expiratory flow rate (PEFR) of three hundred and forty cigarette smokers, age and sex-matched with PEFR of equal number of non-smokers. Results: The mean PEFR of ...
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Design and construction of a novel Coriolis mass flow rate meter
Mehendale, A.; Zwikker, Rini; Jouwsma, Wybren
2009-01-01
The Coriolis principle for measuring flow rates has great advantages compared to other flow measurement principles, the most important being that mass flow is measured directly. Up to now the measurement of low flow rates posed a great challenge. In a joint research project, the University of Twente
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Sodium flow rate measurement method of annular linear induction pumps
International Nuclear Information System (INIS)
Araseki, Hideo; Kirillov, Igor R.; Preslitsky, Gennady V.
2012-01-01
Highlights: ► We found a new method of flow rate monitoring of electromagnetic pump. ► The method is very simple and does not require a large space. ► The method was verified with an experiment and a numerical analysis. ► The experimental data and the numerical results are in good agreement. - Abstract: The present paper proposes a method for measuring sodium flow rate of annular linear induction pumps. The feature of the method lies in measuring the leaked magnetic field with measuring coils near the stator end on the outlet side and in correlating it with the sodium flow rate. This method is verified through an experiment and a numerical analysis. The data obtained in the experiment reveals that the correlation between the leaked magnetic field and the sodium flow rate is almost linear. The result of the numerical analysis agrees with the experimental data. The present method will be particularly effective to sodium flow rate monitoring of each one of plural annular linear induction pumps arranged in parallel in a vessel which forms a large-scale pump unit.
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Directory of Open Access Journals (Sweden)
Yu. M. Timofeev
2016-01-01
Full Text Available The turbulent-flow throttles are used in pneumatic systems and gas-supply ones to restrict or measure gas mass flow. It is customary to install the throttles in joints of pipelines (in teejoints and cross tees or in joints of pipelines with pneumatic automation devices Presently, in designing the pneumatic systems and gas-supply ones a gas mass flow through a throttle is calculated by a known equation derived from the Saint-Venant-Vantсel formula for the adiabatic flow of ideal gas through a nozzle from an unrestrictedly high capacity tank. Neglect of gas velocity at the throttle inlet is one of the assumptions taken in the development of the above equation. As may be seen in practice, in actual systems the diameters of the throttle and the pipe wherein it is mounted can be commensurable. Neglect of the inlet velocity therewith can result in an error when determining the required throttle diameter in design calculation and a flow rate in checking calculation, as well as when measuring a flow rate in the course of the test. The theoretical study has revealed that the flow velocity at the throttle inlet is responsible for two parameter values: the outlet flow velocity and the critical pressure ratio, which in turn determine the gas mass flow value. To calculate the gas mass flow, the dependencies are given in the paper, which allow taking into account the flow rate at the throttle inlet. The analysis of obtained dependencies has revealed that the degree of influence of inlet flow rate upon the mass flow is defined by two parameters: pressure ratio at the throttle and open area ratio of the throttle and the pipe wherein it is mounted. An analytical investigation has been pursued to evaluate the extent to which the gas mass flow through the throttle is affected by the inlet flow rate. The findings of the investigation and the indications for using the present dependencies are given in this paper. By and large the investigation allowed the
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Steady hydromagnetic Couette flow in a rotating system with non ...
African Journals Online (AJOL)
user
energy equation and numerical values of rate of heat transfer at both plates are ... An investigation of MHD flow of an electrically conducting fluid in a rotating ... bounded by stationary free stream whereas MHD flow past a stationary plate ... induced magnetic field produced by fluid motion is negligible in comparison to the ...
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International Nuclear Information System (INIS)
Li, R N; Wang, H Y; Han, W; Shen, Z J; Ma, W
2013-01-01
The screw centrifugal pump is used as an object, and the unsteady numerical simulation of solid-liquid two-phase flow is carried out under different flow rate conditions in one circle by choosing the two-phase flow of sand and water as medium, using the software FLUENT based on the URANS equations, combining with sliding mesh method, and choosing the Mixture multiphase flow model and the SIMPLE algorithm. The results show that, with the flow rate increasing, the change trends for the pressure on volute outlet are almost constant, the fluctuation trends of the impeller axial force have a little change, the pressure and the axial force turn to decrease on the whole, the radial force gradually increases when the impeller maximum radius passes by half a cycle near the volute outlet, and the radial force gradually decreases when the maximum radius passes by the other half a cycle in a rotation cycle. The distributions of the solid particles are very uneven under a small flow rate condition on the face. The solid particles under a big flow rate condition are distributed more evenly than the ones under a small flow rate condition on the back. The theoretical basis and reference are provided for improving its working performance
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A numerical study of a turbulent axisymmetric jet emerging in a co-flowing stream
Energy Technology Data Exchange (ETDEWEB)
Mahmoud, Houda, E-mail: mahhouda2003@yahoo.f [Unite de thermique et thermodynamique des procedes industriels, Ecole Nationale d' Ingenieurs de Monastir, route de Ouardanine, 5020 Monastir (Tunisia); Kriaa, Wassim; Mhiri, Hatem [Unite de thermique et thermodynamique des procedes industriels, Ecole Nationale d' Ingenieurs de Monastir, route de Ouardanine, 5020 Monastir (Tunisia); Palec, Georges Le; Bournot, Philippe [IUSTI, UMR CNRS 6595, 5 Rue Enrico Fermi, Technopole de Chateau-Gombert, 13013 Marseille (France)
2010-11-15
In this work, we propose a numerical study of an axisymmetric turbulent jet discharging into co-flowing stream with different velocities ratios ranging between 0 and {infinity}. The standard k-{epsilon} model and the RSM model were applied in this study. The numerical resolution of the governing equations was carried out using two computed codes: the first is a personal code and the second is a commercial CFD code FLUENT 6.2. These two codes are based on a finite volume method. The present predictions are compared with the experimental data. The results show that the two turbulence models are valid to predict the average and turbulent flow sizes. Also, the effect of the velocities ratios on the flow structure was examined. For R{sub u} > 1, it is noted the appearance of the fall velocity zone due to the presence of a trough low pressure. This fall velocity becomes increasingly intense according to R{sub u} and changes into a recirculation zone for R{sub u} {>=} 4.5. This zone is larger and approaches more the nozzle injection when R{sub u} increases.
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Alam, Md Anik; Shi, Zhenqi; Drennen, James K; Anderson, Carl A
2017-06-30
In-line monitoring of continuous powder flow is an integral part of the continuous manufacturing process of solid oral dosage forms in the pharmaceutical industry. Specifically, monitoring downstream from loss-in-weight (LIW) feeders and/or continuous mixers provides important data about the state of the process. Such measurements support control of the process and thereby enhance product quality. Near Infrared Spectroscopy (NIRS) is a potential PAT tool to monitor the homogeneity of a continuous powder flow stream in pharmaceutical manufacturing. However, the association of analytical results from NIR sampling of the powder stream and the homogeneity (content uniformity) of the resulting tablets provides several challenges; appropriate sampling strategies, adequately robust modeling techniques and poor sensitivities (for low dose APIs) are amongst them. Information from reflectance-based NIRS sampling is limited. The region of the powder bed that is interrogated is confined to the surface where the measurement is made. This potential bias in sampling may, in turn, limit the ability to predict the homogeneity of the finished dosage form. Further, changes to the processing parameters (e.g., rate of powder flow) often have a significant effect on the resulting data. Sample representation, interdependence between process parameters and their effects on powder flow behavior are critical factors for NIRS monitoring of continuous powder flow system. A transmission NIR method was developed as an alternative technique to monitor continuous powder flow and quantify API in the powder stream. Transmission NIRS was used to determine the thickness of the powder stream flowing from a loss-in-weight feeder. The thickness measurement of the powder stream provided an in-depth understanding about the effects of process parameters such as tube angles and powder flow rates on powder flow behaviors. This knowledge based approach helped to define an analytical design space that was
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Acoustofluidics 13: Analysis of acoustic streaming by perturbation methods.
Sadhal, S S
2012-07-07
In this Part 13 of the tutorial series "Acoustofluidics--exploiting ultrasonic standing waves forces and acoustic streaming in microfluidic systems for cell and particle manipulation," the streaming phenomenon is presented from an analytical standpoint, and perturbation methods are developed for analyzing such flows. Acoustic streaming is the phenomenon that takes place when a steady flow field is generated by the absorption of an oscillatory field. This can happen either by attenuation (quartz wind) or by interaction with a boundary. The latter type of streaming can also be generated by an oscillating solid in an otherwise still fluid medium or vibrating enclosure of a fluid body. While we address the first kind of streaming, our focus is largely on the second kind from a practical standpoint for application to microfluidic systems. In this Focus article, we limit the analysis to one- and two-dimensional problems in order to understand the analytical techniques with examples that most-easily illustrate the streaming phenomenon.
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Blood flow rate measurements with indicator techniques revisited
DEFF Research Database (Denmark)
Sejrsen, Per; Bülow, Jens
2009-01-01
In view of the emerging role, disturbances in regional blood flow rate seem to play in the pathogenesis of the metabolic syndrome; we review the concepts of the classical indicator dilution and washout techniques used for determinations of regional blood flow rate. Prerequisites, assumptions......, necessary precautions for the application of these experimental techniques are emphasized. Special attention has been carried out to elucidate the consequence of a choice of indicators having a large distribution volume in the tissues....
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A Compound Detection System Based on Ultrasonic Flow Rate and Concentration
Directory of Open Access Journals (Sweden)
Qing-Hui WANG
2014-02-01
Full Text Available This paper proposes a new detection system for monitoring gas concentration and flow rate. Velocity difference of ultrasonic wave in bi-directional propagation in measured gas is recorded and utilized for computing the online gas concentration and flow rate. Meanwhile, the temperature compensation, return signal processing and error analysis algorithms are applied to improve the accuracy. The experimental results show that, compared with the single sensor measurement of gas flow rate or concentration, the proposed detection system with lower cost and higher accuracy can be applied in the occasion which needs simultaneous monitoring of gas concentration and flow rate.
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Consequences of variation in stream-landscape connections for stream nitrate retention and export
Handler, A. M.; Helton, A. M.; Grimm, N. B.
