WorldWideScience

Sample records for prevalent flow regime

  1. Flow regimes

    International Nuclear Information System (INIS)

    Liles, D.R.

    1982-01-01

    Internal boundaries in multiphase flow greatly complicate fluid-dynamic and heat-transfer descriptions. Different flow regimes or topological configurations can have radically dissimilar interfacial and wall mass, momentum, and energy exchanges. To model the flow dynamics properly requires estimates of these rates. In this paper the common flow regimes for gas-liquid systems are defined and the techniques used to estimate the extent of a particular regime are described. Also, the current computer-code procedures are delineated and introduce a potentially better method is introduced

  2. THE INFLUENCED FLOW REGIMES

    Directory of Open Access Journals (Sweden)

    Gavril PANDI

    2011-03-01

    Full Text Available The influenced flow regimes. The presence and activities ofhumanity influences the uniform environmental system, and in this context, therivers water resources. In concordance with this, the natural runoff regime suffersbigger and deeper changes. The nature of these changes depending on the type anddegree of water uses. The multitude of the use cause different types of influence,whit different quantitative aspects. In the same time, the influences havequalitative connotations, too, regarding to the modifications of the yearly watervolume runoff. So the natural runoff regime is modified. After analyzing thedistribution laws of the monthly runoff, there have been differenced four types ofinfluenced runoff regimes. In the excess type the influenced runoff is bigger thanthe natural, continuously in the whole year. The deficient type is characterized byinverse rapports like the first type, in the whole year. In the sinusoidal type, theinfluenced runoff is smaller than the natural in the period when the water isretained in the lake reservoirs, and in the depletion period the situation inverts. Atthe irregular type the ratio between influenced and natural runoff is changeable ina random meaner monthly. The recognition of the influenced regime and the gradeof influence are necessary in the evaluation and analysis of the usable hydrologicalriver resources, in the flood defence activities, in the complex scheme of thehydrographic basins, in the environment design and so on.

  3. Refrigeration. Two-Phase Flow. Flow Regimes and Pressure Drop

    DEFF Research Database (Denmark)

    Knudsen, Hans-Jørgen Høgaard

    2002-01-01

    The note gives the basic definitions used in two-phase flow. Flow regimes and flow regimes map are introduced. The different contributions to the pressure drop are stated together with an imperical correlation from the litterature.......The note gives the basic definitions used in two-phase flow. Flow regimes and flow regimes map are introduced. The different contributions to the pressure drop are stated together with an imperical correlation from the litterature....

  4. Regimes of flow past a vortex generator

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Okulov, V.L.; Naumov, I.V.

    2012-01-01

    A complete parametric investigation of the development of multi-vortex regimes in a wake past simple vortex generator has been carried out. It is established that the vortex structure in the wake is much more complicated than a simple monopole tip vortex. The vortices were studied by stereoscopic...... particle image velocimetry (SPIV). Based on the obtained SPIV data, a map of the regimes of flow past the vortex generator has been constructed. One region with a developed stable multivortex system on this map reaches the vicinity of the optimum angle of attack of the vortex generator....

  5. Flow regime identification methodology with computerized tomography

    International Nuclear Information System (INIS)

    Teixeira, Alberto Ramon Ferreira; Roberty, Nilson Costa

    2010-01-01

    This work presents a flow identification methodology in multiphase system in stratified oil-water-gas regime. The principle is based on detecting the amount of x-rays attenuated by passing through the duct containing the flow. The radiation interacts with the material and the composite duct fluid, causing the intensity of X ray declines. In this study, was used divergent bean into two and three dimensions. In this case we need to know the source position in order to back project the rays accordingly in a divergent way. In three dimensions, the projections discontinuity determination problem is substituted by the projections images contour determination. Each ray generates one algebraic equation. The system may be solved by the least square method or by some algebraic reconstruction technique such as the ART, MART or q-ART algorithms. The experiment shows that with a single view (a source-detector pair) it is possible to obtain information of a flow inside a duct (the attenuation of the radiation beam). However, it is not possible to make the reconstruction of the flow. Then, we use two views, so getting enough information to reconstruct the flow. The results presented show that the technique may be applied in the successfully flow regime identification. (author)

  6. Constraints on flow regimes in wide-aperture fractures

    Energy Technology Data Exchange (ETDEWEB)

    Ghezzehei, Teamrat A.

    2004-02-28

    In recent years, significant advances have been made in our understanding of the complex flow processes in individual fractures, aided by flow visualization experiments and conceptual modeling efforts. These advances have led to the recognition of several flow regimes in individual fractures subjected to different initial and boundary conditions. Of these, the most important regimes are film flow, rivulet flow, and sliding of droplets. The existence of such significantly dissimilar flow regimes has been a major hindrance in the development of self-consistent conceptual models of flow for single fractures that encompass all the flow regimes. The objective of this study is to delineate the existence of the different flow regimes in individual fractures. For steady-state flow conditions, we developed physical constraints on the different flow regimes that satisfy minimum energy configurations, which enabled us to segregate the wide range of fracture transmissivity (volumetric flow rate per fracture width) into several flow regimes. These are, in increasing order of flow rate, flow of adsorbed films, flow of sliding drops, rivulet flow, stable film flow, and unstable (turbulent) film flow. The scope of this study is limited to wide-aperture fractures with the flow on the opposing sides of fracture being independent.

  7. The metabolic regimes of flowing waters

    Science.gov (United States)

    Bernhardt, Emily S.; Heffernan, Jim B.; Grimm, Nancy B.; Stanley, Emily H.; Harvey, Judson; Arroita, M.; Appling, Alison; Cohen, M.J.; McDowell, William H.; Hall, R.O.; Read, Jordan S.; Roberts, B.J.; Stets, Edward; Yackulic, Charles B.

    2018-01-01

    The processes and biomass that characterize any ecosystem are fundamentally constrained by the total amount of energy that is either fixed within or delivered across its boundaries. Ultimately, ecosystems may be understood and classified by their rates of total and net productivity and by the seasonal patterns of photosynthesis and respiration. Such understanding is well developed for terrestrial and lentic ecosystems but our understanding of ecosystem phenology has lagged well behind for rivers. The proliferation of reliable and inexpensive sensors for monitoring dissolved oxygen and carbon dioxide is underpinning a revolution in our understanding of the ecosystem energetics of rivers. Here, we synthesize our current understanding of the drivers and constraints on river metabolism, and set out a research agenda aimed at characterizing, classifying and modeling the current and future metabolic regimes of flowing waters.

  8. Flow regimes in vertical gas-solid contact systems

    Energy Technology Data Exchange (ETDEWEB)

    Yerushalmi, J.; Cankurt, N. T.; Geldart, D.; Liss, B.

    1976-01-01

    The flow characteristics in fluidized beds, i.e., gas-solid systems, was studied to determine the flow regimes, the interaction of gas and solid in the various flow regimes and the dependence of this interaction and of transition between flow regimes on the properties of the gas and solid, on the gas and solid flow rates, and on the containing vessel. Fluidized beds with both coarse and fine particles are considered. Test results using high speed photography to view the operation of a 2-dimensional bed are discussed. (LCL)

  9. Early Regimes of Water Capillary Flow in Slit Silica Nanochannels

    DEFF Research Database (Denmark)

    Oyarzua, Elton; Walther, Jens Honore; Mejia, Andres

    2015-01-01

    on the dynamics of capillaryfilling. The results indicate that the nanoscale imbibition process is divided into three main flow regimes:an initial regime where the capillary force is balanced only by the inertial drag and characterized by aconstant velocity and a plug flow profile. In this regime, the meniscus...... velocity profiles identify the passage froman inviscid flow to a developing Poiseuille flow. Gas density profiles ahead of the capillary front indicatea transient accumulation of air on the advancing meniscus. Furthermore, slower capillary filling ratescomputed for higher air pressures reveal a significant...... retarding effect of the gas displaced by the advancing meniscus....

  10. Rheological equations in asymptotic regimes of granular flow

    Science.gov (United States)

    Chen, C.-L.; Ling, C.-H.

    1998-01-01

    This paper assesses the validity of the generalized viscoplastic fluid (GVF) model in light of the established constitutive relations in two asymptotic flow regimes, namely, the macroviscous and grain-inertia regimes. A comprehensive review of the literature on constitutive relations in both regimes reveals that except for some material constants, such as the coefficient of restitution, the normalized shear stress in both regimes varies only with the grain concentration, C. It is found that Krieger-Dougherty's relative viscosity, ??*(C), is sufficiently coherent among the monotonically nondecreasing functions of C used in describing the variation of the shear stress with C in both regimes. It not only accurately represents the C-dependent relative viscosity of a suspension in the macroviscous regime, but also plays a role of the radial distribution function that describes the statistics of particle collisions in the grain-inertia regime. Use of ??*(C) alone, however, cannot link the two regimes. Another parameter, the shear-rate number, N, is needed in modelling the rheology of neutrally buoyant granular flows in transition between the two asymptotic regimes. The GVF model proves compatible with most established relations in both regimes.

  11. How will climate change modify river flow regimes in Europe?

    Directory of Open Access Journals (Sweden)

    C. Schneider

    2013-01-01

    Full Text Available Worldwide, flow regimes are being modified by various anthropogenic impacts and climate change induces an additional risk. Rising temperatures, declining snow cover and changing precipitation patterns will interact differently at different locations. Consequently, in distinct climate zones, unequal consequences can be expected in matters of water stress, flood risk, water quality, and food security. In particular, river ecosystems and their vital ecosystem services will be compromised as their species richness and composition have evolved over long time under natural flow conditions. This study aims at evaluating the exclusive impacts of climate change on river flow regimes in Europe. Various flow characteristics are taken into consideration and diverse dynamics are identified for each distinct climate zone in Europe. In order to simulate present-day natural flow regimes and future flow regimes under climate change, the global hydrology model WaterGAP3 is applied. All calculations for current and future conditions (2050s are carried out on a 5' × 5' European grid. To address uncertainty, bias-corrected climate forcing data of three different global climate models are used to drive WaterGAP3. Finally, the hydrological alterations of different flow characteristics are quantified by the Indicators of Hydrological Alteration approach. Results of our analysis indicate that on the European scale, climate change can be expected to modify flow regimes remarkably. This is especially the case in the Mediterranean (due to drier conditions with reduced precipitation across the year and in the boreal climate zone (due to reduced snowmelt, increased precipitation, and strong temperature rises. In the temperate climate zone, impacts increase from oceanic to continental. Regarding single flow characteristics, strongest impacts on timing were found for the boreal climate zone. This applies for both high and low flows. Flow magnitudes, in turn, will be

  12. Flow regime analysis of non-Newtonian duct flows

    Science.gov (United States)

    Speetjens, Michel; Rudman, Murray; Metcalfe, Guy

    2006-01-01

    Reoriented duct flows of generalized Newtonian fluids are an idealization of non-Newtonian fluid flow in industrial in-line mixers. Based on scaling analysis and computation we find that non-Newtonian duct flows have several limit behaviors, in the sense that such flows can become (nearly) independent of one or more of the rheological and dynamical control parameters, simplifying the general flow and mixing problem. These limit flows give several levels of modeling complexity to the full problem of non-Newtonian duct flow. We describe the sets of simplified flow models and their corresponding regions of validity. This flow-model decomposition captures the essential rheological and dynamical characteristics of the reoriented duct flows and enables a more efficient and systematic study and design of flow and mixing of non-Newtonian fluids in ducts. Key aspects of the flow-model decomposition are demonstrated via a specific, but representative, duct flow.

  13. Microgravity Flow Regime Data: Buoyancy and Mixing Apparatus Effects

    Science.gov (United States)

    Shephard, Adam; Best, Frederick

    2010-01-01

    Zero-g two-phase flow data set qualification and flight experiment design have not been standardized and as a result, agreement among researchers has not been reached regarding what experimental conditions adequately approximate those of microgravity. The effects of buoyancy forces and mixing apparatus on the flow regime transitions are presented in this study. The gravity conditions onboard zero-g aircraft are at best 10-3 g which is used to approximate the 10-5 g conditions of microgravity, thus the buoyancy forces present on zero-g aircraft can become significantly large and unrepresentative of microgravity. When buoyancy forces approach those of surface tension forces, buoyancy induced coalescence occurs. When discussing flow regime transitions, these large buoyancy forces lead to flow regime transitions which otherwise would not occur. The buoyancy attributes of the two-phase flow data sets available in the literature are evaluated to determine which data sets exhibit buoyancy induced transitions. Upon comparison of the representative data sets, the affects of different mixing apparatus can be seen in the superficial velocity flow regime maps.

  14. Measurement of flow in supercritical flow regime using cutthroat flumes

    Indian Academy of Sciences (India)

    [6] Smith R E, Chery D L, Renard K G and Gwinn W R 1981. Supercritical flow flumes for measuring sediment-laden flow,. United States Department of Agriculture, Technical Bulletin number 1655. [7] Manekar V L, Porey P D and Ingle R N 2007 Discharge rela- tion for cutthroat flume under free flow condition. J. Irrig.

  15. Flow Regime Identification of Co-Current Downward Two-Phase Flow With Neural Network Approach

    International Nuclear Information System (INIS)

    Hiroshi Goda; Seungjin Kim; Ye Mi; Finch, Joshua P.; Mamoru Ishii; Jennifer Uhle

    2002-01-01

    Flow regime identification for an adiabatic vertical co-current downward air-water two-phase flow in the 25.4 mm ID and the 50.8 mm ID round tubes was performed by employing an impedance void meter coupled with the neural network classification approach. This approach minimizes the subjective judgment in determining the flow regimes. The signals obtained by an impedance void meter were applied to train the self-organizing neural network to categorize these impedance signals into a certain number of groups. The characteristic parameters set into the neural network classification included the mean, standard deviation and skewness of impedance signals in the present experiment. The classification categories adopted in the present investigation were four widely accepted flow regimes, viz. bubbly, slug, churn-turbulent, and annular flows. These four flow regimes were recognized based upon the conventional flow visualization approach by a high-speed motion analyzer. The resulting flow regime maps classified by the neural network were compared with the results obtained through the flow visualization method, and consequently the efficiency of the neural network classification for flow regime identification was demonstrated. (authors)

  16. Flow regime classification in air-magnetic fluid two-phase flow.

    Science.gov (United States)

    Kuwahara, T; De Vuyst, F; Yamaguchi, H

    2008-05-21

    A new experimental/numerical technique of classification of flow regimes (flow patterns) in air-magnetic fluid two-phase flow is proposed in the present paper. The proposed technique utilizes the electromagnetic induction to obtain time-series signals of the electromotive force, allowing us to make a non-contact measurement. Firstly, an experiment is carried out to obtain the time-series signals in a vertical upward air-magnetic fluid two-phase flow. The signals obtained are first treated using two kinds of wavelet transforms. The data sets treated are then used as input vectors for an artificial neural network (ANN) with supervised training. In the present study, flow regimes are classified into bubbly, slug, churn and annular flows, which are generally the main flow regimes. To validate the flow regimes, a visualization experiment is also performed with a glycerin solution that has roughly the same physical properties, i.e., kinetic viscosity and surface tension, as a magnetic fluid used in the present study. The flow regimes from the visualization are used as targets in an ANN and also used in the estimation of the accuracy of the present method. As a result, ANNs using radial basis functions are shown to be the most appropriate for the present classification of flow regimes, leading to small classification errors.

  17. Fluid flows of mixed regimes in porous media

    Science.gov (United States)

    Celik, Emine; Hoang, Luan; Ibragimov, Akif; Kieu, Thinh

    2017-02-01

    In porous media, there are three known regimes of fluid flows, namely, pre-Darcy, Darcy, and post-Darcy. Because of their different natures, these are usually treated separately in the literature. To study complex flows when all three regimes may be present in different portions of a same domain, we use a single equation of motion to unify them. Several scenarios and models are then considered for slightly compressible fluids. A nonlinear parabolic equation for the pressure is derived, which is degenerate when the pressure gradient is either small or large. We estimate the pressure and its gradient for all time in terms of initial and boundary data. We also obtain their particular bounds for large time which depend on the asymptotic behavior of the boundary data but not on the initial one. Moreover, the continuous dependence of the solutions on initial and boundary data and the structural stability for the equation are established.

  18. Measurement of flow in supercritical flow regime using cutthroat flumes

    Indian Academy of Sciences (India)

    the width is kept horizontal and the walls are kept vertical. Therefore, throughout the length of the cutthroat flume ..... J. Irrig. Drain Eng. 133(5): 495–499. [8] Thornton C I, Smith Brian A, Abt Steven R and. Robeson Michael D 2009 Supercritical flow measurement using a small parshall flume. J. Irrig. Drain. Eng. 135(5): 683–.

  19. Anthropogenic Water Uses and River Flow Regime Alterations by Dams

    Science.gov (United States)

    Ferrazzi, M.; Botter, G.

    2017-12-01

    Dams and impoundments have been designed to reconcile the systematic conflict between patterns of anthropogenic water uses and the temporal variability of river flows. Over the past seven decades, population growth and economic development led to a marked increase in the number of these water infrastructures, so that unregulated free-flowing rivers are now rare in developed countries and alterations of the hydrologic cycle at global scale have to be properly considered and characterized. Therefore, improving our understanding of the influence of dams and reservoirs on hydrologic regimes is going to play a key role in water planning and management. In this study, a physically based analytic approach is combined to extensive hydrologic data to investigate natural flow regime alterations downstream of dams in the Central-Eastern United States. These representative case studies span a wide range of different uses, including flood control, water supply and hydropower production. Our analysis reveals that the most evident effects of flood control through dams is a decrease in the intra-seasonal variability of flows, whose extent is controlled by the ratio between the storage capacity for flood control and the average incoming streamflow. Conversely, reservoirs used for water supply lead to an increase of daily streamflow variability and an enhanced inter-catchment heterogeneity. Over the last decades, the supply of fresh water required to sustain human populations has become a major concern at global scale. Accordingly, the number of reservoirs devoted to water supply increased by 50% in the US. This pattern foreshadows a possible shift in the cumulative effect of dams on river flow regimes in terms of inter-catchment homogenization and intra-annual flow variability.

  20. Exterior foam drainage and flow regime switch in the foams.

    Science.gov (United States)

    Anazadehsayed, Abdolhamid; Rezaee, Nastaran; Naser, Jamal

    2018-02-01

    The three-dimensional flow in exterior microscale foams including the Plateau borders and nodes are investigated by solving Navier-stoke and continuity equations. First, we show the effect of the interfacial mobility and film thickness on the dimensionless mean velocity of the exterior foams. The velocity of the exterior node-PB is similar to the velocity of single exterior Plateau border. Next, we calculated the pressure difference of each element separately and obtained their hydraulic resistances. We found out that the hydraulic resistance of the exterior Plateau border is always larger than the hydraulic resistance of the exterior node, resulting in a consistent channel-dominated regime. However, For the interior foams, there is a value of interfacial mobility where the node's resistance overcomes the channel's resistance, resulting in a switch from the channel-dominated regime to a node-dominated regime. This switching point is dependent on the relative length of the channels. Hence, we obtained an approximation of the interfacial mobility switching points versus the relative length of channels. Moreover, in a form of approximation master curve, we showed the dependence of mean velocities of foams and channels' hydraulic resistances to a dimensionless combined parameter of Λ -1 that contains interfacial mobility and film thickness together. For both the exterior and interior nodes, the velocity and hydraulic resistance are almost constant for various Boussinesq numbers since interfacial mobility has a marginal effect on node's flow. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Detection of changes in flow regime of rivers in Poland

    Directory of Open Access Journals (Sweden)

    Wrzesiński Dariusz

    2018-03-01

    Full Text Available The aim of this study is to detect changes in flow regime of rivers in Poland. On the basis of daily discharges recorded in 1951-2010 at 159 gauging stations located on 94 rivers regularities in the variability of the river flow characteristics in the multi-year period and in the annual cycle were identified and also their spatial uniformity was examined. In order to identify changes in the characteristics of river regime, similarities of empirical distribution functions of the 5-day sets (pentads of discharges were analyzed and the percent shares of similar and dissimilar distributions of the 5-day discharge frequencies in the successive 20-year sub-periods were compared with the average values of discharges recorded in 1951-2010. Three alternative methods of river classification were employed and in the classification procedure use was made of the Ward’s hierarchical clustering method. This resulted in identification of groups of rivers different in terms of the degree of transformation of their hydrological regimes in the multi-year and annual patterns.

  2. Upper flow-regime structures in a Pleistocene carbonate ramp (Favignana, Italy): diagnostic criteria and implications

    Science.gov (United States)

    Slootman, Arnoud; Cartigny, Matthieu; de Boer, Poppe; Moscariello, Andrea

    2017-04-01

    This work presents key diagnostic criteria for the recognition of upper flow-regime sedimentary structures in clastic cool-water carbonate accumulations, illustrated by the excellent exposures of the Pleistocene carbonate ramp succession of Favignana Island (Italy). Cool-water carbonate sedimentation has dominated Mediterranean shelves since the Early Pliocene. Of the various types of marine limestones, cool-water carbonates behave most similar to siliciclastics. They typically develop ramp morphologies with skeletal sand and gravel, consisting of the remains of heterozoan organisms. Resedimentation of this loose carbonate debris during high-energy events such as storms and, more rarely, tsunamis is the norm. Off-ramp supercritical sediment density flows are important contributors to basinward sediment transport as evidenced by the prevalence of backset-stratification bounded by composite erosion surfaces, locally defining spoon-shaped scours-fills, in beds exceeding several metres in thickness. Sedimentary structures created by upper flow-regime bedforms like antidunes, chute-and-pools and cyclic steps as seen on Favignana Island, which form in association with in-phase waves and hydraulic jumps, are not commonly mentioned in carbonate ramp depositional models. For each of the bedforms we present diagnostic criteria to explain otherwise enigmatic sedimentary structures. Thick beds deposited by supercritical sediment density flows have major implications for the distribution of porosity and permeability in carbonate sandstone bodies, especially where they host hydrocarbon and/or water accumulations. The correct identification of upper flow-regime sedimentary structures in carbonate ramp accumulations is therefore important.

  3. Predicting regime shifts in flow of the Colorado River

    Science.gov (United States)

    Gangopadhyay, Subhrendu; McCabe, Gregory J.

    2010-01-01

    The effects of continued global warming on water resources are a concern for water managers and stake holders. In the western United States, where the combined climatic demand and consumptive use of water is equal to or greater than the natural supply of water for some locations, there is growing concern regarding the sustainability of future water supplies. In addition to the adverse effects of warming on water supply, another issue for water managers is accounting for, and managing, the effects of natural climatic variability, particularly persistently dry and wet periods. Analyses of paleo-reconstructions of Upper Colorado River basin (UCRB) flow demonstrate that severe sustained droughts, and persistent pluvial periods, are a recurring characteristic of hydroclimate in the Colorado River basin. Shifts between persistently dry and wet regimes (e.g., decadal to multi-decadal variability (D2M)) have important implications for water supply and water management. In this study paleo-reconstructions of UCRB flow are used to compute the risks of shifts between persistently wet and dry regimes given the length of time in a specific regime. Results indicate that low frequency variability of hydro-climatic conditions and the statistics that describe this low frequency variability can be useful to water managers by providing information about the risk of shifting from one hydrologic regime to another. To manage water resources in the future water managers will have to understand the joint hydrologic effects of natural climate variability and global warming. These joint effects may produce future hydrologic conditions that are unprecedented in both the instrumental and paleoclimatic records.

  4. Flow and heat transfer regimes during quenching of hot surfaces

    International Nuclear Information System (INIS)

    Barnea, Y.; Elias, E.

    1993-05-01

    Reflooding experiments have been performed to study flow and heat transfer regimes in a heated annular vertical channel under supercooled inlet conditions. A gamma densitometer was employed to determine the void fraction as a function of the distance from the quench front. Surface heat fluxes were determined by fast measurements of the temperature spatial distribution. Two quench front is shown to lie in the transition boiling region which spreads into the dry and wet segments of the heated surface. (authors) 5 refs, 3 figs

  5. Generation of leachate and the flow regime in landfills

    Energy Technology Data Exchange (ETDEWEB)

    Bendz, D.

    1998-06-01

    In this thesis the generation of leachate and the presence and movement of water in landfilled municipal solid waste (MSW) is investigated. The precipitation-leachate discharge relationship for landfills was found to be dominated by evaporation, accumulation in the soil cover, accumulation in the solid waste and fast gravitational flow in a network of channels. The flow regime is governed by the heterogeneity of the internal geometry of the landfill, which is characterized by a discrete structure, significant horizontal stratification, structural voids, impermeable surfaces, and low capillarity. Also the boundary conditions, that is the water input pattern, has shown to be important for the flow process. Based on this, landfilled waste can be conceptualized as a dual domain medium, consisting of a channel domain and a matrix domain. The matrix flow is slow and diffusive, whereas the channel flow is assumed to be driven solely by gravity and to take place as a thin viscous film on solid surfaces. A kinematic wave model for unsaturated infiltration and internal drainage in the channel domain is presented. The model employs a two-parameter power expression as macroscopic flux law. Solutions were derived for the cases when water enters the channel domain laterally and when water enters from the upper end. The model parameters were determined and interpreted in terms of the internal geometry of the waste medium by fitting the model to one set of infiltration and drainage data derived from a large scale laboratory experiment under transient conditions. The model was validated using another set of data from a sequence of water input events and was shown to perform accurately. A solute transport model was developed by coupling a simple piston flux expression and a mobile-immobile conceptualization of the transport domains with the water flow model. Breakthrough curves derived from steady and transient tracer experiments where interpreted with the model. The transport

  6. Wind-Driven Ecological Flow Regimes Downstream from Hydropower Dams

    Science.gov (United States)

    Kern, J.; Characklis, G. W.

    2012-12-01

    challenge, the following study was designed to investigate the potential for wind power integration to alter riparian flow regimes below hydroelectric dams. A hydrological model of a three-dam cascade in the Roanoke River basin (Virginia, USA) is interfaced with a simulated electricity market (i.e. a unit commitment problem) representing the Dominion Zone of PJM Interconnection. Incorporating forecasts of electricity demand, hydro capacity and wind availability, a mixed-integer optimization program minimizes the system cost of meeting hourly demand and reserve requirements by means of a diverse generation portfolio (e.g. nuclear, fossil, hydro, and biomass). A secondary 'balancing' energy market is executed if real-time wind generation is less than the day-ahead forecast, calling upon reserved generation resources to meet the supply shortfall. Hydropower release schedules are determined across a range of wind development scenarios (varying wind's fraction of total installed generating capacity, as well as its geographical source region). Flow regimes for each wind development scenario are compared against both historical and simulated flows under current operations (negligible wind power), as well as simulated natural flows (dam removal), in terms of ecologically relevant flow metrics. Results quantify the ability of wind power development to alter within-week stream flows downstream from hydropower dams.

  7. Comparison of differential pressure model based on flow regime for gas/liquid two-phase flow

    International Nuclear Information System (INIS)

    Dong, F; Zhang, F S; Li, W; Tan, C

    2009-01-01

    Gas/liquid two-phase flow in horizontal pipe is very common in many industry processes, because of the complexity and variability, the real-time parameter measurement of two-phase flow, such as the measurement of flow regime and flow rate, becomes a difficult issue in the field of engineering and science. The flow regime recognition plays a fundamental role in gas/liquid two-phase flow measurement, other parameters of two-phase flow can be measured more easily and correctly based on the correct flow regime recognition result. A multi-sensor system is introduced to make the flow regime recognition and the mass flow rate measurement. The fusion system is consisted of temperature sensor, pressure sensor, cross-section information system and v-cone flow meter. After the flow regime recognition by cross-section information system, comparison of four typical differential pressure (DP) models is discussed based on the DP signal of v-cone flow meter. Eventually, an optimum DP model has been chosen for each flow regime. The experiment result of mass flow rate measurement shows it is efficient to classify the DP models by flow regime.

  8. Study on flow parameters of fractal porous media in the high-velocity fluid flow regime

    Science.gov (United States)

    Qi, Mei; Xu, Hui; Yang, Chao; Qu, Tailai; Kong, lingxiao; Wu, Shucheng; Zeng, Baoquan; Xu, Haixia

    2017-12-01

    High-velocity fluid flow, which will result in the region of the wellbore or fracture, is generally in the turbulent flow regime and has drawn tremendous attention in petroleum engineering field. Turbulent factor is the key parameter, which is widely used to describe high-velocity flow in porous media. In this work, a theoretical model for turbulent factor in fractal porous media in the high-velocity fluid flow regime is developed. Moreover, a novel analytical expression for the permeability in porous media based on Wu's resistance model is also derived. Then, the analytical Kozeny-Carman constant with no empirical constant is obtained. The predictions of permeability-porosity relation by the current mathematical models have been validated by comparing with available experimental data. Furthermore, the effects of structural parameters of porous media on the curve of velocity and pressure drop are discussed in detail.

  9. Flow measurement in bubbly and slug flow regimes using the electromagnetic flowmeter developed

    International Nuclear Information System (INIS)

    Cha, Jae Eun; Ahn, Yeh Chan; Seo, Kyung Woo; Kim, Moo Hwan

    2002-01-01

    In order to investigate the characteristics of electromagnetic flowmeter in two-phase flow, an AC electromagnetic flowmeter was designed and manufactured. In various flow conditions, the signals and noises from the flowmeter were obtained and analyzed by comparison with the observed flow patterns with a high speed CCD camera. The experiment with the void simulators in which rod shaped non-conducting material was used was carried out to investigate the effect of the bubble position and the void fraction on the flowmeter. Based on the results from the void simulator, two-phase flow experiments encompassed from bubbly to slug flow regime were conducted. The simple relation ΔU TP = ΔU SP /(1-α) was verified with measurements of the potential difference and the void fraction. Due to the lack of homogeneity in a real two-phase flow, the discrepancy between the relation and the present measurement was slightly increased with void fraction and also liquid volumetric flux j f . Whereas there is no difference in the shape of the raw signal between single-phase flow and bubbly flow, the signal amplitude for bubbly flow is higher than that for single-phase flow at the same water flow rate, since the passage area of the water flow is reduced. In the case of slug flow, the phase and the amplitude of the flowmeter output show dramatically the flow characteristics around each slug bubble and the position of a slug bubble itself. Therefore, the electromagnetic flowmeter shows a good possibility of being useful for identifying the flow regimes

  10. Dynamic analysis of slug flow regime in two-phase flow

    International Nuclear Information System (INIS)

    Kwak, Nam Yee; Lee, Jae Young; Kim, Man Woong

    2008-01-01

    The bubble dynamics in the two-phase flow is complicated to be modeled but we have reliable model to estimate fortunately. However, they are working well for the one dimensional analysis only. Also, the three dimensional knowledge is requested in the industry strongly, but we have still confusion in the two-phase analysis. Especially recent arguments are set at the several points: (1) the flow regime transition between the slug flow and churn flow (2) flow regimes for the inclined tubes. We have been studied flow regime map for the inclined tube and we met both unsolved issues. In the center of the debate there was a slug bubble phenomenon. Therefore, we decided to study the dynamic and geometric characteristics of slug bubble in terms of the inclination and analytic understanding. As a first step of the study, we finished to design and construct the facility and instrumentation. And we are now studying the existing analytical models and comparing them with our experimental data

  11. Flow regime and deposition pattern of evaporating binary mixture droplet suspended with particles.

    Science.gov (United States)

    Zhong, Xin; Duan, Fei

    2016-02-01

    The flow regimes and the deposition pattern have been investigated by changing the ethanol concentration in a water-based binary mixture droplet suspended with alumina nanoparticles. To visualize the flow patterns, Particle Image Velocimetry (PIV) has been applied in the binary liquid droplet containing the fluorescent microspheres. Three distinct flow regimes have been revealed in the evaporation. In Regime I, the vortices and chaotic flows are found to carry the particles to the liquid-vapor interface and to promote the formation of particle aggregation. The aggregates move inwards in Regime II as induced by the Marangoni flow along the droplet free surface. Regime III is dominated by the drying of the left water and the capillary flow driving particles radially outward is observed. The relative weightings of Regimes I and II, which are enhanced with an increasing load of ethanol, determine the motion of the nanoparticles and the formation of the final drying pattern.

  12. Linear stability analysis of laminar flow near a stagnation point in the slip flow regime

    Science.gov (United States)

    Essaghir, E.; Oubarra, A.; Lahjomri, J.

    2017-12-01

    The aim of the present contribution is to analyze the effect of slip parameter on the stability of a laminar incompressible flow near a stagnation point in the slip flow regime. The analysis is based on the traditional normal mode approach and assumes parallel flow approximation. The Orr-Sommerfeld equation that governs the infinitesimal disturbance of stream function imposed to the steady main flow, which is an exact solution of the Navier-Stokes equation satisfying slip boundary conditions, is obtained by using the powerful spectral Chebyshev collocation method. The results of the effect of slip parameter K on the hydrodynamic characteristics of the base flow, namely the velocity profile, the shear stress profile, the boundary layer, displacement and momentum thicknesses are illustrated and discussed. The numerical data for these characteristics, as well as those of the eigenvalues and the corresponding wave numbers recover the results of the special case of no-slip boundary conditions. They are found to be in good agreement with previous numerical calculations. The effects of slip parameter on the neutral curves of stability, for two-dimensional disturbances in the Reynolds-wave number plane, are then obtained for the first time in the slip flow regime for stagnation point flow. Furthermore, the evolution of the critical Reynolds number against the slip parameter is established. The results show that the critical Reynolds number for instability is significantly increased with the slip parameter and the flow turn out to be more stable when the effect of rarefaction becomes important.

  13. Study on flow regimes of high-pressure and dense-phase pneumatic conveying

    International Nuclear Information System (INIS)

    Lu Peng; Chen Xiaoping; Liang Cai; Pu Wenhao; Zhou Yun; Xu Pan; Zhao Changsui

    2009-01-01

    High-pressure and dense-phase pneumatic conveying of pulverized coal is a key technology in the field of large-scale entrained bed coal gasification. Flow regime plays an important role in two-phase flow because it affects not only flow behavior and safety operation, but also the reliability of practical processes. Few references and experiences in high-pressure and dense-phase conveying are available, especially for the flow regimes. And because of the high stickiness and electrostatic attraction of pulverized coal to the pipe wall, it is very difficult to make out the flow regimes in the conveying pipe by visualization method. Thus quartz powder was chosen as the conveyed material to study the flow regime. High-speed digital video camera was employed to photograph the flow patterns. Experiments were conducted on a pilot scale experimental setup at the pressure up to 3.6MPa. With the decrease in superficial gas velocity, three distinguishable flow regimes were observed: stratified flow, dune flow and plug flow. The characteristics of pressure traces acquired by high frequency response pressure transmitter and their EMD (Empirical Mode Decomposition) characteristics were correlated strongly with the flow regimes. Combining high-speed photography and pressure signal analysis together can make the recognition of flow patterns in the high-pressure and dense-phase pneumatic conveying system more accurate. The present work will lead to better understanding of the flow regime transition under high-pressure.

  14. Two-phase interfacial area and flow regime modeling in FLOWTRAN-TF code

    International Nuclear Information System (INIS)

    Smith, F.G. III; Lee, S.Y.; Flach, G.P.; Hamm, L.L.

    1992-01-01

    FLOWTRAN-TF is a new two-component, two-phase thermal-hydraulics code to capture the detailed assembly behavior associated with loss-of-coolant accident analyses in multichannel assemblies of the SRS reactors. The local interfacial area of the two-phase mixture is computed by summing the interfacial areas contributed by each of three flow regimes. For smooth flow regime transitions, the code uses an interpolation technique in terms of component void fraction for each basic flow regime

  15. Experimental and numerical investigation of flow around a sphere with dimples for various flow regimes

    Directory of Open Access Journals (Sweden)

    Bogdanović-Jovanović Jasmina B.

    2012-01-01

    Full Text Available Flow over a sphere is a typical bluff-body flow with many engineering applications. However, it has not been studied in depth, as compared to flow over a circular cylinder, because of the difficulties in the experimental set-up as well as in the computational approach for studying flow over a sphere. The main challenges are to understand the flow hydrodynamics and to clarify the flow pattern around a dimpled sphere because the flow pattern complying with the dimple structure on its surface is very complicated. In this paper experimental and numerical investigations of the fluid flow around a sphere with dimples, are represented. The sphere with dimples is placed in a quadratic cross section duct (measuring section and numerical simulation results are obtained by solving RANS equations. Furthermore, experimental measurements are carried out using a Laser-Doppler Anemometer (LDA. Experimental and numerical results of flow velocity fields were compared for three different flow regimes (Re=8×103, 2×104 and 4×104. Numerical investigation was performed for wide range of Reynolds numbers (Re=270%106. The final purpose of this paper is experimental and numerical determination of velocity field, separation point, pressure and drag coefficient, the length of reverse flow region in the wake and RANS turbulent model which gives the best results for engineering practice.

  16. Natural flow regimes of the Ozark-Ouachita Interior Highlands region

    Science.gov (United States)

    Leasure, D. R.; Magoulick, Daniel D.; Longing, S. D.

    2016-01-01

    Natural flow regimes represent the hydrologic conditions to which native aquatic organisms are best adapted. We completed a regional river classification and quantitative descriptions of each natural flow regime for the Ozark–Ouachita Interior Highlands region of Arkansas, Missouri and Oklahoma. On the basis of daily flow records from 64 reference streams, seven natural flow regimes were identified with mixture model cluster analysis: Groundwater Stable, Groundwater, Groundwater Flashy, Perennial Runoff, Runoff Flashy, Intermittent Runoff and Intermittent Flashy. Sets of flow metrics were selected that best quantified nine ecologically important components of these natural flow regimes. An uncertainty analysis was performed to avoid selecting metrics strongly affected by measurement uncertainty that can result from short periods of record. Measurement uncertainties (bias, precision and accuracy) were assessed for 170 commonly used flow metrics. The ranges of variability expected for select flow metrics under natural conditions were quantified for each flow regime to provide a reference for future assessments of hydrologic alteration. A random forest model was used to predict the natural flow regimes of all stream segments in the study area based on climate and catchment characteristics, and a map was produced. The geographic distribution of flow regimes suggested distinct ecohydrological regions that may be useful for conservation planning. This project provides a hydrologic foundation for future examination of flow–ecology relationships in the region. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

  17. Numerical study of the bubbly flow regime in micro-channel flow boiling

    Science.gov (United States)

    Bhuvankar, Pramod; Dabiri, Sadegh

    2017-11-01

    Two-phase flow accompanied by boiling in micro-channel heat sinks is an effective means for heat removal from computer chips. We present a numerical study of flow boiling in micro-channels with conjugate heat transfer with a focus on the bubbly flow regime. The bubbles are assumed to nucleate at a pre-determined location and frequency. The Navier Stokes equations are solved using a single fluid formulation with the Front tracking method. Phase change is implemented using the deficit in heat flux across the bubble interface. The analytical solution for bubble growth in a superheated liquid is used as a benchmark to validate the mentioned numerical method. Water and FC-72 are studied as the operating fluids in a micro-channel made of Copper with a focus on hotspot mitigation. The micro-channel of cross-section 231 μm × 1000 μm , is used to study the effects of vertical up-flow, vertical down-flow and horizontal flow of the mentioned fluids on the heat transfer coefficients. A simple film model accounting for mass and energy conservation is applied wherever the bubble approaches closer than a cell width to the wall. The results of the simulation are compared with existing experimental data for bubble growth rates and heat transfer coefficients.

  18. System-focused environmental flow regime prescription, monitoring and adaptive management

    Science.gov (United States)

    Hetherington, David; Lexartza Artza, Irantzu

    2016-04-01

    The definition of appropriate environmental flow regimes through hydropower schemes and water storage reservoirs is key part of mitigation. Insufficient (magnitude and variability) environmental flows can result in much environmental harm with negative impacts being encountered by morphological, ecological and societal systems. Conventionally, environmental flow regimes have been determined by using generic protocols and guidance such as the Tennant method of environmental flow estimation. It is generally accepted that such approaches to minimum environmental flow definition, although being a useful starting point, are not universally applicable across catchment typologies and climatic regions. Such approaches will not always produce conditions that would be associated with 'Good Ecological Status' under the Water framework Directive (or equivalent). Other similar approaches to minimum environmental flow estimation are used that are specific to geographies, yet still the associated guidance rarely thoroughly covers appropriate definition for healthy holistic systems across the flow regime. This paper draws on experience of system-focused environmental flow regime determination in the UK and the Georgian Caucasus Mountains, which allowed for a critical analysis of more conventional methods to be undertaken. The paper describes a recommended approach for determining appropriate environmental flow regimes based on analysis of the impacted geomorphological, ecological and societal systems in a way which is sensitive to the local holistic environment and associated complexities and interactions. The paper suggests that a strong understanding of the local geomorphology in key in predicting how flows will manifest habitat differently across the flow regime, and be spatially dynamic. Additionally, an understanding of the geomorphological system allows the flow of course and fine sediment to be factored into the initial suggested environmental flow regime. It is suggested

  19. Development of objective flow regime identification method using self-organizing neural network

    International Nuclear Information System (INIS)

    Lee, Jae Young; Kim, Nam Seok; Kwak, Nam Yee

    2004-01-01

    Two-phase flow shows various flow patterns according to the amount of the void and its relative velocity to the liquid flow. This variation directly affect the interfacial transfer which is the key factor for the design or analysis of the phase change systems. Especially the safety analysis of the nuclear power plant has been performed based on the numerical code furnished with the proper constitutive relations depending highly upon the flow regimes. Heavy efforts have been focused to identify the flow regime and at this moment we stand on relative very stable engineering background compare to the other research field. However, the issues related to objectiveness and transient flow regime are still open to study. Lee et al. and Ishii developed the method for the objective and instantaneous flow regime identification based on the neural network and new index of probability distribution of the flow regime which allows just one second observation for the flow regime identification. In the present paper, we developed the self-organized neural network for more objective approach to this problem. Kohonen's Self-Organizing Map (SOM) has been used for clustering, visualization, and abstraction. The SOM is trained through unsupervised competitive learning using a 'winner takes it all' policy. Therefore, its unsupervised training character delete the possible interference of the regime developer to the neural network training. After developing the computer code, we evaluate the performance of the code with the vertically upward two-phase flow in the pipes of 25.4 and 50.4 cmm I.D. Also, the sensitivity of the number of the clusters to the flow regime identification was made

  20. Flow regime, void fraction and interfacial area transport and characteristics of co-current downward two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Lokanathan, Manojkumar [School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907-2088 (United States); Hibiki, Takashi [School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, IN 47907-2017 (United States)

    2016-10-15

    Highlights: • Downward flow regime maps and models were studied for 25.4 to 101.6 mm pipe diameters. • Effect of flow inlet on flow transition, void & interfacial area profile were studied. • Bubble void profiles were associated with the interfacial forces for downward flow. • Flow regime pressure drop and interfacial friction factor were studied. • The most applicable and accurate downward drift-flux correlation was determined. - Abstract: Downward two-phase flow is observed in light water reactor accident scenarios such as loss of coolant accident (LOCA) and loss of heat sink accident (LOHS) due to loss of feed water or a secondary pipe break. Hence, a comprehensive literature review has been performed for the co-current downward two-phase flow with information on the flow regime transitions and flow characteristics for each regime in the downward flow. The review compares the experimental data of the flow regime map and the current available transition models. Objectivity of the data varies on the method utilized as a certain degree of subjectivity is still present in the most objective method. Nevertheless, experimental data through subjective methods such as direct visualization or analysis of a wire mesh sensor (WMS) data were still studied in this review. Despite the wide range of flow regime data for numerous pipe sizes, a consensus was not reached for the effect of pipe sizes on flow regime transition. However, it is known that a larger pipe results in greater degree of coalescence at lower gas flow rates (Hibiki et al., 2004). The introduction of a flow straightener at the inlet led to less coring and fluid rotation and inevitably, reduced bubble coalescence. This also resulted in the disappearance of the kinematic shock wave phenomenon, contrary to an inlet without a flow straightener. The effect of flow inlet, flow location, pipe diameter and bubble interfacial forces on the radial distribution as well as bubble coalescence and breakup rate

  1. Geography and Regional Planning: Changing Flow Regime and its ...

    African Journals Online (AJOL)

    That the climatic variables jointly significantly explained the general seasonal pattern of water level regime (F > p < 0.05) was identified. This was corroborated by the significance of the explanatory coefficients of two of the variables by the multiple and step- wise regression. Thus monthly deviation in rainfall and evaporation ...

  2. Classifying low flow hydrological regimes at a regional scale

    NARCIS (Netherlands)

    Kirkby, M.J.; Gallart, F.; Kjeldsen, T.R.; Irvine, B.J.; Froebrich, J.; Porto, Lo A.; Girolamo, De A.

    2011-01-01

    The paper uses a simple water balance model that partitions the precipitation between actual evapotranspiration, quick flow and delayed flow, and has sufficient complexity to capture the essence of climate and vegetation controls on this partitioning. Using this model, monthly flow duration curves

  3. Classifying low flow hydrological regimes at a regional scale

    Directory of Open Access Journals (Sweden)

    M. J. Kirkby

    2011-12-01

    Full Text Available The paper uses a simple water balance model that partitions the precipitation between actual evapotranspiration, quick flow and delayed flow, and has sufficient complexity to capture the essence of climate and vegetation controls on this partitioning. Using this model, monthly flow duration curves have been constructed from climate data across Europe to address the relative frequency of ecologically critical low flow stages in semi-arid rivers, when flow commonly persists only in disconnected pools in the river bed. The hydrological model is based on a dynamic partitioning of precipitation to estimate water available for evapotranspiration and plant growth and for residual runoff. The duration curve for monthly flows has then been analysed to give an estimate of bankfull flow based on recurrence interval. Arguing from observed ratios of cross-sectional areas at flood and low flows, hydraulic geometry suggests that disconnected flow under "pool" conditions is approximately 0.1% of bankfull flow. Flow duration curves define a measure of bankfull discharge on the basis of frequency. The corresponding frequency for pools is then read from the duration curve, using this (0.1% ratio to estimate pool discharge from bank full discharge. The flow duration curve then provides an estimate of the frequency of poorly connected pool conditions, corresponding to this discharge, that constrain survival of river-dwelling arthropods and fish. The methodology has here been applied across Europe at 15 km resolution, and the potential is demonstrated for applying the methodology under alternative climatic scenarios.

  4. Gas-Kinetic Computational Algorithms for Hypersonic Flows in Continuum and Transitional Regimes, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I project explores two gas-kinetic computational algorithms for simulation of hypersonic flows in both continuum and transitional regimes. One is the...

  5. Review of Mixed Convection Flow Regime Map of a Vertical pipe

    International Nuclear Information System (INIS)

    Chae, Myeong-Seon; Chung, Bum-Jin; Kang, Gyeong-Uk

    2015-01-01

    In a vertical pipe, the natural convective force due to buoyancy acts upward only, but forced convective force can be either upward or downward. This determines buoyancy-aided and buoyancy-opposed flows depending on the direction of forced flow with respect to the buoyancy forces. Furthermore, depending on the exchange mechanism, the flow condition is classified into laminar and turbulent. In laminar mixed convection, buoyancy-aided flow presents enhanced heat transfer compared to the pure forced convection and buoyancy-opposed flow shows impaired heat transfer as the flow velocity affected by the buoyancy forces. However, in turbulent mixed convection, buoyancy-aided flow shows an impairment of the heat transfer rate for small buoyancy, and a gradational enhancement for large buoyancy. In this study, the existing flow regime map on mixed convection in a vertical pipe was reviewed through an analysis of literatures. Using the investigated data and heat transfer correlations, the flow regime map was reconstructed independently, and compared with the existing one. This study reviewed the limitations of the classical mixed convection flow regime map. Using the existing data and heat transfer correlations by Martinelli and Boelter and Watzinger and Johnson, the flow regime map was reconstructed independently. The results revealed that the existing map used the data selectively among the experimental and theoretical results, and a detailed description for lines forming mixed convection and transition regime were not given. And the information about uncertainty analysis and the evidentiary data were given insufficiently. The flow regime map and investigator commonly used the diameter as the characteristic length for both Re and Gr in place of the height of the heated wall, though the buoyancy forces are proportional to the third power of the height of heated wall

  6. Evidence of Vortex Jamming in Abrikosov Vortex Flux Flow Regime

    OpenAIRE

    Karapetrov, G.; Yefremenko, V.; Mihajlović, G.; Pearson, J. E.; Iavarone, M.; Novosad, V.; Bader, S. D.

    2012-01-01

    We report on dynamics of non-local Abrikosov vortex flow in mesoscopic superconducting Nb channels. Magnetic field dependence of the non-local voltage induced by the flux flow shows that vortices form ordered vortex chains. Voltage asymmetry (rectification) with respect to the direction of vortex flow is evidence that vortex jamming strongly moderates vortex dynamics in mesoscopic geometries. The findings can be applied to superconducting devices exploiting vortex dynamics and vortex manipula...

  7. A mechanistic determination of horizontal flow regime bound using void wave celerity

    Energy Technology Data Exchange (ETDEWEB)

    Park, J.W. [Ajou Univ., Suwon (Korea, Republic of)

    1995-09-01

    The two-phase flow regime boundaries in a horizontal channel has been investigated by using the behavior of the second order void wave celerities. The average two-fluid model has been constituted with closure relations for horizontally stratified and bubbly flows. A vapor phase turbulent stress model for a smooth interface geometry has been included. It is found that the second order waves (i.e., eigenvalues) propagate in opposite direction with almost the same speed when the liquid phase is stationary. Using the well-posedness limit of the two-phase system, the dispersed-stratified flow regime boundary has been modeled. Two-phase Froude number has been theoretically found to be a convenient parameter in quantifying the flow regime boundary as a function of the void fraction. It is found that interaction between void wave celerities become stronger as the two-phase Froude number is reduced. This result should be interpreted as that gravity and the relative velocity are key parameters in determining flow regime boundaries in a horizontal flow. The influence of the vapor phase turbulent stress found to stabilize the flow stratification. This study clearly shows that the average two-fluid model is very effective for a mechanistic determination of horizontal flow regimes if appropriate closure relations are developed.

  8. The impact of stormwater source-control strategies on the (low) flow regime of urban catchments.

    Science.gov (United States)

    Hamel, Perrine; Fletcher, Tim D

    2014-01-01

    Stormwater management strategies increasingly recognise the need to emulate the pre-development flow regime, in addition to reducing pollutant concentrations and loads. However, it is unclear whether current design approaches for stormwater source-control techniques are effective in restoring the whole flow regime, and in particular low flows, towards their pre-development levels. We therefore modelled and compared a range of source-control stormwater management strategies, including some specifically tailored towards enhancing baseflow processes. The strategies were assessed based on the total streamflow volume and three low flow metrics. Strategies based on harvesting tanks showed much greater volume reduction than those based on raingardens. Strategies based on a low flow rate release, aimed at mimicking natural baseflow, failed to completely restore the baseflow regime. We also found that the sensitivity of the low flow metrics to the proportion of catchment treated varied amongst metrics, illustrating the importance of metrics selection in the assessment of stormwater strategies. In practice, our results suggest that realistic scenarios using low flow release from source-control techniques may not be able to fully restore the low flow regime, at least for perennial streams. However, a combination of feasibly-sized tanks and raingardens is likely to restore the baseflow regime to a great extent, while also benefitting water quality through the retention and filtration processes.

  9. A mechanistic determination of horizontal flow regime bound using void wave celerity

    International Nuclear Information System (INIS)

    Park, J.W.

    1995-01-01

    The two-phase flow regime boundaries in a horizontal channel has been investigated by using the behavior of the second order void wave celerities. The average two-fluid model has been constituted with closure relations for horizontally stratified and bubbly flows. A vapor phase turbulent stress model for a smooth interface geometry has been included. It is found that the second order waves (i.e., eigenvalues) propagate in opposite direction with almost the same speed when the liquid phase is stationary. Using the well-posedness limit of the two-phase system, the dispersed-stratified flow regime boundary has been modeled. Two-phase Froude number has been theoretically found to be a convenient parameter in quantifying the flow regime boundary as a function of the void fraction. It is found that interaction between void wave celerities become stronger as the two-phase Froude number is reduced. This result should be interpreted as that gravity and the relative velocity are key parameters in determining flow regime boundaries in a horizontal flow. The influence of the vapor phase turbulent stress found to stabilize the flow stratification. This study clearly shows that the average two-fluid model is very effective for a mechanistic determination of horizontal flow regimes if appropriate closure relations are developed

  10. Analytical Simulation of Flow and Heat Transfer of Two-Phase Nanofluid (Stratified Flow Regime

    Directory of Open Access Journals (Sweden)

    Mohammad Abbasi

    2014-01-01

    Full Text Available Nanofluids have evoked immense interest from researchers all around the globe due to their numerous potential benefits and applications in important fields such as cooling electronic parts, cooling car engines and nuclear reactors. An analytical study of fluid flow of in-tube stratified regime of two-phase nanofluid has been carried out for CuO, Al2O2, TiO3, and Au as applied nanoparticles in water as the base liquid. Liquid film thickness, convective heat transfer coefficient, and dryout length have been calculated. Among the considered nano particles, Al2O3 and TiO2 because of providing more amounts of heat transfer along with longer lengths of dryout found as the most appropriate nanoparticles to achieve cooling objectives.

  11. Using regional flow classes as references to analyse flow regime anomalies across a set of regulated Canadian rivers

    Science.gov (United States)

    McLaughlin, Fraser; Lapointe, Michel; Bourque, Guillaume; Boisclair, Daniel

    2014-11-01

    It is well established that a river's natural flow regime is a key determinant of ecological integrity and that dam regulated-flow releases can be detrimental to biotic communities and even affect river ecosystem structure (e.g. Poff and Zimmerman, 2010). Regional flow classes, groups of rivers that share similar natural flow regimes (called 'river types' by Poff and Zimmerman (2010)) and to which regional fish communities are 'adapted', have been proposed as units of analysis to identify significant damming related flow alteration (e.g. Poff, 1996; Poff and Zimmerman, 2010; McManamay et al., 2012a). Specifically, the natural range of flow behaviour within regional classes can be used to identify clearly anomalous flow features in rivers regulated by dams. Through ordination analysis on 70 ecologically important flow indices, we isolated five distinctive regional groupings of natural flow regimes among the 96 unregulated rivers located in study regions of South Eastern and South Western Canada, selected based on watershed characteristics as possible references for the 13 hydro-regulated, NSERC-HydroNet study rivers in British Columbia, Alberta, Ontario, Quebec and New Brunswick. The distinguishing characteristics of natural flow regimes within each flow class are explored through visualization in principal component space. The 16 regulated HydroNet sites were assigned to appropriate regional flow classes through discriminant function analysis based on shared geographic location and watershed characteristics. Anomalous flow features in the regulated rivers are then characterized by type and strength, based on identification of flow indices that are significantly different from observed natural variability in the relevant regional class. The magnitude distributions and the main axes of variability in index anomalies are analysed, across regions and regulation types (storage, peaking and run-of-the-river (RoR)). We also discuss the potential biological implications of

  12. Role of a naturally varying flow regime in Everglades restoration

    Science.gov (United States)

    Harvey, Judson; Wetzel, Paul R.; Lodge, Thomas E.; Engel, Victor C.; Ross, Michael S.

    2017-01-01

    The Everglades is a low-gradient floodplain predominantly on organic soil that undergoes seasonally pulsing sheetflow through a network of deepwater sloughs separated by slightly higher elevation ridges. The seasonally pulsing flow permitted the coexistence of ridge and slough vegetation, including the persistence of productive, well-connected sloughs that seasonally concentrated prey and supported wading bird nesting success. Here we review factors contributing to the origin and to degradation of the ridge and slough ecosystem in an attempt to answer “How much flow is needed to restore functionality”? A key restoration objective is to increase sheetflow lost during the past century to reestablish interactions between flow, water depth, vegetation production and decomposition, and transport of flocculent organic sediment that build and maintain ridge and slough distinctions. Our review finds broad agreement that perturbations of water level depth and its fluctuations were primary in the degradation of landscape functions, with critical contributions from perturbed water quality, and flow velocity and direction. Whereas water levels are expected to be improved on average across a range of restoration scenarios that replace between 79 and 91% of predrainage flows, the diminished microtopography substantially decreases the probability of timely improvements in some areas whereas others that retain microtopographic differences are poised for restoration benefits. New advances in predicting restoration outcomes are coming from biophysical modeling of ridge–slough dynamics, system-wide measurements of landscape functionality, and large-scale flow restoration experiments, including active management techniques to kick-start slough regeneration.

  13. A Risk-Based Ecohydrological Approach to Assessing Environmental Flow Regimes

    Science.gov (United States)

    Mcgregor, Glenn B.; Marshall, Jonathan C.; Lobegeiger, Jaye S.; Holloway, Dean; Menke, Norbert; Coysh, Julie

    2018-03-01

    For several decades there has been recognition that water resource development alters river flow regimes and impacts ecosystem values. Determining strategies to protect or restore flow regimes to achieve ecological outcomes is a focus of water policy and legislation in many parts of the world. However, consideration of existing environmental flow assessment approaches for application in Queensland identified deficiencies precluding their adoption. Firstly, in managing flows and using ecosystem condition as an indicator of effectiveness, many approaches ignore the fact that river ecosystems are subjected to threatening processes other than flow regime alteration. Secondly, many focus on providing flows for responses without considering how often they are necessary to sustain ecological values in the long-term. Finally, few consider requirements at spatial-scales relevant to the desired outcomes, with frequent focus on individual places rather than the regions supporting sustainability. Consequently, we developed a risk-based ecohydrological approach that identifies ecosystem values linked to desired ecological outcomes, is sensitive to flow alteration and uses indicators of broader ecosystem requirements. Monitoring and research is undertaken to quantify flow-dependencies and ecological modelling is used to quantify flow-related ecological responses over an historical flow period. The relative risk from different flow management scenarios can be evaluated at relevant spatial-scales. This overcomes the deficiencies identified above and provides a robust and useful foundation upon which to build the information needed to support water planning decisions. Application of the risk assessment approach is illustrated here by two case studies.

  14. Comprehensive assessment of dam impacts on flow regimes with consideration of interannual variations

    Science.gov (United States)

    Zhang, Yongyong; Shao, Quanxi; Zhao, Tongtiegang

    2017-09-01

    Assessing the impact of human intervention on flow regimes is important in policy making and resource management. Previous impact assessments of dam regulation on flow regimes have focused on long-term average patterns, but interannual variations, which are important characteristics to be considered, have been ignored. In this study, the entire signatures of hydrograph variations of Miyun Reservoir in northern China were described by forty flow regime metrics that incorporate magnitude, variability and frequency, duration, timing, and rate of change for flow events based on a long-term synchronous observation series of inflow and outflow. Principal component analysis and cluster analysis were used to reduce the multidimensionality of the metrics and time and to determine impact patterns and their interannual shifts. Statistically significant driving factors of impact pattern variations were identified. We found that dam regulation resulted in four main impact classes on the flow regimes and that the regulated capacity was interannually attenuated from 1973 to 2010. The impact patterns alternated between the highly regulated class with extremely decreasing flow magnitude, slight variability, and extreme intermittency and the slightly regulated class with extremely increasing flow magnitude, slight variability, and extreme intermittency from 1973 to 1987 and then stabilized in the latter class from 1988 to 2001. After 2001, the pattern gradually changed from the moderately regulated class with moderately decreasing flow magnitude, extreme variability, and extreme intermittency to the slightly regulated class with slightly decreasing flow magnitude, slight variability, and no intermittency. Decreasing precipitation and increasing drought were the primary drivers for the interannual variations of the impact patterns, and inflow variability was the most significant factor affecting the patterns, followed by flow event frequency and duration, magnitude, and timing. This

  15. SEASONAL FLOW REGIME ON THE RIVERS FROM CĂLIMANI MOUNTAINS

    OpenAIRE

    HÎRLAV C.; PORCUŢAN ADRIANA

    2015-01-01

    In this study we try to analyze some important hydrometric problems such as the seasonal river flow regime on the rivers from Căliman Mountains, regime types and regime’s space and time variation. The seasonal river flow repartition is determined by the way all supply sources combine during the entire year. In all seasons it can be observed a strong correlation between flow values and basins’ average altitude. This study uses data from 14 hydrometric stations, with rivers that belong to three...

  16. Intermittent Flow Regimes in a Transonic Fan Airfoil Cascade

    Directory of Open Access Journals (Sweden)

    J. Lepicovsky

    2004-01-01

    velocity.To date, this flow behavior has only been observed in a linear transonic cascade. Further research is necessary to confirm this phenomenon occurs in actual transonic fans and is not the by-product of an endwall restricted linear cascade.

  17. Flow regimes of adiabatic gas-liquid two-phase under rolling conditions

    Science.gov (United States)

    Yan, Chaoxing; Yan, Changqi; Sun, Licheng; Xing, Dianchuan; Wang, Yang; Tian, Daogui

    2013-07-01

    Characteristics of adiabatic air/water two-phase flow regimes under vertical and rolling motion conditions were investigated experimentally. Test sections are two rectangular ducts with the gaps of 1.41 and 10 mm, respectively, and a circular tube with 25 mm diameter. Flow regimes were recorded by a high speed CCD-camera and were identified by examining the video images. The experimental results indicate that the characteristics of flow patterns in 10 mm wide rectangular duct under vertical condition are very similar to those in circular tube, but different from the 1.41 mm wide rectangular duct. Channel size has a significant influence on flow pattern transition, boundary of which in rectangular channels tends asymptotically towards that in the circular tube with increasing the width of narrow side. Flow patterns in rolling channels are similar to each other, nevertheless, the effect of rolling motion on flow pattern transition are significantly various. Due to the remarkable influences of the friction shear stress and surface tension in the narrow gap duct, detailed flow pattern maps of which under vertical and rolling conditions are indistinguishable. While for the circular tube with 25 mm diameter, the transition from bubbly to slug flow occurs at a higher superficial liquid velocity and the churn flow covers more area on the flow regime map as the rolling period decreases.

  18. Noncondensable gas effect on film condensation of boundary layer flow in the entire mixed convection regime

    International Nuclear Information System (INIS)

    Liao, Y.; Guentay, S.

    2009-01-01

    The mixed convection regime for film condensation is enveloped by free convection at one end and forced convection at the other. At both ends, the noncondensable gas effect on film condensation was established in the pioneering work by Sparrow and Minkowycz. But most practical flows are in the mixed convection regime, where it was observed in recent experiments that the pioneering work could not be applied satisfactorily. The current work tries to bridge the gap by presenting a generic boundary layer formulation of the noncondensable gas effect in the entire mixed convection regime. The current formulation is reduced to two specific cases which mathematically coincide with the pioneering work at two ends. In between, the current work fills the gap by presenting solution for the full spectrum of the mixed convection regime. The presented mixed convection solution intermediates between Minkowycz's prediction on the free convection flow and Sparrow's prediction on the forced convection flow, and is in fair agreement with the recent experiments performed in the mixed convection regime. It is found that although a slight vapor flow imposed on free convection has little effect on film condensation in the absence of noncondensable gases, a slight gas flow imposed on condensation in the presence of noncondensable gases can drastically affect the mass transfer boundary and reduce the accumulation of gas at the interface due to a strong coupling between hydrodynamics and convective mass diffusion. (author)

  19. Enstrophy transport conditional on local flow topologies in different regimes of premixed turbulent combustion

    KAUST Repository

    Papapostolou, Vassilios

    2017-09-11

    Enstrophy is an intrinsic feature of turbulent flows, and its transport properties are essential for the understanding of premixed flame-turbulence interaction. The interrelation between the enstrophy transport and flow topologies, which can be assigned to eight categories based on the three invariants of the velocity-gradient tensor, has been analysed here. The enstrophy transport conditional on flow topologies in turbulent premixed flames has been analysed using a Direct Numerical Simulation database representing the corrugated flamelets (CF), thin reaction zones (TRZ) and broken reaction zones (BRZ) combustion regimes. The flame in the CF regime exhibits considerable flame-generated enstrophy, and the dilatation rate and baroclinic torque contributions to the enstrophy transport act as leading order sink and source terms, respectively. Consequently, flow topologies associated with positive dilatation rate values, contribute significantly to the enstrophy transport in the CF regime. By contrast, enstrophy decreases from the unburned to the burned gas side for the cases representing the TRZ and BRZ regimes, with diminishing influences of dilatation rate and baroclinic torque. The enstrophy transport in the TRZ and BRZ regimes is governed by the vortex-stretching and viscous dissipation contributions, similar to non-reacting flows, and topologies existing for all values of dilatation rate remain significant contributors.

  20. Heat transfer regimes for a flow of water at supercritcal conditions in vertical channels

    Science.gov (United States)

    Deev, V. I.; Kharitonov, V. S.; Churkin, A. N.; Baisov, A. M.

    2017-11-01

    Heat transfer regimes observed in experiments with water at supercritical conditions flowing in vertical channels of various cross-sections (such as round pipes, annulus, or rod bundles) are analyzed. In accordance with the established practice, the normal and the deteriorated heat transfer regimes were singled out as the basic regimes specific for heat carriers with highly variable properties. At the same time, it has been established that most published experimental data on supercritical pressure water heat transfer along the length of test sections demonstrate combined (or transient) heat transfer regimes. The features can be presented as a superposition of characteristics of the above-mentioned basic regimes. The combined regimes are not stable in certain ranges of water flow conditions in which sudden transitions between the basic regimes can occur. A system of similarity criteria governing heat transfer rate in the vicinity of the critical point is examined. As applicable to cores of water-cooled reactors, due to a small hydraulic diameter of cooling channels, buoyancy forces acting in these channels are negligible as compared with the inertia effects caused by thermal acceleration of the flow and viscous force. This concept yields two integrated criteria whose use in the correction factors for the basic heat transfer equation, which we proposed previously for the normal regimes, adequately (with an error of 20-25%) describes the specific of the heat transfer coefficient in the normal, deteriorated, and combined regimes. A system of equations is proposed for design calculation of heat transfer in channels of nuclear reactors cooled with supercritical pressure water.

  1. Flow Regime Transition in Inner Grooved Minichannel Cold Plates for Cooling Hybrid Electric Power Electronics

    Science.gov (United States)

    2013-01-01

    fluids and channel sizes. Adiabatic models do not account for thermal interactions inside the channel. This is important to consider in diabatic ...electronic cooling applications where heat is typically added to the two- phase mixture. Specifically, diabatic conditions could be expected to...shift transition boundaries between bubbly/intermittent and stratified/intermittent regimes (16). As a result, diabatic flow regime maps have been

  2. Precise Void Fraction Measurement in Two-phase Flows Independent of the Flow Regime Using Gamma-ray Attenuation

    Directory of Open Access Journals (Sweden)

    E. Nazemi

    2016-02-01

    Full Text Available Void fraction is an important parameter in the oil industry. This quantity is necessary for volume rate measurement in multiphase flows. In this study, the void fraction percentage was estimated precisely, independent of the flow regime in gas–liquid two-phase flows by using γ-ray attenuation and a multilayer perceptron neural network. In all previous studies that implemented a multibeam γ-ray attenuation technique to determine void fraction independent of the flow regime in two-phase flows, three or more detectors were used while in this study just two NaI detectors were used. Using fewer detectors is of advantage in industrial nuclear gauges because of reduced expense and improved simplicity. In this work, an artificial neural network is also implemented to predict the void fraction percentage independent of the flow regime. To do this, a multilayer perceptron neural network is used for developing the artificial neural network model in MATLAB. The required data for training and testing the network in three different regimes (annular, stratified, and bubbly were obtained using an experimental setup. Using the technique developed in this work, void fraction percentages were predicted with mean relative error of <1.4%.

  3. Economic interpretation of environmental flow regime downstream diverted river reaches.

    Science.gov (United States)

    Gorla, Lorenzo; Perona, Paolo

    2013-04-01

    Water demand for hydropower production is increasing together with the consciousness of the importance of riparian ecosystems and biodiversity. Some Cantons in Switzerland and other alpine regions in Austria and in Sud Tirol (Italy) started replacing the inadequate concept of Minimum Flow Requirement (MFR) with a dynamic one, by releasing a fix percentage of the total inflow (e.g. 25 %) to the environment. In the same direction Perona et al. (in revision) mathematically formulated a method particularly suitable for small hydropower plants, handling the environment as a non-traditional water use, which competes with exploitators. This model uses the Principle of Equal Marginal Utility (PEMU) as optimal water allocation rule for generating like-natural flow releases while maximizing the aggregate economic benefit of all uses (Gorla and Perona, in revision). In this paper we show how redistribution policies can be interpreted in terms of PEMU, particularly we focus at traditional water repartition rules, such as the MFR, but also to dynamic ones like proportional redistribution. For the first case we show both ecological and economical arguments suggesting its inappropriateness; in the second case we highlight explicit points of strength and weakness, and suggest ways of improvement. For example the flow release allocation rule can be changed from inflow-independent ones (e.g., proportional redistribution), to inflow-dependent ones (e.g., non-proportional). The latters, having fewer constraints, can generally lead to better both ecological and economical performances. A class of simple functions, based on the PEMU, is then proposed as a suitable solution in run-of-river or small hydropower plants. Each water repartition policy underlies an ecosystem monetization. We explicit the value of the ecosystem health underlying each policy by means of the PEMU under a few assumptions, and discuss how the theoretic efficient redistribution law obtained by our approach is

  4. The Role of Forests in Regulating the River Flow Regime of Large Basins of the World

    Science.gov (United States)

    Salazar, J. F.; Villegas, J. C.; Mercado-Bettin, D. A.; Rodríguez, E.

    2017-12-01

    Many natural and social phenomena depend on river flow regimes that are being altered by global change. Understanding the mechanisms behind such alterations is crucial for predicting river flow regimes in a changing environment. Here we explore potential linkages between the presence of forests and the capacity of river basins for regulating river flows. Regulation is defined here as the capacity of river basins to attenuate the amplitude of the river flow regime, that is to reduce the difference between high and low flows. We first use scaling theory to show how scaling properties of observed river flows can be used to classify river basins as regulated or unregulated. This parsimonious classification is based on a physical interpretation of the scaling properties (particularly the scaling exponents) that is novel (most previous studies have focused on the interpretation of the scaling exponents for floods only), and widely-applicable to different basins (the only assumption is that river flows in a given river basin exhibit scaling properties through well-known power laws). Then we show how this scaling framework can be used to explore global-change-induced temporal variations in the regulation capacity of river basins. Finally, we propose a conceptual hypothesis (the "Forest reservoir concept") to explain how large-scale forests can exert important effects on the long-term water balance partitioning and regulation capacity of large basins of the world. Our quantitative results are based on data analysis (river flows and land cover features) from 22 large basins of the world, with emphasis in the Amazon river and its main tributaries. Collectively, our findings support the hypothesis that forest cover enhances the capacity of large river basins to maintain relatively high mean river flows, as well as to regulate (ameliorate) extreme river flows. Advancing towards this quantitative understanding of the relation between forest cover and river flow regimes is

  5. Flow regime analysis for fluid injection into a confined aquifer: implications for CO2 sequestration

    Science.gov (United States)

    Guo, B.; Zheng, Z.; Celia, M. A.; Stone, H.

    2015-12-01

    Carbon dioxide injection into a confined saline aquifer may be modeled as an axisymmetric two-phase flow problem. Assuming the two fluids segregate in the vertical direction due to strong buoyancy, and neglecting capillary pressure and miscibility, the lubrication approximation leads to a nonlinear advection-diffusion equation that describes the evolution of the sharp fluid-fluid interface. The flow behaviors in the system are controlled by two dimensionless groups: M, the viscosity ratio of the displaced fluid relative to injected fluid, and Γ , the gravity number, which represents the relative importance of buoyancy and fluid injection. Four different analytical solutions can be derived as the asymptotic approximations, representing specific values of the parameter pairs. The four solutions correspond to: (1) Γ 1; and (4) Γ >> 1, any M values. The first two of these solutions are new, while the third corresponds to the solution of Nordbotten and Celia (2006) for confined injections and the fourth corresponds to the solution of (Lyle et al., 2005) for gravity currents in an unconfined aquifer. Overall, the various axisymmetric flows can be summarized in a Γ-M regime diagram with five distinct dynamic behaviors including the four asymptotic regimes and an intermediate regime (Fig. 1). Data from a number of CO2 injection sites around the world can be used to compute the two dimensionless groups Γ and M associated with each injection. When plotted on the regime diagram, these values show the flow behavior for each injection and how the values vary from site to site. For all the CO2 injections, M is always larger than 1, while Γ can range from 0.01 up to 100. The pairs of (Γ, M) with lower Γ values correspond to solution (3), while the ones with higher Γ values can move up to the intermediate regime and the flow regime for solution (4). The higher values of Γ correspond to pilot-scale injections with low injection rates; most industrial-scale injection

  6. Flow regime patterns and their controlling factors in the Ebro basin (Spain)

    Science.gov (United States)

    Bejarano, M. Dolores; Marchamalo, Miguel; García de Jalón, Diego; González del Tánago, Marta

    2010-05-01

    SummaryNatural intra-annual flow fluctuations vary between rivers, being a determining factor for aquatic insects, fish and riparian communities which are adapted to the habitat conditions and different flows throughout the seasons. Moreover, restoration of seasonal flow patterns plays an important role in achieving good ecological status of rivers, through the preservation and/or recovery of components and processes of natural river ecosystems. In this work we: (a) classify fluvial segments in the Ebro basin (North-Eastern Spain) according to the intra-annual variability of flows under natural conditions using statistical cluster analysis of monthly mean flow data; (b) characterise the resulting flow typologies according to several ecologically important hydrological variables; (c) analyse the relationships between flow regimes of fluvial segments and physical variables from their catchments; and finally (d) predict the most probable natural flow regime using logistic models based on the most determinant physical characteristics. Fifteen natural flow typologies were described in the Ebro basin, which were characterised in terms of flow fluctuation through the year as well as timing, flow ratio and duration of the maximum and minimum flows. Precipitation, biogeography and geology of catchments showed the highest correlations with flow regimes. Basin size, mean elevation and slope were also correlated. The logistic model we developed had a prediction success of 72% in the Ebro basin. The definition of the natural hydrological conditions (to which the biological communities are tailored), even when flow data are not available, is an important support in the management of river ecosystems. It is especially suitable for setting goals in aquatic ecosystem conservation or restoration projects.

  7. Critical Regimes of Two-Phase Flows with a Polydisperse Solid Phase

    CERN Document Server

    Barsky, Eugene

    2010-01-01

    This book brings to light peculiarities of the formation of critical regimes of two-phase flows with a polydisperse solid phase. A definition of entropy is formulated on the basis of statistical analysis of these peculiarities. The physical meaning of entropy and its correlation with other parameters determining two-phase flows are clearly defined. The interrelations and main differences between this entropy and the thermodynamic one are revealed. The main regularities of two-phase flows both in critical and in other regimes are established using the notion of entropy. This parameter serves as a basis for a deeper insight into the physics of the process and for the development of exhaustive techniques of mass exchange estimation in such flows. The book is intended for graduate and postgraduate students of engineering studying two-phase flows, and to scientists and engineers engaged in specific problems of such fields as chemical technology, mineral dressing, modern ceramics, microelectronics, pharmacology, po...

  8. Flow regime effects on non-cavitating injection nozzles over spray behavior

    Energy Technology Data Exchange (ETDEWEB)

    Payri, R., E-mail: rpayri@mot.upv.e [CMT-Motores Termicos, Universidad Politecnica de Valencia, Camino de Vera s/n, Valencia E-46022 (Spain); Salvador, F.J.; Gimeno, J.; Novella, R. [CMT-Motores Termicos, Universidad Politecnica de Valencia, Camino de Vera s/n, Valencia E-46022 (Spain)

    2011-02-15

    This paper deals with the influence of flow regime (laminar, transition or turbulent) on the internal flow behavior, and how it affects the spray development in diesel nozzles. In particular, the research described here aims at studying and quantifying the internal flow regime effects on the spray behavior. With this purpose, internal flow results, based on mass flow rate and momentum flux measurements performed on three different tapered nozzles and which helped to determine the flow regime, has been taken into account as a point of departure for the spray behavior analysis. Thus, in this work, spray macroscopic visualization tests have been performed and analyzed which clearly revealed a change in the behavior of the angle and penetration of the spray related to the change of the flow nature. Moreover, with all the experimental data available, it has been possible to relate macroscopic parameters of the spray with those describing the internal flow (momentum and effective velocity) or the geometry of the nozzle (length or diameter) through correlations.

  9. Flow Regime Destabilizing Effect on Fluid elastic Instability of Tube Array Preferentially Flexible to the Flow Direction

    International Nuclear Information System (INIS)

    Lee, Kanghee; Shin, Changhwan; Olala, Stephen; Mureithi, Njuki

    2015-01-01

    U bend region of operating SG is excited by the inclined cross flow due to the gradual change of hydraulic resistance force. The effect of tube array's flexibility direction on FEI is investigated by Khalvatti for rotated triangular tube in single phase (air) cross flow. He showed that FEI strongly depend on the flexibility angle. Reducing bundle flexibility to the flow direction ranging from 90 (out-of-flow direction) to 0 (in-flow direction) degree has a nonlinearly-varying stabilizing effect. Joly studies the same problem under high void fraction in two phase cross flow over 70 % to 90 %. With the Joly's experimental work, there is oddly low-valued Conner's constant in case of higher degree of angle of attack. This gives the motivation to our experimental study for fluid elastic instability of tube array in two phase cross flow. As the flow rate goes up, tube response was measured for each steady state flow condition by the strain gauge. Damping, peak frequency, and the critical velocity were estimated from the response spectrum. It seems that the flow regime for high void fraction can destabilize tube array with preferential flexibility over 60 degree. Because an intermittent flow is inherently unstable compared to the uniform bubbly flow, thus out-of-flow motion of tubes can be more fragile to the unstably rising intermittent flow. From the visual inspection, lateral tube motion seems to block the flow path periodically. Enlarged bubble in an intermittent flow regime can be squeezed-up at the flow gap between tubes

  10. Altered stream-flow regimes and invasive plant species: The Tamarix case

    Science.gov (United States)

    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.

  11. Experimental observations of pressure oscillations and flow regimes in an analogue volcanic system

    Science.gov (United States)

    Lane, S.J.; Chouet, B.A.; Phillips, J.C.; Dawson, P.; Ryan, G.A.; Hurst, E.

    2001-01-01

    Gas-liquid flows, designed to be analogous to those in volcanic conduits, are generated in the laboratory using organic gas-gum rosin mixtures expanding in a vertically mounted tube. The expanding fluid shows a range of both flow and pressure oscillation behaviors. Weakly supersaturated source liquids produce a low Reynolds number flow with foam expanding from the top surface of a liquid that exhibits zero fluid velocity at the tube wall; i.e., the conventional "no-slip" boundary condition. Pressure oscillations, often with strong long-period characteristics and consistent with longitudinal and radial resonant oscillation modes, are detected in these fluids. Strongly supersaturated source liquids generate more energetic flows that display a number of flow regimes. These regimes include a static liquid source, viscous flow, detached flow (comprising gas-pockets-at-wall and foam-in-gas annular flow, therefore demonstrating strong radial heterogeneity), and a fully turbulent transonic fragmented or mist flow. Each of these flow regimes displays characteristic pressure oscillations that can be related to resonance of flow features or wall impact phenomena. The pressure oscillations are produced by the degassing processes without the need of elastic coupling to the confining medium or flow restrictors and valvelike features. The oscillatory behavior of the experimental flows is compared to seismoacoustic data from a range of volcanoes where resonant oscillation of the fluid within the conduit is also often invoked as controlling the observed oscillation frequencies. On the basis of the experimental data we postulate on the nature of seismic signals that may be measured during large-scale explosive activity. Copyright 2001 by the American Geophysical Union.

  12. Energy-based upscaling of immiscible two-phase flow in porous media: flow regimes and applicability conditions

    Science.gov (United States)

    Picchi, Davide; Battiato, Ilenia

    2017-11-01

    Empirical or theoretical extensions of Darcy's law for immiscible two-phase flow have shown significant limitations in properly modelling the flow at the continuum-scale. We tackle this problem by proposing a set of upscaled equations based on pore-scale flow regimes, i.e., the topology of flowing phases. The incompressible Navier-Stokes equation is upscaled by means of multi-scale expansions and its closures derived from the mechanical energy balance for different flow regimes at the pore-scale. We also derive the applicability conditions of the upscaled equations based on the order of magnitude of relevant dimensionless numbers, i.e., Eotvos, Reynolds, Capillary, Froude numbers, and the viscosity and density ratio of the system. We demonstrate that the classical two-phase Darcy law is recovered for a limited range of operative conditions and it is compatible only with the connected-pathway flow regime, while additional terms accounting for interfacial and wall interactions should be incorporated to model accurately ganglia or drop traffic flow.

  13. Theoretical and pragmatic modelling of governing equations for a two-phase flow in bubbly and annular flow regimes

    International Nuclear Information System (INIS)

    Bottoni, M.; Sengpiel, W.

    1992-01-01

    Starting from the rigorous formulation of the conservation equations for mass, momentum and enthalpy, derived for a two-phase flow by volume averaging microscopic balance equations over Eulerian control cells, the article discusses the formulation of the terms describing exchanges between the phases. Two flow regimes are taken into consideration, bubbly flow, applicable for small or medium void fractions, and annular flow, for large void fractions. When lack of knowledge of volume-averaged physical quantities make the rigorously formulated terms useless for computational purposes, modelling of these terms is discussed. 3 figs., 15 refs

  14. River flow regime and snow cover of the Pamir Alay (Central Asia) in a changing climate

    NARCIS (Netherlands)

    Chevallier, P.; Pouyaud, B.; Mojaisky, M.; Bolgov, M.; Olsson, O.; Bauer, M.; Froebrich, J.

    2014-01-01

    The Vakhsh and Pyandj rivers, main tributaries of the Amu Darya River in the mountainous region of the Pamir Alay, play an important role in the water resources of the Aral Sea basin (Central Asia). In this region, the glaciers and snow cover significantly influence the water cycle and flow regime,

  15. Dry granular flows down an inclined channel: experimental investigations on the frictional-collisional regime.

    Science.gov (United States)

    Ancey, Christophe

    2002-01-01

    This paper presents experimental results on dry granular flows down an inclined rough channel. Different flow regimes were identified depending on the Froude number. For Froude numbers exceeding a critical value (function of the channel slope), flow was characterized by a fairly linear velocity profile and a discharge equation in the form q varies with h(n) with q the flow rate per unit width, h the flow depth, and n an exponent in the range 2-3 (regime A). When the Froude number was lower than the critical value, the flow was characterized by a convex velocity profile and a discharge equation of the form q varies with h(n), with n ranging from 0.97 to 1.16, producing the striking result that the mean velocity was constant for a given inclination of the channel (regime B). Experimental data were used to test three theoretical models developed to describe dry granular flows in a frictional-collisional regime. Savage's model provides results that capture experimental trends well and yield the correct magnitude for velocity and discharge for regime A, but it reproduces the dependence of the discharge on the channel slope for only a narrow range of slopes [S. B. Savage, in U.S./Japan Seminar on New Models and Constitutive Relations in the Mechanics of Granular Materials, Ithaca, 1982, edited by J. T. Jenkins and M. Satake (Elsevier Science Publishers, Amsterdam, 1982), p. 261]. In contrast, Mills et al.'s model is less refined and requires fitting an input parameter to give the correct magnitude of velocity but it successfully accounts for the variation in the discharge with slope for regime A for a wide range of slopes [Mills, Loggia, and Tixier, Europhys. Lett. 45, 733 (1999); Eur. Phys. J. E 1, 5 (2000)]. Ancey and Evesque's model is also crude in determining the density profile but manages to provide velocity profiles and discharge equations in good agreement with experimental data for regime B [C. Ancey and P. Evesque, Phys. Rev. E 62, 8349 (2000)].

  16. Flow regime alterations under changing climate in two river basins: Implications for freshwater ecosystems

    Science.gov (United States)

    Gibson, C.A.; Meyer, J.L.; Poff, N.L.; Hay, L.E.; Georgakakos, A.

    2005-01-01

    We examined impacts of future climate scenarios on flow regimes and how predicted changes might affect river ecosystems. We examined two case studies: Cle Elum River, Washington, and Chattahoochee-Apalachicola River Basin, Georgia and Florida. These rivers had available downscaled global circulation model (GCM) data and allowed us to analyse the effects of future climate scenarios on rivers with (1) different hydrographs, (2) high future water demands, and (3) a river-floodplain system. We compared observed flow regimes to those predicted under future climate scenarios to describe the extent and type of changes predicted to occur. Daily stream flow under future climate scenarios was created by either statistically downscaling GCMs (Cle Elum) or creating a regression model between climatological parameters predicted from GCMs and stream flow (Chattahoochee-Apalachicola). Flow regimes were examined for changes from current conditions with respect to ecologically relevant features including the magnitude and timing of minimum and maximum flows. The Cle Elum's hydrograph under future climate scenarios showed a dramatic shift in the timing of peak flows and lower low flow of a longer duration. These changes could mean higher summer water temperatures, lower summer dissolved oxygen, and reduced survival of larval fishes. The Chattahoochee-Apalachicola basin is heavily impacted by dams and water withdrawals for human consumption; therefore, we made comparisons between pre-large dam conditions, current conditions, current conditions with future demand, and future climate scenarios with future demand to separate climate change effects and other anthropogenic impacts. Dam construction, future climate, and future demand decreased the flow variability of the river. In addition, minimum flows were lower under future climate scenarios. These changes could decrease the connectivity of the channel and the floodplain, decrease habitat availability, and potentially lower the ability

  17. Characterizing effects of hydropower plants on sub-daily flow regimes

    Science.gov (United States)

    Bejarano, María Dolores; Sordo-Ward, Álvaro; Alonso, Carlos; Nilsson, Christer

    2017-07-01

    A characterization of short-term changes in river flow is essential for understanding the ecological effects of hydropower plants, which operate by turning the turbines on or off to generate electricity following variations in the market demand (i.e., hydropeaking). The goal of our study was to develop an approach for characterizing the effects of hydropower plant operations on within-day flow regimes across multiple dams and rivers. For this aim we first defined ecologically meaningful metrics that provide a full representation of the flow regime at short time scales from free-flowing rivers and rivers exposed to hydropeaking. We then defined metrics that enable quantification of the deviation of the altered short-term flow regime variables from those of the unaltered state. The approach was successfully tested in two rivers in northern Sweden, one free-flowing and another regulated by cascades of hydropower plants, which were additionally classified based on their impact on short-term flows in sites of similar management. The largest differences between study sites corresponded to metrics describing sub-daily flow magnitudes such as amplitude (i.e., difference between the highest and the lowest hourly flows) and rates (i.e., rise and fall rates of hourly flows). They were closely followed by frequency-related metrics accounting for the numbers of within-day hourly flow patterns (i.e., rises, falls and periods of stability of hourly flows). In comparison, between-site differences for the duration-related metrics were smallest. In general, hydropeaking resulted in higher within-day flow amplitudes and rates and more but shorter periods of a similar hourly flow patterns per day. The impacted flow feature and the characteristics of the impact (i.e., intensity and whether the impact increases or decreases whatever is being described by the metric) varied with season. Our approach is useful for catchment management planning, defining environmental flow targets

  18. Exploring the significance of the fluidized flow regime for avalanche hazard mapping

    Science.gov (United States)

    Issler, Dieter; Gauer, Peter

    Observational and experimental evidence suggests that it is important to explicitly account for the fluidized flow regime in avalanche hazard mapping due to its high mobility, intermediate density and high velocity. We explore the differences from conventional runout modelling by implementing an extension of the Norem-Irgens-Schieldrop (NIS) rheology in a simple mass-point model. When the dispersive stresses and the excess pore pressure equal the overburden pressure, the flow height increases and the density diminishes until a new equilibrium is reached, determined by the different density dependencies of the two parameters of the dispersive stresses. Fluidization requires sufficiently steep terrain; when it occurs it leads to substantially higher velocities than compared to the dense-flow regime. The model parameters are strongly constrained by their physical meaning and vary little between widely different avalanches. However, in all test cases we obtained better agreement between simulated and observed runout distances and pressure effects than with conventional models.

  19. Flow topologies in different regimes of premixed turbulent combustion: A direct numerical simulation analysis

    KAUST Repository

    Wacks, Daniel H.

    2016-12-02

    The distributions of flow topologies within the flames representing the corrugated flamelets, thin reaction zones, and broken reaction zone regimes of premixed turbulent combustion are investigated using direct numerical simulation data of statistically planar turbulent H-2-air flames with an equivalence ratio phi = 0.7. It was found that the diminishing influence of dilatation rate with increasing Karlovitz number has significant influences on the statistical behaviors of the first, second, and third invariants (i.e., P, Q, and R) of the velocity gradient tensor. These differences are reflected in the distributions of the flow topologies within the flames considered in this analysis. This has important consequences for those topologies that make dominant contributions to the scalar-turbulence interaction and vortex-stretching terms in the scalar dissipation rate and enstrophy transport equations, respectively. Detailed physical explanations are provided for the observed regime dependences of the flow topologies and their implications on the scalar dissipation rate and enstrophy transport.

  20. Assessing flow regime alterations in a temporary river – the River Celone case study

    Directory of Open Access Journals (Sweden)

    De Girolamo Anna Maria

    2015-09-01

    Full Text Available In this paper, we present an approach to evaluate the hydrological alterations of a temporary river. In these rivers, it is expected that anthropogenic pressures largely modify low-flow components of the flow regime with consequences for aquatic habitat and diversity in invertebrate species. First, by using a simple hydrological index (IARI river segments of the Celone stream (southern Italy whose hydrological regime is significantly influenced by anthropogenic activities have been identified. Hydrological alteration has been further classified through the analysis of two metrics: the degree (Mf and the predictability of dry flow conditions (Sd6. Measured streamflow data were used to calculate the metrics in present conditions (impacted. Given the lack of data from pristine conditions, simulated streamflow time series were used to calculate the metrics in reference conditions. The Soil and Water Assessment Tool (SWAT model was used to estimate daily natural streamflow. Hydrological alterations associated with water abstractions, point discharges and the presence of a reservoir were assessed by comparing the metrics (Mf, Sd6 before and after the impacts. The results show that the hydrological regime of the river segment located in the upper part of the basin is slightly altered, while the regime of the river segment downstream of the reservoir is heavily altered. This approach is intended for use with ecological metrics in defining the water quality status and in planning streamflow management activities.

  1. Asymptotic preserving and all-regime Lagrange-Projection like numerical schemes: application to two-phase flows in low mach regime

    International Nuclear Information System (INIS)

    Girardin, Mathieu

    2014-01-01

    Two-phase flows in Pressurized Water Reactors belong to a wide range of Mach number flows. Computing accurate approximate solutions of those flows may be challenging from a numerical point of view as classical finite volume methods are too diffusive in the low Mach regime. In this thesis, we are interested in designing and studying some robust numerical schemes that are stable for large time steps and accurate even on coarse meshes for a wide range of flow regimes. An important feature is the strategy to construct those schemes. We use a mixed implicit-explicit strategy based on an operator splitting to solve fast and slow phenomena separately. Then, we introduce a modification of a Suliciu type relaxation scheme to improve the accuracy of the numerical scheme in some regime of interest. Two approaches have been used to assess the ability of our numerical schemes to deal with a wide range of flow regimes. The first approach, based on the asymptotic preserving property, has been used for the gas dynamics equations with stiff source terms. The second approach, based on the all-regime property, has been used for the gas dynamics equations and the homogeneous two-phase flows models HRM and HEM in the low Mach regime. We obtained some robustness and stability properties for our numerical schemes. In particular, some discrete entropy inequalities are shown. Numerical evidences, in 1D and in 2D on unstructured meshes, assess the gain in term of accuracy and CPU time of those asymptotic preserving and all-regime numerical schemes in comparison with classical finite volume methods. (author) [fr

  2. Sensitivity of Regulated Flow Regimes to Climate Change in the Western United States

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Tian [Pacific Northwest National Laboratory, Richland, Washington; Voisin, Nathalie [Pacific Northwest National Laboratory, Richland, Washington; Leng, Guoyong [Pacific Northwest National Laboratory, Richland, Washington; Huang, Maoyi [Pacific Northwest National Laboratory, Richland, Washington; Kraucunas, Ian [Pacific Northwest National Laboratory, Richland, Washington

    2018-03-01

    Water management activities or flow regulations modify water fluxes at the land surface and affect water resources in space and time. We hypothesize that flow regulations change the sensitivity of river flow to climate change with respect to unmanaged water resources. Quantifying these changes in sensitivity could help elucidate the impacts of water management at different spatiotemporal scales and inform climate adaptation decisions. In this study, we compared the emergence of significant changes in natural and regulated river flow regimes across the Western United States from simulations driven by multiple climate models and scenarios. We find that significant climate change-induced alterations in natural flow do not cascade linearly through water management activities. At the annual time scale, 50% of the Hydrologic Unit Code 4 (HUC4) sub-basins over the Western U.S. regions tend to have regulated flow regime more sensitive to the climate change than natural flow regime. Seasonality analyses show that the sensitivity varies remarkably across the seasons. We also find that the sensitivity is related to the level of water management. For 35% of the HUC4 sub-basins with the highest level of water management, the summer and winter flows tend to show a heightened sensitivity to climate change due to the complexity of joint reservoir operations. We further demonstrate that the impacts of considering water management in models are comparable to those that arises from uncertainties across climate models and emission scenarios. This prompts further climate adaptation studies research about nonlinearity effects of climate change through water management activities.

  3. Modelling of a single-component two-phase flow regime map in a horizontal pipe with rod bundles

    International Nuclear Information System (INIS)

    Busono, P.; Chang, J.S.; Krishnan, V.S.

    2004-01-01

    Many flow regime maps in current use for modelling two-phase flow with rod bundles were developed for adiabatic situations and without interface mass transfer being taken into account. This paper describes the development of a flow regime map which includes the modelling the mass transfer between the two phases. The model used is a modified form of the mechanistic model proposed by Osamusali and Chang. The effect of interfacial mass transfer on flow regime transitions predicted by the new model is discussed in detail in this paper. (author)

  4. Stream flow regime of springs in the Mantiqueira Mountain Range region, Minas Gerais State

    Directory of Open Access Journals (Sweden)

    Alisson Souza de Oliveira

    2014-09-01

    Full Text Available The stream flow regime of four springs located in the Mantiqueira Mountain Range region (MG was evaluated and correlated to the respective recharge area, relief characteristics, land cover and physical and hydrologic soil characteristics. The streamflow regime was characterized by monitoring of discharges, calculating the surface runoff and specific discharge and by modeling the discharge over the recession period using the Maillet method. As all recharge areas have similar relief the effect of it on the streamflow was not possible to identify. Analysis included determining the effect of drainage area size, soil characteristics and land cover on the indicators of the streamflow regime. Size of the recharge area had a positive influence on the indicators mean discharge and surface runoff volume and on the regulation of the streamflow regime (springs L4 and L1. The spring under the smallest area of influence provided the worst results for the above mentioned indicators (spring L3. The effect of forest cover (natural and planted, associated with soil characteristics, was evidenced by the indicators surface runoff (in depth and specific yield, both independent of the recharge area size (springs L4 and L2. The interaction of area size, soil characteristics and forest cover (natural and planted provided the best results for all indicators of streamflow regime in the springs studied in the Mantiqueira Mountain Range (spring L4.

  5. The effects of competing trade regimes on bilateral trade flows: case of Serbia

    Directory of Open Access Journals (Sweden)

    Predrag Bjelić

    2012-12-01

    Full Text Available The aim of this paper is to investigate the effects of competing trade regimes on Serbian trade with its most significant (traditional partners, like European Union and CEFTA 2006 signatories, and other untraditional trade partners with favourable trade regime, like the USA. To this end, gravity model with bilateral and time effects is estimated by Hausman-Taylor AR(1 instrumental variable estimator, using panel data on bilateral trade between Serbia and its main trade partners during the period 2001-2010. The results indicate that overall level of development and difference in factor endowments stimulate Serbia’s exports, which is in accordance with theoretical foundation that inter-industry trade is predominant in exports of less developed countries. Moreover, competing trade regimes appear as important determinant of Serbia’s trade relations, whereas additional liberalization of trade regime with the USA as untraditional trade partner, even asymmetrical to Serbia’s favour, cannot divert trade flows from traditional partners in the long-run. This could mean that distance plays more prominent role in bilateral trade than the degree of liberalization of trade regimes in case of Serbia. The result could be due to the contemporaneous effects of trade preferences granted to Serbia by the EU and other CEFTA 2006 signatories, main trading partners of Serbia.

  6. Flow adjustment inside large finite-size wind farms approaching the infinite wind farm regime

    Science.gov (United States)

    Wu, Ka Ling; Porté-Agel, Fernando

    2017-04-01

    Due to the increasing number and the growing size of wind farms, the distance among them continues to decrease. Thus, it is necessary to understand how these large finite-size wind farms and their wakes could interfere the atmospheric boundary layer (ABL) dynamics and adjacent wind farms. Fully-developed flow inside wind farms has been extensively studied through numerical simulations of infinite wind farms. The transportation of momentum and energy is only vertical and the advection of them is neglected in these infinite wind farms. However, less attention has been paid to examine the length of wind farms required to reach such asymptotic regime and the ABL dynamics in the leading and trailing edges of the large finite-size wind farms. Large eddy simulations are performed in this study to investigate the flow adjustment inside large finite-size wind farms in conventionally-neutral boundary layer with the effect of Coriolis force and free-atmosphere stratification from 1 to 5 K/km. For the large finite-size wind farms considered in the present work, when the potential temperature lapse rate is 5 K/km, the wind farms exceed the height of the ABL by two orders of magnitude for the incoming flow inside the farms to approach the fully-developed regime. An entrance fetch of approximately 40 times of the ABL height is also required for such flow adjustment. At the fully-developed flow regime of the large finite-size wind farms, the flow characteristics match those of infinite wind farms even though they have different adjustment length scales. The role of advection at the entrance and exit regions of the large finite-size wind farms is also examined. The interaction between the internal boundary layer developed above the large finite-size wind farms and the ABL under different potential temperature lapse rates are compared. It is shown that the potential temperature lapse rate plays a role in whether the flow inside the large finite-size wind farms adjusts to the fully

  7. Characterisation of the flow regimes of arbitrary manoeuvre in absolute and relative frames

    CSIR Research Space (South Africa)

    Gledhill, Irvy MA

    2011-09-01

    Full Text Available Characterisation of the flow regimes of arbitrary manoeuvre in absolute and relative frames I. Gledhill1 and J. Nordstr?m2 1Aeronautical Systems Competency Area, Defence, Peace, Safety and Security Operational Unit, CSIR 2 Dept of Mathematics, U Link... perturbations: dynamic derivatives - Relative frame terms: ? Roohani and Skews 2007?2011 ? In the inertial frame: - Inoue et al. ? CSIR 2011 www.csir.co.za U=Uinf U=0 Theory Background to present work ? Transformation between...

  8. Predicting bulk powder flow dynamics in a continuous mixer operating in transitory regimes

    OpenAIRE

    Ammarcha , Chawki; Gatumel , Cendrine; Dirion , Jean-Louis; Cabassud , Michel; Mizonov , Vadim; Berthiaux , Henri

    2012-01-01

    International audience; Over recent years there has been increasing interest in continuous powder mixing processes, due mainly to the development of on-line measurement techniques. However, our understanding of these processes remains limited, particularly with regard to their flow and mixing dynamics. In the present work, we study the behaviour of a pilot-scale continuous mixer during transitory regimes, in terms of hold-up weight and outflow changes. We present and discuss experimental resu...

  9. Low Flow Regimes of the Tarim River Basin, China: Probabilistic Behavior, Causes and Implications

    Directory of Open Access Journals (Sweden)

    Peng Sun

    2018-04-01

    Full Text Available Droughts are a frequent occurrence in Xinjiang, China, and therefore fundamental to determining their hydrologic characteristics is low flow analysis. To that end, 11 probability distribution functions and 26 copulas functions were employed to analyze the changing characteristics of low flow regime (defined as seven-day low flow of the Tarim River Basin. Results indicated that: (1 The Wakeby distribution satisfactorily described the probabilistic behavior of the low flow regime. According to Akaike Information Criterion (AIC, Bayesian Information Criterions (BIC, maximum likelihood, and other residual-based metrics, Tawn copula, Farlie–Gumbel–Morgenstern copula and Frank copula were the best choice and used in this current study. (2 After 1987, hydrological droughts of longer return periods were prone to higher occurrence frequency. (3 The low flow volume has been increasing in recent years due to the temperature-induced increase of snowmelt and increasing precipitation. However, hydrological droughts can be expected to occur due to the massive increase in water demand from the development of irrigated agriculture, increasing arable land and livestock farming. As a result, the water shortage in the lower Tarim River Basin will be increasingly severe under the influence of climate change and human activities. To alleviate the shortage would call for the development of water-saving agricultural irrigation, water-saving technology, conservation of eco-environment and sustainable development of local socio-economy.