2017-12-01
Hydrologic and material connections among streams, the surrounding terrestrial landscape, and groundwater systems fluctuate between extremes in dryland watersheds, yet the consequences of this variation for stream nutrient retention and export remain uncertain. We explored how seasonal variation in hydrologic connection among streams, landscapes, and groundwater affect nitrate and ammonium concentrations across a dryland stream network and how this variation mediates in-stream nitrate uptake and watershed export. We conducted spatial surveys of stream nitrate and ammonium concentration across the 1200 km2 Oak Creek watershed in central Arizona (USA). In addition, we conducted pulse releases of a solution containing biologically reactive sodium nitrate, with sodium chloride as a conservative hydrologic tracer, to estimate nitrate uptake rates in the mainstem (Q>1000 L/s) and two tributaries. Nitrate and ammonium concentrations generally increased from headwaters to mouth in the mainstem. Locally elevated concentrations occurred in spring-fed tributaries draining fish hatcheries and larger irrigation ditches, but did not have a substantial effect on the mainstem nitrogen load. Ambient nitrate concentration (as N) ranged from below the analytical detection limit of 0.005 mg/L to 0.43 mg/L across all uptake experiments. Uptake length—average stream distance traveled for a nutrient atom from the point of release to its uptake—at ambient concentration ranged from 250 to 704 m and increased significantly with higher discharge, both across streams and within the same stream on different experiment dates. Vertical uptake velocity and aerial uptake rate ranged from 6.6-10.6 mm min-1 and 0.03 to 1.4 mg N m-2 min-1, respectively. Preliminary analyses indicate potentially elevated nitrogen loading to the lower portion of the watershed during seasonal precipitation events, but overall, the capacity for nitrate uptake is high in the mainstem and tributaries. Ongoing work
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Critical heat flux and exit film flow rate in a flow boiling system
International Nuclear Information System (INIS)
Ueda, Tatsuhiro; Isayama, Yasushi
1981-01-01
The critical heat flux in a flowing boiling system is an important problem in the evaporating tubes with high thermal load such as nuclear reactors and boilers, and gives the practical design limit. When the heat flux in uniformly heated evaporating tubes is gradually raised, the tube exit quality increases, and soon, the critical heat flux condition arises, and the wall temperature near tube exit rises rapidly. In the region of low exit quality, the critical heat flux condition is caused by the transition from nucleating boiling, and in the region of high exit quality, it is caused by dry-out. But the demarcation of both regions is not clear. In this study, for the purpose of obtaining the knowledge concerning the critical heat flux condition in a flowing boiling system, the relation between the critical heat flux and exit liquid film flow rate was examined. For the experiment, a uniformly heated vertical tube supplying R 113 liquid was used, and the measurement in the range of higher heating flux and mass velocity than the experiment by Ueda and Kin was carried out. The experimental setup and experimental method, the critical heat flux and exit quality, the liquid film flow rate at heating zone exit, and the relation between the critical heat flux and the liquid film flow rate at exit are described. (Kako, I.)
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Time-Based Data Streams: Fundamental Concepts for a Data Resource for Streams
Energy Technology Data Exchange (ETDEWEB)
Beth A. Plale
2009-10-10
Real time data, which we call data streams, are readings from instruments, environmental, bodily or building sensors that are generated at regular intervals and often, due to their volume, need to be processed in real time. Often a single pass is all that can be made on the data, and a decision to discard or keep the instance is made on the spot. Too, the stream is for all practical purposes indefinite, so decisions must be made on incomplete knowledge. This notion of data streams has a different set of issues from a file, for instance, that is byte streamed to a reader. The file is finite, so the byte stream is becomes a processing convenience more than a fundamentally different kind of data. Through the duration of the project we examined three aspects of streaming data: the first, techniques to handle streaming data in a distributed system organized as a collection of web services, the second, the notion of the dashboard and real time controllable analysis constructs in the context of the Fermi Tevatron Beam Position Monitor, and third and finally, we examined provenance collection of stream processing such as might occur as raw observational data flows from the source and undergoes correction, cleaning, and quality control. The impact of this work is severalfold. We were one of the first to advocate that streams had little value unless aggregated, and that notion is now gaining general acceptance. We were one of the first groups to grapple with the notion of provenance of stream data also.
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International Nuclear Information System (INIS)
Nazrul Hizam Yusoff and Wan Zakaria Wan MuhdTahir
2006-01-01
A number of discharge measurements using radioisotope and current metering techniques at selected streams in Sg. Weng Experimental Catchment were conducted by MINT and JPS gauging teams starting from 2003-2005. This study aims to prepare stage-discharge relationships or rating curves of the selected streams during variable flow conditions. The rating curve of the stream is one of the important parameters and usually appraised in certain routine operations of hydrological studies. It may be used in the planning of water resources management and flood control scheme. The radioisotope method employed in this study involved the injection of short-lived radioisotope tracer, that is, technetium-99m ( 99m Tc having its half-life ∼ 6.023 hrs) which was supplied from a high activity technetium generator (55.5 Gbq). Measurement of stream discharges were concurrently undertaken by JPS staff using a current meter type 0TT-C2 mounted on a wading rod at selected gauging stations for comparison purposes. Methodologies from the two methods of discharge measurements, comparison of results and identifying the uncertainties (errors) in performing the measurement during low, medium and high turbulent flows were explained in this paper. Generally, the entire results of streamflow data (2003-2005) measured by both methods during low flows (Q 3 /s) exhibit almost comparable values to each other. However, for moderate flows (1.0 m 3 /s 3 /s), the different in gauging results are slightly higher using radioisotope method ( i.e. Q isotope > Q current meter and may goes up to 40%) , and during high turbulent flows (Q>6.0 m 3 /s) the radioisotope method presented more than 40% higher discharge values as compared to the measurement made by the conventional current-meter. Observation made on site anticipated that inaccurate gauging data measured by conventional means during high flow and turbulent conditions are expected. The average estimated measurement error associated with isotope method
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Contaminant Dynamics and Trends in Hyperalkaline Urban Streams
Riley, Alex; Mayes, William
2015-04-01
Streams in post-industrial urban areas can have multiple contemporary and historic pressures impacting upon their chemical and ecological status. This paper presents analysis of long term data series (up to 36 years in length) from two small streams in northern England (catchment areas 0.5-0.6km2). Around 3.5 million m3 of steel making slags and other wastes were deposited in the headwater areas of the Howden Burn and Dene Burn in northeast England up to the closure of the workings in the early 1980s. This has led to streams draining from the former workings which have a hyperalkaline ambient pH (mean of 10.3 in both streams), elevated alkalinity (up to 487 mg/L as CaCO3) from leaching of lime and other calcium oxides / silicates within the slag, and enrichment of some trace elements (e.g. aluminium (Al), lithium (Li) and zinc (Zn)) including those which form oxyanions mobile at high pH such as vanadium (V). The high ionic strength of the waters and calcium enrichment also leads to waters highly supersaturated with calcium carbonate. Trace contaminant concentrations are strongly positively correlated, and concentrations generally diminish with increased flow rate suggesting the key source of metals in the system is the highly alkaline groundwater draining from the slag mounds. Some contaminants (notably Cr and ammonium) increase with high flow suggesting sources related to urban runoff and drainage from combined sewer overflows into one of the catchments. Loading estimates instream show that many of the contaminants (e.g. Al, V and Zn) are rapidly attenuated in secondary calcium carbonate-dominated deposits that precipitate vigorously on the streambeds with rates of up to 250 g CaCO3/m2/day. These secondary sinks limit the mobility of many contaminants in the water column, while concentrations in secondary deposits are relatively low given the rapid rates at which Ca is also attenuated. Long-term trend analysis showed modest declines in calcium and alkalinity over
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Cutaneous blood flow rate in areas with and without arteriovenous anastomoses during exercise
DEFF Research Database (Denmark)
Midttun, M.; Sejrsen, Per
1998-01-01
Arteriovenous anastomoses, capillaries, cutaneous bllod flow rate, exercise, finger blood flow, skin blood flow......Arteriovenous anastomoses, capillaries, cutaneous bllod flow rate, exercise, finger blood flow, skin blood flow...
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Directory of Open Access Journals (Sweden)
Muhammad Audy Bazly
2015-12-01
Full Text Available This paper aims to analyze Internet-based streaming video service in the communication media with variable bit rates. The proposed scheme on Dynamic Adaptive Streaming over HTTP (DASH using the internet network that adapts to the protocol Hyper Text Transfer Protocol (HTTP. DASH technology allows a video in the video segmentation into several packages that will distreamingkan. DASH initial stage is to compress the video source to lower the bit rate video codec uses H.26. Video compressed further in the segmentation using MP4Box generates streaming packets with the specified duration. These packages are assembled into packets in a streaming media format Presentation Description (MPD or known as MPEG-DASH. Streaming video format MPEG-DASH run on a platform with the player bitdash teritegrasi bitcoin. With this scheme, the video will have several variants of the bit rates that gave rise to the concept of scalability of streaming video services on the client side. The main target of the mechanism is smooth the MPEG-DASH streaming video display on the client. The simulation results show that the scheme based scalable video streaming MPEG- DASH able to improve the quality of image display on the client side, where the procedure bufering videos can be made constant and fine for the duration of video views
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Godsey, S.; Kirchner, J. W.; Whiting, J. A.
2016-12-01
Temporary headwater streams - both intermittent and ephemeral waterways - supply water to approximately 1/3 of the US population, and 60% of streams used for drinking water are temporary. Stream ecologists increasingly recognize that a gradient of processes across the drying continuum affect ecosystems at dynamic terrestrial-aquatic interfaces. Understanding the hydrological controls across that gradient of drying may improve management of these sensitive systems. One possible control on surface flows includes transpiration losses from either the riparian zone or the entire watershed. We mapped several stream networks under extreme low flow conditions brought on by severe drought in central Idaho and California in 2015. Compared to previous low-flow stream length estimates, the active drainage network had generally decreased by a very small amount across these sites, perhaps because stored water buffered the precipitation decrease, or because flowing channel heads are fixed by focused groundwater flow emerging at springs. We also examined the apparent sources of water for both riparian and hillslope trees using isotopic techniques. During drought conditions, we hypothesized that riparian trees - but not those far from flowing streams - would be sustained by streamflow recharging riparian aquifers, and thus would transpire water that was isotopically similar to streamflow because little soil water would remain available below the wilting point and stream water would be sustain those trees. We found a more complex pattern, but in most places stream water and water transpired by trees were isotopically distinct regardless of flow intermittency or tree location. We also found that hillslope trees outside of the riparian zone appeared to be using different waters from those used by riparian trees. Finally, we explore subsurface controls on network extent, showing that bedrock characteristics can influence network stability and contraction patterns.
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Salmon carcass movements in forest streams
Burke Strobel; Daniel R. Shivley; Brett B. Roper
2009-01-01
The movements of salmon carcasses over time were studied in two forest streams in the context of a large-scale salmon carcass supplementation program. The objectives were to assess both the level of treatment after stream flows had displaced carcasses and to evaluate whether the magnitude of carcass movements outside of a given reach could be predicted. The movements...
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Comparison of deliverable and exhaustible pressurized air flow rates in laboratory gloveboxes
International Nuclear Information System (INIS)
Compton, J.A.
1994-01-01
Calculations were performed to estimate the maximum credible flow rates of pressurized air into Plutonium Process Support Laboratories gloveboxes. Classical equations for compressible fluids were used to estimate the flow rates. The calculated maxima were compared to another's estimates of glovebox exhaust flow rates and corresponding glovebox internal pressures. No credible pressurized air flow rate will pressurize a glovebox beyond normal operating limits. Unrestricted use of the pressurized air supply is recommended
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Ascough, J. C.; David, O.; Heathman, G. C.; Smith, D. R.; Green, T. R.; Krause, P.; Kipka, H.; Fink, M.