  10. Flow Regime Changes: From Impounding a Temperate Lowland River to Small Hydropower Operations

    Directory of Open Access Journals (Sweden)

    Petras Punys

    2015-07-01

    Full Text Available This article discusses the environmental issues facing small hydropower plants (SHPs operating in temperate lowland rivers of Lithuania. The research subjects are two medium head reservoir type hydro schemes considered within a context of the global fleet of SHPs in the country. This research considers general abiotic indicators (flow, level, water retention time in the reservoirs of the stream that may affect the aquatic systems. The main idea was to test whether the hydrologic regime has been altered by small hydropower dams. The analysis of changes in abiotic indicators is a complex process, including both pre- and post-reservoir construction and post commissioning of the SHPs under operation. Downstream hydrograph (flow and stage ramping is also an issue for operating SHPs that can result in temporary rapid changes in flow and consequently negatively impact aquatic resources. This ramping has been quantitatively evaluated. To avoid the risk of excessive flow ramping, the types of turbines available were evaluated and the most suitable types for the natural river flow regime were identified. The results of this study are to allow for new hydro schemes or upgrades to use water resources in a more sustainable way.

  11. Lattice Boltzmann Simulations in the Slip and Transition Flow Regime with the Peano Framework

    KAUST Repository

    Neumann, Philipp

    2012-01-01

    We present simulation results of flows in the finite Knudsen range, which is in the slip and transition flow regime. Our implementations are based on the Lattice Boltzmann method and are accomplished within the Peano framework. We validate our code by solving two- and three-dimensional channel flow problems and compare our results with respective experiments from other research groups. We further apply our Lattice Boltzmann solver to the geometrical setup of a microreactor consisting of differently sized channels and a reactor chamber. Here, we apply static adaptive grids to fur-ther reduce computational costs. We further investigate the influence of using a simple BGK collision kernel in coarse grid regions which are further away from the slip boundaries. Our results are in good agreement with theory and non-adaptive simulations, demonstrating the validity and the capabilities of our adaptive simulation software for flow problems at finite Knudsen numbers.

  12. Linking Flow Regime and Water Quality in Rivers: a Challenge to Adaptive Catchment Management

    Directory of Open Access Journals (Sweden)

    Christer Nilsson

    2008-12-01

    Full Text Available Water quality describes the physicochemical characteristics of the water body. These vary naturally with the weather and with the spatiotemporal variation of the water flow, i.e., the flow regime. Worldwide, biota have adapted to the variation in these variables. River channels and their riparian zones contain a rich selection of adapted species and have been able to offer goods and services for sustaining human civilizations. Many human impacts on natural riverine environments have been destructive and present opportunities for rehabilitation. It is a big challenge to satisfy the needs of both humans and nature, without sacrificing one or the other. New ways of thinking, new policies, and institutional commitment are needed to make improvements, both in the ways water flow is modified in rivers by dam operations and direct extractions, and in the ways runoff from adjacent land is affected by land-use practices. Originally, prescribed flows were relatively static, but precepts have been developed to encompass variation, specifically on how water could be shared over the year to become most useful to ecosystems and humans. A key aspect is how allocations of water interact with physicochemical variation of water. An important applied question is how waste releases and discharge can be managed to reduce ecological and sanitary problems that might arise from inappropriate combinations of flow variation and physicochemical characteristics of water. We review knowledge in this field, provide examples on how the flow regime and the water quality can impact ecosystem processes, and conclude that most problems are associated with low-flow conditions. Given that reduced flows represent an escalating problem in an increasing number of rivers worldwide, managers are facing enormous challenges.

  13. A probabilistic approach to quantifying spatial patterns of flow regimes and network-scale connectivity

    Science.gov (United States)

    Garbin, Silvia; Alessi Celegon, Elisa; Fanton, Pietro; Botter, Gianluca

    2017-04-01

    The temporal variability of river flow regime is a key feature structuring and controlling fluvial ecological communities and ecosystem processes. In particular, streamflow variability induced by climate/landscape heterogeneities or other anthropogenic factors significantly affects the connectivity between streams with notable implication for river fragmentation. Hydrologic connectivity is a fundamental property that guarantees species persistence and ecosystem integrity in riverine systems. In riverine landscapes, most ecological transitions are flow-dependent and the structure of flow regimes may affect ecological functions of endemic biota (i.e., fish spawning or grazing of invertebrate species). Therefore, minimum flow thresholds must be guaranteed to support specific ecosystem services, like fish migration, aquatic biodiversity and habitat suitability. In this contribution, we present a probabilistic approach aiming at a spatially-explicit, quantitative assessment of hydrologic connectivity at the network-scale as derived from river flow variability. Dynamics of daily streamflows are estimated based on catchment-scale climatic and morphological features, integrating a stochastic, physically based approach that accounts for the stochasticity of rainfall with a water balance model and a geomorphic recession flow model. The non-exceedance probability of ecologically meaningful flow thresholds is used to evaluate the fragmentation of individual stream reaches, and the ensuing network-scale connectivity metrics. A multi-dimensional Poisson Process for the stochastic generation of rainfall is used to evaluate the impact of climate signature on reach-scale and catchment-scale connectivity. The analysis shows that streamflow patterns and network-scale connectivity are influenced by the topology of the river network and the spatial variability of climatic properties (rainfall, evapotranspiration). The framework offers a robust basis for the prediction of the impact of

  14. Granular-flow rheology: Role of shear-rate number in transition regime

    Science.gov (United States)

    Chen, C.-L.; Ling, C.-H.

    1996-01-01

    This paper examines the rationale behind the semiempirical formulation of a generalized viscoplastic fluid (GVF) model in the light of the Reiner-Rivlin constitutive theory and the viscoplastic theory, thereby identifying the parameters that control the rheology of granular flow. The shear-rate number (N) proves to be among the most significant parameters identified from the GVF model. As N ??? 0 and N ??? ???, the GVF model can reduce asymptotically to the theoretical stress versus shear-rate relations in the macroviscous and graininertia regimes, respectively, where the grain concentration (C) also plays a major role in the rheology of granular flow. Using available data obtained from the rotating-cylinder experiments of neutrally buoyant solid spheres dispersing in an interstitial fluid, the shear stress for granular flow in transition between the two regimes proves dependent on N and C in addition to some material constants, such as the coefficient of restitution. The insufficiency of data on rotating-cylinder experiments cannot presently allow the GVF model to predict how a granular flow may behave in the entire range of N; however, the analyzed data provide an insight on the interrelation among the relevant dimensionless parameters.

  15. Can stormwater control measures restore altered urban flow regimes at the catchment scale?

    Science.gov (United States)

    Li, Congying; Fletcher, Tim D.; Duncan, Hugh P.; Burns, Matthew J.

    2017-06-01

    Over the last 20-30 years, there has been an evolution in urban stormwater management towards the use of stormwater control measures (SCMs) at or near the source of the runoff. These approaches aim to protect or restore natural elements of the flow regime. However, evidence of the success of such approaches is to date limited. We reviewed attempts to both model and monitor the catchment-scale hydrological consequences of SCMs. While many catchment-scale studies on the hydrologic effects of SCMs are based on computer simulation, these modeling approaches are limited by many uncertainties. The few existing monitoring studies provide early indications of the potential of SCMs to deliver more natural flow regimes, but many questions remain. There is an urgent need for properly monitored studies that aim to assess the hydrologic effects of SCMs at the catchment scale. In future monitoring studies, these hydrologic effects need to be characterized using appropriate flow metrics at a range of scales (from site scale to catchment scale), and changes to flow metrics by SCMs need to be assessed using robust statistical methods. Such studies will give confidence to stormwater and river managers of the feasibility and benefits of "low impact" approaches to stormwater management.

  16. Gas-kinetic unified algorithm for hypersonic flows covering various flow regimes solving Boltzmann model equation in nonequilibrium effect

    International Nuclear Information System (INIS)

    Li, Zhihui; Ma, Qiang; Wu, Junlin; Jiang, Xinyu; Zhang, Hanxin

    2014-01-01

    Based on the Gas-Kinetic Unified Algorithm (GKUA) directly solving the Boltzmann model equation, the effect of rotational non-equilibrium is investigated recurring to the kinetic Rykov model with relaxation property of rotational degrees of freedom. The spin movement of diatomic molecule is described by moment of inertia, and the conservation of total angle momentum is taken as a new Boltzmann collision invariant. The molecular velocity distribution function is integrated by the weight factor on the internal energy, and the closed system of two kinetic controlling equations is obtained with inelastic and elastic collisions. The optimization selection technique of discrete velocity ordinate points and numerical quadrature rules for macroscopic flow variables with dynamic updating evolvement are developed to simulate hypersonic flows, and the gas-kinetic numerical scheme is constructed to capture the time evolution of the discretized velocity distribution functions. The gas-kinetic boundary conditions in thermodynamic non-equilibrium and numerical procedures are studied and implemented by directly acting on the velocity distribution function, and then the unified algorithm of Boltzmann model equation involving non-equilibrium effect is presented for the whole range of flow regimes. The hypersonic flows involving non-equilibrium effect are numerically simulated including the inner flows of shock wave structures in nitrogen with different Mach numbers of 1.5-Ma-25, the planar ramp flow with the whole range of Knudsen numbers of 0.0009-Kn-10 and the three-dimensional re-entering flows around tine double-cone body

  17. Experimental and numerical analyses of flow and mixing regimes in an arrow-like micro mixer

    Science.gov (United States)

    Salvetti, Maria Vittoria; Mariotti, Alessandro; Galletti, Chiara; Brunazzi, Elisabetta

    2017-11-01

    T-mixers are among the most common micro devices. We focus here on a geometrical modification of a T-mixer obtained by varying the angle between the axis of the inlet channels and that of the main conduit, so that an `arrow-like' configuration is obtained. Previous numerical studies indicated that for this type of configuration the steady engulfment regime occurs at lower Reynolds numbers than for T-mixers. However, with further increasing the Reynolds number, an unexpected reduction of the degree of mixing is observed, due to the presence of a strong vortical structure at the center of the mixing channel. Such a behavior is not observed in T-mixers. A synergic analysis combining experimental flow visualizations and numerical simulations of an arrow-like micro mixer is presented here. Experimental flow visualizations are compared with the scalar field behavior obtained in the simulations, which is in turn connected with the vorticity fields and dynamics, available in numerical simulations. This analysis is aimed at: (i) further characterizing the steady engulfment regime and (ii) investigating the unsteady periodic regimes, eventually occurring by increasing the Reynolds number, which have not been addressed so far in the literature for this type of geometry. University of Pisa - PRA-2017-49.

  18. Blurring the boundary between rapid granular flow and dense granular flow regimes: Evidence from DEM simulations

    Science.gov (United States)

    Tripathi, Anurag; Prasad, Mahesh; Kumar, Puneet

    2017-11-01

    The saturation of the effective friction coefficient for granular flows at high inertial numbers has been assumed widely by researchers, despite little simulation/experimental evidence. In contrast, a recent simulation study of plane shear flows by Mandal and Khakhar, suggests that the effective friction coefficient becomes maximum and then starts to decrease with increase in the inertial number for I > 0.5 . In order to investigate whether such a dip at higher inertial numbers is indeed a feature of granular rheology, we perform DEM simulations of chute flow of highly inelastic disks. We show that steady, fully developed flows are possible at inclinations much higher than those normally reported in literature. At such high inclinations, the flow is characterised by a significant slip at the base; the height of the layer increases by more than 300 % and kinetic energy of the layer increases by nearly 5 orders of magnitude. We observe, for the first time, steady chute flows at inertial number I 2 and show that the dip at higher inertial numbers can be observed in case of chute flow as well. The predictions of modified μ - I rheology, however, seem to remain valid in the bulk of the layer for packing fractions as low as 0.2. AT acknowledges the funding obtained from IIT Kanpur through the initiation Grant for this study.

  19. Big data analytics : predicting traffic flow regimes from simulated connected vehicle messages using data analytics and machine learning.

    Science.gov (United States)

    2016-12-25

    The key objectives of this study were to: 1. Develop advanced analytical techniques that make use of a dynamically configurable connected vehicle message protocol to predict traffic flow regimes in near-real time in a virtual environment and examine ...

  20. Regimes of Axisymmetric Flow and Scaling Laws in a Rotating Annulus with Local Convective Forcing

    Directory of Open Access Journals (Sweden)

    Susie Wright

    2017-07-01

    Full Text Available We present a numerical study of axisymmetric flow in a rotating annulus in which local thermal forcing, via a heated annular ring on the outside of the base and a cooled circular disk in the centre of the top surface, drives convection. This new configuration is a variant of the classical thermally-driven annulus, where uniform heating and cooling are applied through the outer and inner sidewalls respectively. The annulus provides an analogue to a planetary circulation and the new configuration, with its more relaxed vertical thermal boundary conditions, is expected to better emulate vigorous convection in the tropics and polar regions as well as baroclinic instability in the mid-latitude baroclinic zone. Using the Met Office/Oxford Rotating Annulus Laboratory (MORALS code, we have investigated a series of equilibrated, two dimensional axisymmetric flows across a large region of parameter space. These are characterized in terms of their velocity and temperature fields. When rotation is applied several distinct flow regimes may be identified for different rotation rates and strengths of differential heating. These regimes are defined as a function of the ratio of the horizontal Ekman layer thickness to the non-rotating thermal boundary layer thickness and are found to be similar to those identified in previous annulus experiments. Convection without rotation is also considered and the scaling of the heat transport with Rayleigh number is calculated. This is then compared with existing work on the classical annulus as well as horizontal and Rayleigh-Bénard convection. As with previous studies on both rotating and non-rotating convection the system’s behaviour is found to be aspect ratio dependent. This dependence is seen in the scaling of the non-rotating Nusselt number and in transitions between regimes in the rotating case although further investigation is required to fully explain these observations.

  1. Convective boiling regimes of a normal helium (4.2 K) thermosyphon flow

    International Nuclear Information System (INIS)

    Benkheira, L.; Baudouy, B.; Souhar, M.

    2006-01-01

    In this work, the different convective boiling regimes of a normal helium (4.2 K) flow in natural circulation, simulating the cooling system of the superconducting magnet of the CMS detector of the CERN-LHC (Large Hadron Collider), are studied. Experiments have been performed using a thermosyphon loop with copper tubes of 10 mm and 14 mm diameter, uniformly heated. Local temperature measurements have permitted to characterize the different heat transfer modes with respect to the heat flux, and in particular the nucleate boiling to film boiling transition. (J.S.)

  2. About the high flow regime of the rivers of Kosovo and Metohia

    Directory of Open Access Journals (Sweden)

    Živković Nenad

    2009-01-01

    Full Text Available The examples from Kosovo and Metohia attempted to point to some problems in the domain of hydrogeographic regionalization. The river water regime, especially the phase of high flows which marks this regime, has been the topic of almost all researches which treat water resources of drainage basins. However, the thing that has not been achieved till now is the unique solution by which the classification of rivers would be made according to this feature. On this example it has been shown that even some older methods, based on genetic analysis of hydrograms and of global type, as well as some recent ones, with lot of quantitative entry and regional approaches, cannot with certainty answer all the challenges which river regimes bring with themselves. This work shows that apart from climate, orographic and physiognomic features of drainage basins, the periods of data processing and the analysis of individual intra-annual series of discharges are very important as well. Discretization on time periods shorter than one month, as well as elimination of the extreme values of discharges in the longtime series is recommended for the future research.

  3. Investigation of flow regime in debris bed formation behavior with nonspherical particles

    Directory of Open Access Journals (Sweden)

    Songbai Cheng

    2018-02-01

    Full Text Available It is important to clarify the characteristics of flow regimes underlying the debris bed formation behavior that might be encountered in core disruptive accidents of sodium-cooled fast reactors. Although in our previous publications, by applying dimensional analysis technique, an empirical model, with its reasonability confirmed over a variety of parametric conditions, has been successfully developed to predict the regime transition and final bed geometry formed, so far this model is restricted to predictions of debris mixtures composed of spherical particles. Focusing on this aspect, in this study a new series of experiments using nonspherical particles have been conducted. Based on the knowledge and data obtained, an extension scheme is suggested with the purpose of extending the base model to cover the particle-shape influence. Through detailed analyses and given our current range of experimental conditions, it is found that, by coupling the base model with this scheme, respectable agreement between experiments and model predictions for the regime transition can be achieved for both spherical and nonspherical particles. Knowledge and evidence from our work might be utilized for the future improvement of design of an in-vessel core catcher as well as the development and verification of sodium-cooled fast reactor severe accident analysis codes in China.

  4. An implicit scheme with memory reduction technique for steady state solutions of DVBE in all flow regimes

    Science.gov (United States)

    Yang, L. M.; Shu, C.; Yang, W. M.; Wu, J.

    2018-04-01

    High consumption of memory and computational effort is the major barrier to prevent the widespread use of the discrete velocity method (DVM) in the simulation of flows in all flow regimes. To overcome this drawback, an implicit DVM with a memory reduction technique for solving a steady discrete velocity Boltzmann equation (DVBE) is presented in this work. In the method, the distribution functions in the whole discrete velocity space do not need to be stored, and they are calculated from the macroscopic flow variables. As a result, its memory requirement is in the same order as the conventional Euler/Navier-Stokes solver. In the meantime, it is more efficient than the explicit DVM for the simulation of various flows. To make the method efficient for solving flow problems in all flow regimes, a prediction step is introduced to estimate the local equilibrium state of the DVBE. In the prediction step, the distribution function at the cell interface is calculated by the local solution of DVBE. For the flow simulation, when the cell size is less than the mean free path, the prediction step has almost no effect on the solution. However, when the cell size is much larger than the mean free path, the prediction step dominates the solution so as to provide reasonable results in such a flow regime. In addition, to further improve the computational efficiency of the developed scheme in the continuum flow regime, the implicit technique is also introduced into the prediction step. Numerical results showed that the proposed implicit scheme can provide reasonable results in all flow regimes and increase significantly the computational efficiency in the continuum flow regime as compared with the existing DVM solvers.

  5. I-V curves of Y-Ba-Cu-O microbridges in the flux flow regime

    International Nuclear Information System (INIS)

    Kalisky, B.; Wolfus, Y.; Yeshurun, Y.; Koren, G.; Huebener, R.P.

    2004-01-01

    We report on measurements of I-V curves in microbridges of thin Y-Ba-Cu-O films of different thickness, in the presence of external magnetic fields up to 6 T. A discontinuity is observed at a critical voltage, V*, in the flux flow regime, reflecting an electronic instability, as predicted by Larkin and Ovchinnikov (LO), and in agreement with results reported by Doettinger et al. [Phys. Rev. Let. 73 (1994) 1691]. The critical voltage, V*, and the flux flow resistance, R 0 , in the limit V→0, are calculated by fitting the data to the LO model. We find that the vortex critical velocity, v*, at the instability, derived from V*, decreases with magnetic field and film thickness. These results, not predicted by the LO theory, reflect the dependence of the (spatially averaged) quasiparticle energy relaxation rate on magnetic field and film thickness

  6. Characterisation of two-phase horizontal flow regime transition by the application of time-frequency analysis methods

    International Nuclear Information System (INIS)

    Seleghim, Paulo

    1996-01-01

    This work concerns the development of a methodology which objective is to characterize and diagnose two-phase flow regime transitions. The approach is based on the fundamental assumption that a transition flow is less stationary than a flow with an established regime. In a first time, the efforts focused on: 1) the design and construction of an experimental loop, allowing to reproduce the main horizontal two-phase flow patterns, in a stable and controlled way, 2) the design and construction of an electrical impedance probe, providing an imaged information of the spatial phase distribution in the pipe, the systematic study of the joint time-frequency and time-scale analysis methods, which permitted to define an adequate parameter quantifying the un-stationary degree. In a second time, in order to verify the fundamental assumption, a series of experiments were conducted, which objective was to demonstrate the correlation between un-stationary and regime transition. The un-stationary degree was quantified by calculating the Gabor's transform time-frequency covariance of the impedance probe signals. Furthermore, the phenomenology of each transition was characterized by the joint moments and entropy. The results clearly show that the regime transitions are correlated with local-time frequency covariance peaks, which demonstrates that these regime transitions are characterized by a loss of stationarity. Consequently, the time-frequency covariance constitutes an objective two-phase flow regime transition indicator. (author) [fr

  7. Dynamics of Bubbly-magma Flow in Conduits: Stress and Expansion Regimes of Magma Fragmentation

    Science.gov (United States)

    Mitani, N. K.; Koyaguchi, T.; Ida, Y.

    2002-12-01

    Explosive volcanic eruptions are characterized by magma fragmentation, that is, the process through which a bubbly magma is changed into a gas-pyroclast dispersion. Two criteria of mechanisms have been proposed for the magma fragmentation so far. First, magma fragments when stress or strain rate of magma around bubbles exceeds a critical value. Second, magma disrupts due to the instability of thin magma-foam. Which criterion is actually applicable is not yet known. In order to clarify the physics of the magma fragmentation, we numerically study one-dimensional steady flows with bubble growth in conduits. The spherical cell model is used to calculate expansion of bubbles in ascending visco-elastic magma. The stress around bubbles generally grows as magma ascends and the pressure difference between bubbles and surrounding magma increases. In some conditions, the stress becomes critically large only when the flow velocity approaches the sound speed meeting the choking condition. In other conditions, the stress becomes large enough as magma pressure drops with bubble pressure kept almost unchanged. These two distinct types may correspond to the above two criteria of fragmentation mechanisms. In the former case, void fraction becomes close to unity before the stress reaches the strength of magma. In such case, the magma does not fragment due to the visco-elastic deformations but fragments by the instability of the thin magma-foam (`expansion' regime). In the latter case, on the other hand, the stress reaches the magma strength at much lower void fractions. In such case, the magma fragments due to the visco-elastic deformation around bubbles (`stress' regime). The `expansion' and `stress' regimes occur when the ratio of the initial wall-friction stress to the magma strength is sufficiently smaller and greater than unity, respectively.

  8. The impact of interpreted flow regimes during constant head injection tests on the estimated transmissivity from injection tests and difference flow logging

    Energy Technology Data Exchange (ETDEWEB)

    Hjerne, Calle; Ludvigsson, Jan-Erik; Harrstroem, Johan [Geosigma AB, Uppsala (Sweden)

    2013-04-15

    A large number of constant head injection tests were carried out in the site investigation at Forsmark using the Pipe String System, PSS3. During the original evaluation of the tests the dominating transient flow regimes during both the injection and recovery period were interpreted together with estimation of hydraulic parameters. The flow regimes represent different flow and boundary conditions during the tests. Different boreholes or borehole intervals may display different distributions of flow regimes. In some boreholes good agreement was obtained between the results of the injection tests and difference flow logging with Posiva flow log (PFL) but in other boreholes significant discrepancies were found. The main objective of this project is to study the correlation between transient flow regimes from the injection tests and other borehole features such as transmissivity, depth, geology, fracturing etc. Another subject studied is whether observed discrepancies between estimated transmissivity from difference flow logging and injection tests can be correlated to interpreted flow regimes. Finally, a detailed comparison between transient and stationary evaluation of transmissivity from the injection tests in relation to estimated transmissivity from PFL tests in corresponding sections is made. Results from previous injection tests in 5 m sections in boreholes KFM04, KFM08A and KFM10A were used. Only injection tests above the (test-specific) measurement limit regarding flow rate are included in the analyses. For all of these tests transient flow regimes were interpreted. In addition, results from difference flow logging in the corresponding 5 m test sections were used. Finally, geological data of fractures together with rock and fracture zone properties have been used in the correlations. Flow regimes interpreted from the injection period of the tests are generally used in the correlations but deviations between the interpreted flow regimes from the injection and

  9. The impact of interpreted flow regimes during constant head injection tests on the estimated transmissivity from injection tests and difference flow logging

    International Nuclear Information System (INIS)

    Hjerne, Calle; Ludvigsson, Jan-Erik; Harrstroem, Johan

    2013-04-01

    A large number of constant head injection tests were carried out in the site investigation at Forsmark using the Pipe String System, PSS3. During the original evaluation of the tests the dominating transient flow regimes during both the injection and recovery period were interpreted together with estimation of hydraulic parameters. The flow regimes represent different flow and boundary conditions during the tests. Different boreholes or borehole intervals may display different distributions of flow regimes. In some boreholes good agreement was obtained between the results of the injection tests and difference flow logging with Posiva flow log (PFL) but in other boreholes significant discrepancies were found. The main objective of this project is to study the correlation between transient flow regimes from the injection tests and other borehole features such as transmissivity, depth, geology, fracturing etc. Another subject studied is whether observed discrepancies between estimated transmissivity from difference flow logging and injection tests can be correlated to interpreted flow regimes. Finally, a detailed comparison between transient and stationary evaluation of transmissivity from the injection tests in relation to estimated transmissivity from PFL tests in corresponding sections is made. Results from previous injection tests in 5 m sections in boreholes KFM04, KFM08A and KFM10A were used. Only injection tests above the (test-specific) measurement limit regarding flow rate are included in the analyses. For all of these tests transient flow regimes were interpreted. In addition, results from difference flow logging in the corresponding 5 m test sections were used. Finally, geological data of fractures together with rock and fracture zone properties have been used in the correlations. Flow regimes interpreted from the injection period of the tests are generally used in the correlations but deviations between the interpreted flow regimes from the injection and

  10. Modeling the evolution of riparian woodlands facing climate change in three European rivers with contrasting flow regimes.

    Directory of Open Access Journals (Sweden)

    Rui P Rivaes

    Full Text Available Global circulation models forecasts indicate a future temperature and rainfall pattern modification worldwide. Such phenomena will become particularly evident in Europe where climate modifications could be more severe than the average change at the global level. As such, river flow regimes are expected to change, with resultant impacts on aquatic and riparian ecosystems. Riparian woodlands are among the most endangered ecosystems on earth and provide vital services to interconnected ecosystems and human societies. However, they have not been the object of many studies designed to spatially and temporally quantify how these ecosystems will react to climate change-induced flow regimes. Our goal was to assess the effects of climate-changed flow regimes on the existing riparian vegetation of three different European flow regimes. Cases studies were selected in the light of the most common watershed alimentation modes occurring across European regions, with the objective of appraising expected alterations in the riparian elements of fluvial systems due to climate change. Riparian vegetation modeling was performed using the CASiMiR-vegetation model, which bases its computation on the fluvial disturbance of the riparian patch mosaic. Modeling results show that riparian woodlands may undergo not only at least moderate changes for all flow regimes, but also some dramatic adjustments in specific areas of particular vegetation development stages. There are circumstances in which complete annihilation is feasible. Pluvial flow regimes, like the ones in southern European rivers, are those likely to experience more pronounced changes. Furthermore, regardless of the flow regime, younger and more water-dependent individuals are expected to be the most affected by climate change.

  11. Modeling the evolution of riparian woodlands facing climate change in three European rivers with contrasting flow regimes.

    Science.gov (United States)

    Rivaes, Rui P; Rodríguez-González, Patricia M; Ferreira, Maria Teresa; Pinheiro, António N; Politti, Emilio; Egger, Gregory; García-Arias, Alicia; Francés, Felix

    2014-01-01

    Global circulation models forecasts indicate a future temperature and rainfall pattern modification worldwide. Such phenomena will become particularly evident in Europe where climate modifications could be more severe than the average change at the global level. As such, river flow regimes are expected to change, with resultant impacts on aquatic and riparian ecosystems. Riparian woodlands are among the most endangered ecosystems on earth and provide vital services to interconnected ecosystems and human societies. However, they have not been the object of many studies designed to spatially and temporally quantify how these ecosystems will react to climate change-induced flow regimes. Our goal was to assess the effects of climate-changed flow regimes on the existing riparian vegetation of three different European flow regimes. Cases studies were selected in the light of the most common watershed alimentation modes occurring across European regions, with the objective of appraising expected alterations in the riparian elements of fluvial systems due to climate change. Riparian vegetation modeling was performed using the CASiMiR-vegetation model, which bases its computation on the fluvial disturbance of the riparian patch mosaic. Modeling results show that riparian woodlands may undergo not only at least moderate changes for all flow regimes, but also some dramatic adjustments in specific areas of particular vegetation development stages. There are circumstances in which complete annihilation is feasible. Pluvial flow regimes, like the ones in southern European rivers, are those likely to experience more pronounced changes. Furthermore, regardless of the flow regime, younger and more water-dependent individuals are expected to be the most affected by climate change.

  12. Evaluation of Spatial Pattern of Altered Flow Regimes on a River Network Using a Distributed Hydrological Model.

    Science.gov (United States)

    Ryo, Masahiro; Iwasaki, Yuichi; Yoshimura, Chihiro; Saavedra V, Oliver C

    2015-01-01

    Alteration of the spatial variability of natural flow regimes has been less studied than that of the temporal variability, despite its ecological importance for river ecosystems. Here, we aimed to quantify the spatial patterns of flow regime alterations along a river network in the Sagami River, Japan, by estimating river discharge under natural and altered flow conditions. We used a distributed hydrological model, which simulates hydrological processes spatiotemporally, to estimate 20-year daily river discharge along the river network. Then, 33 hydrologic indices (i.e., Indicators of Hydrologic Alteration) were calculated from the simulated discharge to estimate the spatial patterns of their alterations. Some hydrologic indices were relatively well estimated such as the magnitude and timing of maximum flows, monthly median flows, and the frequency of low and high flow pulses. The accuracy was evaluated with correlation analysis (r > 0.4) and the Kolmogorov-Smirnov test (α = 0.05) by comparing these indices calculated from both observed and simulated discharge. The spatial patterns of the flow regime alterations varied depending on the hydrologic indices. For example, both the median flow in August and the frequency of high flow pulses were reduced by the maximum of approximately 70%, but these strongest alterations were detected at different locations (i.e., on the mainstream and the tributary, respectively). These results are likely caused by different operational purposes of multiple water control facilities. The results imply that the evaluation only at discharge gauges is insufficient to capture the alteration of the flow regime. Our findings clearly emphasize the importance of evaluating the spatial pattern of flow regime alteration on a river network where its discharge is affected by multiple water control facilities.

  13. Evaluation of Spatial Pattern of Altered Flow Regimes on a River Network Using a Distributed Hydrological Model

    Science.gov (United States)

    Ryo, Masahiro; Iwasaki, Yuichi; Yoshimura, Chihiro; Saavedra V., Oliver C.

    2015-01-01

    Alteration of the spatial variability of natural flow regimes has been less studied than that of the temporal variability, despite its ecological importance for river ecosystems. Here, we aimed to quantify the spatial patterns of flow regime alterations along a river network in the Sagami River, Japan, by estimating river discharge under natural and altered flow conditions. We used a distributed hydrological model, which simulates hydrological processes spatiotemporally, to estimate 20-year daily river discharge along the river network. Then, 33 hydrologic indices (i.e., Indicators of Hydrologic Alteration) were calculated from the simulated discharge to estimate the spatial patterns of their alterations. Some hydrologic indices were relatively well estimated such as the magnitude and timing of maximum flows, monthly median flows, and the frequency of low and high flow pulses. The accuracy was evaluated with correlation analysis (r > 0.4) and the Kolmogorov–Smirnov test (α = 0.05) by comparing these indices calculated from both observed and simulated discharge. The spatial patterns of the flow regime alterations varied depending on the hydrologic indices. For example, both the median flow in August and the frequency of high flow pulses were reduced by the maximum of approximately 70%, but these strongest alterations were detected at different locations (i.e., on the mainstream and the tributary, respectively). These results are likely caused by different operational purposes of multiple water control facilities. The results imply that the evaluation only at discharge gauges is insufficient to capture the alteration of the flow regime. Our findings clearly emphasize the importance of evaluating the spatial pattern of flow regime alteration on a river network where its discharge is affected by multiple water control facilities. PMID:26207997

  14. Can water sensitive urban design systems help to preserve natural channel-forming flow regimes in an urbanised catchment?

    Science.gov (United States)

    Wella-Hewage, Chathurika Subhashini; Alankarage Hewa, Guna; Pezzaniti, David

    2016-01-01

    Increased stormwater runoff and pollutant loads due to catchment urbanisation bring inevitable impacts on the physical and ecological conditions of environmentally sensitive urban streams. Water sensitive urban design (WSUD) has been recognised as a possible means to minimise these negative impacts. This paper reports on a study that investigated the ability of infiltration-based WSUD systems to replicate the predevelopment channel-forming flow (CFF) regime in urban catchments. Catchment models were developed for the 'pre-urban', 'urban' and 'managed' conditions of a case study catchment and the hydrological effect on CFF regime was investigated using a number of flow indices. The results clearly show that changes to flow regime are apparent under urban catchment conditions and are even more severe under highly urbanised conditions. The use of WSUD systems was found to result in the replication of predevelopment flow regimes, particularly at low levels of urbanisation. Under highly urbanised conditions (of managed catchments) overcontrol of the CFF indices was observed as indicated by flow statistics below their pre-urban values. The overall results suggest that WSUD systems are highly effective in replicating the predevelopment CFF regime in urban streams and could be used as a means to protect environmentally sensitive urban streams.

  15. Intermediate regime and a phase diagram of red blood cell dynamics in a linear flow

    Science.gov (United States)

    Levant, Michael; Steinberg, Victor

    2016-12-01

    In this paper we investigate the in vitro dynamics of a single rabbit red blood cell (RBC) in a planar linear flow as a function of a shear stress σ and the dynamic viscosity of outer fluid ηo. A linear flow is a generalization of previous studies dynamics of soft objects including RBC in shear flow and is realized in the experiment in a microfluidic four-roll mill device. We verify that the RBC stable orientation dynamics is found in the experiment being the in-shear-plane orientation and the RBC dynamics is characterized by observed three RBC dynamical states, namely tumbling (TU), intermediate (INT), and swinging (SW) [or tank-treading (TT)] on a single RBC. The main results of these studies are the following. (i) We completely characterize the RBC dynamical states and reconstruct their phase diagram in the case of the RBC in-shear-plane orientation in a planar linear flow and find it in a good agreement with that obtained in early experiments in a shear flow for human RBCs. (ii) The value of the critical shear stress σc of the TU-TT(SW) transition surprisingly coincides with that found in early experiments in spite of a significant difference in the degree of RBC shape deformations in both the SW and INT states. (iii) We describe the INT regime, which is stationary, characterized by strong RBC shape deformations and observed in a wide range of the shear stresses. We argue that our observations cast doubts on the main claim of the recent numerical simulations that the only RBC spheroidal stress-free shape is capable to explain the early experimental data. Finally, we suggest that the amplitude dependence of both θ and the shape deformation parameter D on σ can be used as the quantitative criterion to determine the RBC stress-free shape.

  16. Ecohydrological modeling and environmental flow regime in the Formoso River, Minas Gerais State, Brazil.

    Science.gov (United States)

    Guedes, Hugo A S; Silva, Demetrius D; Dergam, Jorge A; Elesbon, Abrahão A A

    2016-01-01

    This paper aimed at determining the environmental flow regime in a 1 km stretch of the Formoso River, MG, using River2D model. To carry out the ecohydrological modeling, the following information was used: bathymetry, physical and hydraulic features, and the Habitat Suitability Index for species of the Hypostomus auroguttatus. In the River2D, the Weighted Usable Areas were determined from the average long-term streamflows with percentage from 10% to 100%. Those streamflows were simulated for the later construction of optimization matrices that maximize the habitat area throughout the year. For H. auroguttatus Juvenile, higher values of Weighted Usable Area were associated with the percentage of 60% and 70% of the average long-term streamflows in October and September, respectively. For H. auroguttatus Adult, the highest value of Weighted Usable Area was associated with the percentage of 100% of the average long-term streamflow in September. The environmental flows found for this stretch of the Formoso River varied over the year. The lowest environmental flow was observed in December (2.85 m3 s-1), while the highest was observed in May (4.13 m3 s-1). This paper shows the importance of ecohydrological studies in forming a basis for water resources management actions.

  17. Ecohydrological modeling and environmental flow regime in the Formoso River, Minas Gerais State, Brazil

    Directory of Open Access Journals (Sweden)

    HUGO A. S. GUEDES

    Full Text Available ABSTRACT This paper aimed at determining the environmental flow regime in a 1 km stretch of the Formoso River, MG, using River2D model. To carry out the ecohydrological modeling, the following information was used: bathymetry, physical and hydraulic features, and the Habitat Suitability Index for species of the Hypostomus auroguttatus. In the River2D, the Weighted Usable Areas were determined from the average long-term streamflows with percentage from 10% to 100%. Those streamflows were simulated for the later construction of optimization matrices that maximize the habitat area throughout the year. For H. auroguttatus Juvenile, higher values of Weighted Usable Area were associated with the percentage of 60% and 70% of the average long-term streamflows in October and September, respectively. For H. auroguttatus Adult, the highest value of Weighted Usable Area was associated with the percentage of 100% of the average long-term streamflow in September. The environmental flows found for this stretch of the Formoso River varied over the year. The lowest environmental flow was observed in December (2.85 m3 s-1, while the highest was observed in May (4.13 m3 s-1. This paper shows the importance of ecohydrological studies in forming a basis for water resources management actions.

  18. Modeling the relations between flow regime components, species traits, and spawning success of fishes in warmwater streams

    Science.gov (United States)

    Craven, S.W.; Peterson, J.T.; Freeman, Mary C.; Kwak, T.J.; Irwin, E.

    2010-01-01

    Modifications to stream hydrologic regimes can have a profound influence on the dynamics of their fish populations. Using hierarchical linear models, we examined the relations between flow regime and young-of-year fish density using fish sampling and discharge data from three different warmwater streams in Illinois, Alabama, and Georgia. We used an information theoretic approach to evaluate the relative support for models describing hypothesized influences of five flow regime components representing: short-term high and low flows; short-term flow stability; and long-term mean flows and flow stability on fish reproductive success during fish spawning and rearing periods. We also evaluated the influence of ten fish species traits on fish reproductive success. Species traits included spawning duration, reproductive strategy, egg incubation rate, swimming locomotion morphology, general habitat preference, and food habits. Model selection results indicated that young-of-year fish density was positively related to short-term high flows during the spawning period and negatively related to flow variability during the rearing period. However, the effect of the flow regime components varied substantially among species, but was related to species traits. The effect of short-term high flows on the reproductive success was lower for species that broadcast their eggs during spawning. Species with cruiser swimming locomotion morphologies (e.g., Micropterus) also were more vulnerable to variable flows during the rearing period. Our models provide insight into the conditions and timing of flows that influence the reproductive success of warmwater stream fishes and may guide decisions related to stream regulation and management. ?? 2010 US Government.

  19. Monitoring strategies of stream phosphorus under contrasting climate-driven flow regimes

    DEFF Research Database (Denmark)

    Goyenola, Guillermo; Meerhoff, Marianna; Teixeira-de Mello, Franco

    2015-01-01

    Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of phosphorus (P) from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns and the pe...... relevant in currently flashy systems and also in systems where climate change predictions suggest an increase in stream flashiness.......Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of phosphorus (P) from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns...... and the performance of alternative monitoring strategies in streams under contrasting climate-driven flow regimes. We compared a set of paired streams draining lowland micro-catchments under temperate climate and stable discharge conditions (Denmark) and under sub-tropical climate and flashy conditions (Uruguay). We...

  20. Residence times and alluvial architecture of a sediment superslug in response to different flow regimes

    Science.gov (United States)

    Moody, John A.

    2017-10-01

    A superslug was deposited in a basin in the Colorado Front Range Mountains as a consequence of an extreme flood following a wildfire disturbance in 1996. The subsequent evolution of this superslug was measured by repeat topographic surveys (31 surveys from 1996 through 2014) of 18 cross sections approximately uniformly spaced over 1500 m immediately above the basin outlet. These surveys allowed the identification within the superslug of chronostratigraphic units deposited and eroded by different geomorphic processes in response to different flow regimes. Over the time period of the study, the superslug went through aggradation, incision, and stabilization phases that were controlled by a shift in geomorphic processes from generally short-duration, episodic, large-magnitude floods that deposited new chronostratigraphic units to long-duration processes that eroded units. These phases were not contemporaneous at each channel cross section, which resulted in a complex response that preserved different chronostratigraphic units at each channel cross section having, in general, two dominant types of alluvial architecture-laminar and fragmented. Age and transit-time distributions for these two alluvial architectures evolved with time since the extreme flood. Because of the complex shape of the distributions they were best modeled by two-parameter Weibull functions. The Weibull scale parameter approximated the median age of the distributions, and the Weibull shape parameter generally had a linear relation that increased with time since the extreme flood. Additional results indicated that deposition of new chronostratigraphic units can be represented by a power-law frequency distribution, and that the erosion of units decreases with depth of burial to a limiting depth. These relations can be used to model other situations with different flow regimes where vertical aggradation and incision are dominant processes, to predict the residence time of possible contaminated

  1. Estimating Nitrogen Loss across Varying Flow Regimes in a Southeastern Floodplain Using a Multidimensional Ecohydraulic Model

    Science.gov (United States)

    Jones, C.; Scott, D.; Noe, G. B.; Harvey, J. W.

    2011-12-01

    Excess nitrogen (N) flux from the landscape to riverine systems has led to the degradation of many downstream water bodies. Hypoxic zones in both the Gulf of Mexico and Chesapeake Bay can be attributed to the increase in anthropogenic N sources during the last century. Typically, the majority of N flux occurs during flood events. Floodplains act as buffers during these periods of inundation, providing critical ecosystem services such as flood peak attenuation, depositional zones for the removal of sediments and contaminants, and biological hotspots for nutrient transformation. Specifically, regions of overbank inundation and backwater promote steep redox gradients at the sediment-water interface, leading to N removal through denitrification. In many Southeastern floodplains, it appears that this process is limited by the amount of N transported into hydraulically connected regions, making the duration of the hydroperiod (i.e. residence time) the driving force behind N removal. Therefore, in the face of a changing climate, it is imperative that we explore the relationships between changes in flow regime and nutrient retention/removal in our floodplains. In this study, these processes are examined within a Southeastern floodplain using a dynamically linked 1D-2D hydrodynamic model. A 12 km reach of the Tangipahoa River, located in Southeastern Louisiana, was selected for this study. Channel and floodplain bathymetry was developed using a combination of surveyed data and high resolution LIDAR while the boundary conditions were established using stream gauges at the inlet/outlet of the reach. Floodplain stage was recorded at multiple locations and was used to validate model results. Nitrogen removal/retention was modeled using the simplified assumption of a first order decay mechanism. Results from this model were used to correlate changes in flow regime (i.e. flood frequency and duration) to nitrogen removal.

  2. Computational thermal-fluid dynamics analysis of the laminar flow regime in the meander flow geometry characterizing the heat exchanger used in high temperature superconducting current leads

    International Nuclear Information System (INIS)

    Rizzo, Enrico; Heller, Reinhard; Richard, Laura Savoldi; Zanino, Roberto

    2013-01-01

    Highlights: • The laminar regime in the meander flow geometry has been analysed with a previously validated computational strategy. • Several meander flow geometries as well as flow conditions have been analysed. • A range for the Reynolds number has been defined in which the flow can be considered laminar. • Correlations for the pressure drop and the heat transfer coefficients in the laminar regime have been derived. • A comparison between the computed the experimental pressure drop of the W7-X HTS current lead prototype is presented. -- Abstract: The Karlsruhe Institute of Technology and the Politecnico di Torino have developed and validated a computational thermal-fluid dynamics (CtFD) strategy for the systematic analysis of the thermal-hydraulics inside the meander flow heat exchanger used in high-temperature superconducting current leads for fusion applications. In the recent past, the application of this CtFD technique has shown that some operating conditions occurring in these devices may not reach the turbulent regime region. With that motivation, the CtFD analysis of the helium thermal-fluid dynamics inside different meander flow geometries is extended here to the laminar flow regime. Our first aim is to clarify under which operative conditions the flow regime can be considered laminar and how the pressure drop as well as the heat transfer are related to the geometrical parameters and to the flow conditions. From the results of this analysis, correlations for the pressure drop and for the heat transfer coefficient in the meander flow geometry have been derived, which are applicable with good accuracy to the design of meander flow heat exchangers over a broad range of geometrical parameters

  3. NAO influence on precipitation, river flow regimes and hydroelectric power generation in the Iberian Peninsula

    Science.gov (United States)

    Trigo, R. M.; Pozo-Vazquez, D.; Castro-Diez, Y.; Osborn, T.; Gámis-Fortis, S.; Esteban-Parra, M. J.

    2003-04-01

    The Iberian Peninsula area is characterised by large values of inter-annual variability of precipitation. As a consequence river flow is also characterised by large disparities between wet and dry years, especially in southern Iberia. This situation portrays a major problem in water resources management in general, and production of hydroelectricity in particular. In Portugal the hydroelectric production represents (on an average year of precipitation) one third of the total Portuguese electricity production but its absolute value can vary by a factor of almost three between wet (16 TWh) and dry (6 TWh) years. Similarly the Spanish hydroelectric production accounts, on average, for 20% of total Spanish production, however the actual production presents a wide range of values, varying between wet (40 TWh) and dry (20 TWh) years. The possibility of establishing strong relationship between river flow and relatively simple large-scale atmospheric circulation indices is very attractive. Only recently it has been recognised that the strong control exerted by the NAO on precipitation over the Mediterranean basin could be directly reflected on the seasonal flow of rivers across the region. In this work, we have assessed the impact of the NAO in winter river flow regimes for the three main international Iberian rivers, namely the Douro (north), the Tagus (centre) and the Guadiana (south). Throughout most of the 20th century, the winter JFM river flow is better related with one month lagged (DJF) NAO index than with the simultaneous (JFM) NAO index. Correlation values for the period 1973-1998 are impressive; -0.76 for Douro, -0.77 for Tejo and -0.79 for Guadiana, being consistently of higher magnitude than those obtained for previous decades. The increase in the magnitude of the correlation since the 1970s is related with the observed higher impact of the NAO on the region's precipitation, but it might be also related with the increase in water storage volume obtained with

  4. Insights into the Sensitivity and Resilience of Riparian Ecosystems to Flow Regime Shifts Through a Coupled Ecogeomorpic Model

    Science.gov (United States)

    Diehl, R. M.; Wilcox, A. C.; Merritt, D. M.

    2017-12-01

    Management of river systems relies on an understanding of the relationship between flow and ecosystem properties. Flow response curves formalize this relationship by empirically linking the form and/or function of the biota or physical template of a river system to a change in flow properties. To gain insight into the coupled nature of riparian ecosystems, and make predictions about their response to a change in discharge, we built an ecogeomorphic model from a series of flow response curves based on data collected on the Yampa and Green Rivers, Colorado and Utah. These curves relate attributes of the flow regime to the 1) presence/absence of groupings of functionally similar plants (riparian response guilds), 2) plant cover density, and 3) plot-scale topographic response to a single flood event. Our model successfully identifies the spatial distribution of suitable plant guild habitat and has moderate success predicting the magnitude and direction of the geomorphic response to flood events. The shape of the resulting response curves are non-linear and exhibit clear thresholds. These features suggest that ecogeomorphic processes that shape riparian communities are at times highly sensitive, and at other times highly resilient, to the magnitude and direction of shifts in the flow regime. We explore this observation by comparing the trajectory of riparian ecosystem adjustment for three future flow scenarios in the Yampa River. The six plant guilds we model all show sensitivity to shifts in some part of the flow regime, and resilience to others. Erosional and depositional patterns respond in part to the shifts in guild distributions, but also in part in response to changes in flow hydraulics. Use of guilds in our model facilitates generalization across large environmental gradients and across systems. The linkages among environmental conditions, riparian plant community dynamics, and morphodynamics represented in our ecogeomorphic model makes this approach a powerful

  5. Phosphorus mobilization in rewetted peat and sand at variable flow rate and redox regimes

    DEFF Research Database (Denmark)

    Kjærgaard, Charlotte; Heiberg, Lisa; Jensen, Henning S.

    2012-01-01

    the upward percolation of groundwater with variable O2 content and flow rate, we investigated the hydro-biogeochemical Fe and P dynamics in intact cores of a carbon rich peat and carbon poor sand. Percolation of deionized water with high, low or no O2 supply at 10 °C caused markedly different in situ redox...... is not exposed to reducing conditions, unless the soil is actually infiltrated by anoxic water, causing an increase in TP release rates from 5.8 (oxic) to 7.6 (anoxic) mg P m−2 day−1. Hydrology turned out as a major factor controlling TP release, as a four-fold increase in flow rate increased the P release rate...... regimes in the two soils during 21 or 67 days of continuous percolation at either 1 or 4 mm h−1. Anoxic conditions occurred in the peat soil at both low oxygen supply and anoxic infiltration, causing reductive Fe(III) dissolution with high Fe(II) and P effluent concentrations and total P (TP) release...

  6. Kolmogorov Complexity Based Information Measures Applied to the Analysis of Different River Flow Regimes

    Directory of Open Access Journals (Sweden)

    Dragutin T. Mihailović

    2015-05-01

    Full Text Available We have used the Kolmogorov complexities and the Kolmogorov complexity spectrum to quantify the randomness degree in river flow time series of seven rivers with different regimes in Bosnia and Herzegovina, representing their different type of courses, for the period 1965–1986. In particular, we have examined: (i the Neretva, Bosnia and the Drina (mountain and lowland parts, (ii the Miljacka and the Una (mountain part and the Vrbas and the Ukrina (lowland part and then calculated the Kolmogorov complexity (KC based on the Lempel–Ziv Algorithm (LZA (lower—KCL and upper—KCU, Kolmogorov complexity spectrum highest value (KCM and overall Kolmogorov complexity (KCO values for each time series. The results indicate that the KCL, KCU, KCM and KCO values in seven rivers show some similarities regardless of the amplitude differences in their monthly flow rates. The KCL, KCU and KCM complexities as information measures do not “see” a difference between time series which have different amplitude variations but similar random components. However, it seems that the KCO information measures better takes into account both the amplitude and the place of the components in a time series.

  7. Discharge Computation of Trapezoidal Side Weir in Subcritical Flow Regime Using Conventional Weir Theory

    Directory of Open Access Journals (Sweden)

    S. Riahi

    2016-02-01

    Full Text Available Introduction: Side weir structures are extensively used in hydraulic engineering, irrigation and environmental engineering, and it usually consists of a main weir and a lateral channel. Side weirs are also used as an emergency structure. This structure is installed on one side or both sides of the main channel to divert the flow from the main channel to the side channel. Lateral outflow takes place when the water surface in the main channel rises above the weir sill. Flow over a side weir is a typical case of spatially varied flow with decreasing discharge. There have been extensive studies on side weir overflows. Most of the previous theoretical analysis and experimental research works are related to the flow over rectangular side weirs in rectangular main channels. In the current study, the flow conditions over a trapezoidal side weir located in a rectangular main channel in subcritical flow regime is considered. Materials and Methods: The experiments were performed in a rectangular open channel having provisions for a side weir at one side of the channel. The main channel was horizontal with 12 m length, 0.25 m width, and 0.5 m height, and it was installed on a frame; lateral channel that has a length of 6 m, width of 0.25 m, and height of 1 m. It was set up parallel to the main channel; walls and its bed were made up of Plexiglas plates. The side weir was positioned at a distance of 6 m from the channel’s entrance. A total of 121 experiments on trapezoidal side weirs were carried out. Results and Discussion: For trapezoidal side weir, effective non-dimensionnal parameters were identified using dimensional analysis and Buckingham's Pi-Theorem. Finally, the following non-dimensional parameters were considered as the most effective ones on the discharge coefficient of the trapezoidal side weir flow. in which Fr1= upstream Froude number, P= hight of the trapezoidal side weir, y1= upstream water depth, z=side slope of the trapezoidal side weir

  8. Effects of flow regime and flooding on heavy metal availability in sediment and soil of a dynamic river system

    NARCIS (Netherlands)

    Poot, A.; Gillissen, F.; Koelmans, A.A.

    2007-01-01

    The acid volatile sulphide (AVS) and simultaneously extracted metals (¿SEM) method is increasingly used for risk assessment of toxic metals. In this study, we assessed spatial and temporal variations of AVS and ¿SEM in river sediments and floodplain soils, addressing influence of flow regime and

  9. Bubble Size Control to Improve Oxygen-Based Bleaching: Characterization of Flow Regimes in Pulp-Water-Gas Three-Phase Flows

    Energy Technology Data Exchange (ETDEWEB)

    S.M. Ghiaasiaan and Seppo Karrila

    2006-03-20

    Flow characteristics of fibrous paper pulp-water-air slurries were investigated in a vertical circular column 1.8 m long, with 5.08 cm diameter. Flow structures, gas holdup (void fraction), and the geometric and population characteristics of gas bubbles were experimentally investigated, using visual observation, Gamma-ray densitometry, and flash X-ray photography. Five distinct flow regimes could be visually identified: dispersed bubbly, layered bubbly, plug, churn-turbulent, and slug. Flow regime maps were constructed, and the regime transition lines were found to be sensitive to consistency. The feasibility of using artificial neural networks (ANNs) for the identification of the flow regimes, using the statistical characteristics of pressure fluctuations measured by a single pressure sensor, was demonstrated. Local pressure fluctuations at a station were recorded with a minimally-intrusive transducer. Three-layer, feed-forward ANNs were designed that could identify the four major flow patterns (bubbly, plug, churn, and slug) well. The feasibility of a transportable artificial neural network (ANN) - based technique for the classification of flow regimes was also examined. Local pressures were recorded at three different locations using three independent but similar transducers. An ANN was designed, trained and successfully tested for the classification of the flow regimes using one of the normalized pressure signals (from Sensor 1). The ANN trained and tested for Sensor 1 predicted the flow regimes reasonably well when applied directly to the other two sensors, indicating a good deal of transportability. An ANN-based method was also developed, whereby the power spectrum density characteristics of other sensors were adjusted before they were used as input to the ANN that was based on Sensor 1 alone. The method improved the predictions. The gas-liquid interfacial surface area concentration was also measured in the study. The gas absorption technique was applied

  10. A dry-spot model for the prediction of critical heat flux in water boiling in bubbly flow regime

    International Nuclear Information System (INIS)

    Ha, Sang Jun; No, Hee Cheon

    1997-01-01

    This paper presents a prediction of critical heat flux (CHF) in bubbly flow regime using dry-spot model proposed recently by authors for pool and flow boiling CHF and existing correlations for forced convective heat transfer coefficient, active site density and bubble departure diameter in nucleate boiling region. Without any empirical constants always present in earlier models, comparisons of the model predictions with experimental data for upward flow of water in vertical, uniformly-heated round tubes are performed and show a good agreement. The parametric trends of CHF have been explored with respect to variation in pressure, tube diameter and length, mass flux and inlet subcooling

  11. Fluctuating zonal flows in the I-mode regime in Alcator C-Moda)

    Science.gov (United States)

    Cziegler, I.; Diamond, P. H.; Fedorczak, N.; Manz, P.; Tynan, G. R.; Xu, M.; Churchill, R. M.; Hubbard, A. E.; Lipschultz, B.; Sierchio, J. M.; Terry, J. L.; Theiler, C.

    2013-05-01

    Velocity fields and density fluctuations of edge turbulence are studied in I-mode [F. Ryter et al., Plasma Phys. Controlled Fusion 40, 725 (1998)] plasmas of the Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] tokamak, which are characterized by a strong thermal transport barrier in the edge while providing little or no barrier to the transport of both bulk and impurity particles. Although previous work showed no clear geodesic-acoustic modes (GAM) on C-Mod, using a newly implemented, gas-puff-imaging based time-delay-estimate velocity inference algorithm, GAM are now shown to be ubiquitous in all I-mode discharges examined to date, with the time histories of the GAM and the I-mode specific [D. Whyte et al., Nucl. Fusion 50, 105005 (2010)] Weakly Coherent Mode (WCM, f = 100-300 kHz, Δf/f≈0.5, and kθ≈1.3 cm-1) closely following each other through the entire duration of the regime. Thus, the I-mode presents an example of a plasma state in which zero frequency zonal flows and GAM continuously coexist. Using two-field (density-velocity and radial-poloidal velocity) bispectral methods, the GAM are shown to be coupled to the WCM and to be responsible for its broad frequency structure. The effective nonlinear growth rate of the GAM is estimated, and its comparison to the collisional damping rate seems to suggest a new view on I-mode threshold physics.

  12. Evaluation of piping heat transfer, piping flow regimes, and steam generator heat transfer for the Semiscale Mod-1 isothermal tests

    International Nuclear Information System (INIS)

    French, R.T.

    1975-08-01

    Selected experimental data pertinent to piping heat transfer, transient fluid flow regimes, and steam generator heat transfer obtained during the Semiscale Mod-1 isothermal blowdown test series (Test Series 1) are analyzed. The tests in this first test series were designed to provide counterparts to the LOFT nonnuclear experiments. The data from the Semiscale Mod-1 intact and broken loop piping are evaluated to determine the surface heat flux and average heat transfer coefficients effective during the blowdown transient and compared with well known heat transfer correlations used in the RELAP4 computer program. Flow regimes in horizontal pipe sections are calculated and compared with data obtained from horizontal and vertical densitometers and with an existing steady state flow map. Effects of steam generator heat transfer are evaluated quantitatively and qualitatively. The Semiscale Mod-1 data and the analysis presented in this report are valuable for evaluating the adequacy and improving the predictive capability of analytical models developed to predict system response to piping heat transfer, piping flow regimes, and steam generator heat transfer during a postulated loss-of-coolant accident (LOCA) in a pressurized water reactor (PWR). 16 references. (auth)

  13. Place, Capital Flows and Property Regimes: The Elites’ Former Houses in Beijing’s South Luogu Lane

    Directory of Open Access Journals (Sweden)

    Zhifen Cheng

    2014-12-01

    Full Text Available Place is seen as a process whereby social and cultural forms are reproduced. This process is closely linked to capital flows, which are, in turn, shaped by changing property regimes. However, relatively little attention has been paid to the relationship between property regimes, capital flows and place-making. The goal of this paper is to highlight the role of changing property regimes in the production of place. Our research area is South Luogu Lane (SLL in Central Beijing. We take elites’ former houses in SLL as the main unit of analysis in this study. From studying this changing landscape, we draw four main conclusions. First, the location of SSL was critical in enabling it to emerge as a high-status residential community near the imperial city. Second, historical patterns of capital accumulation influenced subsequent rounds of private investment into particular areas of SLL. Third, as laws relating to the ownership of land and real estate changed fundamentally in the early 1950s and again in the 1980s, the target and intensity of capital flows into housing in SLL changed too. Fourth, these changes in capital flow are linked to ongoing changes in the place image of SLL.

  14. What Do They Have in Common? Drivers of Streamflow Spatial Correlation and Prediction of Flow Regimes in Ungauged Locations

    Science.gov (United States)

    Betterle, A.; Radny, D.; Schirmer, M.; Botter, G.

    2017-12-01

    The spatial correlation of daily streamflows represents a statistical index encapsulating the similarity between hydrographs at two arbitrary catchment outlets. In this work, a process-based analytical framework is utilized to investigate the hydrological drivers of streamflow spatial correlation through an extensive application to 78 pairs of stream gauges belonging to 13 unregulated catchments in the eastern United States. The analysis provides insight on how the observed heterogeneity of the physical processes that control flow dynamics ultimately affect streamflow correlation and spatial patterns of flow regimes. Despite the variability of recession properties across the study catchments, the impact of heterogeneous drainage rates on the streamflow spatial correlation is overwhelmed by the spatial variability of frequency and intensity of effective rainfall events. Overall, model performances are satisfactory, with root mean square errors between modeled and observed streamflow spatial correlation below 10% in most cases. We also propose a method for estimating streamflow correlation in the absence of discharge data, which proves useful to predict streamflow regimes in ungauged areas. The method consists in setting a minimum threshold on the modeled flow correlation to individuate hydrologically similar sites. Catchment outlets that are most correlated (ρ>0.9) are found to be characterized by analogous streamflow distributions across a broad range of flow regimes.

  15. Scaling relation and regime map of explosive gas–liquid flow of binary Lennard-Jones particle system

    KAUST Repository

    Inaoka, Hajime

    2012-02-01

    We study explosive gasliquid flows caused by rapid depressurization using a molecular dynamics model of Lennard-Jones particle systems. A unique feature of our model is that it consists of two types of particles: liquid particles, which tend to form liquid droplets, and gas particles, which remain supercritical gaseous states under the depressurization realized by simulations. The system has a pipe-like structure similar to the model of a shock tube. We observed physical quantities and flow regimes in systems with various combinations of initial particle number densities and initial temperatures. It is observed that a physical quantity Q, such as pressure, at position z measured along a pipe-like system at time t follows a scaling relation Q(z,t)=Q(zt) with a scaling function Q(ζ). A similar scaling relation holds for time evolution of flow regimes in a system. These scaling relations lead to a regime map of explosive flows in parameter spaces of local physical quantities. The validity of the scaling relations of physical quantities means that physics of equilibrium systems, such as an equation of state, is applicable to explosive flows in our simulations, though the explosive flows involve highly nonequilibrium processes. In other words, if the breaking of the scaling relations is observed, it means that the explosive flows cannot be fully described by physics of equilibrium systems. We show the possibility of breaking of the scaling relations and discuss its implications in the last section. © 2011 Elsevier B.V. All rights reserved.

  16. E × B flow shear drive of the linear low-n modes of EHO in the QH-mode regime [E × B flow shear drive of EHO in the QH-mode regime

    International Nuclear Information System (INIS)

    Xu, G. S.; Wan, B. N.; Wang, Y. F.

    2017-01-01

    A new mechanism is identified for driving the edge harmonic oscillations (EHOs) in the quiescent H-mode (QH-mode) regime, where a strong E × B flow shear destabilizes low-n kink/peeling modes, separately from the previously found Kelvin-Helmholtz drive. We find that the differential advection of mode vorticity by sheared E × B flows modifies the two-dimensional pattern of mode electrostatic potential perpendicular to the magnetic field lines, which in turn causes a radial expansion of the mode structure, an increase of field line bending away from the mode rational surface, and a reduction of inertial stabilization. This enhances the kink drive as the parallel wavenumber increases significantly away from the rational surface where the magnetic shear is also strong. A newly developed model reproduces the observations that at high E × B flow shear only a few low-n modes remain unstable, consistent with the EHO behavior, while at low E × B flow shear the unstable mode spectrum is significantly broadened, consistent with the low-n broadband electromagnetic turbulence behavior observed recently in the DIII-D tokamak. This destabilization is also shown to be independent of the sign of the flow shear, as observed experimentally, and has not been taken into 2 / 46 account in previous pedestal linear stability analyses. Verification of the veracity of this EHO mechanism will require analysis of the nonlinear evolution of low-n kink/peeling modes so destabilized in the linear regime.

  17. Application of radial basis function in densitometry of stratified regime of liquid-gas two phase flows

    International Nuclear Information System (INIS)

    Roshani, G.H.; Nazemi, E.; Roshani, M.M.

    2017-01-01

    In this paper, a novel method is proposed for predicting the density of liquid phase in stratified regime of liquid-gas two phase flows by utilizing dual modality densitometry technique and artificial neural network (ANN) model of radial basis function (RBF). The detection system includes a 137 Cs radioactive source and two NaI(Tl) detectors for registering transmitted and scattered photons. At the first step, a Monte Carlo simulation model was utilized to obtain the optimum position for the scattering detector in dual modality densitometry configuration. At the next step, an experimental setup was designed based on obtained optimum position for detectors from simulation in order to generate the required data for training and testing the ANN. The results show that the proposed approach could be successfully applied for predicting the density of liquid phase in stratified regime of gas-liquid two phase flows with mean relative error (MRE) of less than 0.701. - Highlights: • Density of liquid phase in stratified regime of two phase flows was predicted. • Combination of dual modality densitometry technique and ANN was utilized. • Detection system includes a 137 Cs radioactive source and two NaI(Tl) detectors. • MCNP simulation was done to obtain the optimum position for the scattering detector. • An experimental setup was designed to generate the required data for training the ANN.

  18. Heat and Mass Transfer Effect on MHD Flow of a Viscoelastic Fluid through a Porous Medium Bounded by an Oscillating Porous Plate in Slip Flow Regime

    Directory of Open Access Journals (Sweden)

    S. N. Sahoo

    2013-01-01

    Full Text Available Unsteady flow of an eclectically conducting and incompressible viscoelastic liquid of the Walter model with simultaneous heat and mass transfer near an oscillating porous plate in slip flow regime under the influence of a transverse magnetic field of uniform strength is presented. The governing equations of the flow field are solved by a regular perturbation method for small elastic parameter, and the expressions for the velocity, temperature, concentration, skin friction , the heat flux in terms of the Nusselt number , and the rate of mass transfer in terms of the Sherwood number are obtained. The effects of the important flow parameters on the dynamics are discussed. Findings of the study reveal that the rarefaction parameter accelerates the fluid particles in the flow domain. Elastic parameter contributes to sudden fall of the velocity near the plate. Magnetic force contributes to greater skin friction as the time elapses. Destructive reaction reduces, whereas generative reaction enhances the concentration distribution.

  19. Effect of sampling regime on estimation of basal metabolic rate and standard evaporative water loss using flow-through respirometry.

    Science.gov (United States)

    Cooper, C E; Withers, P C

    2010-01-01

    Strict criteria have been established for measurement of basal metabolic rate and standard evaporative water loss to ensure that data can be compared intra- and interspecifically. However, data-sampling regimes vary, from essentially continuous sampling to interrupted (switching) systems with data recorded periodically at more widely spaced intervals. Here we compare one continuous and three interrupted sampling regimes to determine whether sampling regime has a significant effect on estimation of basal metabolic rate or standard evaporative water loss. Compared to continuous 20-s sampling averaged over 20 min, sampling every 6 min and averaging over 60 min overestimated basal metabolic rate and evaporative water loss, sampling every 3 min and averaging over 21 min underestimated basal metabolic rate, and sampling every 12 min and averaging over 36 min showed no difference in estimates. Increasing the period over which the minimum mean was calculated significantly increased estimates of physiological variables. Reducing the frequency of sampling from 20 s to a longer interval of 3, 6, or 12 min underestimated basal metabolic rate but not evaporative water loss. This indicates that sampling frequency per se influences estimates of basal metabolic rate and that differences are not just an artifact of differences in the period over which the mean is calculated. Sampling regime can have a highly significant influence on estimation of standard physiological variables, although the actual differences between sampling regimes were generally small (usually <5%). Although continuous sampling is the preferred sampling regime for open-flow respirometry studies, if time and cost are prohibitive, then use of an appropriate switching system will result in smaller errors than measuring individuals continuously for shorter periods.

  20. Effect of ac electric field on the dynamics of a vesicle under shear flow in the small deformation regime

    Science.gov (United States)

    Sinha, Kumari Priti; Thaokar, Rochish M.

    2018-03-01

    Vesicles or biological cells under simultaneous shear and electric field can be encountered in dielectrophoretic devices or designs used for continuous flow electrofusion or electroporation. In this work, the dynamics of a vesicle subjected to simultaneous shear and uniform alternating current (ac) electric field is investigated in the small deformation limit. The coupled equations for vesicle orientation and shape evolution are derived theoretically, and the resulting nonlinear equations are handled numerically to generate relevant phase diagrams that demonstrate the effect of electrical parameters on the different dynamical regimes such as tank treading (TT), vacillating breathing (VB) [called trembling (TR) in this work], and tumbling (TU). It is found that while the electric Mason number (Mn), which represents the relative strength of the electrical forces to the shear forces, promotes the TT regime, the response itself is found to be sensitive to the applied frequency as well as the conductivity ratio. While higher outer conductivity promotes orientation along the flow axis, orientation along the electric field is favored when the inner conductivity is higher. Similarly a switch of orientation from the direction of the electric field to the direction of flow is possible by a mere change of frequency when the outer conductivity is higher. Interestingly, in some cases, a coupling between electric field-induced deformation and shear can result in the system admitting an intermediate TU regime while attaining the TT regime at high Mn. The results could enable designing better dielectrophoretic devices wherein the residence time as well as the dynamical states of the vesicular suspension can be controlled as per the application.

  1. The effects of human land use on flow regime and water chemistry of headwater streams in the highlands of Chiapas

    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.

  2. Final report for Fundamental study of long-short interfacial wave interactions with application for flow regime development

    CERN Document Server

    McCready, M

    2000-01-01

    The long waves that cause slugs almost always form more slowly than short waves, and linear stability always predicts that the growth rate for long waves is much less than that for short waves. However, at many conditions above neutral stability, long waves dominate the wave field. Three different studies were undertaken as part of the funded work: (1) linear interaction for unsteady flows; (2) wave evolution in oil-water channel flows; (3) retrograde stability and subcritical bifurcations. The oil-water system was used as a surrogate for gas-liquid systems because the gas phase is usually turbulent, and this complication is thus avoided although the phenomena involved are similar. The following overall conclusions about flow regime development were reached: (a) Oscillations in pressure and flow rate, due to interfacial waves or a malfunctioning pump, can cause significant growth rate changes in short waves within narrow FR-equency ranges, but probably do not have a large effect on long waves and thus regime ...

  3. A dry-spot model for the prediction of critical heat flux in water boiling in bubbly flow regime

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Sang Jun; No, Hee Cheon [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1997-12-31

    This paper presents a prediction of critical heat flux (CHF) in bubbly flow regime using dry-spot model proposed recently by authors for pool and flow boiling CHF and existing correlations for forced convective heat transfer coefficient, active site density and bubble departure diameter in nucleate boiling region. Without any empirical constants always present in earlier models, comparisons of the model predictions with experimental data for upward flow of water in vertical, uniformly-heated round tubes are performed and show a good agreement. The parametric trends of CHF have been explored with respect to variations in pressure, tube diameter and length, mass flux and inlet subcooling. 16 refs., 6 figs., 1 tab. (Author)

  4. Optical reflection probe for the measurement of local void fraction, bubble velocity, bubble size and for the identification of flow regime

    International Nuclear Information System (INIS)

    Berti, M.

    1983-11-01

    Within the scope of two-phase flow measurement technique optical probes have been investigated for measurement of local void fraction, bubble velocity, bubble-size and identification of flow regime. Single and double probes used normal to flow need a calibration factor due to the effects of bubble deformation and bubble deflexion by the probe tips. (Auth.)

  5. Study of Plasma Flows Generated in Plasma Focus Discharge in Different Regimes of Working Gas Filling

    Science.gov (United States)

    Voitenko, D. A.; Ananyev, S. S.; Astapenko, G. I.; Basilaia, A. D.; Markolia, A. I.; Mitrofanov, K. N.; Myalton, V. V.; Timoshenko, A. P.; Kharrasov, A. M.; Krauz, V. I.

    2017-12-01

    Results are presented from experimental studies of the plasma flows generated in the KPF-4 Phoenix Mather-type plasma focus device (Sukhum Physical Technical Institute). In order to study how the formation and dynamics of the plasma flow depend on the initial distribution of the working gas, a system of pulsed gas puffing into the discharge volume was developed. The system allows one to create profiled gas distributions, including those with a reduced gas density in the region of plasma flow propagation. Results of measurements of the magnetic field, flow profile, and flow deceleration dynamics at different initial distributions of the gas pressure are presented.

  6. Experimental investigation on single-phase pressure losses in nuclear debris beds: Identification of flow regimes and effective diameter

    Energy Technology Data Exchange (ETDEWEB)

    Clavier, R., E-mail: remi.clavier@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire (IRSN) – PSN-RES/SEREX/LE2M, Cadarache bât. 327, 13115 St Paul-lez-Durance (France); Chikhi, N., E-mail: nourdine.chikhi@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire (IRSN) – PSN-RES/SEREX/LE2M, Cadarache bât. 327, 13115 St Paul-lez-Durance (France); Fichot, F. [Institut de Radioprotection et de Sûreté Nucléaire (IRSN) – PSN-RES/SAG/LEPC, Cadarache bât. 700, 13115 St Paul-lez-Durance (France); Quintard, M. [Université de Toulouse – INPT – UPS – Institut de Mécanique des Fluides de Toulouse (IMFT), Allée Camille Soula, F-31400 Toulouse (France); CNRS – IMFT, F-31400 Toulouse (France)

    2015-10-15

    Highlights: • Single-phase pressure drops versus flow rates in particle beds are measured. • Conditions are representative of the reflooding of a nuclear fuel debris bed. • Darcy, weak inertial, strong inertial and weak turbulent regimes are observed. • A Darcy–Forchheimer law is found to be a good approximation in this domain. • A predictive correlation is derived from new experimental data. - Abstract: During a severe nuclear power plant accident, the degradation of the reactor core can lead to the formation of debris beds. The main accident management procedure consists in injecting water inside the reactor vessel. Nevertheless, large uncertainties remain regarding the coolability of such debris beds. Motivated by the reduction of these uncertainties, experiments have been conducted on the CALIDE facility in order to investigate single-phase pressure losses in representative debris beds. In this paper, these results are presented and analyzed in order to identify a simple single-phase flow pressure loss correlation for debris-bed-like particle beds in reflooding conditions, which cover Darcean to Weakly Turbulent flow regimes. The first part of this work is dedicated to study macro-scale pressure losses generated by debris-bed-like particle beds, i.e., high sphericity (>80%) particle beds with relatively small size dispersion (from 1 mm to 10 mm). A Darcy–Forchheimer law, involving the sum of a linear term and a quadratic deviation, with respect to filtration velocity, has been found to be relevant to describe this behavior in Darcy, Strong Inertial and Weak Turbulent regimes. It has also been observed that, in a restricted domain (Re = 15 to Re = 30) between Darcy and Weak Inertial regimes, deviation is better described by a cubic term, which corresponds to the so-called Weak Inertial regime. The second part of this work aims at identifying expressions for coefficients of linear and quadratic terms in Darcy–Forchheimer law, in order to obtain a

  7. Occurrence of phthalate esters in sediments in Qiantang River, China and inference with urbanization and river flow regime.

    Science.gov (United States)

    Sun, Jianqiang; Huang, Jing; Zhang, Anping; Liu, Weiping; Cheng, Wenwei

    2013-03-15

    Phthalate esters (PAEs), a group of emerging organic contaminants, have become a serious issue arousing much attention for their ubiquitous presence and hazardous impact on the environment. This study provides the first data on distribution of PAEs in the sediments in the Qiantang River, Zhejiang Province, China, and the inference with urbanization and river flow regime. PAEs were detected in all 23 sediment samples analyzed, and the total concentrations of their 16 congeners in sediments ranged from 0.59 to 6.74μg/g dry weight (dw), with the geometric mean value of 2.03μg/g dw. Of the 16 PAE congeners, di-n-butyl phthalate (DnBP), diisobutyl phthalate (DiBP), and di(2-ethylhexyl) phthalate (DEHP) were present in all sediment samples. The PAEs concentrations in urban regions were higher than those in rural regions because of higher discharge of PAEs from plastic materials in urbanized areas. Concentrations of PAEs were positively correlated with sediment organic matter (fOM) and negatively correlated with logistic value of annual average flow volume at sample sites. River flow regime modified by man-made dams significantly affected the distribution of PAEs. Analysis of congener composition of PAEs indicated that the DEHP was predominant congener in the Qiantang River. The normalized concentration of DEHP exceeded recommended environmental risk limit (ERL). Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Long-Term Downstream Effects of a Dam on a Lowland River Flow Regime: Case Study of the Upper Narew

    Directory of Open Access Journals (Sweden)

    Paweł Marcinkowski

    2017-10-01

    Full Text Available Most European riverine ecosystems suffer from the negative influence of impoundments on flow regime. Downstream effects of dams lead to a number of environmental and socioeconomic risks and, therefore, should be thoroughly examined in specific contexts. Our study aims to quantify the downstream effects of the Siemianówka Reservoir (Upper Narew, Poland, using statistical analysis of key elements of the river’s flow regime, such as the flow duration and recurrence of floods and droughts. In a comparative study on control catchments not influenced by impoundments (the Supraśl and Narewka Rivers, we revealed the following downstream effects of the analyzed dam: significant shortening of spring floods, reduction of the duration and depth of summer droughts, decrease of the maximum discharge, and homogenization of the discharge hydrographs. Although we determined a significant decrease in the duration of summer floods in the “before” and “after” dam function periods, we showed that this issue is regional, climate-related, and replicated in control catchments, rather than an evident downstream effect of the dam. We conclude that significant hydrological downstream effects of the Siemianówka dam–reservoir system could have been the main driver inducing the deterioration of the anastomosing stretch of the Narew River downstream of the dam.

  9. Overcoming Information Limitations for the Prescription of an Environmental Flow Regime for a Central American River

    Directory of Open Access Journals (Sweden)

    Peter C. Esselman

    2010-03-01

    Full Text Available Hydropower dam construction is expanding rapidly in Central America because of the increasing demand for electricity. Although hydropower can provide a low-carbon source of energy, dams can also degrade socially valued riverine and riparian ecosystems and the services they provide. Such degradation can be partially mitigated by the release of environmental flows below dams. However, environmental flows have been applied infrequently to dams in Central America, partly because of the lack of information on the ecological, social, and economic aspects of rivers. This paper presents a case study of how resource and information limitations were addressed in the development of environmental flow recommendations for the Patuca River in Honduras below a proposed hydroelectric dam. To develop flow recommendations, we applied a multistep process that included hydrological analysis and modeling, the collection of traditional ecological knowledge (TEK during field trips, expert consultation, and environmental flow workshops for scientists, water managers, and community members. The final environmental flow recommendation specifies flow ranges for different components of river hydrology, including low flows for each month, high-flow pulses, and floods, in dry, normal, and wet years. The TEK collected from local and indigenous riverine communities was particularly important for forming hypotheses about flow-dependent ecological and social factors that may be vulnerable to disruption from dam-modified river flows. We show that our recommended environmental flows would have a minimal impact on the dam's potential to generate electricity. In light of rapid hydropower development in Central America, we suggest that environmental flows are important at the local scale, but that an integrated landscape perspective is ultimately needed to pursue hydropower development in a manner that is as ecologically sustainable as possible.

  10. Experimental study on effect of channel size on upward air-water two-phase flow regimes in vertical channels

    International Nuclear Information System (INIS)

    Yan Chaoxing; Yan Changqi; Sun Licheng; Wang Yang

    2012-01-01

    A visualized study of flow patterns was carried out for air-water two-phase flow in two narrow rectangular ducts (40 mm × l.41 mm, 40 mm × 10 mm) and a circular tube with a diameter of 25 mm, respectively. The superficial velocity air and water were in the range of 0.03-24.71 m/s and 0.03-3.73 m/s. All the bubble, slug, churn and annular flows occurred in the three channels. Characteristics of flow patterns in the 40 mm × 10 mm duct are very similar to those in circular tube, but different from the 40 mm × l.41 mm duct. Detailed flow regime maps of the three channels were presented. The experimental results show that the channel size has a significant influence on flow pattern transition, boundary of which in rectangular channels tends asymptotically towards that in the circular tube with increasing the width of narrow side. (authors)

  11. Contribution to numerical methods for all Mach flow regimes and to fluid-porous coupling for the simulation of homogeneous two-phase flows in nuclear reactors

    International Nuclear Information System (INIS)

    Zaza, Chady

    2015-01-01

    The numerical simulation of steam generators of pressurized water reactors is a complex problem, involving different flow regimes and a wide range of length and time scales. An accidental scenario may be associated with very fast variations of the flow with an important Mach number. In contrast in the nominal regime the flow may be stationary, at low Mach number. Moreover whatever the regime under consideration, the array of U-tubes is modelled by a porous medium in order to avoid taking into account the complex geometry of the steam generator, which entails the issue of the coupling conditions at the interface with the free-fluid. We propose a new pressure-correction scheme for cell-centered finite volumes for solving the compressible Navier-Stokes and Euler equations at all Mach number. The existence of a discrete solution, the consistency of the scheme in the Lax sense and the positivity of the internal energy were proved. Then the scheme was extended to the homogeneous two-phase flow models of the GENEPI code developed at CEA. Lastly a multigrid-AMR algorithm was adapted for using our pressure-correction scheme on adaptive grids. Regarding the second issue addressed in this work, the numerical simulation of a fluid flow over a porous bed involves very different length scales. Macroscopic interface models - such as Ochoa-Tapia-Whitaker or Beavers-Joseph law for a viscous flow - represent the transition region between the free-fluid and the porous region by an interface of discontinuity associated with specific transmission conditions. An extension to the Beavers-Joseph law was proposed for the convective regime. By introducing a jump in the kinetic energy at the interface, we recover an interface condition close to the Beavers-Joseph law but with a non-linear slip coefficient, which depends on the free-fluid velocity at the interface and on the Darcy velocity. The validity of this new transmission condition was assessed with direct numerical simulations at

  12. Classification of gap flow regimes in two side-by-side circular cylinders

    CSIR Research Space (South Africa)

    Atkins, M

    2014-02-01

    Full Text Available at an intermediate gap spacing ranging between e.g., 1.2 = T/D = 2.2. The flow passing between the cylinders - gap flow - is biased towards one cylinder (Fig.1.(b)). The wake pattern behind that cylinder has a narrow near-wake (n) with a higher vortex shedding...

  13. Effects of Hall current on convective heat generating fluid in slip flow regime

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S.S.; Ram, P.C. (Kenyatta Univ., Nairobi (KE). Dept. of Mathematics); Stower, G.X. (Jomo Kenyatta Univ. College of Agriculture and Technology, Nairobi (KE). Dept. of Mathematics and Computer Science)

    1992-08-01

    The problem of free convection flow of a viscous heat generating rarefied gas is considered for the case when a strong magnetic field is imposed perpendicularly to the plane of flow. Analytical expressions for the velocity field and temperature are obtained, and the influence of the Hall currents m and the heat source parameter {delta} on the velocity field and temperature are discussed. (Author).

  14. Identification of two-phase flow regimes by time-series modeling

    International Nuclear Information System (INIS)

    King, C.H.; Ouyang, M.S.; Pei, B.S.

    1987-01-01

    The identification of two-phase flow patterns in pipes or ducts is important to the design and operation of thermal-hydraulic systems, especially in the nuclear reactor cores of boiling water reactors or in the steam generators of pressurized water reactors. Basically, two-phase flow shows some fluctuating characteristics even at steady-state conditions. These fluctuating characteristics can be analyzed by statistical methods for obtaining flow signatures. There have been a number of experimental studies conducted that are concerned with the statistical properties of void fraction or pressure pulsation in two-phase flow. In this study, the authors propose a new technique of identifying the patterns of air-water two-phase flow in a vertical pipe. This technique is based on analyzing the statistic characteristics of the pressure signals of the test loop by time-series modeling

  15. Structure of two-phase adiabatic flow in air sparging regime in vertical cylindrical channel with water

    Directory of Open Access Journals (Sweden)

    V. I. Solonin

    2014-01-01

    Full Text Available The article presents a research of two-phase adiabatic flow in air sparging regime in vertical cylindrical channel filled with water. A purpose of the work is to obtain experimental data for further analysis of a character of the moving phases. Research activities used the optic methods PIV (Particle Image Visualization because of their noninvasiveness to obtain data without disturbing effect on the flow. A laser sheet illuminated the fluorescence particles, which were admixed in water along the channel length. A digital camera recorded their motion for a certain time interval that allowed building the velocity vector fields. As a result, gas phase velocity components typical for a steady area of the channel and their relations for various intensity of volume air rate were obtained. A character of motion both for an air bubble and for its surrounding liquid has been conducted. The most probable direction of phases moving in the channel under sparging regime is obtained by building the statistic scalar fields. The use of image processing enabled an analysis of the initial area of the air inlet into liquid. A characteristic curve of the bubbles offset from the axis for various intensity of volume gas rate and channel diameter is defined. A character of moving phases is obtained by building the statistic scalar fields. The values of vertical components of liquid velocity in the inlet part of channel are calculated. Using the obtained data of the gas phase velocities a true void fraction was calculated. It was compared with the values of void fraction, calculated according to the liquid level change in the channel. Obtained velocities were compared with those of the other researchers, and a small difference in their values was explained by experimental conditions. The article is one of the works to research the two-phase flows with no disturbing effect on them. Obtained data allow us to understand a character of moving the two-phase flows in

  16. Consistent lattice Boltzmann modeling of low-speed isothermal flows at finite Knudsen numbers in slip-flow regime: Application to plane boundaries.

    Science.gov (United States)

    Silva, Goncalo; Semiao, Viriato

    2017-07-01

    The first nonequilibrium effect experienced by gaseous flows in contact with solid surfaces is the slip-flow regime. While the classical hydrodynamic description holds valid in bulk, at boundaries the fluid-wall interactions must consider slip. In comparison to the standard no-slip Dirichlet condition, the case of slip formulates as a Robin-type condition for the fluid tangential velocity. This makes its numerical modeling a challenging task, particularly in complex geometries. In this work, this issue is handled with the lattice Boltzmann method (LBM), motivated by the similarities between the closure relations of the reflection-type boundary schemes equipping the LBM equation and the slip velocity condition established by slip-flow theory. Based on this analogy, we derive, as central result, the structure of the LBM boundary closure relation that is consistent with the second-order slip velocity condition, applicable to planar walls. Subsequently, three tasks are performed. First, we clarify the limitations of existing slip velocity LBM schemes, based on discrete analogs of kinetic theory fluid-wall interaction models. Second, we present improved slip velocity LBM boundary schemes, constructed directly at discrete level, by extending the multireflection framework to the slip-flow regime. Here, two classes of slip velocity LBM boundary schemes are considered: (i) linear slip schemes, which are local but retain some calibration requirements and/or operation limitations, (ii) parabolic slip schemes, which use a two-point implementation but guarantee the consistent prescription of the intended slip velocity condition, at arbitrary plane wall discretizations, further dispensing any numerical calibration procedure. Third and final, we verify the improvements of our proposed slip velocity LBM boundary schemes against existing ones. The numerical tests evaluate the ability of the slip schemes to exactly accommodate the steady Poiseuille channel flow solution, over

  17. Consistent lattice Boltzmann modeling of low-speed isothermal flows at finite Knudsen numbers in slip-flow regime: Application to plane boundaries

    Science.gov (United States)

    Silva, Goncalo; Semiao, Viriato

    2017-07-01

    The first nonequilibrium effect experienced by gaseous flows in contact with solid surfaces is the slip-flow regime. While the classical hydrodynamic description holds valid in bulk, at boundaries the fluid-wall interactions must consider slip. In comparison to the standard no-slip Dirichlet condition, the case of slip formulates as a Robin-type condition for the fluid tangential velocity. This makes its numerical modeling a challenging task, particularly in complex geometries. In this work, this issue is handled with the lattice Boltzmann method (LBM), motivated by the similarities between the closure relations of the reflection-type boundary schemes equipping the LBM equation and the slip velocity condition established by slip-flow theory. Based on this analogy, we derive, as central result, the structure of the LBM boundary closure relation that is consistent with the second-order slip velocity condition, applicable to planar walls. Subsequently, three tasks are performed. First, we clarify the limitations of existing slip velocity LBM schemes, based on discrete analogs of kinetic theory fluid-wall interaction models. Second, we present improved slip velocity LBM boundary schemes, constructed directly at discrete level, by extending the multireflection framework to the slip-flow regime. Here, two classes of slip velocity LBM boundary schemes are considered: (i) linear slip schemes, which are local but retain some calibration requirements and/or operation limitations, (ii) parabolic slip schemes, which use a two-point implementation but guarantee the consistent prescription of the intended slip velocity condition, at arbitrary plane wall discretizations, further dispensing any numerical calibration procedure. Third and final, we verify the improvements of our proposed slip velocity LBM boundary schemes against existing ones. The numerical tests evaluate the ability of the slip schemes to exactly accommodate the steady Poiseuille channel flow solution, over

  18. Determination of gas & liquid two-phase flow regime transitions in wellbore annulus by virtual mass force coefficient when gas cut

    Science.gov (United States)

    Qu, Junbo; Yan, Tie; Sun, Xiaofeng; Chen, Ye; Pan, Yi

    2017-10-01

    With the development of drilling technology to deeper stratum, overflowing especially gas cut occurs frequently, and then flow regime in wellbore annulus is from the original drilling fluid single-phase flow into gas & liquid two-phase flow. By using averaged two-fluid model equations and the basic principle of fluid mechanics to establish the continuity equations and momentum conservation equations of gas phase & liquid phase respectively. Relationship between pressure and density of gas & liquid was introduced to obtain hyperbolic equation, and get the expression of the dimensionless eigenvalue of the equation by using the characteristic line method, and analyze wellbore flow regime to get the critical gas content under different virtual mass force coefficients. Results show that the range of equation eigenvalues is getting smaller and smaller with the increase of gas content. When gas content reaches the critical point, the dimensionless eigenvalue of equation has no real solution, and the wellbore flow regime changed from bubble flow to bomb flow. When virtual mass force coefficients are 0.50, 0.60, 0.70 and 0.80 respectively, the critical gas contents are 0.32, 0.34, 0.37 and 0.39 respectively. The higher the coefficient of virtual mass force, the higher gas content in wellbore corresponding to the critical point of transition flow regime, which is in good agreement with previous experimental results. Therefore, it is possible to determine whether there is a real solution of the dimensionless eigenvalue of equation by virtual mass force coefficient and wellbore gas content, from which we can obtain the critical condition of wellbore flow regime transformation. It can provide theoretical support for the accurate judgment of the annular flow regime.

  19. Balancing power production and instream flow regime for small scale hydropower

    Science.gov (United States)

    Perona, P.; Gorla, L.; Characklis, G. W.

    2013-12-01

    Flow diversion from river and torrent main stems is a common practice to feed water uses such run-of-river and mini-hydropower, irrigation, etc. Considering the worldwide increasing water demand, it becomes mandatory to take the importance of riparian ecosystems and related biodiversity into account before starting such practices. In this paper, we use a simple hydro-economic model (Perona et al., 2013, Gorla and Perona, 2013) to show that redistribution policies at diversion nodes allow for a clear bio-economic interpretation of residual flows. This model uses the Principle of Equal Marginal Utility (PEMU) as optimal water allocation rule for generating natural-like flow releases while maximizing the aggregated economic benefits of both the riparian environment and the traditional use (e.g., hydropower). We show that both static and dynamic release polices such Minimal Flow, and Proportional/Non-proportional Repartitions, respectively, can all be represented in terms of PEMU, making explicit the value of the ecosystem health underlying each policy. The related ecological and economical performances are evaluated by means of hydrological/ecological indicators. We recommend taking this method into account as a helpful tool guiding political, economical and ecological decisions when replacing the inadequate concept of Minimum Flow Requirement (MFR) with dynamic ones. References Perona, P., D. Dürrenmatt and G. Characklis (2013) Obtaining natural-like flow releases in diverted river reaches from simple riparian benefit economic models. Journal of Environmental Management, 118: 161-169, http://dx.doi.org/10.1016/j.jenvman.2013.01.010 Gorla, L. and P. Perona (2013) On quantifying ecologically sustainable flow releases in a diverted river reach. Journal of Hydrology, 489: 98- 107, http://dx.doi.org/10.1016/j.jhydrol.2013.02.043

  20. Flow regime in a restored wetland determines trophic links and species composition in the aquatic macroinvertebrate community

    International Nuclear Information System (INIS)

    González-Ortegón, E.; Walton, M.E.M.; Moghaddam, B.; Vilas, C.; Prieto, A.; Kennedy, H.A.; Pedro Cañavate, J.; Le Vay, L.

    2015-01-01

    In a restored wetland (South of Spain), where different flow regimes control water exchange with the adjacent Guadalquivir estuary, the native Palaemon varians coexists with an exotic counterpart species Palaemon macrodactylus. This controlled m/acrocosm offers an excellent opportunity to investigate how the effects of water management, through different flow regimes, and the presence of a non-native species affect the aquatic community and the trophic niche (by gut contents and C-N isotopic composition) of the native shrimp Palaemon varians. We found that increased water exchange rate (5% day −1 in mixed ponds vs. 0.1% day −1 in extensive ponds) modified the aquatic community of this wetland; while extensive ponds are dominated by isopods and amphipods with low presence of P. macrodactylus, mixed ponds presented high biomass of mysids, corixids, copepods and both shrimp species. An estuarine origin of nutrients and primary production might explain seasonal and spatial differences found among ponds of this wetland. A combined analysis of gut contents and isotopic composition of the native and the exotic species showed that: (1) native P. varians is mainly omnivorous (2) while the non-native P. macrodactylus is more zooplanktivorous and (3) a dietary overlap occurred when both species coexist at mixed ponds where a higher water exchange and high abundance of mysids and copepods diversifies the native species' diet. Thus differences in the trophic ecology of both species are clearly explained by water management. This experimental study is a valuable tool for integrated management between river basin and wetlands since it allows quantification of wetland community changes in response to the flow regime. - Highlights: • Flow regimen is a major determinant of physicochemical habitat of a wetland. • Water exchanges wetland-estuary modify its aquatic community and trophic links. • Omnivory and physiological tolerance key in the resistance of a wetland

  1. Spatial sap flow and xylem anatomical characteristics in olive trees under different irrigation regimes.

    Science.gov (United States)

    López-Bernal, Álvaro; Alcántara, Esteban; Testi, Luca; Villalobos, Francisco J

    2010-12-01

    The compensation heat pulse (CHP) method is widely used to estimate sap flow and transpiration in conducting organs of woody plants. Previous studies have reported a natural azimuthal variability in sap flow, which could have practical implications in locating the CHP probes and integrating their output. Sap flow of several olive trees (Olea europaea L. cv. 'Arbequina') previously grown under different irrigation treatments were monitored by the CHP method, and their xylem anatomical characteristics were analyzed from wood samples taken at the same location in which the probes were installed. A significant azimuthal variability in the sap flow was found in a well-irrigated olive tree monitored by eight CHP probes. The azimuthal variability was well related to crown architecture, but poorly to azimuthal differences in the xylem anatomical characteristics. Well-irrigated and deficit-irrigated olive trees showed similar xylem anatomical characteristics, but they differed in xylem growth and in the ratio of nocturnal-to-diurnal sap flow (N/D index). The results of this work indicate that transpiration cannot be accurately estimated by the CHP method in olive trees if a small number of sensors are employed and that the N/D index could be used as a sensitive water status indicator.

  2. Identification method of gas-liquid two-phase flow regime based on image wavelet packet information entropy and genetic neural network

    International Nuclear Information System (INIS)

    Zhou Yunlong; Chen Fei; Sun Bin

    2008-01-01

    Based on the characteristic that wavelet packet transform image can be decomposed by different scales, a flow regime identification method based on image wavelet packet information entropy feature and genetic neural network was proposed. Gas-liquid two-phase flow images were captured by digital high speed video systems in horizontal pipe. The information entropy feature from transformation coefficients were extracted using image processing techniques and multi-resolution analysis. The genetic neural network was trained using those eigenvectors, which was reduced by the principal component analysis, as flow regime samples, and the flow regime intelligent identification was realized. The test result showed that image wavelet packet information entropy feature could excellently reflect the difference between seven typical flow regimes, and the genetic neural network with genetic algorithm and BP algorithm merits were with the characteristics of fast convergence for simulation and avoidance of local minimum. The recognition possibility of the network could reach up to about 100%, and a new and effective method was presented for on-line flow regime. (authors)

  3. Impacts of changing climate and snow cover on the flow regime of Jhelum River, Western Himalayas

    KAUST Repository

    Azmat, Muhammad

    2016-11-17

    This study examines the change in climate variables and snow cover dynamics and their impact on the hydrological regime of the Jhelum River basin in Western Himalayas. This study utilized daily streamflow records from Mangla dam, spanning a time period of 19 years (1995–2013), along with precipitation and temperature data over 52 years (1961–2013) from 12 different climate stations in the catchment. Additionally, moderate-resolution imaging spectroradiometer (MODIS) remote sensing product MOD10A2 was utilized to analyze the change in snow cover dynamics during 2000–2013. The Pearson and Kendall rank correlation tests were used to scrutinize snow cover trends and correlation between temperature, precipitation, snow cover area (SCA) and streamflows records. Basin-wide trend analysis showed a slightly increasing tendency in temperature (τ = 0.098) and precipitation (τ = 0.094), during the years 1961–2013. The changes in streamflow indicated a positive (r > 0.12) relationship with respect to temperature but variable trends (r = −0.45–0.41) with respect to precipitation during both the winter and monsoon seasons. This indicates that temperature has a significant impact on the hydrological regime of the basin. MODIS data-based investigations suggested an expansion in SCA during 2000–2013. The changes in SCA of high-altitude zones (>2000 m a.s.l.) depicted a stronger positive correlation with climate variables and streamflow compared with those obtained for low-altitude regions (<2000 m a.s.l.). Overall, these results signify that high-altitude areas contribute to the streamflow largely in the form of snow- and glacier-melt during the early summer season. The streamflow is then further augmented by monsoon rainfall in the low-elevation regions during late summer.

  4. Contribution to the analysis and the modelling of turbulent flows in mixed convection regime, application to radioactive waste management

    International Nuclear Information System (INIS)

    Lecocq, Y.

    2008-12-01

    In the frame of radioactive waste management, this work aims to study the flow around a heating wall-mounted cylinder in crossflow in URANS approach. Well-known limitations of first order turbulence models lead us to consider second order turbulence modelling. In that frame, a heat transfer model is developed and validated on academic test cases. To begin with, when mixed convection regime is dominant, these simulations, completed by an isotherm one, all performed with low-Reynolds k-w SST model, give prominence to several eddy structures registered by the bibliography. One simulation is also performed with the high-Reynolds Rij-epsilon SSG model. With the k-w SST model, the heat transfer is correctly reproduced compared to the VALIDA experiment lead by the CEA, though with the Rij-epsilon SSG model, it is strongly under-estimated. It is supposed that it comes from the use of wall functions. Subsequently, when natural convection is predominant, flow topology becomes completely different and the heat transfer becomes less accurate to the VALIDA experiment. Following Durbin's approach, the Elliptic Blending-Renolds Stress Model EBRSM, consists in accounting for wall effects, and in wall blockage in particular. Following this formalism, an Elliptic Blending-Algebraic Flux Model is developed, the EBAFM. With this model, a priori tests in the three convection regimes and then simulations on the same test cases show major improvements in flow predictions. This leads to an interesting perspective to an intermediate model between SGDH and transport equations. (author)

  5. Potential impacts of climate change on flow regime and fish habitat in mountain rivers of the south-western Balkans.

    Science.gov (United States)

    Papadaki, Christina; Soulis, Konstantinos; Muñoz-Mas, Rafael; Martinez-Capel, Francisco; Zogaris, Stamatis; Ntoanidis, Lazaros; Dimitriou, Elias

    2016-01-01

    The climate change in the Mediterranean area is expected to have significant impacts on the aquatic ecosystems and particular in the mountain rivers and streams that often host important species such as the Salmo farioides, Karaman 1938. These impacts will most possibly affect the habitat availability for various aquatic species resulting to an essential alteration of the water requirements, either for dams or other water abstractions, in order to maintain the essential levels of ecological flow for the rivers. The main scope of this study was to assess potential climate change impacts on the hydrological patterns and typical biota for a south-western Balkan mountain river, the Acheloos. The altered flow regimes under different emission scenarios of the Intergovernmental Panel on Climate Change (IPCC) were estimated using a hydrological model and based on regional climate simulations over the study area. The Indicators of Hydrologic Alteration (IHA) methodology was then used to assess the potential streamflow alterations in the studied river due to predicted climate change conditions. A fish habitat simulation method integrating univariate habitat suitability curves and hydraulic modeling techniques were used to assess the impacts on the relationships between the aquatic biota and hydrological status utilizing a sentinel species, the West Balkan trout. The most prominent effects of the climate change scenarios depict severe flow reductions that are likely to occur especially during the summer flows, changing the duration and depressing the magnitude of the natural low flow conditions. Weighted Usable Area-flow curves indicated the limitation of suitable habitat for the native trout. Finally, this preliminary application highlighted the potential of science-based hydrological and habitat simulation approaches that are relevant to both biological quality elements (fish) and current EU Water policy to serve as efficient tools for the estimation of possible climate

  6. Predicting critical heat flux in slug flow regime of uniformly heated ...

    African Journals Online (AJOL)

    Numerical computation code (PWR-DNBP) has been developed to predict Critical Heat Flux (CHF) of forced convective flow of water in a vertical heated channel. The code was based on the liquid sub-layer model, with the assumption that CHF occurred when the liquid film thickness between the heated surface and vapour ...

  7. Three-dimensional flow past a fixed or freely vibrating cylinder in the early turbulent regime

    Science.gov (United States)

    Gsell, Simon; Bourguet, Rémi; Braza, Marianna

    2018-01-01

    The three-dimensional structure of the flow downstream of a circular cylinder, either fixed or subjected to vortex-induced vibrations, is investigated by means of numerical simulation, at Reynolds number 3900, based on the cylinder diameter and current velocity. The flow exhibits pronounced fluctuations distributed along the span in all studied cases. Qualitatively, it is characterized by spanwise undulations of the shear layers separating from the body and the development of vortices elongated in the plane normal to its axis (planar vortices). A quantitative analysis of crossflow vorticity fluctuations in the spanwise direction reveals a peak of fluctuation amplitude in the near region (i.e., area of formation of the spanwise wake vortices) and opposite trends of the spanwise wavelength in the shear layer and wake regions; the wavelength tends to decrease as a function of the streamwise distance in the shear layers down to a minimum value close to 0.5 body diameters and then slowly increases further in the wake. The spanwise structure of the flow is differently altered in these two regions, once the cylinder vibrates. In the shear layer region, body motion is associated with an enhancement of planar vortex formation. The amplification of vorticity spanwise fluctuations in this region is accompanied by a reduction of the spanwise wavelength; it is found to decrease as a function of the instantaneous Reynolds number based on the instantaneous flow velocity seen by the moving body, following the global trend of the wavelength versus Reynolds number previously reported for fixed cylinders. In the wake region, the flow spanwise structure is essentially unaltered compared to the fixed body case, in spite of the major distortions of the streamwise and crossflow length scales.