2010-12-01
The Object Modeling System 3 (OMS3), currently being developed by the USDA-ARS Agricultural Systems Research Unit and Colorado State University (Fort Collins, CO), provides a component-based environmental modeling framework which allows the implementation of single- or multi-process modules that can be developed and applied as custom-tailored model configurations. OMS3 as a “lightweight” modeling framework contains four primary foundations: modeling resources (e.g., components) annotated with modeling metadata; domain specific knowledge bases and ontologies; tools for calibration, sensitivity analysis, and model optimization; and methods for model integration and performance scalability. The core is able to manage modeling resources and development tools for model and simulation creation, execution, evaluation, and documentation. OMS3 is based on the Java platform but is highly interoperable with C, C++, and FORTRAN on all major operating systems and architectures. The ARS Conservation Effects Assessment Project (CEAP) Watershed Assessment Study (WAS) Project Plan provides detailed descriptions of ongoing research studies at 14 benchmark watersheds in the United States. In order to satisfy the requirements of CEAP WAS Objective 5 (“develop and verify regional watershed models that quantify environmental outcomes of conservation practices in major agricultural regions”), a new watershed model development approach was initiated to take advantage of OMS3 modeling framework capabilities. Specific objectives of this study were to: 1) disaggregate and refactor various agroecosystem models (e.g., J2K-S, SWAT, WEPP) and implement hydrological, N dynamics, and crop growth science components under OMS3, 2) assemble a new modular watershed scale model for fully-distributed transfer of water and N loading between land units and stream channels, and 3) evaluate the accuracy and applicability of the modular watershed model for estimating stream flow and N dynamics. The
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Users Manual for the Geospatial Stream Flow Model (GeoSFM)
Artan, Guleid A.; Asante, Kwabena; Smith, Jodie; Pervez, Md Shahriar; Entenmann, Debbie; Verdin, James P.; Rowland, James
2008-01-01
The monitoring of wide-area hydrologic events requires the manipulation of large amounts of geospatial and time series data into concise information products that characterize the location and magnitude of the event. To perform these manipulations, scientists at the U.S. Geological Survey Center for Earth Resources Observation and Science (EROS), with the cooperation of the U.S. Agency for International Development, Office of Foreign Disaster Assistance (USAID/OFDA), have implemented a hydrologic modeling system. The system includes a data assimilation component to generate data for a Geospatial Stream Flow Model (GeoSFM) that can be run operationally to identify and map wide-area streamflow anomalies. GeoSFM integrates a geographical information system (GIS) for geospatial preprocessing and postprocessing tasks and hydrologic modeling routines implemented as dynamically linked libraries (DLLs) for time series manipulations. Model results include maps that depicting the status of streamflow and soil water conditions. This Users Manual provides step-by-step instructions for running the model and for downloading and processing the input data required for initial model parameterization and daily operation.
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Energy Technology Data Exchange (ETDEWEB)
Schmidt, C.; Krieg, R.; Bayer-Raich, M.; Leschik, S. [Helmholtz-Zentrum fuer Umweltforschung GmbH - UFZ, Department Hydrogeologie, Leipzig (Germany); Kalbus, E. [Eberhard-Karls-Universitaet Tuebingen, Zentrum fuer Angewandte Geowissenschaften (ZAG), Tuebingen (Germany); UFZ - Helmholtz-Zentrum fuer Umweltforschung GmbH, Department Umweltinformatik, Leipzig (Germany); Reinstorf, F. [Hochschule Magdeburg-Stendal, Fachbereich Wasser- und Kreislaufwirtschaft, Magdeburg (Germany); Martienssen, M. [Helmholtz-Zentrum fuer Umweltforschung GmbH - UFZ, Department Hydrogeologie, Halle/Saale (Germany); Schirmer, M. [EAWAG, das Wasserforschungs-Institut des ETH-Bereichs, Abteilung Wasserressourcen und Trinkwasser, Duebendorf (Switzerland)
2008-09-15
As a result of intensive industrial, mining, and urban development, numerous large-scale contaminated areas exist in Germany. These so-called megasites represent a challenge to risk assessment and remediation strategies. At the Bitterfeld megasite, the contaminated groundwater interacts with the local streams. Along a stream reach 280 m long, the mass flow rates of chlorinated benzenes were estimated by combining integral pumping tests, streambed temperature mapping, and analyses of contaminant concentrations in the streambed sediments. On average, a total mass flow rate of 617 mg d{sup -1} monochlorobenzene (MCB) and 157 mg d{sup -1} dichlorobenzene (DCB) is released from the adjoining aquifer into the stream along the investigated reach. Further, the streambed sediment acts as the dominant contaminant source. Considering the streambed sediments, the contaminant mass flow rate to the river increases to values between 2,355 and 4,323 mg d{sup -1} MCB and between 892 and 3,587 mg d{sup -1} DCB. (orig.) [German] Als Folge intensiver industrieller, bergbaulicher und urbaner Nutzung gibt es in Deutschland zahlreiche grossflaechig kontaminierte Standorte. Diese so genannten Megasites stellen eine grosse Herausforderung fuer die Risikobewertung und Sanierung dar. An der Megasite Bitterfeld kommt es zudem zu Wechselwirkungen zwischen kontaminiertem Grundwasser und den lokalen Vorflutern. An einem 280 m langen Flussabschnitt wurden durch die Kombination integraler Pumpversuche, Kartierung der Flussbettsedimenttemperaturen und Analysen der Schadstoffkonzentrationen im Flussbettsediment die Schadstoffmassenstroeme chlorierter Benzole abgeschaetzt, die mit der Grundwasserstroemung aus dem Aquifer und dem Flussbettsediment in den Vorfluter gelangen. Im Mittel gelangt am untersuchten Flussabschnitt eine Fracht von 617 mg d{sup -1} Monochlorbenzen (MCB) und 157 mg d{sup -1} Dichlorbenzen (DCB) aus dem Aquifer in den Vorfluter. Das Flussbettsediment des untersuchten Vorfluters
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Turnbull, S. J.
2017-12-01
Within the US Army Corps of Engineers (USACE), reservoirs are typically operated according to a rule curve that specifies target water levels based on the time of year. The rule curve is intended to maximize flood protection by specifying releases of water before the dominant rainfall period for a region. While some operating allowances are permissible, generally the rule curve elevations must be maintained. While this operational approach provides for the required flood control purpose, it may not result in optimal reservoir operations for multi-use impoundments. In the Russian River Valley of California a multi-agency research effort called Forecast-Informed Reservoir Operations (FIRO) is assessing the application of forecast weather and streamflow predictions to potentially enhance the operation of reservoirs in the watershed. The focus of the study has been on Lake Mendocino, a USACE project important for flood control, water supply, power generation and ecological flows. As part of this effort the Engineer Research and Development Center is assessing the ability of utilizing the physics based, distributed watershed model Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model to simulate stream flows, reservoir stages, and discharges while being driven by weather forecast products. A key question in this application is the effect of watershed model resolution on forecasted stream flows. To help resolve this question, GSSHA models of multiple grid resolutions, 30, 50, and 270m, were developed for the upper Russian River, which includes Lake Mendocino. The models were derived from common inputs: DEM, soils, land use, stream network, reservoir characteristics, and specified inflows and discharges. All the models were calibrated in both event and continuous simulation mode using measured precipitation gages and then driven with the West-WRF atmospheric model in prediction mode to assess the ability of the model to function in short term, less than one week
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Functional differentiation between fish assemblages from forested and deforested streams
Directory of Open Access Journals (Sweden)
Fabrício Barreto Teresa
Full Text Available We tested the hypothesis that streams in deforested areas shelter different fish communities to nearby forested areas, and that these disparities are due to environmental parameters that limit or benefit different species according to their functional traits. We compared the community composition of three south east Brazilian streams flanked by riparian forest with three nearby streams in deforested areas. The following functional traits were considered: diet, habitat use, water flow preference, size, and hypoxia tolerance. Differentiation between forested and deforested streams corresponded with the different contributions of three functional groups. Species reported in the literature to be hypoxia tolerant, and exhibiting a variable combination of the other traits prevailed in deforested streams, although we did not find substantial differences in oxygen levels between forested and deforested streams. In forested streams, benthic species associated with a high water flow and an insectivorous diet were dominant. Changes in streams induced by deforestation which are associated with habitat availability, food resources, and physicochemical conditions appear to restrict the occurrence of specialized species and instead benefit tolerant generalists.
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Measurement of flow rate in the third loop of PWR
International Nuclear Information System (INIS)
Gao Shufan.
1986-01-01
The range of flow rate was 14000-50000 m 3 /h. The diameter of main tube was 2.6 m. A special made pitot set was placed on the main tube in order to accurately measure the flow rate. A cross slideway and a guide devicc were used to prevent the pitot vibration. Method of equal annular area was used in the measurement. The error was less than 4.2%. A pitot cylinder flowmeter was set also on the main tube to supervise the total flow rate of the third loop
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An Experimental study on a Method of Computing Minimum flow rate
International Nuclear Information System (INIS)
Cho, Yeon Sik; Kim, Tae Hyun; Kim, Chang Hyun
2009-01-01
Many pump reliability problems in the Nuclear Power Plants (NPPs) are being attributed to the operation of the pump at flow rates well below its best efficiency point(BEP). Generally, the manufacturer and the user try to avert such problems by specifying a minimum flow, below which the pump should not be operated. Pump minimum flow usually involves two considerations. The first consideration is normally termed the 'thermal minimum flow', which is that flow required to prevent the fluid inside the pump from reaching saturation conditions. The other consideration is often referred to as 'mechanical minimum flow', which is that flow required to prevent mechanical damage. However, the criteria for specifying such a minimum flow are not clearly understood by all parties concerned. Also various factor and information for computing minimum flow are not easily available as considering for the pump manufacturer' proprietary. The objective of this study is to obtain experimental data for computing minimum flow rate and to understand the pump performances due to low flow operation. A test loop consisted of the pump to be used in NPPs, water tank, flow rate measurements and piping system with flow control devices was established for this study
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Numerical study of thermoviscous effects in ultrasound-induced acoustic streaming in microchannels
DEFF Research Database (Denmark)
Muller, Peter Barkholt; Bruus, Henrik
2014-01-01
We present a numerical study of thermoviscous effects on the acoustic streaming flow generated by an ultrasound standing-wave resonance in a long straight microfluidic channel containing a Newtonian fluid. These effects enter primarily through the temperature and density dependence of the fluid...... viscosity. The resulting magnitude of the streaming flow is calculated and characterized numerically, and we find that even for thin acoustic boundary layers, the channel height affects the magnitude of the streaming flow. For the special case of a sufficiently large channel height, we have successfully...
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Cool-down flow-rate limits imposed by thermal stresses in LNG pipelines
Novak, J. K.; Edeskuty, F. J.; Bartlit, J. R.
Warm cryogenic pipelines are usually cooled to operating temperature by a small, steady flow of the liquid cryogen. If this flow rate is too high or too low, undesirable stresses will be produced. Low flow-rate limits based on avoidance of stratified two-phase flow were calculated for pipelines cooled with liquid hydrogen or nitrogen. High flow-rate limits for stainless steel and aluminum pipelines cooled by liquid hydrogen or nitrogen were determined by calculating thermal stress in thick components vs flow rate and then selecting some reasonable stress limits. The present work extends these calculations to pipelines made of AISI 304 stainless steel, 6061 aluminum, or ASTM A420 9% nickel steel cooled by liquid methane or a typical natural gas. Results indicate that aluminum and 9% nickel steel components can tolerate very high cool-down flow rates, based on not exceeding the material yield strength.