  8. Impacts of Land Use Change on the Natural Flow Regime: A Case Study in the Meramec River Watershed in Eastern Missouri, USA

    Science.gov (United States)

    Wu, C. L.; Knouft, J.; Chu, M.

    2017-12-01

    The natural flow regime within a watershed can be considered as the expected temporal patterns of streamflow variation in the absence of human impacts. While ecosystems have evolved to function under these conditions, the natural flow regime of most rivers has been significantly altered by human activities. Land use change, including the development of agriculture and urbanization, is a primary cause of the loss of natural flow regimes. These changes have altered discharge volume, timing, and variability, and consequently affected the structure and functioning of river ecosystems. The Meramec River watershed is located in east central Missouri and changes in land use have been the primary factor impacting flow regimes across the watershed. In this study, a watershed model, the Soil and Water Assessment Tool (SWAT), was developed to simulate a long-term time series of streamflow (1978-2014) within the watershed. Model performance was evaluated using statistical metrics and graphical technique including R-squared, Nash-Sutcliffe efficiency, cumulative error, and 1:1-ratio comparison between observed and simulated variables. The calibrated and validated SWAT model was then used to quantify the responses of the watershed when it was a forested natural landscape. An Indicator of Hydrologic Alteration (IHA) approach was applied to characterize the flow regime under the current landcover conditions as well as the simulated natural flow regime under the no land use change scenario. Differences in intra- and inter-annual ecologically relevant flow metrics were then compared using SWAT model outputs in conjunction with the IHA approach based on model outputs from current and no land use change conditions. This study provides a watershed-scale understanding of effects of land use change on a river's flow variability and provides a framework for the development of restoration plans for heavily altered watersheds.

  9. Numerical simulation of three-dimensional augmented Burnett equations for hypersonic flow in continuum-transition regime

    Science.gov (United States)

    Yun, Keon-Young

    For the computation of hypersonic flowfields about space vehicles in low earth orbits, where the local Knudsen numbers (Kn) lie in continuum-transition regime, a set of extended three-dimensional hydrodynamic equations are required which are more accurate than the Navier-Stokes equations and computationally more efficient than the Direct Simulation Monte Carlo (DSMC) computations in this regime. In this thesis, the three-dimensional augmented Burnett equations are derived from the Chapman-Enskog expansion of the Boltzmann equation to O(Kn 2) and adding the augmented terms (linear third-order super Burnett terms with coefficients determined from linearized stability analysis to ensure stability of the augmented Burnett equations to small wavelength disturbances). The three-dimensional augmented Burnett equations are applied to compute the three-dimensional hypersonic blunt body flows for various range of Knudsen numbers and Mach numbers. An explicit time-stepping scheme with Steger-Warming flux vector splitting is employed to discretize the convective flux terms. Stress and heat flux terms are central differenced. For the wall boundary conditions, the first-order Maxwell-Smoluchowski slip boundary conditions are employed. The computational results are compared with the Navier-Stokes solutions, the existing augmented Burnett solutions of Zhong, and the available DSMC results. The comparisons show that the difference between the Navier-Stokes and the augmented Burnett solutions is very small at Knudsen numbers less than 0.01; the difference becomes significant as the Knudsen number increases. The comparisons also show that the augmented Burnett solutions are much closer to the DSMC results in the continuum-transition regime than the Navier-Stokes calculations.

  10. Identification method for gas-liquid two-phase flow regime based on singular value decomposition and least square support vector machine

    International Nuclear Information System (INIS)

    Sun Bin; Zhou Yunlong; Zhao Peng; Guan Yuebo

    2007-01-01

    Aiming at the non-stationary characteristics of differential pressure fluctuation signals of gas-liquid two-phase flow, and the slow convergence of learning and liability of dropping into local minima for BP neural networks, flow regime identification method based on Singular Value Decomposition (SVD) and Least Square Support Vector Machine (LS-SVM) is presented. First of all, the Empirical Mode Decomposition (EMD) method is used to decompose the differential pressure fluctuation signals of gas-liquid two-phase flow into a number of stationary Intrinsic Mode Functions (IMFs) components from which the initial feature vector matrix is formed. By applying the singular vale decomposition technique to the initial feature vector matrixes, the singular values are obtained. Finally, the singular values serve as the flow regime characteristic vector to be LS-SVM classifier and flow regimes are identified by the output of the classifier. The identification result of four typical flow regimes of air-water two-phase flow in horizontal pipe has shown that this method achieves a higher identification rate. (authors)

  11. Unconfined laminar nanofluid flow and heat transfer around a rotating circular cylinder in the steady regime

    Directory of Open Access Journals (Sweden)

    Bouakkaz Rafik

    2017-06-01

    Full Text Available In this work, steady flow-field and heat transfer through a copper- water nanofluid around a rotating circular cylinder with a constant nondimensional rotation rate α varying from 0 to 5 was investigated for Reynolds numbers of 5–40. Furthermore, the range of nanoparticle volume fractions considered is 0–5%. The effect of volume fraction of nanoparticles on the fluid flow and heat transfer characteristics are carried out by using a finite-volume method based commercial computational fluid dynamics solver. The variation of the local and the average Nusselt numbers with Reynolds number, volume fractions, and rotation rate are presented for the range of conditions. The average Nusselt number is found to decrease with increasing value of the rotation rate for the fixed value of the Reynolds number and volume fraction of nanoparticles. In addition, rotation can be used as a drag reduction technique.

  12. Assessing the flow regime in a contaminated fractured and karstic dolostone aquifer supplying municipal water

    Science.gov (United States)

    Perrin, Jérôme; Parker, Beth L.; Cherry, John A.

    2011-04-01

    SummaryThe Silurian dolostone bedrock in Ontario, Canada, is a broad 400 km long swath northward from Niagara Falls through the Bruce Peninsula that represents an important water source for municipal, industrial, and agricultural uses. Where the Quaternary overburden is thin or absent, karst is common. This study concerns an urban area where the dolostone aquifer is 100 m thick beneath up to 50 m thick Quaternary deposits and where karst features identified by borehole information are common. Hydraulic tests show moderate to large bulk rock hydraulic conductivity and rock core tests indicate much smaller matrix hydraulic conductivity than the bulk rock values. Therefore, the aquifer is essentially a dual permeability, fully saturated system in which conduits occur within a network of ubiquitous extensive, horizontally- and vertically-interconnected fractures. Karst features are concentrated in a thin zone at the top-of-rock, likely representing former epikarst, and also in a thicker zone in the middle of the aquifer. Some pumping test results and large yields of some municipal wells are consistent with conduit occurrences. However, atmospheric tritium, distributed-source contamination (Cl -, NO3-), and a point-source pesticide plume (metolachlor) show detailed concentration distributions lacking influence of flow in conduits. Detailed hydraulic head profiles also show no influence of conduit flow. This study shows that when designing monitoring networks for groundwater quality and source water protection in similar contexts, locating conduits is not necessary because contaminant distributions are governed by the combined influences of the rock matrix, fractures and conduits, the hydraulic boundary conditions, and the interconnected fracture network with only minimal conduit effects. Prior to glaciations, an integrated karstic aquifer could develop with flow controlled by conduits; however, this original, converging flow system became non-functional when the

  13. Development of a new IHA method for impact assessment of climate change on flow regime

    Science.gov (United States)

    Yang, Tao; Cui, Tong; Xu, Chong-Yu; Ciais, Philippe; Shi, Pengfei

    2017-09-01

    The Indicators of Hydrologic Alteration (IHA) based on 33 parameters in five dimensions (flow magnitude, timing, duration, frequency and change rate) have been widely used in evaluation of hydrologic alteration in river systems. Yet, inter-correlation seriously exists amongst those parameters, therefore constantly underestimates or overestimates actual hydrological changes. Toward the end, a new method (Representative-IHA, RIHA) is developed by removing repetitions based on Criteria Importance Through Intercriteria Correlation (CRITIC) algorithm. RIHA is testified in evaluating effects of future climate change on hydro-ecology in the Niger River of Africa. Future flows are projected using three watershed hydrological models forced by five general circulation models (GCMs) under three Representative Concentration Pathways (RCPs) scenarios. Results show that: (1) RIHA is able to eliminate self-correlations amongst IHA indicators and identify the dominant characteristics of hydrological alteration in the Upper Niger River, (2) March streamflow, September streamflow, December streamflow, 30-day annual maximum, low pluses duration and fall rates tends to increase over the period 2010-2099, while July streamflow and 90-day annual minimum streamflow shows decrease, (3) the Niger River will undergo moderate flow alteration under RCP8.5 in 2050s and 2080s and low alteration other scenarios, (4) future flow alteration may induce increase water temperatures, reduction dissolved oxygen and food resources. Consequently, aquatic biodiversity and fish community of Upper Niger River would become more vulnerable in the future. The new method enables more scientific evaluation for multi-dimensional hydrologic alteration under the context of climate change.

  14. FKPP fronts in cellular flows: the large-P\\'eclet regime

    OpenAIRE

    Tzella, Alexandra; Vanneste, Jacques

    2015-01-01

    We investigate the propagation of chemical fronts arising in Fisher--Kolmogorov--Petrovskii--Piskunov (FKPP) type models in the presence of a steady cellular flow. In the long-time limit, a steadily propagating pulsating front is established. Its speed, on which we focus, can be obtained by solving an eigenvalue problem closely related to large-deviation theory. We employ asymptotic methods to solve this eigenvalue problem in the limit of small molecular diffusivity (large P\\'eclet number, $\\...

  15. Valley-scale morphology drives differences in fluvial sediment budgets and incision rates during contrasting flow regimes

    Science.gov (United States)

    Weber, M. D.; Pasternack, G. B.

    2017-07-01

    High-resolution topographic surveys using LiDAR and multibeam sonar can be used to characterize and quantify fluvial change. This study used repeat surveys to explore how topographic change, fluvial processes, sediment budgets, and aggradation and incision rates vary across spatial scales and across two contrasting decadal flow regimes in a regulated gravel/cobble river. A novel method for quantifying digital elevation model uncertainty was developed and applied to a topographic change detection analysis from 2006/2008 to 2014. During this period, which had four modest 3-5 year floods, most sediment was laterally redistributed through bank erosion and channel migration. Erosion primarily occurred in the floodplain (97,000 m3), terraces (80,000 m3), and lateral bars (58,000 m3); while deposition occurred in the adjacent pools (73,000 m3), fast glides (48,000 m3), and runs (36,000 m3). In contrast, significantly higher magnitude and longer duration floods from 1999 to 2006/2008 caused sediment to be displaced longitudinally, with the upstream reaches exporting sediment and the downstream reaches aggrading. The river maintained floodplain connectivity during both periods, despite different processes dominating the type of connectivity. Larger floods promoted overbank scour and avulsion, while smaller floods promoted bank erosion and lateral migration. This study explores and illustrates how the geomorphic response to contrasting flood regimes in a nonuniform river is highly dependent on which landforms are controlling hydraulics.

  16. Modeling-challenge paradigm using design of experiments for spacecraft immersed in nonstationary, between-regimes, flowing plasma

    Science.gov (United States)

    Koepke, Me; Marchand, R.

    2017-10-01

    A conducting sphere and cylinder under the conditions of nonstationary, between-regimes, flowing plasma is adopted as a test case for a modeling-challenge paradigm based on design of experiments (DOE) methodology that merges numerical simulation and testing. This model/simulation development platform facilitates a red-team/blue-team style challenge aimed at a tailored set of standard experimental conditions and measurements addressing specific questions in spacecraft-environment interactions and assessing the capability of models to describe those conditions. The goal is streamlining the Model/Simulation development process. A byproduct is an enhancement of the interrelationship between experiments in the laboratory and in space. Here, we conceptualize the advantage of the model-challenge over conventional validation in advancing whole-device modeling objectives in basic and applied plasma science.

  17. Seasonal dynamics of trace elements in tidal salt marsh soils as affected by the flow-sediment regulation regime.

    Directory of Open Access Journals (Sweden)

    Junhong Bai

    Full Text Available Soil profiles were collected in three salt marshes with different plant species (i.e. Phragmites australis, Tamarix chinensis and Suaeda salsa in the Yellow River Delta (YRD of China during three seasons (summer and fall of 2007 and the following spring of 2008 after the flow-sediment regulation regime. Total elemental contents of As, Cd, Cu, Pb and Zn were determined using inductively coupled plasma atomic absorption spectrometry to investigate temporal variations in trace elements in soil profiles of the three salt marshes, assess the enrichment levels and ecological risks of these trace elements in three sampling seasons and identify their influencing factors. Trace elements did not change significantly along soil profiles at each site in each sampling season. The highest value for each sampling site was observed in summer and the lowest one in fall. Soils in both P. australis and S. salsa wetlands tended to have higher trace element levels than those in T. chinensis wetland. Compared to other elements, both Cd and As had higher enrichment factors exceeding moderate enrichment levels. However, the toxic unit (TU values of these trace elements did not exceed probable effect levels. Correlation analysis showed that these trace elements were closely linked to soil properties such as moisture, sulfur, salinity, soil organic matter, soil texture and pH values. Principal component analysis showed that the sampling season affected by the flow-sediment regulation regime was the dominant factor influencing the distribution patterns of these trace elements in soils, and plant community type was another important factor. The findings of this study could contribute to wetland conservation and management in coastal regions affected by the hydrological engineering.

  18. Non-invasive classification of gas–liquid two-phase horizontal flow regimes using an ultrasonic Doppler sensor and a neural network

    International Nuclear Information System (INIS)

    Abbagoni, Baba Musa; Yeung, Hoi

    2016-01-01

    The identification of flow pattern is a key issue in multiphase flow which is encountered in the petrochemical industry. It is difficult to identify the gas–liquid flow regimes objectively with the gas–liquid two-phase flow. This paper presents the feasibility of a clamp-on instrument for an objective flow regime classification of two-phase flow using an ultrasonic Doppler sensor and an artificial neural network, which records and processes the ultrasonic signals reflected from the two-phase flow. Experimental data is obtained on a horizontal test rig with a total pipe length of 21 m and 5.08 cm internal diameter carrying air-water two-phase flow under slug, elongated bubble, stratified-wavy and, stratified flow regimes. Multilayer perceptron neural networks (MLPNNs) are used to develop the classification model. The classifier requires features as an input which is representative of the signals. Ultrasound signal features are extracted by applying both power spectral density (PSD) and discrete wavelet transform (DWT) methods to the flow signals. A classification scheme of ‘1-of-C coding method for classification’ was adopted to classify features extracted into one of four flow regime categories. To improve the performance of the flow regime classifier network, a second level neural network was incorporated by using the output of a first level networks feature as an input feature. The addition of the two network models provided a combined neural network model which has achieved a higher accuracy than single neural network models. Classification accuracies are evaluated in the form of both the PSD and DWT features. The success rates of the two models are: (1) using PSD features, the classifier missed 3 datasets out of 24 test datasets of the classification and scored 87.5% accuracy; (2) with the DWT features, the network misclassified only one data point and it was able to classify the flow patterns up to 95.8% accuracy. This approach has demonstrated the

  19. How is the impact of climate change on river flow regimes related to the impact on mean annual runoff? A global-scale analysis

    International Nuclear Information System (INIS)

    Döll, Petra; Schmied, Hannes Müller

    2012-01-01

    To assess the impact of climate change on freshwater resources, change in mean annual runoff (MAR) is only a first indicator. In addition, it is necessary to analyze changes of river flow regimes, i.e. changes in the temporal dynamics of river discharge, as these are important for the well-being of humans (e.g. with respect to water supply) and freshwater-dependent biota (e.g. with respect to habitat availability). Therefore, we investigated, in a global-scale hydrological modeling study, the relation between climate-induced changes of MAR and changes of a number of river flow regime indicators, including mean river discharge, statistical low and high flows, and mean seasonal discharge. In addition, we identified, for the first time at the global scale, where flow regime shifts from perennial to intermittent flow regimes (or vice versa) may occur due to climate change. Climate-induced changes of all considered river flow regime indicators (except seasonal river flow changes) broadly follow the spatial pattern of MAR changes. The differences among the computed changes of MAR due to the application of the two climate models are larger than the differences between the change of MAR and the change of the diverse river flow indicators for one climate model. At the sub-basin and grid cell scales, however, there are significant differences between the changes of MAR, mean annual river discharge, and low and high flows. Low flows are projected to be more than halved by the 2050s in almost twice the area as compared to MAR. Similarly, northern hemisphere summer flows decrease more strongly than MAR. Differences between the high emissions scenario A2 (with emissions of 25 Gt C yr −1 in the 2050s) and the low emissions scenario B2 (16 Gt C yr −1 ) are generally small as compared to the differences due to the two climate models. The benefits of avoided emissions are, however, significant in those areas where flows are projected to be more than halved due to climate change

  20. Two forward-flow regimes in actuator nozzles with large-amplitude pulsation

    Czech Academy of Sciences Publication Activity Database

    Tesař, Václav; Kordík, Jozef

    2013-01-01

    Roč. 191, MAR 1 2013 (2013), s. 34-44 ISSN 0924-4247 R&D Projects: GA ČR(CZ) GCP101/11/J019; GA TA ČR TA02020795; GA ČR GPP101/12/P556 Institutional research plan: CEZ:AV0Z20760514 Institutional support: RVO:61388998 Keywords : nozzle * unsteady flow * velocity profiles Subject RIV: BK - Fluid Dynamics Impact factor: 1.943, year: 2013 http://www.sciencedirect.com/science/article/pii/S0924424712007224

  1. Modeling compressible multiphase flows with dispersed particles in both dense and dilute regimes

    Science.gov (United States)

    McGrath, T.; St. Clair, J.; Balachandar, S.

    2017-06-01

    Many important explosives and energetics applications involve multiphase formulations employing dispersed particles. While considerable progress has been made toward developing mathematical models and computational methodologies for these flows, significant challenges remain. In this work, we apply a mathematical model for compressible multiphase flows with dispersed particles to existing shock and explosive dispersal problems from the literature. The model is cast in an Eulerian framework, treats all phases as compressible, is hyperbolic, and satisfies the second law of thermodynamics. It directly applies the continuous-phase pressure gradient as a forcing function for particle acceleration and thereby retains relaxed characteristics for the dispersed particle phase that remove the constituent material sound velocity from the eigenvalues. This is consistent with the expected characteristics of dispersed particle phases and can significantly improve the stable time-step size for explicit methods. The model is applied to test cases involving the shock and explosive dispersal of solid particles and compared to data from the literature. Computed results compare well with experimental measurements, providing confidence in the model and computational methods applied.

  2. Some free boundary problems in potential flow regime usinga based level set method

    Energy Technology Data Exchange (ETDEWEB)

    Garzon, M.; Bobillo-Ares, N.; Sethian, J.A.

    2008-12-09

    Recent advances in the field of fluid mechanics with moving fronts are linked to the use of Level Set Methods, a versatile mathematical technique to follow free boundaries which undergo topological changes. A challenging class of problems in this context are those related to the solution of a partial differential equation posed on a moving domain, in which the boundary condition for the PDE solver has to be obtained from a partial differential equation defined on the front. This is the case of potential flow models with moving boundaries. Moreover the fluid front will possibly be carrying some material substance which will diffuse in the front and be advected by the front velocity, as for example the use of surfactants to lower surface tension. We present a Level Set based methodology to embed this partial differential equations defined on the front in a complete Eulerian framework, fully avoiding the tracking of fluid particles and its known limitations. To show the advantages of this approach in the field of Fluid Mechanics we present in this work one particular application: the numerical approximation of a potential flow model to simulate the evolution and breaking of a solitary wave propagating over a slopping bottom and compare the level set based algorithm with previous front tracking models.

  3. Modelling ecological flow regime: an example from the Tennessee and Cumberland River basins

    Science.gov (United States)

    Knight, Rodney R.; Gain, W. Scott; Wolfe, William J.

    2012-01-01

    Predictive equations were developed for 19 ecologically relevant streamflow characteristics within five major groups of flow variables (magnitude, ratio, frequency, variability, and date) for use in the Tennessee and Cumberland River basins using stepbackward regression. Basin characteristics explain 50% or more of the variation for 12 of the 19 equations. Independent variables identified through stepbackward regression were statistically significant in 78 of 304 cases (α > 0.0001) and represent four major groups: climate, physical landscape features, regional indicators, and land use. Of these groups, the regional and climate variables were the most influential for determining hydrologic response. Daily temperature range, geologic factor, and rock depth were major factors explaining the variability in 17, 15, and 13 equations, respectively. The equations and independent datasets were used to explore the broad relation between basin properties and streamflow and the implication of streamflow to the study of ecological flow requirements. Key results include a high degree of hydrologic variability among least disturbed Blue Ridge streams, similar hydrologic behaviour for watersheds with widely varying degrees of forest cover, and distinct hydrologic profiles for streams in different geographic regions. Published in 2011. This article is a US Government work and is in the public domain in the USA.

  4. Incorporating Climate Change in Flow Regime Alteration Studies in Hydropower Licensing

    Science.gov (United States)

    Rheinheimer, D. E.; Akhbari, M.; Peek, R.; Yarnell, S. M.; Null, S. E.; Viers, J. H.

    2013-12-01

    The U.S. Federal Energy Regulatory Commission has yet to mandate incorporation of anticipated climate change effects on hydropower system operations when assessing environmental impacts from the renewal of hydropower licenses. One stated reason is the lack of specific project-level specificity in future impacts. We demonstrate how a hydropower system operations model, incorporating the latest climatological realizations (3 GCMs x RCPs 4.5 and 8.5), can be used to assess environmental impacts generally, and hydrological flow alterations in particular, during the hydropower licensing process. We demonstrate that we can, in fact, quantify project-level impacts from climate change, albeit within the context of quantified uncertainty about non-stationary future conditions. The systems operations model analysis encompasses the combined effects of the Yuba River Development Project and Yuba-Bear Drum-Spaulding Projects, an interconnected series of complex hydropower systems located in the Sierra Nevada, California. Daily water system operations are simulated using a monthly-scale optimization model for hydropower decisions. Though there is inherent uncertainty generated by the modeling process and operational assumptions (e.g., static energy demand), there are sufficient data, modeling techniques, and analytical approaches to assess the how management decisions made today may be confounded by non-stationary hydroclimates in 30-50 years, which is the duration of most hydropower licenses. Such decisions need to include adaptive management approaches to address not only non-stationary hydroclimates, but also cumulative impacts to ecological functions and processes caused by serial flow manipulation. This study can help provide the scientific guidance needed to improve climate change policy in hydropower system planning.

  5. A quantitative assessment of the genetic sources of the hydrologic flow regimes in Upper Indus Basin and its significance in a changing climate

    Science.gov (United States)

    Mukhopadhyay, Biswajit; Khan, Asif

    2014-02-01

    Reliable quantitative estimates of contributions melt water of different genetic sources make to river flows in Himalayan river basins are largely unknown. Here we provide such estimates for Upper Indus Basin (UIB). Analyses of historical flow records at 11 gauging stations spanning 14-48 years during a period of record from 1962 to 2010 reveal: a uniform character of annual flow distributions at all gauging stations given by a Gaussian function implying a unique glacio-hydrometeorological condition prevailing throughout the basin controlling four hydrologic flow regimes within UIB. Two low flow regimes occur during the months of October to December (L1) and January to March (L2) and two high flow regimes that occur during April-June (H1) and July-September (H2). For all stations, flow magnitudes follow, H2 > H1 > L1 > L2. In the main stem of Upper Indus River, the contributions to total annual flow volumes (m3) during these flow regimes are 53-62% during H2, 24-32% during H1, 8-9% during L1, and 4-6% during L2. In the main tributaries, these ranges are 47-74% during H2, 15-38% during H1, 8-10% during L1, and 4-6% during L2. Separation of annual hydrographs by linear smoothing and recursive digital filtering technique shows that the annual contribution of melt water (M2) from an elevation band 3500-5300 m to total annual flow volume (m3) varies from 41% to 54% along the main stem of Indus, upstream of the Himalayan foothills. Contribution of melt water (M1) from an elevation band 2500-3500 m varies from 16% to 29%. In the tributaries, annual contributions of M2 vary from 37% to as high as 65%. Similarly, annual contributions of M1 in the tributaries vary from as low as 12% to 34%. Thus, the relative importance of melt water originating from high-altitudes far overweighs that originating from mid-altitudes, in river runoff within UIB. The chief component of M1 is seasonal snows whereas M2 is a mixture of glacial melts, seasonal snows falling in winter and spring

  6. LJUBLJANICA CONNECTS - Restoration of the Ljubljanica River corridor and improvement of the river's flow regime

    Science.gov (United States)

    Zabret, Katarina; Sapač, Klaudija; Šraj, Mojca; Bezak, Nejc; Sečnik, Matej; Vidmar, Andrej; Brilly, Mitja

    2016-04-01

    The project Ljubljanica connects is focused on improving connectivity and living conditions in Ljubljanica River which flows through capital city of Slovenia, Ljubljana. It represents living environment for endangered and Natura 2000 targeted fish species Danube Salmon (Hucho hucho), Danube Roach (Rutilus pigus) and Striped Chub (Leuciscus souffia). The project consists of four sets of activities: concrete restoration actions including improvement of two fish passes, monitoring of fish migration, monitoring of eco-hydrological parameters, and raising of public awareness. To improve living conditions the concrete restoration measures were performed. The reconstructions of sill and two fish passes on the Ljubljanica River have been implemented and barrier's lifting system on the weir was modernized. Above the sill in Zalog there is an oxbow which was disconnected with main river channel during the low flows. Interrupted inflow of fresh water caused very poor living conditions for animals in the oxbow. The raise of the sill helped to improve this situation. One of the fish passes included in the project is more than 100 years old whereas both are protected as cultural and technical heritage. None was working properly and due to the protection no visible nor drastic measures were allowed. With smaller improvements we managed to re-establish their operation. A lifting system of the barrier at the Ambrožev trg gate was outdated and did not allow precise regulation of the water level. Too fast raising of the barrier instantly caused deterioration of eco-hydrological conditions downstream. With modernization of the electromechanical equipment the situation is improved. The fish monitoring helps us to evaluate success of concrete restoration actions. The fish population status is monitored with marking the fish with Visible Implant Elastomer (VIE) tags. Regarding the location of catch we implant tags beneath transparent or translucent tissue combining different tag

  7. Concentrated energy addition for active drag reduction in hypersonic flow regime

    Science.gov (United States)

    Ashwin Ganesh, M.; John, Bibin

    2018-01-01

    Numerical optimization of hypersonic drag reduction technique based on concentrated energy addition is presented in this study. A reduction in wave drag is realized through concentrated energy addition in the hypersonic flowfield upstream of the blunt body. For the exhaustive optimization presented in this study, an in-house high precision inviscid flow solver has been developed. Studies focused on the identification of "optimum energy addition location" have revealed the existence of multiple minimum drag points. The wave drag coefficient is observed to drop from 0.85 to 0.45 when 50 Watts of energy is added to an energy bubble of 1 mm radius located at 74.7 mm upstream of the stagnation point. A direct proportionality has been identified between energy bubble size and wave drag coefficient. Dependence of drag coefficient on the upstream added energy magnitude is also revealed. Of the observed multiple minimum drag points, the energy deposition point (EDP) that offers minimum wave drag just after a sharp drop in drag is proposed as the most optimum energy addition location.

  8. An objective and parsimonious approach for classifying natural flow regimes at a continental scale

    Science.gov (United States)

    Archfield, Stacey A.; Kennen, Jonathan G.; Carlisle, Daren M.; Wolock, David M.

    2014-01-01

    Hydro-ecological stream classification-the process of grouping streams by similar hydrologic responses and, by extension, similar aquatic habitat-has been widely accepted and is considered by some to be one of the first steps towards developing ecological flow targets. A new classification of 1543 streamgauges in the contiguous USA is presented by use of a novel and parsimonious approach to understand similarity in ecological streamflow response. This novel classification approach uses seven fundamental daily streamflow statistics (FDSS) rather than winnowing down an uncorrelated subset from 200 or more ecologically relevant streamflow statistics (ERSS) commonly used in hydro-ecological classification studies. The results of this investigation demonstrate that the distributions of 33 tested ERSS are consistently different among the classification groups derived from the seven FDSS. It is further shown that classification based solely on the 33 ERSS generally does a poorer job in grouping similar streamgauges than the classification based on the seven FDSS. This new classification approach has the additional advantages of overcoming some of the subjectivity associated with the selection of the classification variables and provides a set of robust continental-scale classes of US streamgauges. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

  9. Fast chemical reaction in two-dimensional Navier-Stokes flow: initial regime.

    Science.gov (United States)

    Ait-Chaalal, Farid; Bourqui, Michel S; Bartello, Peter

    2012-04-01

    This paper studies an infinitely fast bimolecular chemical reaction in a two-dimensional biperiodic Navier-Stokes flow. The reactants in stoichiometric quantities are initially segregated by infinite gradients. The focus is placed on the initial stage of the reaction characterized by a well-defined one-dimensional material contact line between the reactants. Particular attention is given to the effect of the diffusion κ of the reactants. This study is an idealized framework for isentropic mixing in the lower stratosphere and is motivated by the need to better understand the effect of resolution on stratospheric chemistry in climate-chemistry models. Adopting a Lagrangian straining theory approach, we relate theoretically the ensemble mean of the length of the contact line, of the gradients along it, and of the modulus of the time derivative of the space-average reactant concentrations (here called the chemical speed) to the joint probability density function of the finite-time Lyapunov exponent λ with two times τ and τ[over ̃]. The time 1/λ measures the stretching time scale of a Lagrangian parcel on a chaotic orbit up to a finite time t, while τ measures it in the recent past before t, and τ[over ̃] in the early part of the trajectory. We show that the chemical speed scales like κ(1/2) and that its time evolution is determined by rare large events in the finite-time Lyapunov exponent distribution. The case of smooth initial gradients is also discussed. The theoretical results are tested with an ensemble of direct numerical simulations (DNSs) using a pseudospectral model.

  10. The evaluation of validity of the RELAP5/Mod3 flow regime map for horizontal small diameter tubes at low pressure

    Energy Technology Data Exchange (ETDEWEB)

    Agafonova, N. [St. Petersburg State Technical Univ. (Russian Federation); Banati, J. [Lappeenranta Univ. of Technology (Finland)

    1997-12-31

    RELAP5/MOD3 code was developed for Western type power water reactors with vertical steam generators. Thus, this code should be validated also for WWER design with horizontal steam generators. In application for horizontal steam generators the situation with two-phase flow inside small diameter tubes is possible when the first circuit pressure drops in accident below the pressure level in the boiling water. It is known that computer codes have not always modelled correctly the two-phase flow inside horizontal tubes at low pressures (less than 4-6 MPa). It may be the result of erroneous prediction of the flow regime. Correct prediction of the flow regime is especially important for the fully or partly stratified flow in horizontal tubes. The aim of this study is the attempt of verification of the flow regime map, which is used in the RELAP5/MOD3 computer code for two-phase flow in horizontal small diameter tubes. `Small diameter tube` means according RELAP5/MOD3 that the inner diameter of the tube is less (or equal) than 0.018 m. The inner tube diameter in horizontal steam generators is equal 0.013 m. (orig.). 19 refs.

  11. Combustion wave propagation regimes in a channel equipped with an array of cross-flow cylindrical obstacles

    Science.gov (United States)

    Pinos, Thomas Arthur Richard

    Flame propagation through a channel equipped with obstacles was studied experimentally. Two types of obstacle geometries were investigated, i.e., wall-mounted cross-flow cylinders and fence-type obstacles mounted on the top and bottom channel surfaces. The motivation for this research is its applications to both high-speed propulsion and industrial explosion safety. The effect of obstacle distribution and blockage ratio on flame acceleration was investigated in a 2.54cm x 7.6cm "narrow" channel with wall-mounted cross-flow cylindrical obstacles. The cylinders were arranged in a "staggered" or "inline" pattern, with blockage ratios of 0.5 and 0.67. Schlieren images were used to study the flame shape and its leading edge velocity for a range of fuel-air mixtures compositions. It was determined that initial flame propagation occurs faster in higher blockage ratios due to the higher frequency perturbation to the flow. Flame acceleration led to different quasi-steady flame and detonation propagation regimes. In general, higher final steady flame velocities were reached in the lower blockage ratios, and detonation limits were found to be influenced by the geometry. The influence of channel width on flame acceleration was also determined using fence-type obstacles with a single blockage ratio. Experiments were performed in a 2.54cm x 7.6cm and 7.6cm x 7.6cm channel. Schlieren images were again used to study the flame shape and to obtain leading edge velocity. The flame tip was found to have a parabolic profile across the channel width for the narrower channel and flatter profile in the wider channel. It was determined that the channel width has a weak effect on the flame velocity down the channel length. As such, flame acceleration was initially only slightly more pronounced in the narrow channel before the reverse became true later in the wide channel.

  12. Using Flow Regime Lightning and Sounding Climatologies to Initialize Gridded Lightning Threat Forecasts for East Central Florida

    Science.gov (United States)

    Lambert, Winifred; Short, David; Volkmer, Matthew; Sharp, David; Spratt, Scott

    2007-01-01

    Each morning, the forecasters at the National Weather Service in Melbourne, FL (NWS MLB) produce an experimental cloud-to-ground (CG) lightning threat index map for their county warning area (CWA) that is posted to their web site (httl://www.srh.weather.gov/mlb/ghwo/lightning.shtml) . Given the hazardous nature of lightning in East Central Florida, especially during the warm season months of May September, these maps help users factor the threat of lightning, relative to their location, into their daily plans. The maps are color-coded in five levels from Very Low to Extreme, with threat level definitions based on the probability of lightning occurrence and the expected amount of CG activity. On a day in which thunderstorms are expected, there are typically two or more threat levels depicted spatially across the CWA. The locations of relative lightning threat maxima and minima often depend on the position and orientation of the low-level ridge axis, forecast propagation and interaction of sea/lake/outflow boundaries, expected evolution of moisture and stability fields, and other factors that can influence the spatial distribution of thunderstorms over the CWA. The lightning threat index maps are issued for the 24-hour period beginning at 1200 UTC each day with a grid resolution of 5 km x 5 km. Product preparation is performed on the AWIPS Graphical Forecast Editor (GFE), which is the standard NWS platform for graphical editing. Until recently, the forecasters created each map manually, starting with a blank map. To improve efficiency of the forecast process, NWS MLB requested that the Applied Meteorology Unit (AMU) create gridded warm season lightning climatologies that could be used as first-guess inputs to initialize lightning threat index maps. The gridded values requested included CG strike densities and frequency of occurrence stratified by synoptic-scale flow regime. The intent was to improve consistency between forecasters while allowing them to focus on the

  13. One-dimensional drift-flux model and constitutive equations for relative motion between phases in various two-phase flow regimes

    International Nuclear Information System (INIS)

    Ishii, M.

    1977-10-01

    In view of the practical importance of the drift-flux model for two-phase flow analysis in general and in the analysis of nuclear-reactor transients and accidents in particular, the kinematic constitutive equation for the drift velocity has been studied for various two-phase flow regimes. The constitutive equation that specifies the relative motion between phases in the drift-flux model has been derived by taking into account the interfacial geometry, the body-force field, shear stresses, and the interfacial momentum transfer, since these macroscopic effects govern the relative velocity between phases. A comparison of the model with various experimental data over various flow regimes and a wide range of flow parameters shows a satisfactory agreement

  14. Direct numerical simulation of a compressible boundary-layer flow past an isolated three-dimensional hump in a high-speed subsonic regime

    Science.gov (United States)

    De Grazia, D.; Moxey, D.; Sherwin, S. J.; Kravtsova, M. A.; Ruban, A. I.

    2018-02-01

    In this paper we study the boundary-layer separation produced in a high-speed subsonic boundary layer by a small wall roughness. Specifically, we present a direct numerical simulation (DNS) of a two-dimensional boundary-layer flow over a flat plate encountering a three-dimensional Gaussian-shaped hump. This work was motivated by the lack of DNS data of boundary-layer flows past roughness elements in a similar regime which is typical of civil aviation. The Mach and Reynolds numbers are chosen to be relevant for aeronautical applications when considering small imperfections at the leading edge of wings. We analyze different heights of the hump: The smaller heights result in a weakly nonlinear regime, while the larger result in a fully nonlinear regime with an increasing laminar separation bubble arising downstream of the roughness element and the formation of a pair of streamwise counterrotating vortices which appear to support themselves.

  15. Linking Flow Regime, Floodplain Lake Connectivity and Fish Catch in a Large River-Floodplain System, the Volga-Akhtuba Floodplain (Russian Federation)

    NARCIS (Netherlands)

    Wolfshaar, van de K.E.; Middelkoop, H.; Addink, E.; Winter, H.V.; Nagelkerke, L.A.J.

    2011-01-01

    River-floodplain systems are amongst the most productive—but often severely impacted—aquatic systems worldwide. We explored the ecological response of fish to flow regime in a large river-floodplain system by studying the relationships between (1) discharge and inundated floodplain area, with a

  16. Linking Flow Regime, Floodplain Lake Connectivity and Fish Catch in a Large River-Floodplain System, the Volga–Akhtuba Floodplain (Russian Federation)

    NARCIS (Netherlands)

    Wolfshaar, K.E. van de; Middelkoop, H.; Addink, E.A.; Winter, H.V.; Nagelkerke, L.A.J.

    2011-01-01

    River-floodplain systems are amongst the most productive—but often severely impacted—aquatic systems worldwide. We explored the ecological response of fish to flow regime in a large riverfloodplain system by studying the relationships between (1) discharge and inundated floodplain area, with a

  17. An integrated model for the natural flow regime in the Cerro Prieto hydrothermal system based upon petrological and isotope geochemical criteria

    Energy Technology Data Exchange (ETDEWEB)

    Elders, W.A.; Williams, A.E.; Hoagland, J..

    1981-01-01

    Studies of cuttings and cores at Cerro Prieto have now been extended to more than 50 boreholes. The aims of this petrological and isotopic work are to determine the shape of the reservoir, its physical properties, and its temperature distribution and flow regime before the steam field was produced.

  18. Characterizing flow regimes for floodplain forest conservation: An assessment of factors affecting sapling growth and survivorship on three cold desert rivers

    Science.gov (United States)

    Andersen, D.C.

    2005-01-01

    I analyzed annual height growth and survivorship of Fremont cottonwood (Populus fremontii S. Watson) saplings on three floodplains in Colorado and Utah to assess responses to interannual variation in flow regime and summer precipitation. Mammal exclosures, supplemented with an insecticide treatment at one site, were used to assess flow regime – herbivore interactions. Multiple regression analyses on data collected over 7–11 years indicated that growth of continuously injury-free saplings was positively related to either peak discharge or the maximum 30-day discharge but was not related to interannual decline in the late-summer river stage (ΔWMIN) or precipitation. Growth was fastest where ΔWMIN was smallest and depth to the late-summer water table moderate (≤1.5 m). Survivorship increased with ΔWMIN where the water table was at shallow depths. Herbivory reduced long-term height growth and survivorship by up to 60% and 50%, respectively. The results support the concept that flow history and environmental context determine whether a particular flow will have a net positive or negative influence on growth and survivorship and suggest that the flow regime that best promotes sapling growth and survival along managed rivers features a short spring flood pulse and constant base flow, with no interannual variation in the hydrograph. Because environmental contexts vary, interannual variation may be necessary for best overall stand performance.

  19. On the use of area-averaged void fraction and local bubble chord length entropies as two-phase flow regime indicators

    International Nuclear Information System (INIS)

    Hernandez, Leonor; Julia, J.E.; Paranjape, Sidharth; Hibiki, Takashi; Ishii, Mamoru

    2010-01-01

    In this work, the use of the area-averaged void fraction and bubble chord length entropies is introduced as flow regime indicators in two-phase flow systems. The entropy provides quantitative information about the disorder in the area-averaged void fraction or bubble chord length distributions. The CPDF (cumulative probability distribution function) of void fractions and bubble chord lengths obtained by means of impedance meters and conductivity probes are used to calculate both entropies. Entropy values for 242 flow conditions in upward two-phase flows in 25.4 and 50.8-mm pipes have been calculated. The measured conditions cover ranges from 0.13 to 5 m/s in the superficial liquid velocity j f and ranges from 0.01 to 25 m/s in the superficial gas velocity j g . The physical meaning of both entropies has been interpreted using the visual flow regime map information. The area-averaged void fraction and bubble chord length entropies capability as flow regime indicators have been checked with other statistical parameters and also with different input signals durations. The area-averaged void fraction and the bubble chord length entropies provide better or at least similar results than those obtained with other indicators that include more than one parameter. The entropy is capable to reduce the relevant information of the flow regimes in only one significant and useful parameter. In addition, the entropy computation time is shorter than the majority of the other indicators. The use of one parameter as input also represents faster predictions. (orig.)

  20. Recent flow regime and sedimentological evolution of a fluvial system as the main factors controlling spatial distribution of arsenic in groundwater (Red River, Vietnam)

    DEFF Research Database (Denmark)

    Kazmierczak, J.; Larsen, F.; Jakobsen, R.

    2016-01-01

    sediments was partially eroded during the Holocene and covered by sand and clay deposited in fluvial environments. Sedimentary processes lead to the development of two flow systems. Shallow groundwater discharges either to the local surface water bodies or, in the areas where low permeable sediments...... isolating Pleistocene and Holocene aquifers were eroded, to the deep groundwater flow system discharging to Red River. Previously reported pattern of arsenic groundwater concentrations decreasing with an increasing sediment age is modified by the observed flow regime. Connection of the younger and older...

  1. Numerical and experimental study of the slug-flow regime in a mixture of castor and paraffin oils in a T-type microchannel

    Science.gov (United States)

    Minakov, A. V.; Shebeleva, A. A.; Yagodnitsyna, A. A.; Kovalev, A. V.; Bilsky, A. V.

    2017-09-01

    The slow-flug regime in a mixture of castor and paraffin oils in a T-type microchannel with crosssectional dimensions of 200 × 400 μm has been studied by numerical and experimental methods. The domain of existence of the slow-flug regime in this system has been determined. Dependence of the paraffin-oil slug length on the ratio of flow rates of the mixture components is established. Comparison of the calculated and experimental data shows their good agreement.

  2. The Implication of Agricultural Expansion on the Groundwater Flow Regime of Saq Aquifer in Al Qassim Region, Saudi Arabia

    Science.gov (United States)

    Alharbi, T.; Mansour Helmy, B. M.

    2017-12-01

    Al-Qassim Region in Saudi Arabia is characterized by expanding agricultural activities. Most agricultural fields are irrigated by groundwater, mainly from the Saq aquifer. Excessive water extraction from this aquifer and arid climatic conditions negatively alter the quality and quantity of the groundwater. In this study, detailed hydrological and hydrogeological investigations were carried out to characterize spatially the potential groundwater recharge zones, deal with the estimation of groundwater balance of the Saq aquifer in the study area and to assess the safe yield of the aquifer. Accordingly, the implication of agricultural expansion on groundwater flow regime of Saq aquifer and its relation with safe yield and groundwater recharge was evaluated. The water-budget was calculated and the main water Inputs and outputs were measured. Change detections of agricultural areas in the region for years, 1983, 1995 and 2005 were conducted using Landsat Satellite images and results were compared to water levels for same years. There are two potential recharge zones for Saq aquifer in the area, both are structurally controlled. The first zone is the outlet of wadi Ar Risha basin in south-eastern corner of the study area. The second is the western water divide of wadi Turfiya basin in the North west. Results of the study also indicated that 96.4 % of the total abstraction is consumed for agriculture supply. The present abstractions exceed both recharge and safe yield of the aquifer system, thus the aquifer is overexploited and mined. The average decrease in groundwater storage during the year 1983-2005 was estimated to be 33.4 Mm3, representing an average yearly decline of 1.98 m of the water table.

  3. Population structure of the hydrocoral Millepora platyphylla in habitats experiencing different flow regimes in Moorea, French Polynesia.

    Directory of Open Access Journals (Sweden)

    Caroline E Dubé

    Full Text Available While the fire coral Millepora platyphylla is an important component of Indo-Pacific reefs, where it thrives in a wide range of environments, the ecological and biological processes driving its distribution and population structure are not well understood. Here, we quantified this species' population structure in five habitats with contrasting hydrodynamic regimes in Moorea, French Polynesia; two in the fore reef: mid and upper slopes, and three in the lagoon: back, fringing and patch reefs. A total of 3651 colonies of fire corals were mapped and measured over 45,000 m2 of surveyed reef. Due to the species' sensitivity to fragmentation in response to strong water movement, hydrodynamic conditions (e.g. waves, pass and lagoonal circulation corresponded to marked differences in colony size distributions, morphology and recruitment dynamics among habitats. The size structure varied among reef habitats with higher proportions of larger colonies in calm nearshore reefs (fringing and patch reefs, while populations were dominated by smaller colonies in the exposed fore reefs. The highest densities of fire corals were recorded in fore reef habitats (0.12-0.20 n.m-2 where the proportion of recruits and juveniles was higher at mid slope populations (49.3% than on the upper slope near where waves break (29.0%. In the latter habitat, most colonies grew as vertical sheets on encrusting bases making them more vulnerable to colony fragmentation, whereas fire corals were encrusting or massive in all other habitats. The lowest densities of M. platyphylla occurred in lagoonal habitats (0.02-0.04 n.m-2 characterized by a combination of low water movement and other physical and biological stressors. This study reports the first evidence of population structure of fire corals in two common reef environments and illustrates the importance of water flow in driving population dynamic processes of these reef-building species.

  4. A regime map for secondary flow structures under physiological and multi-harmonic inflow through a bent tube model for curved arteries

    Science.gov (United States)

    Callahan, Shannon M.; Caldwell, Kirin; Bulusu, Kartik V.; Plesniak, Michael W.

    2012-11-01

    Secondary flow structures are known to affect wall shear stress, which is closely related to atherogenesis and drug particle deposition. A regime map provides a framework to examine phase-wise variations in secondary flow structures under physiological and multi-harmonic inflow waveforms under conditions of a fixed Womersley number (4.2) and curvature ratio (1/7). Experimental PIV data were acquired at the 90-degree location in a 180-degree curved test section of a bent tube model for curved arteries using a blood analog working fluid. Coherent structure detection was performed using a continuous wavelet transform algorithm (PIVlet 1.2) and further analysis was carried out by grouping similar secondary flow structures at a fixed secondary Reynolds numbers. Phase-locked, planar vorticity fields over one period of inflow waveform revealed size, structure and strength similarities in secondary flow morphologies during the acceleration and deceleration phases. The utility of the new regime map lies in the a priori identification of pulsatile secondary flow structures, eliminating the need for exhaustive experimentation or computing, requiring only flow rate measurements that are easily acquired under clinical conditions. Supported by the National Science Foundation, Grant No. CBET-0828903 and GW Center for Biomimetics and Bioinspired Engineering (COBRE).

  5. On natural circulation in High Temperature Gas-Cooled Reactors and pebble bed reactors for different flow regimes and various coolant gases

    International Nuclear Information System (INIS)

    Melesed'Hospital, G.

    1983-01-01

    The use of CO 2 or N 2 (heavy gas) instead of helium during natural circulation leads to improved performance in both High Temperature Gas-Cooled Reactors (HTGR) and in Pebble Bed Reactors (PBR). For instance, the coolant temperature rise corresponding to a coolant pressure level and a rate of afterheat removal could be only 18% with CO 2 as compared to He, for laminar flow in HTGR; this value would be 40% in PBR. There is less difference between HTGR and PBR for turbulent flows; CO 2 is found to be always better than N 2 . These types of results derived from relationships between coolant properties, coolant flow, temperature rise, pressure, afterheat levels and core geometry, are obtained for HTGR and PBR for various flow regimes, both within the core and in the primary loop

  6. Assessment of climate change impact on river flow regimes in The Red River Delta, Vietnam – A case study of the Nhue-Day River Basin

    Directory of Open Access Journals (Sweden)

    Phan Cao Duong

    2016-09-01

    Full Text Available Global warming has caused dramatic changes in regional climate variability, particularly regarding fluctuations in temperature and rainfall. Thus, it is predicted that river flow regimes will be altered accordingly. The purpose of this paper is to present the results of modeling such changes by simulating discharge using the HEC-HMS model. The precipitation was projected using super-high resolution multiple climate models (20 km resolution with newly updated emission scenarios as the input for the HEC-HMS model for flow analysis at the Red River Basin in the northern area of Vietnam. The findings showed that climate change impact on the river flow regimes tend towards a decrease in the dry season and a longer duration of flood flow. A slight runoff reduction is simulated for November while a considerable runoff increase is modeled for July and August amounting to 30% and 25%, respectively. The discharge scenarios serve as a basis for water managers to develop suitable adaptation methods and responses on the river basin scale.