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Middaugh, Christopher R.; Kessinger, Brin; Magoulick, Daniel D.
2018-01-01
Temperature increases due to climate change over the coming century will likely affect smallmouth bass (Micropterus dolomieu) growth in lotic systems at the southern extent of their native range. However, the thermal response of a stream to warming climate conditions could be affected by the flow regime of each stream, mitigating the effects on smallmouth bass populations. We developed bioenergetics models to compare change in smallmouth bass growth rate potential (GRP) from present to future projected monthly stream temperatures across two flow regimes: runoff and groundwater-dominated. Seasonal differences in GRP between stream types were then compared. The models were developed for fourteen streams within the Ozark–Ouachita Interior Highlands in Arkansas, Oklahoma and Missouri, USA, which contain smallmouth bass. In our simulations, smallmouth bass mean GRP during summer months decreased by 0.005 g g−1 day−1 in runoff streams and 0.002 g g−1 day−1 in groundwater streams by the end of century. Mean GRP during winter, fall and early spring increased under future climate conditions within both stream types (e.g., 0.00019 g g−1 day−1 in runoff and 0.0014 g g−1 day−1 in groundwater streams in spring months). We found significant differences in change in GRP between runoff and groundwater streams in three seasons in end-of-century simulations (spring, summer and fall). Potential differences in stream temperature across flow regimes could be an important habitat component to consider when investigating effects of climate change as fishes from various flow regimes that are relatively close geographically could be affected differently by warming climate conditions.
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Flooding in ephemeral streams: incorporating transmission losses
Stream flow in semiarid lands commonly occurs as a form of flash floods in dry ephemeral stream beds. The goal of this research is to couple hydrological and hydraulic models treats channel transmission losses and test the methodology in the USDA-ARS Walnut Gulch Experimental Watershed (WGEW). For h...
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Lovette, J. P.; Duncan, J. M.; Vimal, S.; Band, L. E.
2015-12-01
Natural riparian areas play numerous roles in the maintenance and improvement of stream water quality. Both restoration of riparian areas and improvement of hydrologic connectivity to the stream are often key goals of river restoration projects. These management actions are designed to improve nutrient removal by slowing and treating overland flow delivered from uplands and by storing, treating, and slowly releasing streamwater from overbank inundation during flood events. A major question is how effective this storage of overbank flow is at treating streamwater based on the cumulative time stream discharge at a downstream location has spent in shallower, slower overbank flow. The North Carolina Floodplain Mapping Program maintains a detailed statewide Flood Risk Information System (FRIS) using HEC-RAS modeling, lidar, and detailed surveyed river cross-sections. FRIS provides extensive information regarding channel geometry on approximately 39,000 stream reaches (a slightly coarser spatial resolution than the NHD+v2 dataset) with tens of cross-sections for each reach. We use this FRIS data to calculate volume and discharge from floodplain riparian areas separately from in-channel flow during overbank events. Preliminary results suggest that a small percentage of total annual discharge interacts with the full floodplain extent along a stream reach due to the infrequency of overbank flow events. However, with the significantly different physical characteristics of the riparian area when compared to the channel itself, this overbank flow can provide unique services to water quality. Our project aims to use this information in conjunction with data from the USGS SPARROW program to target non-point source hotspots of Nitrogen and Phosphorus addition and removal. By better understanding the flow dynamics within riparian areas during high flow events, riparian restoration projects can be carried out with improved efficacy.
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Debris flow-induced topographic changes: effects of recurrent debris flow initiation.
Chen, Chien-Yuan; Wang, Qun
2017-08-12
Chushui Creek in Shengmu Village, Nantou County, Taiwan, was analyzed for recurrent debris flow using numerical modeling and geographic information system (GIS) spatial analysis. The two-dimensional water flood and mudflow simulation program FLO-2D were used to simulate debris flow induced by rainfall during typhoon Herb in 1996 and Mindulle in 2004. Changes in topographic characteristics after the debris flows were simulated for the initiation of hydrological characteristics, magnitude, and affected area. Changes in topographic characteristics included those in elevation, slope, aspect, stream power index (SPI), topographic wetness index (TWI), and hypsometric curve integral (HI), all of which were analyzed using GIS spatial analysis. The results show that the SPI and peak discharge in the basin increased after a recurrence of debris flow. The TWI was higher in 2003 than in 2004 and indicated higher potential of landslide initiation when the slope of the basin was steeper. The HI revealed that the basin was in its mature stage and was shifting toward the old stage. Numerical simulation demonstrated that the parameters' mean depth, maximum depth, affected area, mean flow rate, maximum flow rate, and peak flow discharge were increased after recurrent debris flow, and peak discharge occurred quickly.
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Land use and physiographic variability influence stream low flows, yet their interactions and relative influence remain unresolved. Our objective was to assess the influence of land use and watershed geomorphic characteristics on low-flow variability in the southern Blue Ridge Mo...
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Cohen, M. J.; Hensley, R. T.; Spangler, M.; Gooseff, M. N.
2017-12-01
A key organizing idea in stream ecology is the river continuum concept (RCC) which makes testable predictions about network-scale variation in metabolic and community attributes. Using high resolution (ca. 0.1 Hz) Lagrangian sampling of a wide suite of solutes - including nitrate, fDOM, dissolved oyxgen and specific conductance, we sampled the river continuum from headwaters to the sea in the Suwannee River (Florida, USA). We specifically sought to test two predictions that follow from the RCC: first, that changes in metabolism and hydraulics lead to progressive reduction in total N retention but greater diel variation with increasing stream order; and second, that variation in metabolic and nutrient processing rates is larger across stream orders than between low order streams. In addition to providing a novel test of theory, these measurements enabled new insights into the evolution of water quality through a complex landscape, in part because main-stem profiles were obtained for both high and historically low flow conditions. We observed strong evidence of metabolism and nutrient retention at low flow. Both the rate of uptake velocity and the mass retention per unit area declined with increasing stream order, and declined dramatically at high flow. Clear evidence for time varying retention (i.e., diel variation) was observed at low flow, but was masked or absent at high flow. In this geologically complex river - with alluvial, spring-fed, and blackwater headwater streams - variation across low-order streams was large, suggesting the presence of many river continuua across the network. This application of longitudinal sampling and inference underscores the utility of changing reference frames to draw new insights, but also highlights some of the challenges that need to be considered and, where possible, controlled.
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Transition to turbulence and noise radiation in heated coaxial jet flows
Energy Technology Data Exchange (ETDEWEB)
Gloor, Michael, E-mail: gloor@ifd.mavt.ethz.ch; Bühler, Stefan; Kleiser, Leonhard [Institute of Fluid Dynamics, ETH Zurich, 8092 Zurich (Switzerland)
2016-04-15
Laminar-turbulent transition and noise radiation of a parametrized set of subsonic coaxial jet flows with a hot primary (core) stream are investigated numerically by Large-Eddy Simulation (LES) and direct noise computation. This study extends our previous research on local linear stability of heated coaxial jet flows by analyzing the nonlinear evolution of initially laminar flows disturbed by a superposition of small-amplitude unstable eigenmodes. First, a baseline configuration is studied to shed light on the flow dynamics of coaxial jet flows. Subsequently, LESs are performed for a range of Mach and Reynolds numbers to systematically analyze the influences of the temperature and the velocity ratios between the primary and the secondary (bypass) stream. The results provide a basis for a detailed analysis of fundamental flow-acoustic phenomena in the considered heated coaxial jet flows. Increasing the primary-jet temperature leads to an increase of fluctuation levels and to an amplification of far-field noise, especially at low frequencies. Strong mixing between the cold bypass stream and the hot primary stream as well as the intermittent character of the flow field at the end of the potential core lead to a pronounced noise radiation at an aft angle of approximately 35{sup ∘}. The velocity ratio strongly affects the shear-layer development and therefore also the noise generation mechanisms. Increasing the secondary-stream velocity amplifies the dominance of outer shear-layer perturbations while the disturbance growth rates in the inner shear layer decrease. Already for r{sub mic} > 40R{sub 1}, where r{sub mic} is the distance from the end of the potential core and R{sub 1} is the core-jet radius, a perfect 1/r{sub mic} decay of the sound pressure amplitudes is observed. The potential-core length increases for higher secondary-stream velocities which leads to a shift of the center of the dominant acoustic radiation in the downstream direction.
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Balachandran, Uthamalingam; Poeppel, Roger B.; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Udovich, Carl A.
1994-01-01
This invention discloses cross-flow electrochemical reactor cells containing oxygen permeable materials which have both electron conductivity and oxygen ion conductivity, cross-flow reactors, and electrochemical processes using cross-flow reactor cells having oxygen permeable monolithic cores to control and facilitate transport of oxygen from an oxygen-containing gas stream to oxidation reactions of organic compounds in another gas stream. These cross-flow electrochemical reactors comprise a hollow ceramic blade positioned across a gas stream flow or a stack of crossed hollow ceramic blades containing a channel or channels for flow of gas streams. Each channel has at least one channel wall disposed between a channel and a portion of an outer surface of the ceramic blade, or a common wall with adjacent blades in a stack comprising a gas-impervious mixed metal oxide material of a perovskite structure having electron conductivity and oxygen ion conductivity. The invention includes reactors comprising first and second zones seprated by gas-impervious mixed metal oxide material material having electron conductivity and oxygen ion conductivity. Prefered gas-impervious materials comprise at least one mixed metal oxide having a perovskite structure or perovskite-like structure. The invention includes, also, oxidation processes controlled by using these electrochemical reactors, and these reactions do not require an external source of electrical potential or any external electric circuit for oxidation to proceed.
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International Nuclear Information System (INIS)
Nalezny, C.L.; Chapman, R.L.; Martinell, J.S.; Riordon, R.P.; Solbrig, C.W.
1979-01-01
Mass flow is an important measured variable in the Loss-of-Fluid Test (LOFT) Program. Large uncertainties in mass flow measurements in the LOFT piping during LOFT coolant experiments requires instrument testing in a transient two-phase flow loop that simulates the geometry of the LOFT piping. To satisfy this need, a transient two-phase flow loop has been designed and built. The load cell weighing system, which provides reference mass flow measurements, has been analyzed to assess its capability to provide the measurements. The analysis consisted of first performing a thermal-hydraulic analysis using RELAP4 to compute mass inventory and pressure fluctuations in the system and mass flow rate at the instrument location. RELAP4 output was used as input to a structural analysis code SAPIV which is used to determine load cell response. The computed load cell response was then smoothed and differentiated to compute mass flow rate from the system. Comparison between computed mass flow rate at the instrument location and mass flow rate from the system computed from the load cell output was used to evaluate mass flow measurement capability of the load cell weighing system. Results of the analysis indicate that the load cell weighing system will provide reference mass flows more accurately than the instruments now in LOFT
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Ramadan, Islam A; Bailliet, Hélène; Valière, Jean-Christophe
2018-01-01
The influence of both the natural convection and end-effects on Rayleigh streaming pattern in a simple standing-wave thermoacoustic engine is investigated experimentally at different acoustic levels. The axial mean velocity inside the engine is measured using both Laser Doppler Velocimetry and Particle Image Velocimetry. The mean flow patterns are categorized in three different regions referred to as "cold streaming" region, "hot streaming" region, and "end-effects" region. In the cold streaming region, the dominant phenomenon is Rayleigh streaming and the mean velocity measurements correspond well with the theoretical expectations of Rayleigh streaming at low acoustic levels. At higher acoustic levels, the measurements deviate from the theoretical expectations which complies with the literature. In the hot streaming region, temperature measurements reveal that the non-uniformity of the resonator wall temperature is the origin of natural convection flow. Velocity measurements show that natural convection flow superimposes on the Rayleigh streaming flow so that the measured mean velocity deviates from the theoretical expectations of Rayleigh streaming. In the last region, the measured mean velocity is very different from Rayleigh streaming due to the combined effects of both the flow disturbances generated near the extremity of the stack and the natural convection flow.
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International Nuclear Information System (INIS)
James, L.A.; Lee, H.B.; Wire, G.L.; Novak, S.R.; Cullen, W.H.
1997-01-01
Corrosion fatigue crack propagation tests were conducted on a high-sulfur ASTM A302-B plate steel overlaid with weld-deposited Alloy EN82H cladding. The specimens featured semi-elliptical surface cracks penetrating approximately 6.3 mm of cladding into the underlying steel. The initial crack sizes were relatively large with surface lengths of 22.8--27.3 mm, and depths of 10.5--14.1 mm. The experiments were initiated in a quasi-stagnant low-oxygen (O 2 < 10 ppb) aqueous environment at 243 C, under loading conditions (ΔK, R, cyclic frequency) conducive to environmentally assisted cracking (EAC) under quasi-stagnant conditions. Following fatigue testing under quasi-stagnant conditions where EAC was observed, the specimens were then fatigue tested under conditions where active water flow of either 1.7 m/s or 4.7 m/s was applied parallel to the crack. Earlier experiments on unclad surface-cracked specimens of the same steel exhibited EAC under quasi-stagnant conditions, but water flow rates at 1.7 m/s and 5.0 m/s parallel to the crack mitigated EAC. In the present experiments on clad specimens, water flow at approximately the same as the lower of these velocities did not mitigate EAC, and a free stream velocity approximately the same as the higher of these velocities resulted in sluggish mitigation of EAC. The lack of robust EAC mitigation was attributed to the greater crack surface roughness in the cladding interfering with flow induced within the crack cavity. An analysis employing the computational fluid dynamics code, FIDAP, confirmed that frictional forces associated with the cladding crack surface roughness reduced the interaction between the free stream and the crack cavity
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Network Structure as a Modulator of Disturbance Impacts in Streams
Warner, S.; Tullos, D. D.
2017-12-01
This study examines how river network structure affects the propagation of geomorphic and anthropogenic disturbances through streams. Geomorphic processes such as debris flows can alter channel morphology and modify habitat for aquatic biota. Anthropogenic disturbances such as road construction can interact with the geomorphology and hydrology of forested watersheds to change sediment and water inputs to streams. It was hypothesized that the network structure of streams within forested watersheds would influence the location and magnitude of the impacts of debris flows and road construction on sediment size and channel width. Longitudinal surveys were conducted every 50 meters for 11 kilometers of third-to-fifth order streams in the H.J. Andrews Experimental Forest in the Western Cascade Range of Oregon. Particle counts and channel geometry measurements were collected to characterize the geomorphic impacts of road crossings and debris flows as disturbances. Sediment size distributions and width measurements were plotted against the distance of survey locations through the network to identify variations in longitudinal trends of channel characteristics. Thresholds for the background variation in sediment size and channel width, based on the standard deviations of sample points, were developed for sampled stream segments characterized by location as well as geomorphic and land use history. Survey locations were classified as "disturbed" when they deviated beyond the reference thresholds in expected sediment sizes and channel widths, as well as flow-connected proximity to debris flows and road crossings. River network structure was quantified by drainage density and centrality of nodes upstream of survey locations. Drainage density and node centrality were compared between survey locations with similar channel characteristic classifications. Cluster analysis was used to assess the significance of survey location, proximity of survey location to debris flows and road
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Rubio-Gracia, Francesc; Almeida, David; Bonet, Berta; Casals, Frederic; Espinosa, Carmen; Flecker, Alexander S; García-Berthou, Emili; Martí, Eugènia; Tuulaikhuu, Baigal-Amar; Vila-Gispert, Anna; Zamora, Lluis; Guasch, Helena
2017-12-01
Flow regimes are important drivers of both stream community and biogeochemical processes. However, the interplay between community and biogeochemical responses under different flow regimes in streams is less understood. In this study, we investigated the structural and functional responses of periphyton and macroinvertebrates to different densities of the Mediterranean barbel (Barbus meridionalis, Cyprinidae) in two stream reaches differing in flow regime. The study was conducted in Llémena Stream, a small calcareous Mediterranean stream with high nutrient levels. We selected a reach with permanent flow (permanent reach) and another subjected to flow regulation (regulated reach) with periods of flow intermittency. At each reach, we used in situ cages to generate 3 levels of fish density. Cages with 10 barbels were used to simulate high fish density (>7indm -2 ); cages with open sides were used as controls (i.e. exposed to actual fish densities of each stream reach) thus having low fish density; and those with no fish were used to simulate the disappearance of fish that occurs with stream drying. Differences in fish density did not cause significant changes in periphyton biomass and macroinvertebrate density. However, phosphate uptake by periphyton was enhanced in treatments lacking fish in the regulated reach with intermittent flow but not in the permanent reach, suggesting that hydrologic alteration hampers the ability of biotic communities to compensate for the absence of fish. This study indicates that fish density can mediate the effects of anthropogenic alterations such as flow intermittence derived from hydrologic regulation on stream benthic communities and associated biogeochemical processes, at least in eutrophic streams. Copyright © 2017. Published by Elsevier B.V.
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New Jersey StreamStats: A web application for streamflow statistics and basin characteristics
Watson, Kara M.; Janowicz, Jon A.
2017-08-02
StreamStats is an interactive, map-based web application from the U.S. Geological Survey (USGS) that allows users to easily obtain streamflow statistics and watershed characteristics for both gaged and ungaged sites on streams throughout New Jersey. Users can determine flood magnitude and frequency, monthly flow-duration, monthly low-flow frequency statistics, and watershed characteristics for ungaged sites by selecting a point along a stream, or they can obtain this information for streamgages by selecting a streamgage location on the map. StreamStats provides several additional tools useful for water-resources planning and management, as well as for engineering purposes. StreamStats is available for most states and some river basins through a single web portal.Streamflow statistics for water resources professionals include the 1-percent annual chance flood flow (100-year peak flow) used to define flood plain areas and the monthly 7-day, 10-year low flow (M7D10Y) used in water supply management and studies of recreation, wildlife conservation, and wastewater dilution. Additionally, watershed or basin characteristics, including drainage area, percent area forested, and average percent of impervious areas, are commonly used in land-use planning and environmental assessments. These characteristics are easily derived through StreamStats.
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Broadband Shock Noise in Internally-Mixed Dual-Stream Jets
Bridges, James E.
2009-01-01
Broadband shock noise (BBSN) has been studied in some detail in single-flow jets and recently in dual-stream jets with separate flow exhaust systems. Shock noise is of great concern in these latter cases because of the noise created for the aircraft cabin by the underexpanded nozzle flow at cruise. Another case where shock noise is of concern is in the case of future supersonic aircraft that are expected to have bypass ratios small enough to justify internally mixed exhaust systems, and whose mission will push cycles to the point of imperfectly expanded flows. Dual-stream jets with internally mixed plume have some simplifying aspects relative to the separate flow jets, having a single shock structure given by the common nozzle pressure. This is used to separate the contribution of the turbulent shear layer to the broadband shock noise. Shock structure is held constant while the geometry and strength of the inner and merged shear layers are varying by changing splitter area ratio and core stream temperature. Flow and noise measurements are presented which document the efforts at separating the contribution of the inner shear layer to the broadband shock noise.
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Large-scale environmental controls on microbial biofilms in high-alpine streams
Directory of Open Access Journals (Sweden)
T. J. Battin
2004-01-01
Full Text Available Glaciers are highly responsive to global warming and important agents of landscape heterogeneity. While it is well established that glacial ablation and snowmelt regulate stream discharge, linkage among streams and streamwater geochemistry, the controls of these factors on stream microbial biofilms remain insufficiently understood. We investigated glacial (metakryal, hypokryal, groundwater-fed (krenal and snow-fed (rhithral streams - all of them representative for alpine stream networks - and present evidence that these hydrologic and hydrogeochemical factors differentially affect sediment microbial biofilms. Average microbial biomass and bacterial carbon production were low in the glacial streams, whereas bacterial cell size, biomass, and carbon production were higher in the tributaries, most notably in the krenal stream. Whole-cell in situ fluorescence hybridization revealed reduced detection rates of the Eubacteria and higher abundance of α-Proteobacteria in the glacial stream, a pattern that most probably reflects the trophic status of this ecosystem. Our data suggest low flow during the onset of snowmelt and autumn as a short period (hot moment of favorable environmental conditions with pulsed inputs of allochthonous nitrate and dissolved organic carbon, and with disproportionately high microbial growth. Tributaries are relatively more constant and favorable environments than kryal streams, and serve as possible sources of microbes and organic matter to the main glacial channel during periods (e.g., snowmelt of elevated hydrologic linkage among streams. Ice and snow dynamics - and their impact on the amount and composition of dissolved organic matter - have a crucial impact on stream biofilms, and we thus need to consider microbes and critical hydrological episodes in future models of alpine stream communities.
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Data Stream Clustering With Affinity Propagation
Zhang, Xiangliang
2014-07-09
Data stream clustering provides insights into the underlying patterns of data flows. This paper focuses on selecting the best representatives from clusters of streaming data. There are two main challenges: how to cluster with the best representatives and how to handle the evolving patterns that are important characteristics of streaming data with dynamic distributions. We employ the Affinity Propagation (AP) algorithm presented in 2007 by Frey and Dueck for the first challenge, as it offers good guarantees of clustering optimality for selecting exemplars. The second challenging problem is solved by change detection. The presented StrAP algorithm combines AP with a statistical change point detection test; the clustering model is rebuilt whenever the test detects a change in the underlying data distribution. Besides the validation on two benchmark data sets, the presented algorithm is validated on a real-world application, monitoring the data flow of jobs submitted to the EGEE grid.
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Data Stream Clustering With Affinity Propagation
Zhang, Xiangliang; Furtlehner, Cyril; Germain-Renaud, Cecile; Sebag, Michele
2014-01-01
Data stream clustering provides insights into the underlying patterns of data flows. This paper focuses on selecting the best representatives from clusters of streaming data. There are two main challenges: how to cluster with the best representatives and how to handle the evolving patterns that are important characteristics of streaming data with dynamic distributions. We employ the Affinity Propagation (AP) algorithm presented in 2007 by Frey and Dueck for the first challenge, as it offers good guarantees of clustering optimality for selecting exemplars. The second challenging problem is solved by change detection. The presented StrAP algorithm combines AP with a statistical change point detection test; the clustering model is rebuilt whenever the test detects a change in the underlying data distribution. Besides the validation on two benchmark data sets, the presented algorithm is validated on a real-world application, monitoring the data flow of jobs submitted to the EGEE grid.