  7. Fertigação em mudas de citros utilizando-se mangueiras e microtubos sob regime de escoamento turbulento Fertigation on citrus seedlings using hoses and microtubes under turbulent flow regime

    Directory of Open Access Journals (Sweden)

    Wanderley J. Souza

    2011-08-01

    Full Text Available A irrigação localizada utilizando-se microtubo como emissor operando em regime de escoamento turbulento, pode ser uma alternativa viável, tanto técnica como economicamente para a produção de mudas de citros. Objetivou-se, com este trabalho, avaliar o desempenho de um sistema de fertigação na produção de mudas de laranja em viveiro projetado pelo modelo matemático universal, utilizando-se microtubos como emissores, sob regime de escoamento turbulento e comparar o desenvolvimento das plantas fertigadas por microtubos com o sistema em que se utiliza o método tradicional com mangueiras. No dimensionamento do comprimento dos emissores considerou-se o coeficiente K de dissipação de energia localizada através de um microtubo com diâmetro interno de 0,761 mm. O sistema de fertigação apresentou bom desempenho, com valores de grau de entupimento, uniformidade de Christiansen e uniformidade de emissão iguais a 0,50; 99,95 e 98,21%, respectivamente, após 160 dias de estudo. As plantas cultivadas via fertigação com microtubos e mangueiras, não apresentaram diferenças no que se refere ao diâmetro do caule e à altura. Desta forma, o uso de microtubo sob escoamento turbulento apresentou viabilidade técnica para fertigação.The use of localized irrigation using microtube as emitter under turbulent flow regime can be a technically feasible alternative. The objective of this study was to evaluate the performance of a fertigation system in nursery of citrus plants (greenhouse projected by universal mathematical model, using the microtubes as emitters, under turbulent flow rate and to compare the development of the fertigated plants by microtubes to the system that use the traditional method with hoses. In the size of the length of the emitters was considered the K coefficient of localized energy dissipation using a microtube with internal diameter of 0,761 mm. The fertigation system presented great performance with clogging degree

  8. FLOW REGIMES, GAS HOLD-UP AND AXIAL GAS MIXING IN THE GAS-LIQUID MULTISTAGE AGITATED CONTACTOR

    NARCIS (Netherlands)

    BREMAN, BB; BEENACKERS, AACM; BOUMA, MJ

    Experimental data are reported on Row regimes, gas hold-up and axial gas mixing of a gas-liquid Multi-stage Agitated Contactor (MAC), consisting of nine compartments [height, H, over diameter, D = 1; D = 0.09 m) separated by horizontal baffles with an opening of 0.04 m and with one centrally

  9. Exploring the physical controls of regional patterns of flow duration curves – Part 3: A catchment classification system based on regime curve indicators

    Directory of Open Access Journals (Sweden)

    M. Sivapalan

    2012-11-01

    Full Text Available Predictions of hydrological responses in ungauged catchments can benefit from a classification scheme that can organize and pool together catchments that exhibit a level of hydrologic similarity, especially similarity in some key variable or signature of interest. Since catchments are complex systems with a level of self-organization arising from co-evolution of climate and landscape properties, including vegetation, there is much to be gained from developing a classification system based on a comparative study of a population of catchments across climatic and landscape gradients. The focus of this paper is on climate seasonality and seasonal runoff regime, as characterized by the ensemble mean of within-year variation of climate and runoff. The work on regime behavior is part of an overall study of the physical controls on regional patterns of flow duration curves (FDCs, motivated by the fact that regime behavior leaves a major imprint upon the shape of FDCs, especially the slope of the FDCs. As an exercise in comparative hydrology, the paper seeks to assess the regime behavior of 428 catchments from the MOPEX database simultaneously, classifying and regionalizing them into homogeneous or hydrologically similar groups. A decision tree is developed on the basis of a metric chosen to characterize similarity of regime behavior, using a variant of the Iterative Dichotomiser 3 (ID3 algorithm to form a classification tree and associated catchment classes. In this way, several classes of catchments are distinguished, in which the connection between the five catchments' regime behavior and climate and catchment properties becomes clearer. Only four similarity indices are entered into the algorithm, all of which are obtained from smoothed daily regime curves of climatic variables and runoff. Results demonstrate that climate seasonality plays the most significant role in the classification of US catchments, with rainfall timing and climatic aridity index

  10. Unified rheology of vibro-fluidized dry granular media: From slow dense flows to fast gas-like regimes.

    Science.gov (United States)

    Gnoli, Andrea; Lasanta, Antonio; Sarracino, Alessandro; Puglisi, Andrea

    2016-12-07

    Granular media take on great importance in industry and geophysics, posing a severe challenge to materials science. Their response properties elude known soft rheological models, even when the yield-stress discontinuity is blurred by vibro-fluidization. Here we propose a broad rheological scenario where average stress sums up a frictional contribution, generalizing conventional μ(I)-rheology, and a kinetic collisional term dominating at fast fluidization. Our conjecture fairly describes a wide series of experiments in a vibrofluidized vane setup, whose phenomenology includes velocity weakening, shear thinning, a discontinuous thinning transition, and gaseous shear thickening. The employed setup gives access to dynamic fluctuations, which exhibit a broad range of timescales. In the slow dense regime the frequency of cage-opening increases with stress and enhances, with respect to μ(I)-rheology, the decrease of viscosity. Diffusivity is exponential in the shear stress in both thinning and thickening regimes, with a huge growth near the transition.

  11. Effects of flow regimes altered by dams on survival, population declines, and range-wide losses of California river-breeding frogs.

    Science.gov (United States)

    Kupferberg, Sarah J; Palen, Wendy J; Lind, Amy J; Bobzien, Steve; Catenazzi, Alessandro; Drennan, Joe; Power, Mary E

    2012-06-01

    Widespread alteration of natural hydrologic patterns by large dams combined with peak demands for power and water delivery during summer months have resulted in frequent aseasonal flow pulses in rivers of western North America. Native species in these ecosystems have evolved with predictable annual flood-drought cycles; thus, their likelihood of persistence may decrease in response to disruption of the seasonal synchrony between stable low-flow conditions and reproduction. We evaluated whether altered flow regimes affected 2 native frogs in California and Oregon (U.S.A.) at 4 spatial and temporal extents. We examined changes in species distribution over approximately 50 years, current population density in 11 regulated and 16 unregulated rivers, temporal trends in abundance among populations occupying rivers with different hydrologic histories, and within-year patterns of survival relative to seasonal hydrology. The foothill yellow-legged frog (Rana boylii), which breeds only in flowing water, is more likely to be absent downstream of large dams than in free-flowing rivers, and breeding populations are on average 5 times smaller in regulated rivers than in unregulated rivers. Time series data (range = 8 - 19 years) from 5 populations of yellow-legged frogs and 2 populations of California red-legged frogs (R. draytonii) across a gradient of natural to highly artificial timing and magnitude of flooding indicate that variability of flows in spring and summer is strongly correlated with high mortality of early life stages and subsequent decreases in densities of adult females. Flow management that better mimics natural flow timing is likely to promote persistence of these species and others with similar phenology. ©2012 Society for Conservation Biology.

  12. Characterization of performance reference compound kinetics and analyte sampling rate corrections under three flow regimes using nylon organic chemical integrative samplers.

    Science.gov (United States)

    Morrison, Shane A; Belden, Jason B

    2016-09-30

    Performance reference compounds (PRCs) can be spiked into passive samplers prior to deployment. If the dissipation kinetics of PRCs from the sampler corresponds to analyte accumulation kinetics, then PRCs can be used to estimate in-situ sampling rates, which may vary depending on environmental conditions. Under controlled laboratory conditions, the effectiveness of PRC corrections on prediction accuracy of water concentrations were evaluated using nylon organic chemical integrative samplers (NOCIS). Results from PRC calibrations suggest that PRC elimination occurs faster under higher flow conditions; however, minimal differences were observed for PRC elimination between fast flow (9.3cm/s) and slow flow (5.0cm/s) conditions. Moreover, minimal differences were observed for PRC elimination from Dowex Optipore L-493; therefore, PRC corrections did not improve results for NOCIS configurations containing Dowex Optipore L-493. Regardless, results suggest that PRC corrections were beneficial for NOCIS configurations containing Oasis HLB; however, due to differences in flow dependencies of analyte sampling rates and PRC elimination rates across the investigated flow regimes, the use of multiple PRC corrections was necessary. As such, a "Best-Fit PRC" approach was utilized for Oasis HLB corrections using caffeine-(13)C3, DIA-d5, or no correction based on the relative flow dependencies of analytes and these PRCs. Although PRC corrections reduced the variability when in-situ conditions differed from laboratory calibrations (e.g. static versus moderate flow), applying PRC corrections under similar flow conditions increases variability in estimated values. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Two-phase flow patterns and size distribution of droplets in a microfluidic T-junction: Experimental observations in the squeezing regime

    Science.gov (United States)

    Mahdi, Yassine; Daoud, Kamel; Tadrist, Lounès

    2017-04-01

    Generating micrometer sized droplets has been studied in a microfluidic system with T-junction geometry 250 μm in internal diameter and with PTFE capillary tubing. Several experiments were conducted by varying the flow rate of the dispersed phase from 2.78 ṡ10-11 m3 /s to 5.28 ṡ10-9 m3 /s and that of the continuous phase from 2.78 ṡ10-10 m3 /s to 1.94 ṡ10-9 m3 /s. The visualization of different flow regimes (drop, plug, and annular) was carried out for three configurations (not inverted in a horizontal position, inverted in a horizontal position, and inverted in a vertical position) for low capillary numbers. The model of Gauss was also chosen for a droplet size distribution in the dispersed phase, with the flow quality x varying from 0.016 to 0.44. The evolution of the drop size distribution as a function of the flow quality in the dispersed phase shows that the variation coefficient of the droplet's diameter is inversely proportional to the flow quality.

  14. An evaluation of the relations between flow regime components, stream characteristics, species traits and meta-demographic rates of warmwater stream fishes: Implications for aquatic resource management

    Science.gov (United States)

    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.

  15. Evaluation of dynamic loads induced by transient regimes of fluid flows in the pipe systems and devices of reducing the loads and their effects

    International Nuclear Information System (INIS)

    Serban, Viorel; Chirita, Alexandru Mihai; Androne, Marian; Alexandru, Constantin; Ciuca, Camelia; Badara, Janina; Alexandru, Carmen

    1995-01-01

    The paper presents the analytic methods for estimating the dynamic effects induced in pipe systems in transient regimes. They are based on computation programs developed in order to check the behaviour of ECCS and EWS under 'water hammer effect' and the behaviour of the primary circuit system under stresses caused by pipe cracks. Computation examples are presented in order to emphasize the capabilities of the programs to model transient phenomena in complex pipe networks. The overpressure induced by the water hammer effect, as revealed by comparing several transient regimes, depends on the fluid viscosity, the initial speed, the duration of starting the transient regime, the system rigidity, etc. Values several ten times higher that the initial one could be thus reached. An overview of new types of devices designed for damping the effect of water hammer phenomenon, as well as of sustaining supports for pipe systems and equipment able to damp the vibrations produced by the transient regimes of fluid flows and seismic movements is presented. These devices have also to cope with the high shocks produced by pipe breakage as well as high static loads. The paper contains the following sections: 1. Introduction; 2. Evaluating dynamic loads associated to the water hammer phenomenon; 3. Determining loads associated to the water hammer phenomenon for the ECC system of the Cernavoda NPP Unit 1; 4. Device for reducing the water hammer effects; 5. Evaluating dynamic loads associated to pipe cracks; 6. Determining loads associated to pipe cracks in the Cernavoda NPP primary circuit; 7. Devices for absorbing and damping the dynamic loads in pipe systems and equipment; 8. Conclusions. (authors)

  16. An equation of mean velocity of flow in non uniform regime, its relationship with the dispersion phenomenon as time function and its application to study of water quality

    International Nuclear Information System (INIS)

    Constain Aragon, A.; Lemos Ruiz, R.

    2011-01-01

    It is very well known the basic equation of hydraulics discovered by Antoine de Chezy in 1769, which relates in a quadratic from the mean velocity of flow with the slope of energy line and the hydraulic radius, in a uniform regime. This equation has been the central axis of development of hydro metrics as science that faces the huge challenges of penetrating the knowledge of earths streams every time more contaminated. In virtue of that, its mathematical structure and the relationship with other related formulas have been carefully examined, despite the limitation due to constancy of velocity. Starting from chemical considerations rather than dynamic ones as was used to obtain chezys relationship it is possible to establish a second equation for mean velocity of fluid in a non uniform regime that corresponds to averaged movement of a solute poured to steam. This equation will go to relate in an accurate way several aspects hydraulics and mass transport, sight as a single thing, allowing a vital tool for a depth study of water contaminations. to arrive this equation it was reviewed the foundations of mass transport theory in flows, stating a time dependent nature for coefficient currently used in describing dispersion phenomena allowing to interpret properly certain inconsistencies detected long time ago in this theory. It is presented the detailed results of application of this new approach to a small steam and a larger river in Colombia. (Author) 23 refs.

  17. Investigation of grid-enhanced two-phase convective heat transfer in the dispersed flow film boiling regime

    International Nuclear Information System (INIS)

    Miller, D.J.; Cheung, F.B.; Bajorek, S.M.

    2013-01-01

    Highlights: • Experiments were done in the RBHT facility to study the droplet flow in rod bundle. • The presence of a droplet field was found to greatly enhance heat transfer. • A second-stage augmentation was observed downstream of a spacer grid. • This augmentation is due to the breakup of liquid ligaments downstream of the grid. - Abstract: A two-phase dispersed droplet flow investigation of the grid-enhanced heat transfer augmentation has been done using steam cooling with droplet injection experimental data obtained from the Penn State/NRC Rod Bundle Heat Transfer (RBHT) facility. The RBHT facility is a vertical, full length, 7 × 7-rod bundle heat transfer facility having 45 electrically heated fuel rod simulators of 9.5 mm (0.374-in.) diameter on a 12.6 mm (0.496-in.) pitch which simulates a portion of a PWR fuel assembly. The facility operates at low pressure, up to 4 bars (60 psia) and has over 500 channels of instrumentation including heater rod thermocouples, spacer grid thermocouples, closely-spaced differential pressure cells along the test section, several fluid temperature measurements within the rod bundle flow area, inlet and exit flows, absolute pressure, and the bundle power. A series of carefully controlled and well instrumented steam cooling with droplet injection experiments were performed over a range of Reynolds numbers and droplet injection flow rates. The experimental results were analyzed to obtain the axial variation of the local heat transfer coefficients along the rod bundle. At the spacer grid location, the flow was found to be substantially disrupted, with the hydrodynamic and thermal boundary layers undergoing redevelopment. Owing to this flow restructuring, the heat transfer downstream of a grid spacer was found to be augmented above the fully developed flow heat transfer as a result of flow disruption induced by the grid. Furthermore, the presence of a droplet field further enhanced the heat transfer as compared to single

  18. Study of the interaction between a fluid and an oscillating structure: forces and flow regimes, from an isolated cylinder to a bundle of cylinders

    International Nuclear Information System (INIS)

    Duclercq, M.

    2010-01-01

    This thesis presents a 2D numerical and physical study of the dynamics of a viscous incompressible fluid initially at rest, put in motion by forced transverse rectilinear oscillations of a cylinder. That system is described by two dimensionless numbers. The Reynolds number (Re) measures the ratio of the inertial forces to the viscous forces, and the Keulegan-Carpenter number (KC) compares the amplitude of the cylinder oscillations to its diameter. The objective is to determine the influence of those two parameters on the drag and transverse forces exerted by the fluid on the structure, in relation with flow dynamics. The Navier-Stokes equations are numerically solved with a finite element method. Firstly various modes are identified from computational results regarding the flow and forces responses over an oscillation cycle. Flow symmetry properties and vortex patterns are correlated to the time-series of the forces. Besides simulations on long durations compared to the cylinder oscillation period reveal stability domains of the modes in the plane (KC, Re). For some regimes, forces exhibit amplitude fluctuations. They are interpreted notably from forces spectra and flow instabilities. Finally the transition from the problem of one cylinder to the case of a square bundle of 25 cylinders is studied. An energetic approach is proposed to characterize the influence of KC and Re on the global system's behavior, for the isolated cylinder and for the bundle. (author) [fr

  19. Flow regime mapping: outcome, or pre-requisite of tracer tests? (from the standpoint of deep-georeservoir characterization, development, operation, and monitoring)

    Science.gov (United States)

    Ghergut, Julia; Behrens, Horst; Sauter, Martin

    2017-04-01

    Tracer tests in deep-subsurface flow usually yield fluid residence time distributions (RTD) for a sparse selection of fluid spiking and fluid sampling points. Such RTD can be explained more or less adequately assuming certain flow and transport boundary conditions, and a fractured-porous void-space structure in which advective-dispersive transport and possibly partitioning/reactions at interfaces take place. Yet RTD do not by themselves enable to tell 'where' a flow process is taking place. So to say, "to trace is not to track", and 'tracking' would require some complementary kind of mapping, imaging, or monitoring - additionally to the metering of tracer fluxes at the few accessible 'places' in the georeservoir (i. e., deep boreholes) at which fluids can be sampled. We do not feel the need for such 'tracking' capability, when tracer-based RTD are used to predict the thermal lifetime of, say, a geothermal well doublet. However, the ability to 'locate' flow and transport processes (in both space and time) may become critical when facing environmental impacts of deep-georeservoir operation, and liabilities associated with these. On the other hand, it can also be a primary task in reservoir diagnostics and engineering, for instance when facing the question of whether and where to re-frac (in unconventional reservoir development). The poster describes three paradigm settings where a complementary, non-fluid-borne mapping of flow regimes (or at least of flow regime contrasts) appears as a very sensible, if not indispensable counterpart to tracer-based RTD for predicting (or accounting for) deep-georeservoir behavior. These are illustrated with (a) inter-well tracings of geothermally exploited Malm aquifers beneath the Munich metropolitan area, in analogy to past work conducted by Seiler et al. (1989) in the Franconian Alb; (b) single-well spikings of petrothermal or aquifer-based EGS in the N-German sedimentary basin, with two major issues left unresolved by Ghergut et

  20. Comparison of pollen gene flow among four European beech (Fagus sylvatica L.) populations characterized by different management regimes

    NARCIS (Netherlands)

    Piotti, A.; Leonardi, S.; Buiteveld, J.; Geburek, T.; Gerber, S.; Kramer, K.; Vettori, C.; Vendramin, G.G.

    2012-01-01

    The study of the dispersal capability of a species can provide essential information for the management and conservation of its genetic variability. Comparison of gene flow rates among populations characterized by different management and evolutionary histories allows one to decipher the role of

  1. The Impact of Manifold-to-Orifice Turning Angle on Sharp-Edge Orifice Flow Characteristics in both Cavitation and Non-Cavitation Turbulent Flow Regimes (Preprint)

    National Research Council Canada - National Science Library

    Nurick, W. H; Ohanian, T; Talley, D. G; Strakey, P. A

    2007-01-01

    .... This paper deals with predicting the initiation of cavitation, cavitation impacts on Cc, and non-cavitation impacts on Cd from L/D of 5 sharp-edge orifices with both single angle and compound angle directional flow...

  2. Oscillatory MHD convective flow of viscoelastic fluid through a porous medium in a rotating vertical channel in slip-flow regime with thermal radiation and hall current

    International Nuclear Information System (INIS)

    Singh, K.D.

    2013-01-01

    An exact solution of the magnetohydrodynamic (MHD) convective flow of a viscoelastic fluid through a porous medium filled in a vertical channel is obtained. One of the plates of the channel is subjected to a slip-flow condition and the other to a no-slip condition. The pressure gradient in the channel varies periodically with time. The entire system rotates in unison about an axis perpendicular to the planes of the channel plates. The fluid is electrically conducting and a magnetic field of uniform strength is applied along the axis of rotation. The non-uniform temperature difference of the plates is high enough to induce heat radiation. A closed form solution of the equations governing the flow is obtained. The effects of rotation, Hall current, slip-flow parameter, viscoelastic parameter, Grashof number, Reynolds number, permeability of the porous medium etc. are shown graphically on the velocity and skin friction and discussed in detail. (author)

  3. Laboratory Investigation of Rheology and Infiltration Process of Non-Newtonian Fluids through Porous Media in a Non-Isothermal Flow Regime for Effective Remediation of Contaminants

    Science.gov (United States)

    Naseer, F.

    2017-12-01

    Contamination of soil and groundwater by adsorbent (persistent) contaminants have been a major concern. Mine tailings, Acid mine drainage, waste disposal areas, active or abandoned surface and underground mines are some major causes of soil and water contamination. It is need of the hour to develop cost effective and efficient remediation techniques for clean-up of soil and aquifers. The objective of this research is to study a methodology of using non-Newtonian fluids for effective remediation of adsorbent contaminants in porous media under non-isothermal flow regimes. The research comprises of three components. Since, non-Newtonian fluid rheology has not been well studied in cold temperatures, the first component of the objective is to expose a non-Newtonian fluid (Guar gum solution) to different temperatures ranging from 30 °C through -5 °C to understand the change in viscosity, shear strength and contact angle of the fluid. Study of the flow characteristic of non-Newtonian fluids in complex porous media has been limited. Hence, the second component of this study will focus on a comparison of flow characteristics of a Newtonian fluid, non-Newtonian fluid and a combination of both fluids in a glass-tube-bundle setup that will act as a synthetic porous media. The study of flow characteristics will also be done for different thermal regimes ranging from -5 °C to 30 °C. The third component of the research will be to compare the effectiveness Guar gum to remediate a surrogate adsorbed contaminant at a certain temperature from the synthetic porous media. Guar gum is biodegradable and hence it is benign to the environment. Through these experiments, the mobility and behavior of Guar gum under varying temperature ranges will be characterized and its effectiveness in removing contaminants from soils will be understood. The impact of temperature change on the fluid and flow stability in the porous medium will be examined in this research. Guar gum is good suspension

  4. Modelling of arc jet plasma flow in transitional regime by Navier Stokes and state-to-state coupling

    International Nuclear Information System (INIS)

    Alexandrova, T.; Izrar, B.; Lino da Silva, M.; Dudeck, M.

    2005-01-01

    The combination of 2D Navier-Stokes and state-to-state approaches has been used to describe the air plasma flow in an arc-jet. The gas dynamic parameters were calculated in Navier-Stokes approximation in a steady state description without chemical reaction and vibrational exchanges. And then, the set of equations of vibrational level densities and atomic species densities was locally solved. Experimental validations have been performed

  5. A compressible two-phase model for dispersed particle flows with application from dense to dilute regimes

    Science.gov (United States)

    McGrath, Thomas P.; St. Clair, Jeffrey G.; Balachandar, S.

    2016-05-01

    Multiphase flows are present in many important fields ranging from multiphase explosions to chemical processing. An important subset of multiphase flow applications involves dispersed materials, such as particles, droplets, and bubbles. This work presents an Eulerian-Eulerian model for multiphase flows containing dispersed particles surrounded by a continuous media such as air or water. Following a large body of multiphase literature, the driving force for particle acceleration is modeled as a direct function of both the continuous-phase pressure gradient and the gradient of intergranular stress existing within the particle phase. While the application of these two components of driving force is well accepted in much of the literature, other models exist in which the particle-phase pressure gradient itself drives particle motion. The multiphase model treats all phases as compressible and is derived to ensure adherence to the 2nd Law of Thermodynamics. The governing equations are presented and discussed, and a characteristic analysis shows the model to be hyperbolic, with a degeneracy in the case that the intergranular stress, which is modeled as a configuration pressure, is zero. Finally, results from a two sample problems involving shock-induced particle dispersion are presented. The results agree well with experimental measurements, providing initial confidence in the proposed model.

  6. Decision Support System for Evaluation of Gunnison River Flow Regimes With Respect To Resources of the Black Canyon of the Gunnison National Park

    Science.gov (United States)

    Auble, Gregor T.; Wondzell, Mark; Talbert, Colin

    2009-01-01

    This report describes and documents a decision support system for the Gunnison River in Black Canyon of the Gunnison National Park. It is a macro-embedded EXCEL program that calculates and displays indicators representing valued characteristics or processes in the Black Canyon based on daily flows of the Gunnison River. The program is designed to easily accept input from downloaded stream gage records or output from the RIVERWARE reservoir operations model being used for the upstream Aspinall Unit. The decision support system is structured to compare as many as eight alternative flow regimes, where each alternative is represented by a daily sequence of at least 20 calendar years of streamflow. Indicators include selected flow statistics, riparian plant community distribution, clearing of box elder by inundation and scour, several measures of sediment mobilization, trout fry habitat, and federal reserved water rights. Calculation of variables representing National Park Service federal reserved water rights requires additional secondary input files pertaining to forecast and actual basin inflows and storage levels in Blue Mesa reservoir. Example input files representing a range of situations including historical, reconstructed natural, and simulated alternative reservoir operations are provided with the software.

  7. Supercritical strata in Lower Paleozoic fluvial rocks: a super critical link to upper flow regime processes and preservation in nature

    Science.gov (United States)

    Lowe, David; Arnott, Bill

    2015-04-01

    Recent experimental work has much improved our understanding of the lithological attributes of open-channel supercritical flow deposits, namely those formed by antidunes, chutes-and-pools and cyclic steps. However their limited documentation in the ancient sedimentary record brings into question details about their geological preservation. Antidune, chute-and-pool and cyclic step deposits are well developed in sandy ephemeral fluvial deposits of the Upper Cambrian - Lower Ordovician Potsdam Group in the Ottawa Embayment of eastern North America. These high energy fluvial strata form dm- to a few m-thick units intercalated within thick, areally expansive successions of sheet sandstones consisting mostly of wind ripple and adhesion stratification with common deflation lags. Collectively these strata record deposition in a semi-arid environment in which rare, episodic high-energy fluvial events accounted for most of the influx of sediment from upland sources. Following deposition, however, extensive aeolian processes reworked the sediment pile, and hence modified profoundly the preserved stratigraphic record. Antidune deposits occur as 0.2 - 1.6 m thick cosets made up of 2 - 15 cm thick lenticular sets of low angle (≤ 20o) cross-stratified, medium- to coarse-grained sandstone bounded by low-angle (5 - 15o) concave-upward scours and, in many cases, capped by low angle (10 - 15o) convex-upwards symmetrical formsets. Chute-and-pool deposits form single sets, 5 - 55 cm thick and 0.6 - 6 m wide, with scoured bases and low to high angle (5 - 25o) sigmoidal cross-strata consisting of medium- to coarse-grained sandstone. Cyclic step deposits consist of trough cross-stratified sets, 20 cm - 1.6 m thick, 2.5 - 12 m long and 7 - 35 m wide, typically forming trains that laterally are erosively juxtaposed at regularly-spaced intervals. They are composed of medium- to coarse-grained sandstone with concave-up, moderate to high angle (15 - 35o) cross-strata with tangential bases

  8. Prevalence

    Directory of Open Access Journals (Sweden)

    Ahmed E. Mansour

    2013-07-01

    Conclusion: The prevalence of spontaneous bacterial pleuritis in the studied group of patients with hepatic hydrothorax was 14.3%. Patients with advanced liver disease, low pleural fluid protein, or SBP are at risk for spontaneous bacterial pleuritis.

  9. Nitrogen pools and flows during lab-scale degradation of old landfilled waste under different oxygen and water regimes.

    Science.gov (United States)

    Brandstätter, Christian; Laner, David; Fellner, Johann

    2015-09-01

    Nitrogen emissions from municipal solid waste (MSW) landfills occur primarily via leachate, where they pose a long-term pollution problem in the form of ammonium. In-situ aeration was proposed as a remediation measure to mitigate nitrogenous landfill emissions, turning the anaerobic environment to anoxic and subsequently aerobic. As in-depth studies of the nitrogen cycle during landfill aeration had been largely missing, it was the aim of this work to establish a detailed nitrogen balance for aerobic and anaerobic degradation of landfilled MSW based on lab-scale experiments, and also investigating the effect of different water regimes on nitrogen transformation during aeration. Six landfill simulation reactors were operated in duplicate under different conditions: aerated wet (with water addition and recirculation), aerated dry (without water addition) and anaerobic (wet). The results showed that more than 78 % of the initial total nitrogen (TNinit) remained in the solids in all set ups, with the highest nitrogen losses achieved with water addition during aeration. In this case, gaseous nitrogen losses (as N2 due to denitrification) amounted up to 16.6 % of TNinit and around 4 % of TNinit was discharged via leachate. The aerated dry set-up showed lower denitrification rates (2.6-8.8 % of TNinit was released as N2), but was associated with the highest N2O emissions (3.8-3.9 % of TNinit). For the anaerobic treatment the main pathway of nitrogen discharge was the leachate, where NH4 accounted for around 8 % of TNinit. These findings provide the basis for improved management strategies to enhance nitrogen removal during in-situ aeration of old landfills.

  10. The Role of Public-Private Partnerships (PPPs) in Scaling Up Financial Flows in the Post-Kyoto Regime

    International Nuclear Information System (INIS)

    Galluccio, Giulia

    2015-01-01

    The climate change agenda requires adequate financial flows in the near future in order to support mitigation and adaptation efforts and the low-carbon development of emerging and new economies. The potentials of Public-Private Partnerships (PPPs) – as a risk-sharing structure bringing private funds on the table – are presented in the new climate change context. This article discusses and provides recommendations on PPPs as a good financing model to mainstream climate change into the development agenda of emerging and less-developed economies.

  11. Integrated parametric study of a hybrid-stabilized argon–water arc under subsonic, transonic and supersonic plasma flow regimes

    Czech Academy of Sciences Publication Activity Database

    Jeništa, Jiří; Takana, H.; Nishiyama, H.; Bartlová, M.; Aubrecht, V.; Křenek, Petr; Hrabovský, Milan; Kavka, Tetyana; Sember, Viktor; Mašláni, Alan

    2011-01-01

    Roč. 44, č. 43 (2011), s. 435204-435204 ISSN 0022-3727 R&D Projects: GA ČR GAP205/11/2070 Institutional research plan: CEZ:AV0Z20430508 Keywords : hybrid-stabilized electric arc * mass flow rate * net emission coefficients * partial characteristics * Mach number * shock diamonds Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.544, year: 2011 http://iopscience.iop.org/0022-3727/44/43/435204/pdf/0022-3727_44_43_435204.pdf

  12. Restoring Summer Base Flow under a Decentralized Water Management Regime: Constraints, Opportunities, and Outcomes in Mediterranean-Climate California

    Directory of Open Access Journals (Sweden)

    Matthew J. Deitch

    2017-01-01

    Full Text Available Seasonal rainfall dynamics in Mediterranean-climate coastal California place pressures on humans and aquatic ecosystems. Without rainfall during summer, residents and land managers commonly turn to streams and adjacent shallow aquifers to meet domestic, irrigation, and recreational water needs, often depleting the water necessary to support stream biota. The potential for adverse ecological impacts within this coupled natural-human system has led to interest in restoring summer base flow (especially for federally protected steelhead and coho salmon, which depend on flow through the summer dry season for juvenile survival through methods such as reducing dry-season water abstractions. Characterizing constraints and opportunities has proven useful for planning streamflow restoration in Mediterranean-climate coastal California. Biophysical parameters such as ample rainfall and very low summer discharge are critical considerations, but institutional parameters are equally important: regional management practices and state laws can inhibit streamflow restoration, and implementation is dependent on interrelationships among residents, agency staff, and other stakeholders (which we term the egosystem within each watershed. Additionally, while watershed-scale spatial analysis and field-based evaluations provided a solid foundation for exploring streamflow restoration needs, adaptation based on information from local stakeholders was often essential for prioritizing projects and understanding whether projects will have their intended benefits.

  13. Flow regimes and heat transfer modes identification in ANGRA 2 core, during small break in the primary loop with area of 100 cm2, simulated with RELAP5 code

    International Nuclear Information System (INIS)

    Borges, Eduardo M.; Sabundjian, Gaiane

    2015-01-01

    Identifying the flow regimes and the heat transfer modes is important for the analysis of accidents such as the Loss-of-Coolant Accident (LOCA). The aim of this paper is to identify the flow regimes, the heat transfer modes, and the correlations used in the RELAP5/MOD3.2.gama code in ANGRA 2 during the Small-Break Loss-of-Coolant Accident (SBLOCA) with a 100cm 2 -rupture area in the cold leg of primary loop. The Chapter 15 of the Final Safety Analysis Report of ANGRA 2 (FSAR - A2) reports this specific kind of accident. The results from this work demonstrated the several flow regimes and heat transfer modes that can be present in the core of ANGRA 2 during the postulated accident. (author)

  14. Flow regimes and heat transfer modes identification in ANGRA 2 core, during small break in the primary loop with area of 100 cm{sup 2}, simulated with RELAP5 code

    Energy Technology Data Exchange (ETDEWEB)

    Borges, Eduardo M.; Sabundjian, Gaiane, E-mail: gdgian@ipen.br, E-mail: borges.em@hotmail.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Identifying the flow regimes and the heat transfer modes is important for the analysis of accidents such as the Loss-of-Coolant Accident (LOCA). The aim of this paper is to identify the flow regimes, the heat transfer modes, and the correlations used in the RELAP5/MOD3.2.gama code in ANGRA 2 during the Small-Break Loss-of-Coolant Accident (SBLOCA) with a 100cm{sup 2}-rupture area in the cold leg of primary loop. The Chapter 15 of the Final Safety Analysis Report of ANGRA 2 (FSAR - A2) reports this specific kind of accident. The results from this work demonstrated the several flow regimes and heat transfer modes that can be present in the core of ANGRA 2 during the postulated accident. (author)

  15. Thermal regime at the Upper Stillwater dam site, Uinta mountains, Utah: Implications for terrain, microclimate and structural corrections in heat flow studies

    Science.gov (United States)

    Bauer, Michael S.; Chapman, David S.

    1986-08-01

    A detailed study of the subsurface thermal regime at the Upper Stillwater dam site, Uinta Mountains, northeast Utah, has been made. Temperature measurements were made in 36 drillholes located within a 1 km 2 area and ranging in depth from 20 to 97 m. Holes less than about 40 m deep were used only to obtain information about spatial variations in mean annual surface temperature. Several holes in or near talus slopes at the sides of the canyons have temperature minima approaching 0°C between 10 and 20 m indicating the presence of year-round ice at the base of the talus. Another set of holes show transient thermal effects of surface warming resulting from clearing of a construction site 3.5 years prior to our measurements. Most of the remaining holes show conductive behavior and have gradients ranging from 13° to 17°C km -1. Measurements made on 44 core samples yield a thermal conductivity of 5.6 (std. dev. 0.35) W m -1 K -1 for the Precambrian quartzite present. Surface heat flow estimates for these holes range from 70 to 100 mW m -2. However, the local disturbance of the thermal field by topography and microclimate is considerable. A finite difference method used to model these effects yielded a locally corrected Upper Stillwater heat flow of about 75 mW m -2. A final correction to account for the effects of refraction of heat from the low conductivity sedimentary rocks in the Uinta Basin into the high conductivity quartzite at the dam site, produced a regionally corrected Upper Stillwater heat flow between 60 and 65 mW m -2. This value is consistent with the observed heat flow of 60 mW m -2 in the Green River Basin to the north and the Uinta Basin to the south.

  16. Spatiotemporal dynamics of Phormidium cover and anatoxin concentrations in eight New Zealand rivers with contrasting nutrient and flow regimes.

    Science.gov (United States)

    McAllister, Tara G; Wood, Susanna A; Atalah, Javier; Hawes, Ian

    2018-01-15

    Toxic benthic cyanobacterial proliferations, particularly of the genus Phormidium, are a major concern in many countries due to their increasing extent and severity. The aim of this study was to improve the current understanding of the dominant physicochemical variables associated with high Phormidium cover and toxin concentrations. Phormidium cover and anatoxin concentrations were assessed weekly for 30weeks in eight predominately cobble-bed rivers in the South Island of New Zealand. Phormidium cover was highly variable both spatially (among and within sites) and temporally. Generalized additive mixed models (GAMMs) identified site, month of the year, conductivity and nutrient concentrations over the accrual period as significant variables associated with Phormidium cover. Cover was greatest under low to intermediate accrual dissolved inorganic nitrogen (DIN) and dissolved reactive phosphorus (DRP) concentrations. Accrual nutrients had a strong, negative effect on cover at concentrations>0.2mgL -1 DIN and 0.014mgL -1 DRP. The effect of flow was generally consistent across rivers, with cover accruing with time since the last flushing flow. Total anatoxins were detected at all eight study sites, at concentrations ranging from 0.008 to 662.5mgkg -1 dried weight. GAMMs predicted higher total anatoxin concentrations between November and February and during periods of accrual DRP<0.02mgL -1 . This study suggests that multiple physicochemical variables may influence Phormidium proliferations and also evidenced large site-to-site variability. This result highlights a challenge from a management perspective, as it suggests that mitigation options are likely to be site-specific. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Organic waste compounds in streams: Occurrence and aquatic toxicity in different stream compartments, flow regimes, and land uses in southeast Wisconsin, 2006–9

    Science.gov (United States)

    Baldwin, Austin K.; Corsi, Steven R.; Richards, Kevin D.; Geis, Steven W.; Magruder, Christopher

    2013-01-01

    An assessment of organic chemicals and aquatic toxicity in streams located near Milwaukee, Wisconsin, indicated high potential for adverse impacts on aquatic organisms that could be related to organic waste compounds (OWCs). OWCs used in agriculture, industry, and households make their way into surface waters through runoff, leaking septic-conveyance systems, regulated and unregulated discharges, and combined sewage overflows, among other sources. Many of these compounds are toxic at elevated concentrations and (or) known to have endocrine-disrupting potential, and often they occur as complex mixtures. There is still much to be learned about the chronic exposure effects of these compounds on aquatic populations. During 2006–9, the U.S. Geological Survey, in cooperation with the Milwaukee Metropolitan Sewerage District (MMSD), conducted a study to determine the occurrence and potential toxicity of OWCs in different stream compartments and flow regimes for streams in the Milwaukee area. Samples were collected at 17 sites and analyzed for a suite of 69 OWCs. Three types of stream compartments were represented: water column, streambed pore water, and streambed sediment. Water-column samples were subdivided by flow regime into stormflow and base-flow samples. One or more compounds were detected in all 196 samples collected, and 64 of the 69 compounds were detected at least once. Base-flow samples had the lowest detection rates, with a median of 12 compounds detected per sample. Median detection rates for stormflow, pore-water, and sediment samples were more than double that of base-flow samples. Compounds with the highest detection rates include polycyclic aromatic hydrocarbons (PAHs), insecticides, herbicides, and dyes/pigments. Elevated occurrence and concentrations of some compounds were detected in samples from urban sites, as compared with more rural sites, especially during stormflow conditions. These include the PAHs and the domestic waste

  18. Prevalence of cryptococcal infection among advanced HIV patients in Argentina using lateral flow immunoassay.

    Directory of Open Access Journals (Sweden)

    Claudia Frola

    Full Text Available Globally, Latin America ranks third among regions with most cases of AIDS related cryptococcal meningitis. In 2009, a lateral flow immunoassay (LFA for the detection of cryptococcal antigen (CrAg was developed as a potential point-of-care test for diagnosis of cryptococcal infection. In 2011 World Health Organizations recommended on CrAg screening for HIV positive persons with CD4 below 100 cells/μL, followed by preemptive fluconazole treatment. However, in Argentina no formal recommendations for CrAg screening have been issued.HIV positive patients > = 18 years with advanced immunosuppression (CD4 counts ≤100 cells/μL within 3 months or WHO stage III/IV, who visited the hospital between April 1, 2014 and January 31, 2015, were included. The LFA was performed according to the manufacturer's instructions on all serum samples. When CrAg detection was positive, a lumbar puncture was performed to rule out cryptococcal meningitis. Patients without evidence of meningeal involvement were treated with preemptive oral fluconazole in ambulatory care.We included 123 patients. Prevalence of CrAg-positivity was 8.1%. Among the 10 CrAg-positive patients, 6 had meningeal involvement detected through the CSF analysis (CSF India-ink testing, CSF CrAg and culture. The remaining 4 patients with positive CrAg received targeted preemptive treatment with oral fluconazole and were free of cryptococcal disease during the follow-up period. None of the 113 patients with a negative CrAg test result developed cryptococcal disease.This is the first study in Argentina, to our knowledge, describing the prevalence of cryptococcosis and usefulness of CrAg screening. LFA provided early diagnosis to determine a high prevalence of CrAg in our hospital, and that screening for subclinical infection with preemptive antifungal treatment, prevented a substantial proportion of meningeal disease.

  19. Implementation of leak detection techniques in ducts with critical regimen multiphase flow; Implementacao de tecnicas de deteccao de vazamentos em dutos em regime de escoamento multifasico critico

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Rodrigo S.; Maitelli, Andr L.; Doria Neto, Adriao D.; Salazar, Andres O. [Rio Grande do Norte Univ., Natal, RN (Brazil)

    2005-07-01

    This paper presents signals processing techniques and artificial neural networks to identify leaks in multiphase flow pipeline. The greatest difficulty on traditional methods of leak detection (volume balance, pressure point analysis, etc) is that they are insufficient to design an adequate profile for the real conditions of oil pipeline transport. These difficult conditions goes since unevenly soil, that cause columns or vacuum throughout pipelines, until the presence of multi phases like water, gas and oil; plus other components as sand, which use to produce discontinuous flow off and diverse variations. To attenuate these difficulties, the transform wavelet was used to map the signal pressure in different resolution plan allowing the extraction of descriptors that identify leaks patterns and with then to provide training for the neural network multilayer perceptron (MLP) to learning of how to classify this pattern and report whenever this characterize leaks. During the tests were used transient and regime signals and pipelines with punctures with size variations from 1/2'' to 1'' of diameter to simulate leaks and, this way, it was possible to detect leaks with a time window of two minutes. The result show that the proposed descriptors considered, based in statistical methods applied in domain transform, are sufficient to identify leaks patterns and make it possible to train the neural classifier to indicate the occurrence of pipeline leaks. (author)

  20. Prevalence

    Directory of Open Access Journals (Sweden)

    Mohammed Al-Darwish

    2014-07-01

    Conclusion: Results indicated that dental caries prevalence among school children in Qatar has reached critical levels, and is influenced by socio-demographic factors. The mean decayed, missing, and filled teeth values obtained in this study were the second highest detected in the Eastern Mediterranean region.

  1. Prevalence

    Directory of Open Access Journals (Sweden)

    Jeanesse Scerri

    2013-09-01

    Full Text Available Methicillin-resistant Staphylococcus aureus (MRSA is a major nosocomial pathogen worldwide. Malta is one of the countries with the highest MRSA prevalence in Europe, as identified from hospital blood cultures [1]. However, community prevalence of MRSA has never previously been investigated. This study aimed at establishing the prevalence of community MRSA nasal colonization in Maltese individuals and identifying the clonal characteristics of the detected isolates. Nasal swabs were collected from 329 healthy individuals who were also asked to complete a brief questionnaire about risk factors commonly associated with MRSA carriage and infection. The swabs were transported and enriched in a nutrient broth supplemented with NaCl. The presence of MRSA was then determined by culturing on MRSA Select chromogenic agar and then confirming by several assays, including catalase, coagulase and PBP2a agglutination tests. The isolates were assayed for antibiotic susceptibilities and typed by microarray analysis to determine the clonal characteristics of each strain. The prevalence of MRSA nasal colonization in the healthy Maltese population was found to be 8.81% (95% confidence interval [CI], 5.75–11.87%, much higher than that found in other studies carried out in several countries. No statistical association was found between MRSA carriage and demographics or risk factors; however, this was hindered by the small sample size. Almost all the isolates were fusidic-acid resistant. The majority were found to belong to a local endemic clone (CC5 which seems to be replacing the previously prevalent European clone UK-EMRSA-15 in the country. A new clone (CC50-MRSA-V was also characterized. The presence of such a significant community reservoir of MRSA increases the burdens already faced by the local healthcare system to control the MRSA epidemic. Colonization of MRSA in otherwise healthy individuals may represent a risk for endogenous infection and transmission to

  2. Carbon pools and flows during lab-scale degradation of old landfilled waste under different oxygen and water regimes.

    Science.gov (United States)

    Brandstätter, Christian; Laner, David; Fellner, Johann

    2015-06-01

    Landfill aeration has been proven to accelerate the degradation of organic matter in landfills in comparison to anaerobic decomposition. The present study aims to evaluate pools of organic matter decomposing under aerobic and anaerobic conditions using landfill simulation reactors (LSR) filled with 40 year old waste from a former MSW landfill. The LSR were operated for 27 months, whereby the waste in one pair was kept under anaerobic conditions and the four other LSRs were aerated. Two of the aerated LSR were run with leachate recirculation and water addition and two without. The organic carbon in the solid waste was characterized at the beginning and at the end of the experiments and major carbon flows (e.g. TOC in leachate, gaseous CO2 and CH4) were monitored during operation. After the termination of the experiments, the waste from the anaerobic LSRs exhibited a long-term gas production potential of more than 20 NL kg(-1) dry waste, which corresponded to the mineralization of around 12% of the initial TOC (67 g kg(-1) dry waste). Compared to that, aeration led to threefold decrease in TOC (32-36% of the initial TOC were mineralized), without apparent differences in carbon discharge between the aerobic set ups with and without water addition. Based on the investigation of the carbon pools it could be demonstrated that a bit more than 10% of the initially present organic carbon was transformed into more recalcitrant forms, presumably due to the formation of humic substances. The source of anaerobic degradation could be identified mainly as cellulose which played a minor role during aerobic degradation in the experiment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. A free-surface hydrodynamic model for density-stratified flow in the weakly to strongly non-hydrostatic regime

    International Nuclear Information System (INIS)

    Shen, Colin Y.; Evans, Thomas E.

    2004-01-01

    A non-hydrostatic density-stratified hydrodynamic model with a free surface has been developed from the vorticity equations rather than the usual momentum equations. This approach has enabled the model to be obtained in two different forms, weakly non-hydrostatic and fully non-hydrostatic, with the computationally efficient weakly non-hydrostatic form applicable to motions having horizontal scales greater than the local water depth. The hydrodynamic model in both its weakly and fully non-hydrostatic forms is validated numerically using exact nonlinear non-hydrostatic solutions given by the Dubriel-Jacotin-Long equation for periodic internal gravity waves, internal solitary waves, and flow over a ridge. The numerical code is developed based on a semi-Lagrangian scheme and higher order finite-difference spatial differentiation and interpolation. To demonstrate the applicability of the model to coastal ocean situations, the problem of tidal generation of internal solitary waves at a shelf-break is considered. Simulations carried out with the model obtain the evolution of solitary wave generation and propagation consistent with past results. Moreover, the weakly non-hydrostatic simulation is shown to compare favorably with the fully non-hydrostatic simulation. The capability of the present model to simulate efficiently relatively large scale non-hydrostatic motions suggests that the weakly non-hydrostatic form of the model may be suitable for application in a large-area domain while the computationally intensive fully non-hydrostatic form of the model may be used in an embedded sub-domain where higher resolution is needed

  4. Modelling of air flow supply in a room at variable regime by using both K - E and spalart - allmaras turbulent model

    Science.gov (United States)

    Korbut, Vadim; Voznyak, Orest; Sukholova, Iryna; Myroniuk, Khrystyna

    2017-12-01

    The abstract is to The article is devoted to the decision of actual task of air distribution efficiency increasing with the help of swirl and spread air jets to provide normative parameters of air in the production apartments. The mathematical model of air supply with swirl and spread air jets in that type of apartments is improved. It is shown that for reachin of air distribution maximal efficiency it is necessary to supply air by air jets, that intensively extinct before entering into a working area. Simulation of air flow performed with the help of CFD FLUENT (Ansys FLUENT). Calculations of the equation by using one-parameter model of turbulence Spalart-Allmaras are presented. The graphical and the analytical dependences on the basis of the conducted experimental researches, which can be used in subsequent engineering calculations, are shown out. Dynamic parameters of air flow that is created due to swirl and spread air jets at their leakage at variable regime and creation of dynamic microclimate in a room has been determined. Results of experimental investigations of air supply into the room by air distribution device which creates swirl air jets for creation more intensive turbulization air flow in the room are presented. Obtained results of these investigations give possibility to realize engineer calculations of air distribution with swirl air jets. The results of theoretical researches of favourable influence of dynamic microclimate to the man are presented. When using dynamic microclimate, it's possible to decrease conditioning and ventilation system expenses. Human organism reacts favourably on short lasting deviations from the rationed parameters of air environment.

  5. Modelling of air flow supply in a room at variable regime by using both K - E and spalart – allmaras turbulent model

    Directory of Open Access Journals (Sweden)

    Korbut Vadim

    2017-12-01

    Full Text Available The abstract is to The article is devoted to the decision of actual task of air distribution efficiency increasing with the help of swirl and spread air jets to provide normative parameters of air in the production apartments. The mathematical model of air supply with swirl and spread air jets in that type of apartments is improved. It is shown that for reachin of air distribution maximal efficiency it is necessary to supply air by air jets, that intensively extinct before entering into a working area. Simulation of air flow performed with the help of CFD FLUENT (Ansys FLUENT. Сalculations of the equation by using one-parameter model of turbulence Spalart-Allmaras are presented. The graphical and the analytical dependences on the basis of the conducted experimental researches, which can be used in subsequent engineering calculations, are shown out. Dynamic parameters of air flow that is created due to swirl and spread air jets at their leakage at variable regime and creation of dynamic microclimate in a room has been determined. Results of experimental investigations of air supply into the room by air distribution device which creates swirl air jets for creation more intensive turbulization air flow in the room are presented. Obtained results of these investigations give possibility to realize engineer calculations of air distribution with swirl air jets. The results of theoretical researches of favourable influence of dynamic microclimate to the man are presented. When using dynamic microclimate, it’s possible to decrease conditioning and ventilation system expenses. Human organism reacts favourably on short lasting deviations from the rationed parameters of air environment.

  6. Comparative study on the influence of depth, number and arrangement of dimples on the flow and heat transfer characteristics at turbulent flow regimes

    Science.gov (United States)

    Nazari, Saeed; Zamani, Mahdi; Moshizi, Sajad A.

    2018-03-01

    The ensuing study is dedicated to a series of numerical investigations concerning the effects of various geometric parameters of dimpled plates on the flow structure and heat transfer performance in a rectangular duct compared to the smooth plate. These parameters are the arrangement, number and depth of dimples. Two widely used staggered and square patterns in addition to a triangular arrangement, and three dimple depths (Δ = δ/d = 0.25, 0.375 and 0.5) have been chosen for this particular study. All studies have been conducted at three different Reynolds numbers Re = 25,000, 50,000 and 100,000. In order to capture the flow structures in the vicinity of dimples and contributing phenomena related to the boundary layer interactions, fully structured grids with y+ rims of dimples are the causes for improved average Nusselt number in the dimpled surface in comparison to the smooth plate. However, more pressure loss due to the higher friction drag and recirculation zones inside dimples will exist as a drawback in this system. Moreover, for all arrangements increasing dimple ratio Δ has a negative impact on the heat transfer augmentation and also deteriorates the pressure loss, which leads to this fact that Δ = 0.25 serves as the best option for the dimple depth.

  7. Regime change?

    International Nuclear Information System (INIS)

    Pilat, Joseph F.; Budlong-Sylvester, K.W.

    2004-01-01

    Following the 1998 nuclear tests in South Asia and later reinforced by revelations about North Korean and Iraqi nuclear activities, there has been growing concern about increasing proliferation dangers. At the same time, the prospects of radiological/nuclear terrorism are seen to be rising - since 9/11, concern over a proliferation/terrorism nexus has never been higher. In the face of this growing danger, there are urgent calls for stronger measures to strengthen the current international nuclear nonproliferation regime, including recommendations to place civilian processing of weapon-useable material under multinational control. As well, there are calls for entirely new tools, including military options. As proliferation and terrorism concerns grow, the regime is under pressure and there is a temptation to consider fundamental changes to the regime. In this context, this paper will address the following: Do we need to change the regime centered on the Treaty on the Nonproliferation of Nuclear Weapons (NPT) and the International Atomic Energy Agency (IAEA)? What improvements could ensure it will be the foundation for the proliferation resistance and physical protection needed if nuclear power grows? What will make it a viable centerpiece of future nonproliferation and counterterrorism approaches?