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Crevasse-squeeze ridge corridors: Diagnostic features of late-stage palaeo-ice stream activity
Evans, David J. A.; Storrar, Robert D.; Rea, Brice R.
2016-04-01
A 200-km-long and 10-km-wide linear assemblage of till-filled geometrical ridges on the bed of the Maskwa palaeo-ice stream of the late Wisconsinan southwest Laurentide Ice Sheet are interpreted as crevasse-squeeze ridges (CSR) developed during internal flow unit reorganization, immediately prior to ice stream shutdown. Ridge orientations are predominantly orientated WNW-ESE, with a subordinate WSW-ENE alignment, both indicative of ice fracture development transverse to former ice stream flow, as indicated by NNE-SSW aligned MSGL. Subglacial till injection into basal and/or full depth, mode I and II crevasses occurred at the approximate centreline of the ice stream, in response to extension and fracturing. Landform preservation indicates that this took place during the final stages of ice streaming, immediately prior to ice stream shutdown. This linear zone of ice fracturing therefore likely represents the narrowing of the fast-flowing trunk, similar to the plug flow identified in some surging valley glaciers. Lateral drag between the final active flow unit and the slower moving ice on either side is likely recorded by the up-ice bending of the CSR limbs. The resulting CSR corridor, here related to an individual ice stream flow unit, constitutes a previously unreported style of crevasse infilling and contrasts with two existing CSR patterns: (1) wide arcuate zones of CSRs related to widespread fracturing within glacier surge lobes; and (2) narrow concentric arcs of CSRs and recessional push moraines related to submarginal till deformation at active temperate glacier lobes.
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Concentration-Discharge Behavior of Contaminants in a Stream Impacted by Acid Mine Drainage
Shaw, M. E.; Klein, M.; Herndon, E.
2017-12-01
Acid mine drainage (AMD) has severely degraded streams throughout the Appalachian coal region of the United States. AMD occurs when pyrite contained in coal is exposed to water and air during mining activities and oxidized to release high concentrations of sulfate, metals, and acidity into water bodies. Little is known about the concentration-discharge (CQ) relationships of solutes in AMD-impacted streams due to the complicated nature of acid mine drainage systems. For example, streams may receive inputs from multiple sources that include runoff, constructed treatment systems, and abandoned mines that bypass these systems to continue to contaminate the streams. It is important to understand the CQ relationships of contaminants in AMD-impacted streams in order to elucidate contaminant sources and to predict effects on aquatic ecosystems. Here, we study the CQ behaviors of acid and metals in a contaminated watershed in northeastern Ohio where limestone channels have been installed to remediate water draining from a mine pool into the stream. Stream chemistry was measured in samples collected once per day or once per hour during storm events, and stream flow was measured continuously at the watershed outlet. Increases in stream velocity during storm events resulted in an increase in pH (from 3 to 6) that subsequently decreased back to 3 as flow decreased. Additionally, Fe and Mn concentrations in the stream were high during baseflow (7 and 15 mg/L, respectively) and decreased with increasing discharge during storm events. These results indicate that the treatment system is only effective at neutralizing stream acidity and removing metals when water flow through the limestone channel is continuous. We infer that the acidic and metal-rich baseflow derives from upwelling of contaminated groundwater or subsurface flow from a mine pool. Ongoing studies aim to isolate the source of this baseflow contamination and evaluate the geochemical transformations that occur as it
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Compact and tunable size-based dielectrophoretic flow fractionation
International Nuclear Information System (INIS)
Chuang, Han-Sheng; Chung, Tien-Yu; Li, Yun
2014-01-01
A compact and tunable size-based flow fractionation microchip using negative dielectrophoresis (DEP) is presented in this paper. In the microchip, a sample containing a mixture of particles is hydrodynamically focused in a contraction section and then sorted by size after flowing over planar interdigitated electrodes. The electrodes and flow chamber were aligned at an angle of 45° to produce effective sorting. 1, 2.5 and 4.8 µm polystyrene (PS) particles were successfully separated into three distinct streams in a short distance (1 mm) and collected in different outlet channels. The sorting was subjected to flow rates and electric potential. The experimental sorting efficiencies of 1, 2.5 and 4.8 µm particles reached 97.2%, 79.6% and 99.8%, respectively. With the same device, lipid vesicle sorting was demonstrated. 86.9% of vesicles larger than 10 µm were effectively extracted from the sample stream. Likewise, sorting of other biological particles can be achieved in the same fashion. (paper)
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Dholey, S.
2018-04-01
In this paper, we have investigated numerically the laminar unsteady separated stagnation-point flow and heat transfer of a viscous fluid over a moving flat surface in the presence of a time dependent free stream velocity which causes the unsteadiness of this flow problem. The plate is assumed to move in the same or opposite direction of the free stream velocity. The flow is therefore governed by the velocity ratio parameter λ (ratio of the plate velocity to the free stream velocity) and the unsteadiness parameter β. When the plate surface moves in the same direction of the free stream velocity (i.e., when λ > 0), the solution of this flow problem continues for any given value of β. On the other hand, when they move in opposite directions (i.e., when λ heat transfer analysis is that for a given value of λ(= 0), first the heat transfer rate increases with the increase of the Prandtl number Pr and after attaining a maximum value, it decreases and finally tends to be zero for large values of Pr depending upon the values of β > 0. On the contrary, for a given value of β(≤ 0), the rate of heat transfer increases consistently with the increase of Pr.
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Recharge and flow processes in a till aquitard
DEFF Research Database (Denmark)
Schrøder, Thomas Morville; Høgh Jensen, Karsten; Dahl, Mette
1999-01-01
Eastern Denmark is primarily covered by clay till. The transformation of the excess rainfall into laterally diverted groundwater flow, drain flow, stream flow, and recharge to the underlying aquifer is governed by complicatedinterrelated processes. Distributed hydrological models provide a framew......Eastern Denmark is primarily covered by clay till. The transformation of the excess rainfall into laterally diverted groundwater flow, drain flow, stream flow, and recharge to the underlying aquifer is governed by complicatedinterrelated processes. Distributed hydrological models provide...... a framework for assessing the individual flow components and forestablishing the overall water balance. Traditionally such models are calibrated against measurements of stream flow, head in the aquiferand perhaps drainage flow. The head in the near surface clay till deposits have generally not been measured...... the shallow wells and one in the valley adjacent to the stream. Precipitation and stream flow gauging along with potential evaporation estimates from a nearby weather station provide the basic data for the overall water balance assessment. The geological composition was determined from geoelectrical surveys...
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Acoustic Streaming and Its Suppression in Inhomogeneous Fluids
DEFF Research Database (Denmark)
Karlsen, Jonas Tobias; Qiu, Wei; Augustsson, Per
2018-01-01
We present a theoretical and experimental study of boundary-driven acoustic streaming in an inhomogeneous fluid with variations in density and compressibility. In a homogeneous fluid this streaming results from dissipation in the boundary layers (Rayleigh streaming). We show...... that in an inhomogeneous fluid, an additional nondissipative force density acts on the fluid to stabilize particular inhomogeneity configurations, which markedly alters and even suppresses the streaming flows. Our theoretical and numerical analysis of the phenomenon is supported by ultrasound experiments performed...
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International Nuclear Information System (INIS)
Yun, B.J.; Kang, K.H.; Euh, D.J.; Song, C.H.; Baek, W.P.
2005-01-01
Full text of publication follows: A new type instrumentation, average bidirectional flow tube, was suggested to apply to the single and two phase flow condition. Its working principle is similar to that of the Pitot tube. The pressure measured at the front of the flow tube is equal to the total pressure, while that measured at the rear tube is slightly less than static pressure of flow field due to the suction effect at the downstream. It gives an amplification effect of measured pressure difference at the flow tube. The proposed instrumentation has the characteristics that it could be applicable to low flow condition and measure bidirectional flow. It was tested in the air-water vertical and horizontal test sections which have 0.08 m inner diameter. The pressure difference across the average bidirectional flow tube, system pressure, average void fraction and injection phasic mass flow rates were measured on the measuring plane. Test was performed primarily in the single phase water and air flow condition to get the amplification factor k of the flow tube. The test was also performed in the air-water two phase flow condition and the covered flow regimes were bubbly, slug, churn turbulent flow in the vertical pipe and stratified flow in the horizontal pipe. In order to calculate the phasic and total mass flow rates from the measured differential pressure, Chexal drift-flux correlation and momentum exchange factor between the two phases were introduced. The test result shows that the suggested instrumentation with the measured void fraction, Chexal drift-flux correlation and Bosio and Malnes' momentum exchange model can predict the phasic mass flow rates within 15% error compared to the true values. A new momentum exchange model was also suggested and it gives up to 5% improvement of the measured mass flow rate compared to combination of Bosio and Malnes' momentum exchange model. (authors)
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Link between DOC in near surface peat and stream water in an upland catchment.
Clark, Joanna M; Lane, Stuart N; Chapman, Pippa J; Adamson, John K
2008-10-15
Hydrologic transport of dissolved organic carbon (DOC) from peat soils may differ to organo-mineral soils in how they responded to changes in flow, because of differences in soil profile and hydrology. In well-drained organo-mineral soils, low flow is through the lower mineral layer where DOC is absorbed and high flow is through the upper organic layer where DOC is produced. DOC concentrations in streams draining organo-mineral soils typically increase with flow. In saturated peat soils, both high and low flows are through an organic layer where DOC is produced. Therefore, DOC in stream water draining peat may not increase in response to changes in flow as there is no switch in flow path between a mineral and organic layer. To verify this, we conducted a high-resolution monitoring study of soil and stream water at an upland peat catchment in northern England. Our data showed a strong positive correlation between DOC concentrations at -1 and -5 cm depth and stream water, and weaker correlations between concentrations at -20 to -50 cm depth and stream water. Although near surface organic material appears to be the key source of stream water DOC in both peat and organo-mineral soils, we observed a negative correlation between stream flow and DOC concentrations instead of a positive correlation as DOC released from organic layers during low and high flow was diluted by rainfall. The differences in DOC transport processes between peat and organo-mineral soils have different implications for our understanding of long-term changes in DOC exports. While increased rainfall may cause an increase in DOC flux from peat due to an increase in water volume, it may cause a decrease in concentrations. This response is contrary to expected changes in DOC exports from organo-mineral soils, where increase rainfall is likely to result in an increase in flux and concentration.
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Bioassessment in nonperennial streams: Hydrologic stability influences assessment validity
Mazor, R. D.; Stein, E. D.; Schiff, K.; Ode, P.; Rehn, A.