  8. Exploring the physical controls of regional patterns of flow duration curves – Part 2: Role of seasonality, the regime curve, and associated process controls

    Directory of Open Access Journals (Sweden)

    M. Sivapalan

    2012-11-01

    Full Text Available The goal of this paper is to explore the process controls underpinning regional patterns of variations of streamflow regime behavior, i.e., the mean seasonal variation of streamflow within the year, across the continental United States. The ultimate motivation is to use the resulting process understanding to generate insights into the physical controls of another signature of streamflow variability, namely the flow duration curve (FDC. The construction of the FDC removes the time dependence of flows. Thus in order to better understand the physical controls in regions that exhibit strong seasonal dependence, the regime curve (RC, which is closely connected to the FDC, is studied in this paper and later linked back to the FDC. To achieve these aims a top-down modeling approach is adopted; we start with a simple two-stage bucket model, which is systematically enhanced through addition of new processes on the basis of model performance assessment in relation to observations, using rainfall-runoff data from 197 United States catchments belonging to the MOPEX dataset. Exploration of dominant processes and the determination of required model complexity are carried out through model-based sensitivity analyses, guided by a performance metric. Results indicated systematic regional trends in dominant processes: snowmelt was a key process control in cold mountainous catchments in the north and north-west, whereas snowmelt and vegetation cover dynamics were key controls in the north-east; seasonal vegetation cover dynamics (phenology and interception were important along the Appalachian mountain range in the east. A simple two-bucket model (with no other additions was found to be adequate in warm humid catchments along the west coast and in the south-east, with both regions exhibiting strong seasonality, whereas much more complex models are needed in the dry south and south-west. Agricultural catchments in the mid-west were found to be difficult to predict

  9. Performance Evaluation of AI2O3/Water Nanofluid as Coolant in a Double-Tube Heat Exchanger Flowing under a Turbulent Flow Regime

    Directory of Open Access Journals (Sweden)

    Navid Bozorgan

    2012-01-01

    Full Text Available Nanofluids are expected to be a promising coolant candidate in chemical processes for water waste remediation and heat transfer system size reduction. This paper focuses on the potential mass flowrate reduction in exchanger with a given heat exchange capacity using nanofluids. Al2O3 nanoparticles with diameters of 7 nm dispersed in water with volume concentrations up to 2% are selected as a coolant, and their performance in a horizontal double-tube counterflow heat exchanger under turbulent flow conditions is numerically studied. The results show that the flowrate of nanofluid coolant decreases with the increase of concentration of nanoparticles in the exchanger with a given heat exchange capacity. The mass flowrate of the nanofluid at a volume concentration of 2 vol.% is approximately 24.5% lower than that of pure water (base fluid for given conditions. For the pressure drop, the results show that the pressure drop of nanofluid is slightly higher than water and increases with increase of volume concentrations. In addition, the reduction of wall temperature and heat transfer area is estimated.

  10. Influence of ion effects on a space charge limited field emission flow: from non-relativistic to ultra-relativistic regimes

    Science.gov (United States)

    Lin, M. C.; Chang, P. C.; Lu, P. S.; Verboncoeur, J. P.

    2011-10-01

    Influence of ion effects on a space charge limited field emission flow has been studied systematically, by employing both analytical and numerical approaches. In our model, the field emission of electrons is described by the Fowler-Nordheim equation. The cathode plasma and surface properties are considered within the framework of an effective work function approximation. Ionization effects at the anode as well as electron space-charge effects are described by Poisson's equation coupled with the energy conservation equation including the relativistic effects. The calculations are carried out self-consistently to yield the steady states of the bipolar flow. The electric field on the cathode surface is found to be saturated due to space charge effects and is determined by the effective work function approximately. In addition, the upstream ion current bas been treated as a tuning parameter. It is found that the field emission currents in the presence of saturated ion currents can be enhanced to be nearly 1.8, 1.5, and 1.4 times of the cases with no upstream ion current in non-relativistic, intermediate, and ultra-relativistic regimes, respectively. The solutions have also been verified using 1D PIC simulations, as implemented in the OOPD1 code developed by PTSG of UC Berkeley. Work supported by the National Science Council, Taiwan, R.O.C. under Grant No. NSC 96-2112-M-030-004-MY3, National Center for Theoretical Sciences, and National Center for High-Performance Computing, Taiwan, ROC which provides the computing resources.

  11. Flow regime map for two dimensional spouted bed and comparison with simulation by discrete element method; Nijigen funryuso no ryudo jotaizu to risan yosoho ni yoru shumyureshon kekka tono hikaku

    Energy Technology Data Exchange (ETDEWEB)

    Tsuji, T.; Chiba, T.; Shibata, T.; Uemaki, O.; Ito, H. [Hokkaido University, Hokkaido (Japan)

    1999-11-10

    A flow regime map for a two-dimensional spouted bed is constructed from the experimental conditions that cause the fixed bed, spouted bed, bubbling fluidized bed and slugging bed. The map is compared to the one that is made from the simulations using P-TAK, a general-purpose simulation code of gas and particle flow by the discrete element method. Both maps coincide very well, indicating that the discrete element method has big potential for predicting critical flow conditions such as the minimum spouting velocity or the maximum spoutable bed height. (author)

  12. Hydrological regimes in Balkan Area

    International Nuclear Information System (INIS)

    Stanescu, Viorel Alexandru

    2004-01-01

    Physical considerations of the deemed area are first considered in the paper. Then the regime types around the Balkan rivers are described in terms of the following characteristic features: -Types of the regimes defined by the timing of the high and low flow phases; -Regionalisation of the 'micro-types' -Stability of the river flow regimes. The available mean monthly discharge data of the representative rivers allows characterising the river regime of the Balkan area covered by WOISYDES and BALWOIS projects. The classification of the hydrological regimes (types of regimes) was done by assessing the discriminant periods (descriptors of the regime phases) defined by the first, the second and the third highest and lowest monthly values of flows. As sufficient data has been provided by countries involved in the Woisydes/Balwois Project a hydrological regionalisation is performed all around the considered space. The existence of different zones, which are quasi- homogeneous in terms of physiographical properties, the latter especially being expressed by their mean altitudes and the climatic features, allowed to carry out a hydrological regionalisation of the river flow regime types. The regionalisation of the river flow regimes is presented as hydrological maps both referring to each Balkan country and for the entire region as an overall map. The stability of a certain flow regime is an important descriptor of the ecological state of the river during the year. It may be quantitatively expressed by the stability coefficient determined by Corbus and Stanescu as the product between the frequency of the occurrence of any discriminant value in m subsequent month (m = 1,12) and a distribution coefficient along the period that depend on the length of the considered discriminant period. The advantage of this method stands in the fact that for several combinations of subsequent months, the maximisation of the stability coefficient leads to the assessment of the characteristic

  13. Process optimization of CNP removal from industrial soft drink wastewater in a single up flow A2O with continuous feed and intermittent discharge regime.

    Science.gov (United States)

    Nouri, Amir; Zinatizadeh, Ali Akbar

    2018-03-01

    Simultaneous removal of carbon and nutrients (CNP) in a single laboratory-scale bioreactor is advantageous in terms of reactor volume and energy consumption. In this study, an innovative up-flow anaerobic/anoxic/aerobic (A2O) single bioreactor with continuous feed and intermittent discharge (CFID) regime equipped with a movable aerator in the reactor height for simultaneous removal of CNP from soft drinks wastewater was successfully designed, fabricated and operated. The effects of four independent variables, i.e. hydraulic retention time (HRT), aerator height, biomass concentration and nitrogen/soluble chemical oxygen demand (N/sCOD) ratio at three levels in the range of 4-8 h, 37-55.5 cm, 4,000-6,000 -1 , and 0.05-0.2, respectively, on eight process responses were investigated. The central composite design (CCD) and response surface methodology (RSM) were applied to design the experimental conditions, model the obtained data, and optimize the process. The bioreactor provides three conditions with different dissolved oxygen (DO) (anaerobic, anoxic and aerobic) in a single bioreactor by placing the aerator in the middle of the reactor. As a result, the maximum sCOD, total nitrogen (TN) and total phosphorus (TP) removal were about 100, 92 and 41%, respectively. The optimum region obtained was an HRT of 5-11 h, a mixed liquor suspended solids (MLSS) concentration of 4,000-4,700 mgL - 1 , and an aerator height of 46.25 cm, at the N/sCOD ratio of 0.1.

  14. Recent changes (1973-2014 versus 1903-1972) in the flow regime of the Lower Paraná River and current fluvial pollution warnings in its Delta Biosphere Reserve.

    Science.gov (United States)

    Puig, Alba; Olguín Salinas, Héctor F; Borús, Juan A

    2016-06-01

    Alterations in flow regimes of large rivers may originate or increase risks to ecosystems and humans. The Paraná River basin (South America) undergoes human pressures (e.g., heavy damming in the upper basin, deforestation, and mixed pollution) that may affect the water quantity and quality of its terminal Delta (Argentina). In this study, after applying univariate and multivariate change-point detection and trend analyses to the daily data series of flows incoming to the Delta (Paraná-Santa Fe section), flow characteristics were compared by Indicators of Hydrologic Alteration (IHA) and Environmental Flow Components (EFC). Some flood characteristics were also compared from hydrometric levels in the middle Delta (San Pedro station). Chemical and microbiological water variables in the main rivers of the "Paraná Delta" Biosphere Reserve were examined during two extreme hydrologic years (October 2008 to July 2010) to detect potential risk factors in association with hydrologic conditions. In the Lower Paraná River, a historical period (1903-1972) and two more altered periods (1973-1999 wet period and 2000-2014 dry period) were identified. Flow duration curves evidenced different changes in both altered periods, reflecting the joint effect of climatic variability and human influence. The most evident alterations in the flow regime were the lack of record of the extreme-low-flow component, the attenuation of monthly flow seasonality, and the increase in the number of reversals (dry period) and in the variability of maximum and minimum flow dates. These alterations are consistent with the monthly and daily flow regulation by upstream dams evidenced by available data from the current dry period. In the middle Delta, the marked monthly seasonality in flood days decreased only in the wet period. The proportion between the number of flood days exceeding the evacuation level and that of those exceeding the warning level doubled in the wet period but decreased only

  15. Recent changes (1973-2014 versus 1903-1972) in the flow regime of the Lower Paraná River and current fluvial pollution warnings in its Delta Biosphere Reserve

    Science.gov (United States)

    Puig, Alba; Olguín Salinas, Héctor F.; Borús, Juan A.

    2016-06-01

    Alterations in flow regimes of large rivers may originate or increase risks to ecosystems and humans. The Paraná River basin (South America) undergoes human pressures (e.g., heavy damming in the upper basin, deforestation, and mixed pollution) that may affect the water quantity and quality of its terminal Delta (Argentina). In this study, after applying univariate and multivariate change-point detection and trend analyses to the daily data series of flows incoming to the Delta (Paraná-Santa Fe section), flow characteristics were compared by Indicators of Hydrologic Alteration (IHA) and Environmental Flow Components (EFC). Some flood characteristics were also compared from hydrometric levels in the middle Delta (San Pedro station). Chemical and microbiological water variables in the main rivers of the "Paraná Delta" Biosphere Reserve were examined during two extreme hydrologic years (October 2008 to July 2010) to detect potential risk factors in association with hydrologic conditions. In the Lower Paraná River, a historical period (1903-1972) and two more altered periods (1973-1999 wet period and 2000-2014 dry period) were identified. Flow duration curves evidenced different changes in both altered periods, reflecting the joint effect of climatic variability and human influence. The most evident alterations in the flow regime were the lack of record of the extreme-low-flow component, the attenuation of monthly flow seasonality, and the increase in the number of reversals (dry period) and in the variability of maximum and minimum flow dates. These alterations are consistent with the monthly and daily flow regulation by upstream dams evidenced by available data from the current dry period. In the middle Delta, the marked monthly seasonality in flood days decreased only in the wet period. The proportion between the number of flood days exceeding the evacuation level and that of those exceeding the warning level doubled in the wet period but decreased only slightly

  16. Identification of flow regimes and heat transfer modes in Angra-2 core during the simulation of the small break loss of coolant accident of 250 cm{sup 2} in the cold leg of primary loop using RELAP5 code

    Energy Technology Data Exchange (ETDEWEB)

    Borges, Eduardo M.; Sabundjian, Gaiane, E-mail: borges.em@hotmail.com, E-mail: gdjian@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNE-SP), Sao Paulo, SP (Brazil)

    2017-07-01

    The aim of this paper is to identify the flow regimes, the heat transfer modes, and the correlations used by RELAP5/MOD3.2. gamma code in Angra-2 during the Small-Break Loss-of-Coolant Accident (SBLOCA) with a 250cm{sup 2} of rupture area in the cold leg of primary loop. The Chapter 15 of the Final Safety Analysis Report of Angra-2 (FSAR-A2) reports this specific kind of accident. The results from this work demonstrated the several flow regimes and heat transfer modes that can be present in the core of Angra-2 during the postulated accident. The results obtained for Angra-2 nuclear reactor core during the postulated accident were satisfactory when compared with the FSAR-A2. Additionally, the results showed the correct actuation of the ECCS guaranteeing the integrity of the reactor core. (author)

  17. Identification of flow regimes and heat transfer modes in Angra-2 core during the simulation of the small break loss of coolant accident of 250 cm2 in the cold leg of primary loop using RELAP5 code

    International Nuclear Information System (INIS)

    Borges, Eduardo M.; Sabundjian, Gaiane

    2017-01-01

    The aim of this paper is to identify the flow regimes, the heat transfer modes, and the correlations used by RELAP5/MOD3.2. gamma code in Angra-2 during the Small-Break Loss-of-Coolant Accident (SBLOCA) with a 250cm 2 of rupture area in the cold leg of primary loop. The Chapter 15 of the Final Safety Analysis Report of Angra-2 (FSAR-A2) reports this specific kind of accident. The results from this work demonstrated the several flow regimes and heat transfer modes that can be present in the core of Angra-2 during the postulated accident. The results obtained for Angra-2 nuclear reactor core during the postulated accident were satisfactory when compared with the FSAR-A2. Additionally, the results showed the correct actuation of the ECCS guaranteeing the integrity of the reactor core. (author)

  18. Evidence of Zonal-Flow-Driven Limit-Cycle Oscillations during L-H Transition and at H-mode Pedestal of a New Small-ELM Regime in EAST

    DEFF Research Database (Denmark)

    Xu, G.; Wang, H.; Guo, H.

    Small-amplitude edge localized oscillations have been observed, for the first time, in EAST preceding the L-H transition at marginal input power, which manifest themselves as dithering in the divertor D signals at a frequency under 4 kHz, much lower than the GAM frequency. Detailed measurements...... providing a direct evidence of the zonal flows for the L-H transition at marginal input power. Furthermore, near the transition threshold sawtooth heat pulses appear to periodically enhance the dithering, finally triggering the L-H transition after a big sawtooth crash. The zonal flow induced limit...... link between them. A novel predator-prey model, incorporating the evolution of zonal flows, pressure gradient and turbulences at two different frequency ranges, has been developed and successfully reproduced the key features of this newly observed small-ELM regime....

  19. Hydrothermal regime and constraints on reservoir depth of the Jade site in the Mid-Okinawa Trough inferred from heat flow measurements

    Science.gov (United States)

    Kinoshita, Masataka; Yamano, Makoto

    1997-02-01

    Detailed heat flow measurements revealed an enormous heat flow variation (102 to 105 mW m-2) in the Jade hydrothermal field (27°16'N, 127°05'E and water depth 1350 m) located on the slope of the Izena Hole in the Mid-Okinawa Trough. Within the Jade site, heat flow is higher than 1000 mW m-2 and decreases to ˜100 mW m-2 with a 1 km horizontal scale. Near the Jade black smoker, heat flow varies from >30,000 mW m-2 at a hydrothermally altered area to 1700 mW m-2 less than 100 m from it. A large-scale heat flow variation suggests that the base of the escarpment near the Jade site serves as a recharge area for the Jade site. Linear geotherms indicate that the upward Darcian flow within sediments is slower than ˜3 cm yr-1. Thus the fluid circulation pathways would basically be restricted in permeable channels. Estimated conductive heat output rate from the Jade site is 4-7 MW, which is comparable to heat output by a single black smoker vent (˜8 MW). One-dimensional thermal modeling predicts the existence of a boiling zone at ˜200 m beneath the Jade site, which may be overlain by a fractured impermeable layer. The normal chloride content of venting fluids from the black smoker may be explained either by upwelling of fluid which boiled at shallow depth but suffered no phase segregation, or by upwelling of fluid above the boiling interface.

  20. Compliant model of a coupled sequential coronary arterial bypass graft: effects of vessel wall elasticity and non-Newtonian rheology on blood flow regime and hemodynamic parameters distribution.

    Science.gov (United States)

    Kabinejadian, Foad; Ghista, Dhanjoo N

    2012-09-01

    We have recently developed a novel design for coronary arterial bypass surgical grafting, consisting of coupled sequential side-to-side and end-to-side anastomoses. This design has been shown to have beneficial blood flow patterns and wall shear stress distributions which may improve the patency of the CABG, as compared to the conventional end-to-side anastomosis. In our preliminary computational simulation of blood flow of this coupled sequential anastomoses design, the graft and the artery were adopted to be rigid vessels and the blood was assumed to be a Newtonian fluid. Therefore, the present study has been carried out in order to (i) investigate the effects of wall compliance and non-Newtonian rheology on the local flow field and hemodynamic parameters distribution, and (ii) verify the advantages of the CABG coupled sequential anastomoses design over the conventional end-to-side configuration in a more realistic bio-mechanical condition. For this purpose, a two-way fluid-structure interaction analysis has been carried out. A finite volume method is applied to solve the three-dimensional, time-dependent, laminar flow of the incompressible, non-Newtonian fluid; the vessel wall is modeled as a linearly elastic, geometrically non-linear shell structure. In an iteratively coupled approach the transient shell equations and the governing fluid equations are solved numerically. The simulation results indicate a diameter variation ratio of up to 4% and 5% in the graft and the coronary artery, respectively. The velocity patterns and qualitative distribution of wall shear stress parameters in the distensible model do not change significantly compared to the rigid-wall model, despite quite large side-wall deformations in the anastomotic regions. However, less flow separation and reversed flow is observed in the distensible models. The wall compliance reduces the time-averaged wall shear stress up to 32% (on the heel of the conventional end-to-side model) and somewhat

  1. Statistical hydrodynamic models for mixing instability flows in turbulent regime: theoretical 0D evaluation criteria and comparison of one and two-fluid approaches; Modeles hydrodynamiques statistiques pour les ecoulements d'instabilites de melange en regime developpe: criteres theoriques d'evaluation ''0D'' et comparaison des approches mono et bifluides

    Energy Technology Data Exchange (ETDEWEB)

    Llor, A

    2001-07-01

    Theoretical criteria are defined to perform quick analytical evaluations of statistical hydro models for turbulent mixing flows induced by Kelvin-Helmholtz, Rayleigh-Taylor and Richtmyer-Meshkov instabilities. They are based on a global energy balance analysis of the mixing zone ('0D' projection) in the limit of zero Atwood number, for incompressible fluids, and in self-similar regime. It is then shown that single-fluid descriptions must be replaced by two-fluid descriptions, particularly for the Rayleigh-Taylor case with variable acceleration. The interaction between a shock and heterogeneities is also considered. Various approaches for the development of new models are finally given. (author)

  2. Effects of flow regimes altered by dams on survival, population declines, and range-wide losses of California river-breeding frogs

    Science.gov (United States)

    Sarah J. Kupferberg; Wendy J. Palen; Amy J. Lind; Steve Bobzien; Alessandro Catenazzi; Joe Drennan; Mary.  Power

    2012-01-01

    Widespread alteration of natural hydrologic patterns by large dams combined with peak demands for power and water delivery during summer months have resulted in frequent aseasonal flow pulses in rivers of western North America. Native species in these ecosystems have evolved with predictable annual flood-drought cycles; thus, their likelihood of persistence may...

  3. Effects of Flow Regime on Metal Concentrations and the Attainment of Water Quality Standards in a Remediated Stream Reach, Butte, Montana.

    Science.gov (United States)

    Runkel, Robert L; Kimball, Briant A; Nimick, David A; Walton-Day, Katherine

    2016-12-06

    Low-flow synoptic sampling campaigns are often used as the primary tool to characterize watersheds affected by mining. Although such campaigns are an invaluable part of site characterization, investigations which focus solely on low-flow conditions may yield misleading results. The objective of this paper is to demonstrate this point and elucidate the mechanisms responsible for the release of metals during rainfall runoff. This objective is addressed using data from diel and synoptic sampling campaigns conducted over a two-day period. Low-flow synoptic sampling results indicate that concentrations of most constituents meet aquatic standards. This finding is in contrast to findings from a diel sampling campaign that captured dramatic increases in concentrations during rainfall runoff. Concentrations during the rising limb of the hydrograph were 2-23 times concentrations observed during synoptic sampling (most increases were >10-fold), remaining elevated during the receding limb of the hydrograph to produce a clockwise hysteresis loop. Hydrologic mechanisms responsible for the release of metals include increased transport due to resuspension of streambed solids, erosion of alluvial tailings, and overland flow. Rainfall also elevated the alluvial groundwater table and increased infiltration through the vadose zone, likely resulting in dissolution from alluvial tailings that were dry prior to the event.

  4. Drought Conditions Maximize the Impact of High-Frequency Flow Variations on Thermal Regimes and Biogeochemical Function in the Hyporheic Zone.

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2017-03-01

    Anthropogenic activities, such as dam operations, often induce larger and more frequent stage fluctuations than those occurring in natural rivers. However, the long-term impact of such flow variations on thermal and biogeochemical dynamics of the associated hyporheic zone (HZ) is poorly understood. A heterogeneous, two-dimensional thermo-hydro-biogeochemical model revealed an important interaction between high-frequency flow variations and watershed-scale hydrology. High-frequency stage fluctuations had their strongest thermal and biogeochemical impacts when the mean river stage was low during fall and winter. An abnormally thin snowpack in 2015, however, created a low river stage during summer and early fall, whereby high frequency stage fluctuations caused the HZ to be warmer than usual. This study provided the scientific basis to assess the potential ecological consequences of the high-frequency flow variations in a regulated river, as well as guidance on how to maximize the potential benefits—or minimize the drawbacks—of river regulation to river ecosystems.

  5. Kilohertz VLIF (volumetric laser induced fluorescence) measurements in a seeded free gas-phase jet in the transitionally turbulent flow regime

    Science.gov (United States)

    Wu, Yue; Xu, Wenjiang; Ma, Lin

    2018-03-01

    This paper reports the demonstration of instantaneous three-dimension (3D) measurements in turbulent flows at repetition rates up to 10 kHz using VLIF (volumetric laser induced fluorescence). The measurements were performed based on the LIF signal of iodine (I2) vapor seeded in the flow. The LIF signals of I2 vapor were generated volumetrically by a thick laser slab and then simultaneously captured by a total of seven cameras from different perspectives, based on which a 3D tomographic reconstruction was performed to obtain the 3D distribution of I2 vapor concentration. Single-shot measurements obtained in a duration of hundreds of nanoseconds (limited by the pulse duration of the excitation laser) were demonstrated in a 50 × 50 × 50 mm3 at a repetition rate up to 10 kHz. These measurements demonstrated the feasibility and potential of VLIF for resolving the 4D spatiotemporal dynamics of turbulent flows. Based on the experimental results obtained, this work also studied the VLIF signal level and its effects on the reconstruction accuracy under different the measurement conditions, illustrating the capabilities and limitations of performing high speed VLIF measurements.

  6. Modelling of the meridian flow in nominal and partial flow in axial and helico-centrifugal turbomachinery; Modelisation en regime nominal et partiel de l'ecoulement meridien dans les turbomachines axiales et helicocentrifuges

    Energy Technology Data Exchange (ETDEWEB)

    Ercolino, J.

    2001-01-15

    In this study, a fast analysis code for the meridian flow inside turbo-machineries has been developed. This code is based on the resolution of the averaged dynamical equations controlling the internal stationary and non-viscous flow in the relative reference frame. A linear combination of momentum equations has been used in the axial and radial directions to avoid the source term of the equations to become singular. The model developed is particularly adapted to the general case of compression machines, i.e.the mixed machines. Starting with the hypothesis of a finite number of blading and assuming an axisymmetric flow, the equations allowing to calculate the blading forces and the simplified kinematics of blade-to-blade flow have been developed. This kinematics takes into consideration the geometrical data supplied by manufacturers or by global design softwares. This last approach ensures a very efficient link in the framework of turbomachine design projects where the blades geometry is introduced in a very simple way for a first optimization approach. The results obtained seem to be very consistent in nominal flow but also in partial flow conditions as shown by the qualitative comparisons with test results. (J.S.)

  7. An integrated modeling framework for exploring flow regime and water quality changes with increasing biofuel crop production in the U.S. Corn Belt

    Science.gov (United States)

    Yaeger, Mary A.; Housh, Mashor; Cai, Ximing; Sivapalan, Murugesu

    2014-12-01

    To better address the dynamic interactions between human and hydrologic systems, we develop an integrated modeling framework that employs a System of Systems optimization model to emulate human development decisions which are then incorporated into a watershed model to estimate the resulting hydrologic impacts. The two models are run interactively to simulate the coevolution of coupled human-nature systems, such that reciprocal feedbacks between hydrologic processes and human decisions (i.e., human impacts on critical low flows and hydrologic impacts on human decisions on land and water use) can be assessed. The framework is applied to a Midwestern U.S. agricultural watershed, in the context of proposed biofuels development. This operation is illustrated by projecting three possible future coevolution trajectories, two of which use dedicated biofuel crops to reduce annual watershed nitrate export while meeting ethanol production targets. Imposition of a primary external driver (biofuel mandate) combined with different secondary drivers (water quality targets) results in highly nonlinear and multiscale responses of both the human and hydrologic systems, including multiple tradeoffs, impacting the future coevolution of the system in complex, heterogeneous ways. The strength of the hydrologic response is sensitive to the magnitude of the secondary driver; 45% nitrate reduction target leads to noticeable impacts at the outlet, while a 30% reduction leads to noticeable impacts that are mainly local. The local responses are conditioned by previous human-hydrologic modifications and their spatial relationship to the new biofuel development, highlighting the importance of past coevolutionary history in predicting future trajectories of change.

  8. Turbulent conductivity in parallel with iso-velocities in a planar established flow; Conductibilite turbulente parallelement aux isovitesses dans un ecoulement plan en regime etabli

    Energy Technology Data Exchange (ETDEWEB)

    Jullien, F. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires, Direction des piles atomiques

    1968-02-01

    In this thesis are presented the experimental results obtained during the study of the turbulent diffusion of heat using a wire source in a flat air flow. The Taylor statistical theory laws are well respected in the domain studied. The experiments have made it possible to evaluate the influence of the Reynolds number and of the distance from the wall on the quadratic values of velocity fluctuations and on the Lagrange turbulence scales. In particular, the author has found a correlation between the Lagrange scales and the friction coefficient when the Reynolds number varies. A diffusion law is derived from the Taylor theory; it makes it possible to explain more clearly the idea of turbulent conductivity. (author) [French] Cette these presente les resultats experimentaux de l'etude de la diffusion turbulente de la chaleur a partir d'un fil source dans un ecoulement d'air plan. Les lois de la theorie statistique de Taylor sont bien verifiees dans le domaine d'etude. Les experiences ont permis d'evaluer l'influence du nombre de Reynolds et de la distance a la paroi sur les valeurs quadratiques des fluctuations de vitesse et les echelles lagrangiennes de turbulence. En particulier, l'auteur a trouve une correlation entre les echelles lagrangiennes et le coefficient de frottement lorsque le nombre de Reynolds varie. Comme consequences de la theorie de Taylor, une loi de diffusion est etablie et permet de preciser la notion de conductibilite turbulente. (auteur)

  9. Numerical modelling of 2D solid/fluid interactions in explosive volcanic regimes using finite volumes: magma and multiphase flow dynamics induced by seismic elastic waves.

    Science.gov (United States)

    Martin, R.

    2001-12-01

    In many volcanoes like the Popocatepetl, it is not well known if seismicity induces explosive eruptions, or inversely if the dynamics induces seismicity, or how both mechanisms trigger each other. In order to understand this mechanisms we numerically simulate, at greater scales than in laboratory, the behaviour of highly viscous magmas submitted to an incoming PSV wave involving high stresses. For that purpose we use a finite volume scheme of second order with a semi implicit algorithm in time for the fluid and a classical velocity/stress formulation at the second order to describe the elastic waves. The magma is considered as compressible and consists in a high viscous fluid and volatile gases. The gas fractions are computed following a power state law of the pressure. The disturbance of the fluid by the wave causes the pressure to increase and the gas to exsolve. The magma is then submitted to a convection behaviour and can arise through the conduit till reaching a certain depth which defines the location of fragmentation of the mixture. These simulations allow us to conclude that, depending on the magnitude of the wave, a viscous compressible fluid like a magma can be highly disturbed and differ strongly then from the quasistatic and acoustic behaviour classically taken into account in classical modelling of waves travelling through acoustic fluid/elastic solid structures. Depending on the Reynolds number, from laminar to turbulent, the fluid can not any longer be assumed incompressible, irrotational and non viscous. Inversely, when the magma has reached the fragmentation depth in the conduit, the fluid becomes multiphasic with specific exit velocities, pressures, temperatures, particle fractions. It is modelled with one particle phase and one gas phase interacting with drag forces and heat exchange terms. With a similar algorithm as described before, we show that the flow can be expelled at shock speeds and produce travelling elastic waves in the ground through

  10. Flow

    DEFF Research Database (Denmark)

    Knoop, Hans Henrik

    2006-01-01

    FLOW. Orden i hovedet på den fede måde Oplevelsesmæssigt er flow-tilstanden kendetegnet ved at man er fuldstændig involveret, fokuseret og koncentreret; at man oplever stor indre klarhed ved at vide hvad der skal gøres, og i hvilket omfang det lykkes; at man ved at det er muligt at løse opgaven...

  11. Sustainable urban regime adjustments

    DEFF Research Database (Denmark)

    Quitzau, Maj-Britt; Jensen, Jens Stissing; Elle, Morten

    2013-01-01

    The endogenous agency that urban governments increasingly portray by making conscious and planned efforts to adjust the regimes they operate within is currently not well captured in transition studies. There is a need to acknowledge the ambiguity of regime enactment at the urban scale. This direc...

  12. Small Business Tax Regimes

    OpenAIRE

    Yilmaz, Fatih; Coolidge, Jacqueline

    2016-01-01

    Simplified tax regimes for micro and small enterprises in developing countries are intended to facilitate voluntary tax compliance. However, survey evidence suggests that small business taxation based on simplified bookkeeping or turnover is sometimes perceived as too complex for microenterprises in countries with high illiteracy levels. Very simple fixed tax regimes not requiring any book...

  13. Flux scaling: Ultimate regime

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Flux scaling: Ultimate regime. With the Nusselt number and the mixing length scales, we get the Nusselt number and Reynolds number (w'd/ν) scalings: and or. and. scaling expected to occur at extremely high Ra Rayleigh-Benard convection. Get the ultimate regime ...

  14. Measuring autocratic regime stability

    Directory of Open Access Journals (Sweden)

    Joseph Wright

    2016-01-01

    Full Text Available Researchers measure regime stability in autocratic contexts using a variety of data sources that capture distinct concepts. Often this research uses concepts developed for the study of democratic politics, such as leadership change or institutionalized authority, to construct measures of regime breakdown in non-democratic contexts. This article assesses whether the measure a researcher chooses influences the results they obtain by examining data on executive leadership, political authority, and autocratic regimes. We illustrate the conceptual differences between these variables by extending recent studies in the literature on the political consequences of non-tax revenue and unearned foreign income.

  15. Arctic circulation regimes.

    Science.gov (United States)

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L

    2015-10-13

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. © 2015 The Authors.

  16. Dune growth under multidirectional wind regimes

    Science.gov (United States)

    Gadal, C.; Rozier, O.; Claudin, P.; Courrech Du Pont, S.; Narteau, C.

    2017-12-01

    Under unidirectional wind regimes, flat sand beds become unstable to produce periodic linear dunes, commonly called transverse dunes because their main ridges are oriented perpendicular to the air flow. In areas of low sediment availability, the same interactions between flow, transport and topography produce barchan dunes, isolated sand-pile migrating over long distances with a characteristic crescentic shape. For the last fifteen years, barchan dunes and the instability at the origin of transverse dunes have been the subject of numerous studies that have identified a set of characteristic length and time scales with respect to the physical properties of both grains and fluid. This is not the case for dunes developing under multidirectional wind regimes. Under these conditions, dune orientation is measured with respect to the direction of the resultant sand flux. Depending on the wind regime, dunes do not always line up perpendicularly to the resultant sand flux, but can also be at an oblique angle or even parallel to it. These oblique and longitudinal dunes are ubiquitous in all deserts on Earth and planetary bodies because of the seasonal variability of wind orientation. They are however poorly constrained by observations and there is still no complete theoretical framework providing a description of their orientation and initial wavelength. Here, we extend the linear stability analysis of a flat sand of bed done in two dimensions for a unidirectional flow to three dimensions and multidirectional flow regimes. We are able to recover transitions from transverse to oblique or longitudinal dune patterns according to changes in wind regimes. We besides give a prediction for the initial dune wavelength. Our results compare well to previous theory of dune orientation and to field, experimental and numerical data.

  17. East Asian welfare regime

    DEFF Research Database (Denmark)

    Abrahamson, Peter

    2017-01-01

    The paper asks if East Asian welfare regimes are still productivist and Confucian? And, have they developed public care policies? The literature is split on the first question but (mostly) confirmative on the second. Care has to a large, but insufficient extent, been rolled out in the region...

  18. Understanding regime shifts

    DEFF Research Database (Denmark)

    Heymann, Matthias; Nielsen, Kristian Hvidtfelt

    ”. Danish wind power development is all the more surprising, as the innovation process in wind technology was carried to a large extent by non-academic craftsmen and political activists. Many features of this innovation story have been investigated and that research makes it possible to summarize...... the current understanding of the regime shift....

  19. Supply regimes in fisheries

    DEFF Research Database (Denmark)

    Nielsen, Max

    2006-01-01

    Supply in fisheries is traditionally known for its backward bending nature, owing to externalities in production. Such a supply regime, however, exist only for pure open access fisheries. Since most fisheries worldwide are neither pure open access, nor optimally managed, rather between the extrem...

  20. MODELING COMBINING TAX REGIMES

    Directory of Open Access Journals (Sweden)

    Prishchenko E. A.

    2016-03-01

    Full Text Available The article discusses the combination of tax regimes as a result of separation from the operating business of the revenues and costs for system of a united tax on imputed income (UTII with the analysis of the tax consequences of such allocation. Three models of taxation were built: both variants of the simplified system of taxation from UTII and common system of taxation with UTII. We propose a rapid method of the most preferred system of taxation for small businesses’ selection depending material to labor costs ratio. All these results could be implemented in the case when the company starts a new type of activity under the rules UTII, and solves the problem in the framework of the tax regime to conduct this activity - UTII applied or not, based on the criterion of tax savings. Using the relations describing the tax burden when combined tax regimes, we can determine what the yield should have a new business line and what cost structure should it have to reduce the tax burden. The main result is proposed approach that can be used as a tool of tax planning activities of small businesses.

  1. Transition to ballistic regime for heat transport in helium II

    Energy Technology Data Exchange (ETDEWEB)

    Sciacca, Michele, E-mail: michele.sciacca@unipa.it [Dipartimento Scienze Agrarie e Forestali, Università degli studi di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia (Spain); Sellitto, Antonio, E-mail: ant.sellitto@gmail.com [Dipartimento di Matematica, Informatica ed Economia, Università della Basilicata, Campus Macchia Romana, 85100 Potenza (Italy); Jou, David, E-mail: david.jou@uab.cat [Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia (Spain); Institut d' Estudis Catalans, Carme 47, 08001 Barcelona, Catalonia (Spain)

    2014-07-04

    The size-dependent and flux-dependent effective thermal conductivity of narrow capillaries filled with superfluid helium is analyzed from a thermodynamic continuum perspective. The classical Landau evaluation of the effective thermal conductivity of quiescent superfluid, or the Gorter–Mellinck regime of turbulent superfluids, is extended to describe the transition to ballistic regime in narrow channels wherein the radius R is comparable to (or smaller than) the phonon mean-free path ℓ in superfluid helium. To do so, we start from an extended equation for the heat flux incorporating non-local terms, and take into consideration a heat slip flow along the walls of the tube. This leads from an effective thermal conductivity proportional to R{sup 2} (Landau regime) to another one proportional to Rℓ (ballistic regime). We consider two kinds of flows: along cylindrical pipes and along two infinite parallel plates. - Highlights: • Heat transport in counterflow helium in the ballistic regime. • The one-fluid model based on the Extended Thermodynamics is used. • The transition from the Landau regime to the ballistic regime. • The transition from quantum turbulence to ballistic regime.

  2. Pulse regime in formation of fractal fibers

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, B. M., E-mail: bmsmirnov@gmail.com [Joint Institute for High Temperatures (Russian Federation)

    2016-11-15

    The pulse regime of vaporization of a bulk metal located in a buffer gas is analyzed as a method of generation of metal atoms under the action of a plasma torch or a laser beam. Subsequently these atoms are transformed into solid nanoclusters, fractal aggregates and then into fractal fibers if the growth process proceeds in an external electric field. We are guided by metals in which transitions between s and d-electrons of their atoms are possible, since these metals are used as catalysts and filters in interaction with gas flows. The resistance of metal fractal structures to a gas flow is evaluated that allows one to find optimal parameters of a fractal structure for gas flow propagation through it. The thermal regime of interaction between a plasma pulse or a laser beam and a metal surface is analyzed. It is shown that the basic energy from an external source is consumed on a bulk metal heating, and the efficiency of atom evaporation from the metal surface, that is the ratio of energy fluxes for vaporization and heating, is 10{sup –3}–10{sup –4} for transient metals under consideration. A typical energy flux (~10{sup 6} W/cm{sup 2}), a typical surface temperature (~3000 K), and a typical pulse duration (~1 μs) provide a sufficient amount of evaporated atoms to generate fractal fibers such that each molecule of a gas flow collides with the skeleton of fractal fibers many times.

  3. An equation of mean velocity of flow in non uniform regime, its relationship with the dispersion phenomenon as time function and its application to study of water quality; Una ecuacion de la velocidad media del flujo en regimen no uniforme, su relacion con el fenomeno de dispersion como funcion del tiempo y su aplicacion a los estudios de calidad de agua

    Energy Technology Data Exchange (ETDEWEB)

    Constain Aragon, A.; Lemos Ruiz, R.

    2011-07-01

    It is very well known the basic equation of hydraulics discovered by Antoine de Chezy in 1769, which relates in a quadratic from the mean velocity of flow with the slope of energy line and the hydraulic radius, in a uniform regime. This equation has been the central axis of development of hydro metrics as science that faces the huge challenges of penetrating the knowledge of earths streams every time more contaminated. In virtue of that, its mathematical structure and the relationship with other related formulas have been carefully examined, despite the limitation due to constancy of velocity. Starting from chemical considerations rather than dynamic ones as was used to obtain chezys relationship it is possible to establish a second equation for mean velocity of fluid in a non uniform regime that corresponds to averaged movement of a solute poured to steam. This equation will go to relate in an accurate way several aspects hydraulics and mass transport, sight as a single thing, allowing a vital tool for a depth study of water contaminations. to arrive this equation it was reviewed the foundations of mass transport theory in flows, stating a time dependent nature for coefficient currently used in describing dispersion phenomena allowing to interpret properly certain inconsistencies detected long time ago in this theory. It is presented the detailed results of application of this new approach to a small steam and a larger river in Colombia. (Author) 23 refs.

  4. Oral health and welfare state regimes: a cross-national analysis of European countries.

    Science.gov (United States)

    Guarnizo-Herreño, Carol C; Tsakos, Georgios; Sheiham, Aubrey; Watt, Richard G

    2013-06-01

    Very little is known about the potential relationship between welfare state regimes and oral health. This study assessed the oral health of adults in a range of European countries clustered by welfare regimes according to Ferrera's typology and the complementary Eastern type. We analysed data from Eurobarometer wave 72.3, a cross-sectional survey of 31 European countries carried out in 2009. We evaluated three self-reported oral health outcomes: edentulousness, no functional dentition (welfare state regime. The Scandinavian regime showed lower prevalence rates for all outcomes. For edentulousness and no functional dentition, there were higher prevalence rates in the Eastern regime but no significant differences between Anglo-Saxon, Bismarckian, and Southern regimes. The Southern regime presented a higher prevalence of oral impacts on daily living. Results by country indicated that Sweden had the lowest prevalences for edentulousness and no functional dentition, and Denmark had the lowest prevalence for oral impacts. The results suggest that Scandinavian welfare states, with more redistributive and universal welfare policies, had better population oral health. Future research should provide further insights about the potential mechanisms through which welfare-state regimes would influence oral health. © 2013 Eur J Oral Sci.

  5. Asymptomatic cryptococcal antigen prevalence detected by lateral flow assay in hospitalised HIV-infected patients in São Paulo, Brazil.

    Science.gov (United States)

    Vidal, José E; Toniolo, Carolina; Paulino, Adriana; Colombo, Arnaldo; Dos Anjos Martins, Marilena; da Silva Meira, Cristina; Pereira-Chioccola, Vera Lucia; Figueiredo-Mello, Claudia; Barros, Tiago; Duarte, Jequelie; Fonseca, Fernanda; Alves Cunha, Mirella; Mendes, Clara; Ribero, Taiana; Dos Santos Lazera, Marcia; Rajasingham, Radha; Boulware, David R

    2016-12-01

    To determine the prevalence of asymptomatic cryptococcal antigen (CRAG) using lateral flow assay (LFA) in hospitalised HIV-infected patients with CD4 counts 18 years old without prior cryptococcal meningitis, without clinical suspicion of cryptococcal meningitis, regardless of antiretroviral (ART) status, and with CD4 counts <200 cells/μl. Serum CRAG was tested by LFA in all patients, and whole blood CRAG was tested by LFA in positive cases. We enrolled 163 participants of whom 61% were men. The duration of HIV diagnosis was a median of 8 (range, 1-29) years. 26% were antiretroviral (ART)-naïve, and 74% were ART-experienced. The median CD4 cell count was 25 (range, 1-192) cells/μl. Five patients (3.1%; 95%CI, 1.0-7.0%) were asymptomatic CRAG-positive. Positive results cases were cross-verified by performing LFA in whole blood. 3.1% of HIV-infected inpatients with CD4 <200 cells/μl without symptomatic meningitis had cryptococcal antigenemia in São Paulo, suggesting that routine CRAG screening may be beneficial in similar settings in South America. Our study reveals another targeted population for CRAG screening: hospitalised HIV-infected patients with CD4 <200 cells/μl, regardless of ART status. Whole blood CRAG LFA screening seems to be a simple strategy to prevention of symptomatic meningitis. © 2016 John Wiley & Sons Ltd.

  6. Unitary Housing Regimes in Transition

    DEFF Research Database (Denmark)

    Bengtsson, Bo; Jensen, Lotte

    2013-01-01

    to the Danish and Swedish housing regimes are analysed and the responses and outcomes in terms of policy change and/or institutional continuity (path dependence) are compared. Overall, the more decentralized Danish housing regime seems to have resisted pressures for change and retrenchment better so far than...

  7. Simulating future trends in hydrological regimes in Western Switzerland

    Directory of Open Access Journals (Sweden)

    Marianne Milano

    2015-09-01

    New hydrological insights for the region: By the 2060 horizon, the increase in temperature causes a higher ratio of liquid precipitation and a decrease in snow accumulation during winter. These variations give rise to earlier high flow peaks and more severe low flows. Hydrological regimes evolve and rivers become characterized by a pluvial regime. These seasonal hydro-climatic changes are of prior importance in an area where urbanization and irrigation keep increasing: the question arises on the capacity of water resources to meet future water demands.

  8. Transient response of Salix cuttings to changing water level regimes

    Science.gov (United States)

    Gorla, L.; Signarbieux, C.; Turberg, P.; Buttler, A.; Perona, P.

    2015-03-01

    Sustainable water management requires an understanding of the effects of flow regulation on riparian ecomorphological processes. We investigated the transient response of Salix viminalis by examining the effect of water-level regimes on its above-ground and below-ground biomass. Four sets of Salix cuttings, three juveniles (in the first growing season) and one mature (1 year old), were planted and initially grown under the same water-level regime for 1 month. We imposed three different water-level regime treatments representing natural variability, a seasonal trend with no peaks, and minimal flow (characteristic of hydropower) consisting of a constant water level and natural flood peaks. We measured sap flux, stem water potential, photosynthesis, growth parameters, and final root architecture. The mature cuttings were not affected by water table dynamics, but the juveniles displayed causal relationships between the changing water regime, plant growth, and root distribution during a 2 month transient period. For example, a 50% drop in mean sap flux corresponded with a -1.5 Mpa decrease in leaf water potential during the first day after the water regime was changed. In agreement with published field observations, the cuttings concentrated their roots close to the mean water table of the corresponding treatment, allowing survival under altered conditions and resilience to successive stress events. Juvenile development was strongly impacted by the minimum flow regime, leading to more than 60% reduction of both above-ground and below-ground biomass, with respect to the other treatments. Hence, we suggest avoiding minimum flow regimes where Salix restoration is prioritized.

  9. Life history theory predicts fish assemblage response to hydrologic regimes.

    Science.gov (United States)

    Mims, Meryl C; Olden, Julian D

    2012-01-01

    The hydrologic regime is regarded as the primary driver of freshwater ecosystems, structuring the physical habitat template, providing connectivity, framing biotic interactions, and ultimately selecting for specific life histories of aquatic organisms. In the present study, we tested ecological theory predicting directional relationships between major dimensions of the flow regime and life history composition of fish assemblages in perennial free-flowing rivers throughout the continental United States. Using long-term discharge records and fish trait and survey data for 109 stream locations, we found that 11 out of 18 relationships (61%) tested between the three life history strategies (opportunistic, periodic, and equilibrium) and six hydrologic metrics (two each describing flow variability, predictability, and seasonality) were statistically significant (P history strategies, with 82% of all significant relationships observed supporting predictions from life history theory. Specifically, we found that (1) opportunistic strategists were positively related to measures of flow variability and negatively related to predictability and seasonality, (2) periodic strategists were positively related to high flow seasonality and negatively related to variability, and (3) the equilibrium strategists were negatively related to flow variability and positively related to predictability. Our study provides important empirical evidence illustrating the value of using life history theory to understand both the patterns and processes by which fish assemblage structure is shaped by adaptation to natural regimes of variability, predictability, and seasonality of critical flow events over broad biogeographic scales.

  10. Characterization of fluidization regime in circulating fluidized bed reactor with high solid particle concentration using computational fluid dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Chalermsinsuwan, Benjapon; Thummakul, Theeranan; Piumsomboon, Pornpote [Chulalongkorn University, Bangkok (Thailand); Gidaspow, Dimitri [Armour College of Engineering, Chicago (United States)

    2014-02-15

    The hydrodynamics inside a high solid particle concentration circulating fluidized bed reactor was investigated using computational fluid dynamics simulation. Compared to a low solid particle reactor, all the conventional fluidization regimes were observed. In addition, two unconventional fluidization regimes, circulating-turbulent and dense suspension bypassing regimes, were found with only primary gas injection. The circulating-turbulent fluidization regime showed uniformly dense solid particle distribution in all the system directions, while the dense suspension bypassing fluidization regime exhibited the flow of solid particles at only one side system wall. Then, comprehensive fluidization regime clarification and mapping were evaluated using in-depth system parameters. In the circulating-turbulent fluidization regime, the total granular temperature was low compared to the adjacent fluidization regimes. In the dense suspension bypassing fluidization regime, the highest total granular temperature was obtained. The circulating-turbulent and dense suspension bypassing fluidization regimes are suitable for sorption and transportation applications, respectively.

  11. Endogenous Monetary Policy Regime Change

    OpenAIRE

    Troy Davig; Eric M. Leeper

    2006-01-01

    This paper makes changes in monetary policy rules (or regimes) endogenous. Changes are triggered when certain endogenous variables cross specified thresholds. Rational expectations equilibria are examined in three models of threshold switching to illustrate that (i) expectations formation effects generated by the possibility of regime change can be quantitatively important; (ii) symmetric shocks can have asymmetric effects; (iii) endogenous switching is a natural way to formally model preempt...

  12. Hydrodynamic interaction of swimming organisms in an inertial regime

    Science.gov (United States)

    Li, Gaojin; Ostace, Anca; Ardekani, Arezoo M.

    2016-11-01

    We numerically investigate the hydrodynamic interaction of swimming organisms at small to intermediate Reynolds number regimes, i.e., Re˜O (0.1 -100 ) , where inertial effects are important. The hydrodynamic interaction of swimming organisms in this regime is significantly different from the Stokes regime for microorganisms, as well as the high Reynolds number flows for fish and birds, which involves strong flow separation and detached vortex structures. Using an archetypal swimmer model, called a "squirmer," we find that the inertial effects change the contact time and dispersion dynamics of a pair of pusher swimmers, and trigger hydrodynamic attraction for two pullers. These results are potentially important in investigating predator-prey interactions, sexual reproduction, and the encounter rate of marine organisms such as copepods, ctenophora, and larvae.

  13. Quantifying flooding regime in floodplain forests to guide river restoration

    Science.gov (United States)

    Christian O. Marks; Keith H. Nislow; Francis J. Magilligan

    2014-01-01

    Determining the flooding regime needed to support distinctive floodplain forests is essential for effective river conservation under the ubiquitous human alteration of river flows characteristic of the Anthropocene Era. At over 100 sites throughout the Connecticut River basin, the largest river system in New England, we characterized species composition, valley and...

  14. Transition from weak wave turbulence regime to solitonic regime

    Science.gov (United States)

    Hassani, Roumaissa; Mordant, Nicolas

    2017-11-01

    The Weak Turbulence Theory (WTT) is a statistical theory describing the interaction of a large ensemble of random waves characterized by very different length scales. For both weak non-linearity and weak dispersion a different regime is predicted where solitons propagate while keeping their shape unchanged. The question under investigation here is which regime between weak turbulence or soliton gas does the system choose ? We report an experimental investigation of wave turbulence at the surface of finite depth water in the gravity-capillary range. We tune the wave dispersion and the level of nonlinearity by modifying the depth of water and the forcing respectively. We use space-time resolved profilometry to reconstruct the deformed surface of water. When decreasing the water depth, we observe a drastic transition between weak turbulence at the weakest forcing and a solitonic regime at stronger forcing. We characterize the transition between both states by studying their Fourier Spectra. We also study the efficiency of energy transfer in the weak turbulence regime. We report a loss of efficiency of angular transfer as the dispersion of the wave is reduced until the system bifurcates into the solitonic regime. This project has recieved funding from the European Research Council (ERC, Grant Agreement No. 647018-WATU).