2011-12-01
Nonperennial streams pose a challenge for bioassessment, as assessment tools developed in perennial streams may not work in these systems. For example, indices of biotic integrity (IBIs) developed in perennial streams may give improper indications of impairment in nonperennial streams, or may be unstable. We sampled benthic macroinvertebrates from 12 nonperennial streams in southern California. In addition, we deployed loggers to obtain continuous measures of flow. 3 sites were revisited over 2 years. For each site, we calculated several metrics, IBIs, and O/E scores to determine if assessments were consistent and valid throughout the summer. Hydrology varied widely among the streams, with several streams drying between sampling events. IBIs suggested good ecological health at the beginning of the study, but declined sharply at some sites. Multivariate ordination suggested that, despite differences among sites, changes in community structure were similar, with shifts from Ephemeroptera, Plecoptera, and Trichoptera to Coleoptera and more tolerant organisms. Site revisits revealed a surprising level of variability, as 2 of the 3 revisited sites had perennial or near-perennial flow in the second year of sampling. IBI scores were more consistent in streams with stable hydrographs than in those with strongly intermittent hydrographs. These results suggest that nonperennial streams can be monitored successfully, but they may require short index periods and distinct metrics from those used in perennial streams. In addition, better approaches to mapping nonperennial streams are required.
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Evidence for fish dispersal from spatial analysis of stream network topology
Hitt, N.P.; Angermeier, P.L.
2008-01-01
Developing spatially explicit conservation strategies for stream fishes requires an understanding of the spatial structure of dispersal within stream networks. We explored spatial patterns of stream fish dispersal by evaluating how the size and proximity of connected streams (i.e., stream network topology) explained variation in fish assemblage structure and how this relationship varied with local stream size. We used data from the US Environmental Protection Agency's Environmental Monitoring and Assessment Program in wadeable streams of the Mid-Atlantic Highlands region (n = 308 sites). We quantified stream network topology with a continuous analysis based on the rate of downstream flow accumulation from sites and with a discrete analysis based on the presence of mainstem river confluences (i.e., basin area >250 km2) within 20 fluvial km (fkm) from sites. Continuous variation in stream network topology was related to local species richness within a distance of ???10 fkm, suggesting an influence of fish dispersal within this spatial grain. This effect was explained largely by catostomid species, cyprinid species, and riverine species, but was not explained by zoogeographic regions, ecoregions, sampling period, or spatial autocorrelation. Sites near mainstem river confluences supported greater species richness and abundance of catostomid, cyprinid, and ictalurid fishes than did sites >20 fkm from such confluences. Assemblages at sites on the smallest streams were not related to stream network topology, consistent with the hypothesis that local stream size regulates the influence of regional dispersal. These results demonstrate that the size and proximity of connected streams influence the spatial distribution of fish and suggest that these influences can be incorporated into the designs of stream bioassessments and reserves to enhance management efficacy. ?? 2008 by The North American Benthological Society.
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Belt, K. T.; Swan, C. M.; Pouyat, R. V.; Kaushal, S.; Groffman, P. M.; Stack, W. P.; Fisher, G. T.
2006-05-01
A better understanding of how urbanization and trees interact to alter organic matter transport and cycling is needed to assess retention in catchments and streams, as well as to estimate the magnitude of carbon fluxes to the atmosphere and to downstream aquatic ecosystems. The influx of particulate and dissolved organic matter (POM/DOC) to headwater streams normally originates within or near riparian areas, and is important to aquatic food webs in stream ecosystems. Urban catchments, however, have huge effective drainage densities (due to storm drainage infrastructure), which facilitate a POM/DOC "gutter subsidy" to streams that dwarfs riparian inputs and alters benthic litter quality (and represents a major short-circuit in the carbon vegetation-soil cycle.) We measured in-situ leaf litter breakdown rates, flows, DOC, BOD and nutrients in forested, suburban and urban streams of the BES LTER and Baltimore City DPW sampling networks, which encompassed a variety of urban and rural landscapes. Sycamore and Planetree leaf litter in-situ experiments revealed faster breakdown rates for suburban and urban landscape litter than for riparian litter, with rates being much faster than literature values for forested catchments. DOC, BOD and nutrient data (storm and dry weather) from BES/DPW stream sites showed much higher concentrations and loads in the more urbanized catchments and indicate the streams are likely heterotrophic and experience transient but high dissolved oxygen demands. High nutrient concentrations, faster litter breakdown rates, and substantially higher upland urban fluxes of organic matter (particulate and dissolved) in urban streams suggest that export rates are likely substantially higher than in forested systems and that carbon loads to both downstream aquatic systems and to the atmosphere (as CO2) are substantial.
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Acoustic and streaming velocity components in a resonant waveguide at high acoustic levels.
Daru, Virginie; Reyt, Ida; Bailliet, Hélène; Weisman, Catherine; Baltean-Carlès, Diana
2017-01-01
Rayleigh streaming is a steady flow generated by the interaction between an acoustic wave and a solid wall, generally assumed to be second order in a Mach number expansion. Acoustic streaming is well known in the case of a stationary plane wave at low amplitude: it has a half-wavelength spatial periodicity and the maximum axial streaming velocity is a quadratic function of the acoustic velocity amplitude at antinode. For higher acoustic levels, additional streaming cells have been observed. Results of laser Doppler velocimetry measurements are here compared to direct numerical simulations. The evolution of axial and radial velocity components for both acoustic and streaming velocities is studied from low to high acoustic amplitudes. Two streaming flow regimes are pointed out, the axial streaming dependency on acoustics going from quadratic to linear. The evolution of streaming flow is different for outer cells and for inner cells. Also, the hypothesis of radial streaming velocity being of second order in a Mach number expansion, is not valid at high amplitudes. The change of regime occurs when the radial streaming velocity amplitude becomes larger than the radial acoustic velocity amplitude, high levels being therefore characterized by nonlinear interaction of the different velocity components.
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Salamander occupancy in headwater stream networks
Grant, E.H.C.; Green, L.E.; Lowe, W.H.
2009-01-01
1. Stream ecosystems exhibit a highly consistent dendritic geometry in which linear habitat units intersect to create a hierarchical network of connected branches. 2. Ecological and life history traits of species living in streams, such as the potential for overland movement, may interact with this architecture to shape patterns of occupancy and response to disturbance. Specifically, large-scale habitat alteration that fragments stream networks and reduces connectivity may reduce the probability a stream is occupied by sensitive species, such as stream salamanders. 3. We collected habitat occupancy data on four species of stream salamanders in first-order (i.e. headwater) streams in undeveloped and urbanised regions of the eastern U.S.A. We then used an information-theoretic approach to test alternative models of salamander occupancy based on a priori predictions of the effects of network configuration, region and salamander life history. 4. Across all four species, we found that streams connected to other first-order streams had higher occupancy than those flowing directly into larger streams and rivers. For three of the four species, occupancy was lower in the urbanised region than in the undeveloped region. 5. These results demonstrate that the spatial configuration of stream networks within protected areas affects the occurrences of stream salamander species. We strongly encourage preservation of network connections between first-order streams in conservation planning and management decisions that may affect stream species.
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Randall, Allan D.; Freehafer, Douglas A.
2017-08-02
A variety of watershed properties available in 2015 from geographic information systems were tested in regression equations to estimate two commonly used statistical indices of the low flow of streams, namely the lowest flows averaged over 7 consecutive days that have a 1 in 10 and a 1 in 2 chance of not being exceeded in any given year (7-day, 10-year and 7-day, 2-year low flows). The equations were based on streamflow measurements in 51 watersheds in the Lower Hudson River Basin of New York during the years 1958–1978, when the number of streamflow measurement sites on unregulated streams was substantially greater than in subsequent years. These low-flow indices are chiefly a function of the area of surficial sand and gravel in the watershed; more precisely, 7-day, 10-year and 7-day, 2-year low flows both increase in proportion to the area of sand and gravel deposited by glacial meltwater, whereas 7-day, 2-year low flows also increase in proportion to the area of postglacial alluvium. Both low-flow statistics are also functions of mean annual runoff (a measure of net water input to the watershed from precipitation) and area of swamps and poorly drained soils in or adjacent to surficial sand and gravel (where groundwater recharge is unlikely and riparian water loss to evapotranspiration is substantial). Small but significant refinements in estimation accuracy resulted from the inclusion of two indices of stream geometry, channel slope and length, in the regression equations. Most of the regression analysis was undertaken with the ordinary least squares method, but four equations were replicated by using weighted least squares to provide a more realistic appraisal of the precision of low-flow estimates. The most accurate estimation equations tested in this study explain nearly 84 and 87 percent of the variation in 7-day, 10-year and 7-day, 2-year low flows, respectively, with standard errors of 0.032 and 0.050 cubic feet per second per square mile. The equations
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Relationship between xerostomia and salivary flow rates in HIV-infected individuals.
Nittayananta, Wipawee; Chanowanna, Nilnara; Pruphetkaew, Nannapat; Nauntofte, Birgitte
2013-08-01
The aim of the present study was to determine the relationship between self-reported xerostomia and salivary flow rates among HIV-infected individuals. A cross-sectional study was performed on 173 individuals (81 HIV-infected individuals, mean age: 32 years, and 92 non-HIV controls, mean age: 30 years). Subjective complaints of dry mouth, based on a self-report of xerostomia questions, and dry mouth, based on a visual analogue scale (VAS), were recorded along with measurements of salivary flow rate of both unstimulated and wax-stimulated whole saliva. The relationship between subjective responses to the xerostomia questions, the VAS of dry mouth, and objective measurements of salivary flow rates were analyzed. Responses to the questions--Do you carry water or a saliva substitute? and Have you had taste disturbance?--were significantly different between HIV-infected and non-HIV individuals (P flow rate. A significant correlation between the VAS of dry mouth and salivary flow rates was observed (P = 0.023). Responses to self-reported xerostomia questions reflects low unstimulated salivary flow rates. Thus, questions concerning dry mouth might be useful tools to identify HIV-infected individuals with hyposalivation, especially at a resting stage. © 2013 Wiley Publishing Asia Pty Ltd.
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Saturation flow mathematical model based on multiple combinations of lane groups
Energy Technology Data Exchange (ETDEWEB)
Racila, L.
2016-07-01
The ideal value of the traffic stream that can pass through an intersection is known as the saturation flow rate per hour on vehicle green time. The saturation flow is important in the understanding of the traffic light cycle and from there the understanding the Level of Service. The paper wishes to evaluate through a series of applied mathematical methods the effect of different lane grouping and critical lane group concept on the saturation flow rate. The importance of this method is that it creates a base for a signalized intersections timing plan. (Author)
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Modeling sediment concentration of rill flow
Yang, Daming; Gao, Peiling; Zhao, Yadong; Zhang, Yuhang; Liu, Xiaoyuan; Zhang, Qingwen
2018-06-01
Accurate estimation of sediment concentration is essential to establish physically-based erosion models. The objectives of this study were to evaluate the effects of flow discharge (Q), slope gradient (S), flow velocity (V), shear stress (τ), stream power (ω) and unit stream power (U) on sediment concentration. Laboratory experiments were conducted using a 10 × 0.1 m rill flume under four flow discharges (2, 4, 8 and 16 L min-1), and five slope gradients (5°, 10°, 15°, 20° and 25°). The results showed that the measured sediment concentration varied from 87.08 to 620.80 kg m-3 with a mean value of 343.13 kg m-3. Sediment concentration increased as a power function with flow discharge and slope gradient, with R2 = 0.975 and NSE = 0.945. The sediment concentration was more sensitive to slope gradient than to flow discharge. The sediment concentration was well predicted by unit stream power (R2 = 0.937, NSE = 0.865), whereas less satisfactorily by flow velocity (R2 = 0.470, NSE = 0.539) and stream power (R2 = 0.773, NSE = 0.732). In addition, using the equations to simulate the measured sediment concentration of other studies, the result further indicated that slope gradient, flow discharge and unit stream power were good predictors of sediment concentration. In general, slope gradient, flow discharge and unit stream power seem to be the preferred predictors for estimating sediment concentration.
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A study of pipe flow rate measurement using air-coupled ultrasound
International Nuclear Information System (INIS)
Tsukada, Keisuke; Tsuzuki, Nobuyoshi; Kikura, Hiroshige
2013-01-01
A non-contact flow meter employing air-coupled ultrasound is developed in this research. Ultrasonic flow meter is applied to the higher accuracy flow rate measurement, compared with pressure difference flow meter. However, ultrasonic flow meter has difficulty to measure in severe conditions such as in the condition of high temperature, high pressure condition, and radioactive materials in fluid. Especially, in high temperature condition, piezoelectric device in ultrasonic sensors lose the piezoelectricity, and it becomes difficult to transmit or detect ultrasound. Thus, in this research, ultrasonic sensors are fixed in the air. Ultrasonic sensors transmit and detect ultrasound through air, and measure the flow rate in the pipe. However, most of ultrasound is refracted and reflected at the boundaries between air and the pipe. And detected signals are weak. To increase the signal level, we developed focusing ultrasonic sensors that was optimized for the pipe flow measurement. And employing these focusing sensors the flow rate measurement has been done in order to evaluate the air-coupled ultrasonic flow meter by the ultrasonic beam focusing technique. (author)
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Relationship between salivary flow rates and Candida albicans counts.
Navazesh, M; Wood, G J; Brightman, V J
1995-09-01
Seventy-one persons (48 women, 23 men; mean age, 51.76 years) were evaluated for salivary flow rates and Candida albicans counts. Each person was seen on three different occasions. Samples of unstimulated whole, chewing-stimulated whole, acid-stimulated parotid, and candy-stimulated parotid saliva were collected under standardized conditions. An oral rinse was also obtained and evaluated for Candida albicans counts. Unstimulated and chewing-stimulated whole flow rates were negatively and significantly (p Candida counts. Unstimulated whole saliva significantly (p Candida counts of 0 versus or = 500 count. Differences in stimulated parotid flow rates were not significant among different levels of Candida counts. The results of this study reveal that whole saliva is a better predictor than parotid saliva in identification of persons with high Candida albicans counts.
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A Compound Detection System Based on Ultrasonic Flow Rate and Concentration
Qing-Hui WANG; Fang MU; Li-Feng WEI
2014-01-01
This paper proposes a new detection system for monitoring gas concentration and flow rate. Velocity difference of ultrasonic wave in bi-directional propagation in measured gas is recorded and utilized for computing the online gas concentration and flow rate. Meanwhile, the temperature compensation, return signal processing and error analysis algorithms are applied to improve the accuracy. The experimental results show that, compared with the single sensor measurement of gas flow rate or conce...
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This dataset represents the base flow index values within individual, local NHDPlusV2 catchments and upstream, contributing watersheds. Attributes of the landscape layer were calculated for every local NHDPlusV2 catchment and accumulated to provide watershed-level metrics. (See Supplementary Info for Glossary of Terms) The base-flow index (BFI) grid for the conterminous United States was developed to estimate (1) BFI values for ungaged streams, and (2) ground-water recharge throughout the conterminous United States (see Source_Information). Estimates of BFI values at ungaged streams and BFI-based ground-water recharge estimates are useful for interpreting relations between land use and water quality in surface and ground water. The bfi (%) was summarized by local catchment and by watershed to produce local catchment-level and watershed-level metrics as a continuous data type (see Data Structure and Attribute Information for a description).
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Transport of bedload sediment and channel morphology of a southeast Alaska stream.
Margaret A. Estep; Robert L. Beschta
1985-01-01
During 1980-81, transport of bedload sediment and channel morphology were determined at Trap Bay Creek, a third-order stream that drains a 13.5-square kilometer watershed on Chichagof island in southeast Alaska. Bedload sediment was sampled for 10 storms: peak flows ranged from 0.6 to 19.0 cubic meters per second, and transport rates ranged from 4 to 4400 kilograms per...
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Directory of Open Access Journals (Sweden)
Hyun Ju Jung
2009-12-01
Full Text Available The two-dimensional unsteady flow around a vertical axis turbine for tidal stream energy conversion was investigated using a computational fluid dynamics tool solving the Reynolds-Averaged Navier-Stokes equations. The geometry of the turbine blade section was NACA653-018 airfoil. The computational analysis was done at several different angles of attack and the results were compared with the corresponding experimental data for validation and calibration. Simulations were then carried out for the two-dimensional cross section of a vertical axis turbine. The simulation results demonstrated the usefulness of the method for the typical unsteady flows around vertical axis turbines. The optimum turbine efficiency was achieved for carefully selected combinations of the number of blades and tip speed ratios.
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Use of radars to monitor stream discharge by noncontact methods
Costa, J.E.; Cheng, R.T.; Haeni, F.P.; Melcher, N.; Spicer, K.R.; Hayes, E.; Plant, W.; Hayes, K.; Teague, C.; Barrick, D.
2006-01-01
Conventional measurements of river flows are costly, time‐consuming, and frequently dangerous. This report evaluates the use of a continuous wave microwave radar, a monostatic UHF Doppler radar, a pulsed Doppler microwave radar, and a ground‐penetrating radar to measure river flows continuously over long periods and without touching the water with any instruments. The experiments duplicate the flow records from conventional stream gauging stations on the San Joaquin River in California and the Cowlitz River in Washington. The purpose of the experiments was to directly measure the parameters necessary to compute flow: surface velocity (converted to mean velocity) and cross‐sectional area, thereby avoiding the uncertainty, complexity, and cost of maintaining rating curves. River channel cross sections were measured by ground‐penetrating radar suspended above the river. River surface water velocity was obtained by Bragg scattering of microwave and UHF Doppler radars, and the surface velocity data were converted to mean velocity on the basis of detailed velocity profiles measured by current meters and hydroacoustic instruments. Experiments using these radars to acquire a continuous record of flow were conducted for 4 weeks on the San Joaquin River and for 16 weeks on the Cowlitz River. At the San Joaquin River the radar noncontact measurements produced discharges more than 20% higher than the other independent measurements in the early part of the experiment. After the first 3 days, the noncontact radar discharge measurements were within 5% of the rating values. On the Cowlitz River at Castle Rock, correlation coefficients between the USGS stream gauging station rating curve discharge and discharge computed from three different Doppler radar systems and GPR data over the 16 week experiment were 0.883, 0.969, and 0.992. Noncontact radar results were within a few percent of discharge values obtained by gauging station, current meter, and hydroacoustic methods
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Massoudieh, A.; Le, T.; Pachepsky, Y. A.
2014-12-01
E. coli is widely used as an fecal indicator bacteria in streams. It has been shown that the interaction between sediments and the bacteria is an important factor in determining its fate and transport in water bodies. In this presentation parameter estimation and uncertainty analysis of a mechanistic model of bacteria-sediment interaction respectively using a hybrid genetic algorithm and Makov-Chain Monte Carlo (MCMC) approach will be presented. The physically-based model considers the advective-dispersive transport of sediments as well as both free-floating and sediment-associated bacteria in the water column and also the fate and transport of bacteria in the bed sediments in a small stream. The bed sediments are treated as a distributed system which allows modeling the evolution of the vertical distribution of bacteria as a result of sedimentation and resuspension, diffusion and bioturbation in the sediments. One-dimensional St. Venant's equation is used to model flow in the stream. The model is applied to sediment and E. coli concentration data collected during a high flow event in a small stream historically receiving agricultural runoff. Measured total suspended sediments and total E. coli concentrations in the water column at three sections of the stream are used for the parameter estimation. The data on the initial distribution of E. coli in the sediments was available and was used as the initial conditions. The MCMC method is used to estimate the joint probability distribution of model parameters including sediment deposition and erosion rates, critical shear stress for deposition and erosion, attachment and detachment rate constants of E. coli to/from sediments and also the effective diffusion coefficients of E. coli in the bed sediments. The uncertainties associated with the estimated parameters are quantified via the MCMC approach and the correlation between the posterior distribution of parameters have been used to assess the model adequacy and
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Ivan Arismendi; Sherri L. Johnson; Jason B. Dunham; Roy Haggerty
2012-01-01
Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream...
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Surface Runoff in Watershed Modeling—Turbulent or Laminar Flows?
Directory of Open Access Journals (Sweden)
Mark E. Grismer
2016-05-01
Full Text Available Determination of overland sheet flow depths, velocities and celerities across the hillslope in watershed modeling is important towards estimation of surface storage, travel times to streams and soil detachment rates. It requires careful characterization of the flow processes. Similarly, determination of the temporal variation of hillslope-riparian-stream hydrologic connectivity requires estimation of the shallow subsurface soil hydraulic conductivity and soil-water retention (i.e., drainable porosities parameters. Field rainfall and runoff simulation studies provide considerable information and insight into these processes; in particular, that sheet flows are likely laminar and that shallow hydraulic conductivities and storage can be determined from the plot studies. Here, using a 1 m by 2 m long runoff simulation flume, we found that for overland flow rates per unit width of roughly 30–60 mm2/s and bedslopes of 10%–66% with varying sand roughness depths that all flow depths were predicted by laminar flow equations alone and that equivalent Manning’s n values were depth dependent and quite small relative to those used in watershed modeling studies. Even for overland flow rates greater than those typically measured or modeled and using Manning’s n values of 0.30–0.35, often assumed in physical watershed model applications for relatively smooth surface conditions, the laminar flow velocities were 4–5 times greater, while the laminar flow depths were 4–5 times smaller. This observation suggests that travel times, surface storage volumes and surface shear stresses associated with erosion across the landscape would be poorly predicted using turbulent flow assumptions. Filling the flume with fine sand and conducting runoff studies, we were unable to produce sheet flow, but found that subsurface flows were onflow rate, soil depth and slope dependent and drainable porosities were only soil depth and slope dependent. Moreover, both the sand
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Heitmuller, Franklin T.; Asquith, William H.
2008-01-01
The Texas Department of Transportation commonly builds and maintains low-water crossings (LWCs) over streams in the Edwards Plateau in Central Texas. LWCs are low-height structures, typically constructed of concrete and asphalt, that provide acceptable passage over seasonal rivers or streams with relatively low normal-depth flow. They are designed to accommodate flow by roadway overtopping during high-flow events. The streams of the Edwards Plateau are characterized by cobble- and gravel-sized bed material and highly variable flow regimes. Low base flows that occur most of the time occasionally are interrupted by severe floods. The floods entrain and transport substantial loads of bed material in the stream channels. As a result, LWCs over streams in the Edwards Plateau are bombarded and abraded by bed material during floods and periodically must be maintained or even replaced.