  15. Establishing of the flow regimes necessary for maintenance of fish habitat of the Savio River near Cesena (FO); La valutazione delle portate minime per la vita acquatica sul fiume Savio nei pressi di Cesena (FO)

    Energy Technology Data Exchange (ETDEWEB)

    Rambaldi, Anna; Venturini, Loris [SINGEA srl, Ravenna (Italy); Rizzoli, Marco [Regione Emilia Romagna, Bologna (Italy). Servizio Tutela e Sviluppo Fauna

    1997-03-01

    The Physical Habitat Simulation system is used to develop physical habitat versus stream flow functions for three different life stages of Leuciscus cephalus and Barbus barbus plebejus in a reach of the Savio River near the town of Cesena. The physical habitat is simulated using the velocity, the depth and the channel characteristics of the stream. This paper mainly focuses on the instream habitat conditions that influence the carrying capacity of the chosen fish species. Emphasis is placed on the dynamic aspects of the physical stream habitat conditions under changing water supplies.

  16. Channel size influence on the heat flux density at zero net mass flow in the non-linear transport regime between 1.2 and 2.1 K

    Science.gov (United States)

    Frederking, T. H. K.; Yuan, S. W. K.; Lee, J. M.; Sun, G. S.

    1987-01-01

    Porous media and narrow ducts of simple shape at zero net mass flow (ZNMF) are used to investigate the influence of pore size on the entropy/heat convection rate at ZNMF. The study is relevant to the development of specific types of phase separators. Previous work on heat transport by convection is extended to porous media without mass loss. The experimental results show the influence of pore size on heat flux for permeabilities between 10 to the -8th and 10 to the -6th sq cm. ZNMF plug data are found to be similar to results obtained for vapor liquid phase separation.

  17. Friction regimes in the lubricants solid-state regime

    NARCIS (Netherlands)

    Schipper, Dirk J.; Maathuis, O.; Dowson, D.; Taylor, C.M.; Childs, T.H.C.; Dalmaz, G.

    1995-01-01

    Friction measurements were performed in the lubricant's solid-state regime to study the transition from full-film lubrication, in which the separation is maintained by a solidified lubricant, to mixed lubrication. Special attention is paid to the influence of temperature (inlet viscosity) and

  18. On the regimes of premixing

    Energy Technology Data Exchange (ETDEWEB)

    Angelini, S.; Theofanous, T.G.; Yuen, W.W. [California Univ., Santa Barbara, CA (United States). Center for Risk Studies and Safety

    1998-01-01

    The conditions of the MAGICO-2000 experiment are extended to more broadly investigate the regimes of premixing, and the corresponding internal structures of mixing zones. With the help of the data and numerical simulations using the computer code PM-ALPHA, we can distinguish extremes of behavior dominated by inertia and thermal effects - we name these the inertia and thermal regimes, respectively. This is an important distinction that should guide future experiments aimed at code verification in this area. Interesting intermediate behaviors are also delineated and discussed. (author)

  19. Three novel tokamak plasma regimes in TFTR

    International Nuclear Information System (INIS)

    Furth, H.P.

    1985-10-01

    Aside from extending ''standard'' ohmic and neutral beam heating studies to advanced plasma parameters, TFTR has encountered a number of special plasma regimes that have the potential to shed new light on the physics of tokamak confinement and the optimal design of future D-T facilities: (1) High-powered, neutral beam heating at low plasma densities can maintain a highly reactive hot-ion population (with quasi-steady-state beam fueling and current drive) in a tokamak configuration of modest bulk-plasma confinement requirements. (2) Plasma displacement away from limiter contact lends itself to clarification of the role of edge-plasma recycling and radiation cooling within the overall pattern of tokamak heat flow. (3) Noncentral auxiliary heating (with a ''hollow'' power-deposition profile) should serve to raise the central tokamak plasma temperature without deterioration of central region confinement, thus facilitating the study of alpha-heating effects in TFTR. The experimental results of regime (3) support the theory that tokamak profile consistency is related to resistive kink stability and that the global energy confinement time is determined by transport properties of the plasma edge region

  20. Three novel tokamak plasma regimes in TFTR

    Energy Technology Data Exchange (ETDEWEB)

    Furth, H.P.

    1985-10-01

    Aside from extending ''standard'' ohmic and neutral beam heating studies to advanced plasma parameters, TFTR has encountered a number of special plasma regimes that have the potential to shed new light on the physics of tokamak confinement and the optimal design of future D-T facilities: (1) High-powered, neutral beam heating at low plasma densities can maintain a highly reactive hot-ion population (with quasi-steady-state beam fueling and current drive) in a tokamak configuration of modest bulk-plasma confinement requirements. (2) Plasma displacement away from limiter contact lends itself to clarification of the role of edge-plasma recycling and radiation cooling within the overall pattern of tokamak heat flow. (3) Noncentral auxiliary heating (with a ''hollow'' power-deposition profile) should serve to raise the central tokamak plasma temperature without deterioration of central region confinement, thus facilitating the study of alpha-heating effects in TFTR. The experimental results of regime (3) support the theory that tokamak profile consistency is related to resistive kink stability and that the global energy confinement time is determined by transport properties of the plasma edge region.

  1. Educational differentials in disability vary across and within welfare regimes

    DEFF Research Database (Denmark)

    Cambois, Emmanuelle; Solé-Auró, Aïda; Brønnum-Hansen, Henrik

    2016-01-01

    groups (referred to as disability disadvantage) and of the lower prevalence in high social groups (disability advantage); country-specific advantages/disadvantages are discussed regarding the possible influence of welfare regimes. METHODS: Cross-sectional disability prevalence is measured by longstanding......BACKGROUND: Social differentials in disability prevalence exist in all European countries, but their scale varies markedly. To improve understanding of this variation, the article focuses on each end of the social gradient. It compares the extent of the higher disability prevalence in low social...... across education, representing the AL-disadvantage of low-educated and AL-advantage of high-educated groups relative to middle-educated groups. RESULTS: The relative AL-disadvantage of the low-educated groups was small in Sweden (eg, 1.2 (1.0-1.4)), Finland, Romania, Bulgaria and Spain (youngest age...

  2. intensive and extensive feeding regimes

    African Journals Online (AJOL)

    production and reproduction parameters in ram lambs, under intensive and extensive feeding regimes. J.P.C. Greyling* and G.J. Taylor. Department of Animal Science, University of the Orange Free State, PO. Box 339, Bloemfontein,. 9300, South Africa. Received revised 1 July 1999; accepted 28 July 1999. Forty Dorper ...

  3. Monetary regimes in open economies

    NARCIS (Netherlands)

    Korpos, A.

    2006-01-01

    This thesis presents a two-country open economy framework for the analysis of strategic interactions among monetary authorities and wage bargaining institutions. From this perspective, the thesis investigates the economic consequences of replacing flexible and fixed exchange rate regimes with a

  4. Comparing groundwater recharge and base flow in the Bukmoongol ...

    Indian Academy of Sciences (India)

    It can be used for comparing alternate flow regimes, identifying changes in a flow regime through time and for generating flow statistics that can be used to predict the likely ... The Lyn–Hollick filter equation in calculating the base flow component of the hydrograph in RAP software is shown below. It has an alpha value of.

  5. Impedance void-meter and neural networks for vertical two-phase flows

    International Nuclear Information System (INIS)

    Mi, Y.; Li, M.; Xiao, Z.; Tsoukalas, L.H.; Ishii, M.

    1998-01-01

    Most two-phase flow measurements, including void fraction measurements, depend on correct flow regime identification. There are two steps towards successful identification of flow regimes: one is to develop a non-intrusive instrument to demonstrate area-averaged void fluctuations, the other to develop a non-linear mapping approach to perform objective identification of flow regimes. A non-intrusive impedance void-meter provides input signals to a neural mapping approach used to identify flow regimes. After training, both supervised and self-organizing neural network learning paradigms performed flow regime identification successfully. The methodology presented holds considerable promise for multiphase flow diagnostic and measurement applications. (author)

  6. Friction regimes in the lubricants solid-state regime

    OpenAIRE

    Schipper, Dirk J.; Maathuis, O.; Dowson, D.; Taylor, C.M.; Childs, T.H.C.; Dalmaz, G.

    1995-01-01

    Friction measurements were performed in the lubricant's solid-state regime to study the transition from full-film lubrication, in which the separation is maintained by a solidified lubricant, to mixed lubrication. Special attention is paid to the influence of temperature (inlet viscosity) and roughness on this transition. The friction measurements showed that in the lubricants solid-state region three lubrication modes can be distinguished: A) full-film lubrication; separation is maintained b...

  7. Theoretical study of the crossover into hydrodynamic regime in graphene

    Science.gov (United States)

    Ho, Derek; Yudhistira, Indra; Hu, Ben Yu-Kuang; Adam, Shaffique

    Experiments on graphene have recently succeeded in entering the hydrodynamic regime, as demonstrated by successful observations of strong violation of Wiedemann-Franz law, the Gurzhi effect and electronic Poiseuille flow. It is known that electronic systems enter the hydrodynamic regime when electron-electron scattering dominates over electron-impurity and electron-phonon scattering. However, a quantitative study of this transition from the Fermi liquid to hydrodynamic regime is still lacking. In view of this, we quantitatively analyze the electron-electron, electron-impurity and electron-phonon scattering rates as a function of temperature, charge doping and disorder (charge puddle) strength. This yields a quantitative understanding of the onset of hydrodynamic electronic behavior in graphene samples. This work is supported by the National Research Foundation of Singapore under its Fellowship program (NRF-NRFF2012-01) and by the Singapore Ministry of Education and Yale-NUS College through Grant No. R-607-265-01312.

  8. Application of neutral-oxygen water regime at NPP

    International Nuclear Information System (INIS)

    Kruzhilin, G.N.; Dubrovskij, I.S.; Anan'ev, E.P.; Matskevich, E.B.; Gashenko, V.A.; Abakumova, O.N.

    1985-01-01

    A problem of using neutral-oxyoen water regime at NPP is considered. Data on the successful application of such regime at a national NPP with the VK-50 reactor and at some foreign NPP are given. It is noted that oxygen dissolved in a saltless water flow becomes a steel passivating agent forming a strong oxide film on surfaces of stainless- and carbon steels. After the film formation almost complete inhibition of the oxidation and corrosion processes is observe. The conclusion is drawn on the expediency of using the neutral-oxygen water regime at all the NPP equipped with condensate cleaning devices as well as on a wider use of carbon steels

  9. Atmospheric Water-Cycle Regimes and Cloud Regimes

    Science.gov (United States)

    Wong, S.; Fetzer, E. J.; L'Ecuyer, T. S.

    2013-12-01

    The relationship between the atmospheric water vapor budget and cloud properties is investigated by collocated reanalysis fields from Modern Era Retrospective-analysis for Research and Applications (MERRA) and the observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument. Intensities of surface water exchange (precipitation minus evaporation) are analyzed in the space of 'dynamical regimes', which are defined by combination of large-scale water vapor advection and convergence calculated from the MERRA. The atmospheric water vapor sinks associated with mid-latitude storm systems and precipitation in the west coast of United States are mainly driven by the large-scale dynamical advection, while those associated with tropical deep convection and summertime monsoons are mainly driven by water vapor convergence. Subtropical subsidence area over the eastern ocean basins is dominated by strong water vapor divergence. These dynamical regimes are then connected to the collocated MODIS cloud top pressure and cloud optical thickness. Probability density distributions of these MODIS cloud properties associated with each dynamical regime will be presented.

  10. Welfare state regimes, health and health inequalities in adolescence: a multilevel study in 32 countries.

    Science.gov (United States)

    Richter, Matthias; Rathman, Katharina; Nic Gabhainn, Saoirse; Zambon, Alessio; Boyce, William; Hurrelmann, Klaus

    2012-07-01

    Comparative research on health and health inequalities has recently started to establish a welfare regime perspective. The objective of this study was to determine whether different welfare regimes are associated with health and health inequalities among adolescents. Data were collected from the 'Health Behaviour in School-aged Children' study in 2006, including 11- to 15-year-old students from 32 countries (N = 141,091). Prevalence rates and multilevel logistic regression models were calculated for self-rated health (SRH) and health complaints. The results show that between 4 per cent and 7 per cent of the variation in both health outcomes is attributable to differences between countries. Compared to the Scandinavian regime, the Southern regime had lower odds ratios for SRH, while for health complaints the Southern and Eastern regime showed high odds ratios. The association between subjective health and welfare regime was largely unaffected by adjusting for individual socioeconomic position. After adjustment for the welfare regime typology, the country-level variations were reduced to 4.6 per cent for SRH and to 2.9 per cent for health complaints. Regarding cross-level interaction effects between welfare regimes and socioeconomic position, no clear regime-specific pattern was found. Consistent with research on adults this study shows that welfare regimes are important in explaining variations in adolescent health across countries. © 2012 The Authors. Sociology of Health & Illness © 2012 Foundation for the Sociology of Health & Illness/Blackwell Publishing Ltd.

  11. Magnetogasdynamic Flow Acceleration in a Scramjet Nozzle

    National Research Council Canada - National Science Library

    Harrington, Brian

    2004-01-01

    .... The parameters of conductivity pattern and load factor are varied in both inviscid and viscous flow regimes with the intent of increasing axial force exerted on the flow through a scramjet accelerator...

  12. The natural sediment regime in rivers: broadening the foundation for ecosystem management

    Science.gov (United States)

    Wohl, Ellen E.; Bledsoe, Brian P.; Jacobson, Robert B.; Poff, N. LeRoy; Rathburn, Sara L.; Walters, David M.; Wilcox, Andrew C.

    2015-01-01

    Water and sediment inputs are fundamental drivers of river ecosystems, but river management tends to emphasize flow regime at the expense of sediment regime. In an effort to frame a more inclusive paradigm for river management, we discuss sediment inputs, transport, and storage within river systems; interactions among water, sediment, and valley context; and the need to broaden the natural flow regime concept. Explicitly incorporating sediment is challenging, because sediment is supplied, transported, and stored by nonlinear and episodic processes operating at different temporal and spatial scales than water and because sediment regimes have been highly altered by humans. Nevertheless, managing for a desired balance between sediment supply and transport capacity is not only tractable, given current geomorphic process knowledge, but also essential because of the importance of sediment regimes to aquatic and riparian ecosystems, the physical template of which depends on sediment-driven river structure and function.

  13. Variations and controls on crustal thermal regimes in Southeastern Australia

    Science.gov (United States)

    Mather, Ben; McLaren, Sandra; Taylor, David; Roy, Sukanta; Moresi, Louis

    2018-01-01

    The surface heat flow field in Australia has for many years been poorly constrained compared to continental regions elsewhere. 182 recent heat flow determinations and 66 new heat production measurements for Southeastern Australia significantly increase our understanding of local and regional lithospheric thermal regimes and allow for detailed thermal modelling. The new data give a mean surface heat flow for Victoria of 71 ± 15 mW m- 2 which fits within the 61-77 mW m- 2 range reported for Phanerozoic-aged crust globally. These data reveal three new thermally and compositionally distinct heat flow sub-provinces within the previously defined Eastern Heat Flow Province: the Delamerian heat flow sub-province (average surface heat flow 60 ± 9 mW m- 2); the Lachlan heat flow sub-province (average surface heat flow 74 ± 13 mW m- 2); and the Newer Volcanics heat flow sub-province (average surface heat flow 72 ± 16 mW m- 2) which includes extreme values that locally exceed 100 mW m- 2. Inversions of reduced heat flow and crustal differentiation find that the Delamerian sub-province has experienced significant crustal reworking compared to the Lachlan and Newer Volcanics sub-provinces. The latter has experienced volcanism within the last 8 Ma and the degree of variability observed in surface heat flow points (up to 8 mW m- 2 per kilometre laterally) cannot be replicated with steady-state thermal models through this sub-province. In the absence of a strong palaeoclimate signal, aquifer disturbances, or highly enriched granites, we suggest that this high variability arises from localised transient perturbations to the upper crust associated with recent intraplate volcanism. This is supported by a strong spatial correlation of high surface heat flow and known eruption points within the Newer Volcanics heat flow sub-province.

  14. Enhanced regime predictability in atmospheric low-order models due to stochastic forcing.

    Science.gov (United States)

    Kwasniok, Frank

    2014-06-28

    Regime predictability in atmospheric low-order models augmented with stochastic forcing is studied. Atmospheric regimes are identified as persistent or metastable states using a hidden Markov model analysis. A somewhat counterintuitive, coherence resonance-like effect is observed: regime predictability increases with increasing noise level up to an intermediate optimal value, before decreasing when further increasing the noise level. The enhanced regime predictability is due to increased persistence of the regimes. The effect is found in the Lorenz '63 model and a low-order model of barotropic flow over topography. The increased predictability is only present in the regime dynamics, that is, in a coarse-grained view of the system; predictability of individual trajectories decreases monotonically with increasing noise level. A possible explanation for the phenomenon is given and implications of the finding for weather and climate modelling and prediction are discussed. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  15. Physics of zonal flows

    International Nuclear Information System (INIS)

    Itoh, K.; Fujisawa, A.; Itoh, S.-I.; Yagi, M.; Nagashima, Y.; Diamond, P.H.; Tynan, G.R.; Hahm, T.S.

    2006-01-01

    Zonal flows, which means azimuthally symmetric band-like shear flows, are ubiquitous phenomena in nature and the laboratory. It is now widely recognized that zonal flows are a key constituent in virtually all cases and regimes of drift wave turbulence, indeed, so much so that this classic problem is now frequently referred to as ''drift wave-zonal flow turbulence.'' In this review, new viewpoints and unifying concepts are presented, which facilitate understanding of zonal flow physics, via theory, computation and their confrontation with the results of laboratory experiment. Special emphasis is placed on identifying avenues for further progress. (author)

  16. Homogeneous-Heterogeneous Regime Transition in Bubble Columuns

    Czech Academy of Sciences Publication Activity Database

    Růžička, Marek; Zahradník, Jindřich; Drahoš, Jiří; Thomas, N. H.

    2001-01-01

    Roč. 56, č. 15 (2001), s. 4609-4626 ISSN 0009-2509 R&D Projects: GA ČR GA104/98/1435 Grant - others:INCO-COPERNICUS(XE) ERB IC15-CT98-0904 Institutional research plan: CEZ:AV0Z4072921 Keywords : bubble column * flow regime * stability Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.547, year: 2001

  17. The Thermal Regime Around Buried Submarine High-Voltage Cables

    Science.gov (United States)

    Emeana, C. J.; Dix, J.; Henstock, T.; Gernon, T.; Thompson, C.; Pilgrim, J.

    2015-12-01

    The expansion of offshore renewable energy infrastructure and the desire for "trans-continental shelf" power transmission, all require the use of submarine High Voltage (HV) cables. These cables have maximum operating surface temperatures of up to 70oC and are typically buried at depths of 1-2 m beneath the seabed, within the wide range of substrates found on the continental shelf. However, the thermal properties of near surface shelf sediments are poorly understood and this increases the uncertainty in determining the required cable current ratings, cable reliability and the potential effects on the sedimentary environments. We present temperature measurements from a 2D laboratory experiment, designed to represent a buried, submarine HV cable. We used a large (2.5 m-high) tank, filled with water-saturated ballotini and instrumented with 120 thermocouples, which measured the time-dependent 2D temperature distributions around the heat source. The experiments use a buried heat source to represent a series of realistic cable surface temperatures with the aim for identifying the thermal regimes generated within typical non-cohesive shelf sediments: coarse silt, fine sand and very coarse sand. The steady state heat flow regimes, and normalised and radial temperature distributions were assessed. Our results show that at temperatures up to 60°C above ambient, the thermal regimes are conductive for the coarse silt sediments and convective for the very coarse sand sediments even at 7°C above ambient. However, the heat flow pattern through the fine sand sediment shows a transition from conductive to convective heat flow at a temperature of approximately 20°C above ambient. These findings offer an important new understanding of the thermal regimes associated with submarine HV cables buried in different substrates and has huge impacts on cable ratings as the IEC 60287 standard only considers conductive heat flow as well as other potential near surface impacts.

  18. Regime Change and the Role of Airpower

    National Research Council Canada - National Science Library

    Fahrenkrug, David T

    2006-01-01

    Drawing from the vision of airpower theorists and building on insights gained from studies on various regime changes, this thesis advances a theory of regime change and outlines a strategy for the use of airpower...

  19. Regime Change and the Role of Airpower

    National Research Council Canada - National Science Library

    Fahrenkrug, David

    2003-01-01

    Drawing from the vision of airpower theorists, and building on insights gained from studies on various regime changes, this thesis advances a theory of regime change and outlines a strategy for the use of airpower...

  20. Closure relations for shallow granular flows from particle simulations

    OpenAIRE

    Weinhart, Thomas; Thornton, Anthony Richard; Luding, Stefan; Bokhove, Onno

    2012-01-01

    The Discrete Particle Method (DPM) is used to model granular flows down an inclined chute. We observe three major regimes: static piles, steady uniform flows and accelerating flows. For flows over a smooth base, other (quasi-steady) regimes are observed where the flow is either highly energetic and strongly layered in depth for small inclinations, or non-uniform and oscillating for larger inclinations. For steady uniform flows, depth profiles of density, velocity and stress have been obtained...

  1. Can Old Regimes Handle New Wars?

    DEFF Research Database (Denmark)

    Henningsen, Troels

    strengthen Islamist insurgents. Using a comparative case study of the regimes in Chad and Mali from 2003 to 2016 and applying a theoretical framework of regime survival in states with internal anarchy, this paper explains how regimes in the Sahel region defend themselves against insurgents. Surprisingly...

  2. Implementation Regimes and Street-Level Bureaucrats

    DEFF Research Database (Denmark)

    Winter, Søren; T. Dinesen, Peter; J. May, Peter

    -government regimes foster greater policy commitment, attention to rules, and adherence among frontline workers than is the case for a local-government implementation regime. These lead to actions of street-level bureaucrats in central-government regimes that are more in line with national policies than those...

  3. Capital flows, exchange rate regime, and macroeconomic performance in Mexico

    OpenAIRE

    Ibarra, Carlos A.

    2004-01-01

    Este trabajo analiza los efectos a corto plazo de los flujos de capital externo en la demanda agregada en México: su magnitud, los canales de transmisión y la posible influencia en la elección del régimen del tipo de cambio del país. Para motivar este trabajo en la introducción se discute el sistema de flotación en diciembre de 1994, en un contexto de renovada volatilidad de los flujos de capital internacionales. Durante el período de la banda, a principios de los noventa, los ...

  4. Bubble Column with Electrolytes: Gas Holdup and Flow Regimes

    Czech Academy of Sciences Publication Activity Database

    Orvalho, Sandra; Růžička, Marek; Drahoš, Jiří

    2009-01-01

    Roč. 48, č. 17 (2009), s. 8237-8243 ISSN 0888-5885 R&D Projects: GA ČR GA104/07/1110; GA ČR GP104/09/P255; GA AV ČR(CZ) IAA200720801; GA MŠk LA319 Institutional research plan: CEZ:AV0Z40720504 Keywords : bubble column * hydrodynamics * surfactants Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.758, year: 2009

  5. Measuring the effectiveness of international environmental regimes

    Energy Technology Data Exchange (ETDEWEB)

    Helm, C.; Sprinz, D.F.

    1999-05-01

    While past research has emphasized the importance of international regimes for international governance, systematic assessments of regime effects are missing. This article derives a standardized measurement concept for the effectiveness of international environmental regimes by developing an operational rational choice calculus to evaluate actual policy simultaneously against a non-regime counterfactual and a collective optimum. Subsequently, the empirical feasibility of the measurement instrument is demonstrated by way of two international treaties regulating transboundary air pollution in Europe. The results demonstrate that the regimes indeed show positive effects - but fall substantially short of the collective optima. (orig.)

  6. Adaptation in Collaborative Governance Regimes

    Science.gov (United States)

    Emerson, Kirk; Gerlak, Andrea K.

    2014-10-01

    Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program.

  7. Hall effect in hopping regime

    Energy Technology Data Exchange (ETDEWEB)

    Avdonin, A., E-mail: avdonin@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Skupiński, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Grasza, K. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Institute of Electronic Materials Technology, ul. Wólczyńska 133, 01-919 Warszawa (Poland)

    2016-02-15

    A simple description of the Hall effect in the hopping regime of conductivity in semiconductors is presented. Expressions for the Hall coefficient and Hall mobility are derived by considering averaged equilibrium electron transport in a single triangle of localization sites in a magnetic field. Dependence of the Hall coefficient is analyzed in a wide range of temperature and magnetic field values. Our theoretical result is applied to our experimental data on temperature dependence of Hall effect and Hall mobility in ZnO. - Highlights: • Expressions for Hall coefficient and mobility for hopping conductivity are derived. • Theoretical result is compared with experimental curves measured on ZnO. • Simultaneous action of free and hopping conduction channels is considered. • Non-linearity of hopping Hall coefficient is predicted.

  8. Reassessing the nuclear liability regime

    International Nuclear Information System (INIS)

    Havinh Phuong

    1985-01-01

    The nuclear liability regime was thoroughly reviewed by nuclear plant operators, officials of regulatory authorities, and legal and insurance experts at the Symposium on Nuclear Third Party Liability and Insurance, held in September 1984 in Munich, Federal Republic of Germany. The symposium highlighted specific areas where adjustments or improvements would be needed in order to cope with practical problems encountered or emerging issues. By focusing on questions of legitimate concern to the public, it also sought to promote confidence in a compensation system for public protection that is in many ways unique. Topics addressed included the following: greater harmonization of the compensation amounts for nuclear damage established in different countries and in territorial scope; the concept of unlimited liability; the time limitation for compensation claims; the problem of proving causation; the concept of nuclear damage; and insurance coverage

  9. Unitary Housing Regimes in Transition

    DEFF Research Database (Denmark)

    Bengtsson, Bo; Jensen, Lotte

    2013-01-01

    Path dependence is strong in housing institutions and policy. In both Denmark and Sweden, today’s universal and ‘unitary’ (Kemeny) housing regimes can be traced back to institutions that were introduced fifty years back in history or more. Recently, universal and unitary housing systems...... in Scandinavia, and elsewhere, are under challenge from strong political and economic forces. These challenges can be summarized as economic cutbacks, privatization and Europeanization. Although both the Danish and the Swedish housing system are universal and unitary in character, they differ considerably...... in institutional detail. Both systems have corporatist features, however in Denmark public housing is based on local tenant democracy and control, and in Sweden on companies owned and controlled by the municipalities, combined with a centralized system of rent negotiations. In the paper the present challenges...

  10. Apparatus for monitoring two-phase flow

    Science.gov (United States)

    Sheppard, John D.; Tong, Long S.

    1977-03-01

    A method and apparatus for monitoring two-phase flow is provided that is particularly related to the monitoring of transient two-phase (liquid-vapor) flow rates such as may occur during a pressurized water reactor core blow-down. The present invention essentially comprises the use of flanged wire screens or similar devices, such as perforated plates, to produce certain desirable effects in the flow regime for monitoring purposes. One desirable effect is a measurable and reproducible pressure drop across the screen. The pressure drop can be characterized for various known flow rates and then used to monitor nonhomogeneous flow regimes. Another useful effect of the use of screens or plates in nonhomogeneous flow is that such apparatus tends to create a uniformly dispersed flow regime in the immediate downstream vicinity. This is a desirable effect because it usually increases the accuracy of flow rate measurements determined by conventional methods.

  11. Submarine granular flow down a rough plane

    Science.gov (United States)

    Nicolas, Maxime; Cassar, Cyril; Pouliquen, Olivier

    2003-11-01

    We lead experiments of submarine granular flows in a water tank. The particles are spherical 100 microns glass beads and flow down a rough inclined plane from a reservoir with a controlled opening. Different flow regimes are observed, the flow velocity and thickness are measured. The basal water pressure is also measured and give information on the suspension rate of the flow. No flow was observed for an angle below 24 degrees. The flow velocity increases smoothly for a [24-36] degrees inclination range, and a strong velocity increase occurs for inclination over 36 degrees. The thickness of the flow decreases when inclination increases but no abrupt change of thickness is observed around 36 degrees. That suggests that a transition exists between a granular regime, where friction on the rough plane and particle contacts are dominant, and a suspension regime where basal friction vanishes. A thin film ripple instability is also observed for large inclination angles.

  12. Apparatus for monitoring two-phase flow

    International Nuclear Information System (INIS)

    Sheppard, J.D.; Tong, L.S.

    1977-01-01

    A method and apparatus for monitoring two-phase flow is provided that is particularly related to the monitoring of transient two-phase (liquid-vapor) flow rates such as may occur during a pressurized water reactor core blow-down. The present invention essentially comprises the use of flanged wire screens or similar devices, such as perforated plates, to produce certain desirable effects in the flow regime for monitoring purposes. One desirable effect is a measurable and reproducible pressure drop across the screen. The pressure drop can be characterized for various known flow rates and then used to monitor nonhomogeneous flow regimes. Another useful effect of the use of screens or plates in nonhomogeneous flow is that such apparatus tends to create a uniformly dispersed flow regime in the immediate downstream vicinity. This is a desirable effect because it usually increases the accuracy of flow rate measurements determined by conventional methods. 3 claims, 9 figures

  13. External Shocks and Banking Crises in Developing Countries: Does the Exchange Rate Regime Matter?

    OpenAIRE

    Chandima Mendis

    2002-01-01

    This paper examines some determinants of banking crises in developing economies. Specifically, the effects of terms of trade shocks and capital flows are analyzed. The choice of the nominal exchange rate regime is found to be a crucial factor in the way various shocks are transmitted through the monetary sector. A logit model is used on panel data and preliminary results indicate that countries with flexible regimes were able to lessen the impact of external shocks on the domestic economy. Th...

  14. Accommodating human values in the climate regime

    Directory of Open Access Journals (Sweden)

    Rosalind Cook

    2008-12-01

    Full Text Available The climate regime addresses one of the most important challenges facing humankind today. However, while the environmental and economic sides of the problem are well represented, it lacks the inclusion of social and human aspects. The human rights regime, in contrast, is a regime which has been established precisely to implement human values. This article ex-plains the problems of climate change in terms of human values and argues that some proce-dures from the human rights regime offer possibilities for improvement. It is submitted that through the inclusion of human rights instruments, such as individual communication, pro-gressive realisation and authoritative interpretation, the inclusion of human values into the climate regime will be facilitated. This article presents these instruments and discusses their potential for inclusion in the climate regime.

  15. Socioeconomic inequalities in oral health in different European welfare state regimes.

    Science.gov (United States)

    Guarnizo-Herreño, Carol C; Watt, Richard G; Pikhart, Hynek; Sheiham, Aubrey; Tsakos, Georgios

    2013-09-01

    There is very little information about the relationship between welfare regimes and oral health inequalities. We compared socioeconomic inequalities in adults' oral health in five European welfare-state regimes: Scandinavian, Anglo-Saxon, Bismarckian, Southern and Eastern. Using data from the oral health module of the Eurobarometer 72.3 survey, we assessed inequalities in two self-reported oral health measures: no functional dentition (less than 20 natural teeth) and edentulousness (no natural teeth). Occupational social class, education and subjective social status (SSS) were included as socioeconomic position indicators. We estimated age-standardised prevalence rates, ORs, the Relative Index of Inequality (RII) and the Slope Index of Inequality (SII). The Scandinavian regime showed the lowest prevalence rates of the two oral health measures while the Eastern showed the highest. In all welfare regimes there was a general pattern of social gradients by occupational social class and education. Relative educational inequalities in no functional dentition were largest in the Scandinavian welfare regime (RII=3.81; 95% CI 2.68 to 5.42). The Scandinavian and Southern regimes showed the largest relative inequalities in edentulousness by occupation and education, respectively. There were larger absolute inequalities in no functional dentition in the Eastern regime by occupation (SII=42.16; 95% CI 31.42 to 52.89) and in the Southern by SSS (SII=27.92; 95% CI 17.36 to 38.47). Oral health inequalities in adults exist in all welfare-state regimes, but contrary to what may be expected from theory, they are not smaller in the Scandinavian regime. Future work should examine the potential mechanisms linking welfare provision and oral health inequalities.

  16. State Structure and Political Regime Structure

    OpenAIRE

    Paul – Iulian Nedelcu

    2012-01-01

    The political regime is the concrete form of organization and functioning of political system andtherefore, the regime means the concrete way of organize, institutionalize and function a political systemand of the exercise of political power by a social-political force in a social community or global socialistem. The political regime is not limited to institutions and state bodies, but it covers the entire politicalsystem. Form of expression in social practice plan is the result of balance of...

  17. De Facto Regimes in International Law

    OpenAIRE

    Essen, Jonte van

    2012-01-01

    The ambiguous position of de facto regimes in international law has long been the subject of scholarly debate and a source of political conflict. An assessment of the current standing of these regimes in international law and the consequences of actions by international actors on this status has, however, been long overdue. The manner in which de facto regimes are regarded internationally has serious consequences for the individuals under the influence of this legal grey area. Therefore, the ...

  18. Boiling flow through diverging microchannel

    Indian Academy of Sciences (India)

    118–. 1182 kg/m2-s) and heat flux (1.6–19.2 W/cm2) on single and two-phase pressure drop and average heat transfer coefficient has been studied. Concurrently, flow visu- alization is carried out to document the various flow regimes and to ...

  19. Low flow hydrology: a review

    CSIR Research Space (South Africa)

    Smakhtin, VU

    2001-01-10

    Full Text Available prolonged dry weather’. This definition does not make a clear distinction between low flows and droughts. Low flows is a seasonal phenomenon, and an integral component of a flow regime of any river. Drought, on the other hand, is a natural event...-flow generating mechanisms is rather limited. At the same time, identification of relative importance of various low-flow generation mechanisms and factors should ideally precede any low-flow analysis and also form an integral part of developing plans...

  20. Synergies between nonproliferation regimes: A pragmatic approach

    International Nuclear Information System (INIS)

    Findlay, Trevor; Meier, Oliver

    2001-01-01

    Full text: With the recent progress in establishing international nonproliferation regimes, the question of synergies between different verification and monitoring regimes is becoming more acute. Three multilateral and universal nonproliferation organisations covering safeguards on civil nuclear materials, nuclear testing, and chemical weapons are up and running. A regime on biological weapons is under negotiation. Several regional organisations concerned with monitoring nonproliferation commitments in the nuclear field are in place; others are being established. Past discussions on synergies between these regimes have suffered from being too far-reaching. These discussions often have not reflected adequately the political difficulties of cooperation between regimes with different membership, scope and institutional set-up. This paper takes a pragmatic look at exploiting synergies and identifies some potential and real overlaps in the work between different verification regimes. It argues for a bottom-up approach and identifies building blocks for collaboration between verification regimes. By realising such, more limited potential for cooperation, the ground could be prepared for exploiting other synergies between these regimes. (author)

  1. Targeting autocrats : Economic sanctions and regime change

    NARCIS (Netherlands)

    Oechslin, M.C.

    2014-01-01

    When it comes to international economic sanctions, the most frequent goal is regime change and democratization. Yet, past experiences suggest that such sanctions are often ineffective; moreover, quite paradoxically, targeted regimes tend to respond with policies that amplify the sanctions’ harmful

  2. Strengthening the nuclear non-proliferation regime

    International Nuclear Information System (INIS)

    Carlson, J.

    2003-01-01

    Although the nuclear non-proliferation regime has enjoyed considerable success, today the regime has never been under greater threat. Three states have challenged the objectives of the NPT, and there is a technology challenge - the spread of centrifuge enrichment technology and know-how. A major issue confronting the international community is, how to deal with a determined proliferator? Despite this gloomy scenario, however, the non-proliferation regime has considerable strengths - many of which can be developed further. The regime comprises complex interacting and mutually reinforcing elements. At its centre is the NPT - with IAEA safeguards as the Treaty's verification mechanism. Important complementary elements include: restraint in the supply and the acquisition of sensitive technologies; multilateral regimes such as the CTBT and proposed FMCT; various regional and bilateral regimes; the range of security and arms control arrangements outside the nuclear area (including other WMD regimes); and the development of proliferation-resistant technologies. Especially important are political incentives and sanctions in support of non-proliferation objectives. This paper outlines some of the key issues facing the non-proliferation regime

  3. Decentralization and Diversification in Forest Management Regimes ...

    African Journals Online (AJOL)

    In recent years in many African countries, including Tanzania, there has been a shift of paradigm from centralized and state driven forest management regimes to decentralized and people- centred forest management regime. The inception of a Tanzania forest policy of 1998 resulted in the institutionalization of community ...

  4. Multiscale regime shifts and planetary boundaries

    NARCIS (Netherlands)

    Hughes, T.P.; Carpenter, S.; Rockstrom, J.; Scheffer, M.; Walker, B.

    2013-01-01

    Life on Earth has repeatedly displayed abrupt and massive changes in the past, and there is no reason to expect that comparable planetary-scale regime shifts will not continue in the future. Different lines of evidence indicate that regime shifts occur when the climate or biosphere transgresses a

  5. LEGAL MATRIMONIAL REGIME IN B&H

    Directory of Open Access Journals (Sweden)

    Boris Krešić

    2011-12-01

    Full Text Available Matrimonial regime between spouses or between extramarital partners, and between parents and children is regulated by the Family Law Act of Bosnia and Herzegovina Federation, hereinafter FLA B&HF (SG FBiH 35/05, 41/05, Family Law Act of the Republic of Srpska, hereinafter FLA RS (SG RS”54/02, 41/08 and the Family Law Act of Brčko District, hereinafter FLA BD (SG RS, 66/07. Legal rules used for the regulation of the matrimonial regime between spouses, as well as between spouses and third parties make matrimonial regime (Ponjavić, 2005, p. 361. Matrimonial regime between spouses in family legislation in Bosnia and Herzegovina (B&H is regulated in two following ways: as legal matrimonial regime and as contract matrimonial regime. Legal regime is the one which applies on spouses if not arranged otherwise prior to contracting marriage or during marriage. In this paper the author indicates the differences between the legal matrimonial regimes of the two entities as well as those between the entities and Brčko District of Bosnia and Herzegovina.

  6. The simulation of multidimensional multiphase flows

    International Nuclear Information System (INIS)

    Lahey, Richard T.

    2005-01-01

    This paper presents an assessment of various models which can be used for the multidimensional simulation of multiphase flows, such as may occur in nuclear reactors. In particular, a model appropriate for the direct numerical simulation (DNS) of multiphase flows and a mechanistically based, three-dimensional, four-field, turbulent, two-fluid computational multiphase fluid dynamics (CMFD) model are discussed. A two-fluid bubbly flow model, which was derived using potential flow theory, can be extended to other flow regimes, but this will normally involve ensemble-averaging the results from direct numerical simulations (DNS) of various flow regimes to provide the detailed numerical data necessary for the development of flow-regime-specific interfacial and wall closure laws

  7. Convection and exchangers in variable regime; Convection et echangeurs en regime variable

    Energy Technology Data Exchange (ETDEWEB)

    Bagui, F.; Abdelghani-Idrissi, M.A. [Rouen Univ. IUT, Centre de Developpement Durable, 76 - Mont Saint Aignan (France); Bagui, F. [Ecole d' Ingenieurs CESI, 76 - Mont Saint Aignan (France); Desmet, B.; Lalot, S.; Harmand, S. [Valenciennes et du Hainaut-Cambresis Univ., Lab. de Mecanique et Energetique, 59 - Valenciennes (France); Maillet, D. [Institut National Polytechnique, INPL-UHP Nancy-1, LEMTA-CNRS UMR 7563, 54 - Vandoeuvre les Nancy (France)

    2005-07-01

    This session about convection and exchangers in variable regime gathers three articles dealing with: the transient regimes of tubular heat exchangers; heat exchangers and convection in non-permanent regime; and the limitations of the H coefficient: two short-time and short-scale examples. (J.S.)

  8. CRM in the Regime of Nonresonant Bunching

    CERN Document Server

    Bandurkin, I V; Savilov, A V

    2005-01-01

    New regime of electron-wave coupling in cyclotron resonance maser (CRM) is proposed. In this regime, during the most part of interaction process electrons move in the field of rf wave which is relatively far from cyclotron resonance. It is shown, that if resonance mismatch is chosen properly, an effective bunching takes place, an amplitude of forming rf current weakly depending on the velocity spread. Simulations show that, whereas the efficiency of traditional regimes quickly decreases with increasing velocity spread, efficiency of the proposed scheme practically does not change and for relative value of spread in transverse velocities of 40% is twice as large as corresponding efficiency of the conventional regimes. The regime seems to be also prospective for realization of CRM with frequency multiplication. In such a scheme, resonance mismatch for low-frequency wave in bunching section should be such that high-frequency wave be in resonance with the beam. Thus, the device operates like the single-frequency ...

  9. Performance of non-recessed hole-entry hybrid journal bearing operating under turbulent regime

    Directory of Open Access Journals (Sweden)

    Nathi Ram

    2016-03-01

    Full Text Available The effect of turbulent flow on non-recessed hole-entry hybrid journal bearing system has been investigated numerically. For turbulent flow of lubricant in compensated hole-entry hybrid journal bearing by CFV, the Reynolds equation has been modified and solved using finite element method. The performance characteristics parameters of bearing have been presented for different values of Reynolds numbers. The bearing provides the higher values of minimum fluid film thickness and fluid film stiffness coefficients for constant restrictor design parameter when bearing operates under turbulent regime than laminar regime.

  10. Overplanting in offshore wind power plants in different regulatory regimes

    DEFF Research Database (Denmark)

    Wolter, Christoph; Klinge Jacobsen, Henrik; Rogdakis, Georgios

    2016-01-01

    is performed by installing a larger wind power capacity than stipulated in the connection agreement with transmission system operators (TSOs). By developing a discounted cash flow (DCF) model, the paper investigates how both regulatory regimes and geographic characteristics of dedicated offshore wind...... development areas affect the viability of overplanting. The analysis comprises hypothetical scenarios of the distinctive offshore wind markets of the United Kingdom and Denmark and thereby elucidates the key aspects influencing the value of overplanting. This work’s findings show that the UK regulatory...

  11. Dissipation regimes for short wind waves

    Science.gov (United States)

    Caulliez, Guillemette

    2013-02-01

    The dissipation processes affecting short wind waves of centimeter and decimeter scales are investigated experimentally in laboratory. The processes include damping due to molecular viscosity, generation of capillary waves, microbreaking, and breaking. The observations were made in a large wind wave tank for a wide range of fetches and winds, using a laser sheet and a high-resolution video camera. The work aims at constructing a comprehensive picture of dissipative processes in the short wind wave field, to find for which scales particular dissipative mechanism may become important. Four distinct regimes have been identified. For capillary-gravity wave fields, i.e., for dominant waves with scales below 4 cm, viscous damping is found to be the main dissipation mechanism. The gravity-capillary wave fields with dominant wavelength less than 10 cm usually exhibit a train of capillary ripples at the crest wavefront, but no wave breaking. For such waves, the main dissipation process is molecular viscosity occurring through nonlinear energy cascade toward high-frequency motions. Microscale breaking takes place for waves longer than 10 cm and manifests itself in a very localized surface disruption on the forward face of the crest. Such events generate turbulent motions in water and thus enhance wave dissipation. Plunging breaking, characterized by formation of a crest bulge, a microjet hitting the water surface and a splash-up, occurs for short gravity waves of wavelength exceeding 20 cm. Macroscale spilling breaking is also observed for longer waves at high winds. In both cases, the direct momentum transfer from breaking waves to the water flow contributes significantly to wave damping.

  12. Horizontal two phase flow pattern identification by neural networks

    International Nuclear Information System (INIS)

    Crivelaro, Kelen Cristina Oliveira; Seleghim Junior, Paulo; Hervieu, Eric

    1999-01-01

    A multiphase fluid can flow according to several flow regimes. The problem associated with multiphase systems are basically related to the behavior of macroscopic parameters, such as pressure drop, thermal exchanges and so on, and their strong correlation to the flow regime. From the industrial applications point of view, the safety and longevity of equipment and systems can only be assured when they work according to the flow regimes for which they were designed to. This implies in the need to diagnose flow regimes in real time. The automatic diagnosis of flow regimes represents an objective of extreme importance, mainly for applications on nuclear and petrochemical industries. In this work, a neural network is used in association to a probe of direct visualization for the identification of a gas-liquid flow horizontal regimes, developed in an experimental circuit. More specifically, the signals produced by the probe are used to compose a qualitative image of the flow, which is promptly sent to the network for the recognition of the regimes. Results are presented for different transitions among the flow regimes, which demonstrate the extremely satisfactory performance of the diagnosis system. (author)

  13. Radiation linewidth of flux-flow oscillators

    DEFF Research Database (Denmark)

    Koshelets, V.P.; Dmitriev, P.N.; Ermakov, A.B.

    2001-01-01

    (applied magnetic field) are taken. A profile of the FFO radiation line is measured in different regimes of FFO operation and compared to the theoretical models. A Lorentzian shape of the FFO line is observed both at Fiske steps (FSs) in the resonant regime and on the flux-flow step (FFS) at high voltages...

  14. Abrupt climate-independent fire regime changes

    Science.gov (United States)

    Pausas, Juli G.; Keeley, Jon E.

    2014-01-01

    Wildfires have played a determining role in distribution, composition and structure of many ecosystems worldwide and climatic changes are widely considered to be a major driver of future fire regime changes. However, forecasting future climatic change induced impacts on fire regimes will require a clearer understanding of other drivers of abrupt fire regime changes. Here, we focus on evidence from different environmental and temporal settings of fire regimes changes that are not directly attributed to climatic changes. We review key cases of these abrupt fire regime changes at different spatial and temporal scales, including those directly driven (i) by fauna, (ii) by invasive plant species, and (iii) by socio-economic and policy changes. All these drivers might generate non-linear effects of landscape changes in fuel structure; that is, they generate fuel changes that can cross thresholds of landscape continuity, and thus drastically change fire activity. Although climatic changes might contribute to some of these changes, there are also many instances that are not primarily linked to climatic shifts. Understanding the mechanism driving fire regime changes should contribute to our ability to better assess future fire regimes.

  15. De Facto Regimes in International Law

    Directory of Open Access Journals (Sweden)

    Jonte van Essen

    2012-02-01

    Full Text Available The ambiguous position of de facto regimes in international law has long been the subject of scholarly debate and a source of political conflict. An assessment of the current standing of these regimes in international law and the consequences of actions by international actors on this status has, however, been long overdue. The manner in which de facto regimes are regarded internationally has serious consequences for the individuals under the influence of this legal grey area. Therefore, the study into this problem and possible solutions is of great significance. The 2011 developments in Northern Africa underline the need of contemporary research into this area. This essay aims to clarify the position of de facto regimes in international law and the influence on their status by actions of international actors. The author first argues that de facto regimes have rights and obligations under international law, which provide them with (some form of international legal personality. He then pleads for a reconsideration of the contemporary legal treatment of these regimes. The author argues against the current system of government recognition and proposes a system that better addresses the needs of both de facto regimes and the international community. 

  16. Choice of geometry and operating regimes for experimental dual-mode high-speed propane-fueled combustion chamber

    Science.gov (United States)

    Vlasenko, Vladimir; Voloshchenko, Oleg; Sabelnikov, Vladimir; Talyzin, Vadim

    2017-10-01

    The choice of geometry and operatic regimes of an experimental model of combustion chamber with a supersonic flow at the entrance is described. In this model, subsonic or supersonic combustion should be realized, depending on the inflow parameters. Propane will be used as fuel. The model combustor will be tested in T-131B wind tunnel of TsAGI. The goal is creation of experimental database for validation of calculations and physical models of turbulence and combustion. Geometry of chamber has similarities to geometry of model tested at ONERA LAERTE facility within LAPCAT-II project, but other flow regimes are considered. Preliminary 2D URANS calculations were used for the choice of fuel injection scheme. For the chosen flow regime, stabilization of combustion was not obtained for pure propane fuel. Addition of small portion of hydrogen allowed to stabilize the flame. Both subsonic and supersonic combustion regimes are found and analyzed.

  17. Flow transitions in two-dimensional foams.

    Science.gov (United States)

    Gilbreth, Christopher; Sullivan, Scott; Dennin, Michael

    2006-11-01

    For sufficiently slow rates of strain, flowing foam can exhibit inhomogeneous flows. The nature of these flows is an area of active study in both two-dimensional model foams and three dimensional foam. Recent work in three-dimensional foam has identified three distinct regimes of flow [S. Rodts, J. C. Baudez, and P. Coussot, Europhys. Lett. 69, 636 (2005)]. Two of these regimes are identified with continuum behavior (full flow and shear banding), and the third regime is identified as a discrete regime exhibiting extreme localization. In this paper, the discrete regime is studied in more detail using a model two-dimensional foam: a bubble raft. We characterize the behavior of the bubble raft subjected to a constant rate of strain as a function of time, system size, and applied rate of strain. We observe localized flow that is consistent with the coexistence of a power-law fluid with rigid-body rotation. As a function of applied rate of strain, there is a transition from a continuum description of the flow to discrete flow when the thickness of the flow region is approximately ten bubbles. This occurs at an applied rotation rate of approximately 0.07 s-1.

  18. Overview of zonal flow physics

    International Nuclear Information System (INIS)

    Diamond, P.H.; Itoh, K.; Itoh, S.-I.; Hahm, T.S.

    2005-01-01

    Zonal flows, by which we mean azimuthally symmetric band-like shear flows, are ubiquitous phenomena in nature and the laboratory. It is now widely recognized that zonal flows are a key constituent in virtually all cases and regimes of drift wave turbulence, indeed, so much so that this classic problem is now frequently referred to as 'drift wave-zonal flow turbulence'. In this theory overview, we present new viewpoints and unifying concepts which facilitate understanding of zonal flow physics, via theory, computation and their confrontation with the results of laboratory experiment. Special emphasis is placed on identifying avenues for further progress. (author)

  19. Framing of regimes and transition strategies

    DEFF Research Database (Denmark)

    Jensen, Jens Stissing

    2012-01-01

    This article suggests that transition strategies are always formulated in the context of specific representations of the regime and the challenges it faces. It is argued that the framing of a regime affects the envisioning of transition strategies. An analysis of the current development agenda fo...... for the housing construction sector in Denmark reveals the relevance and impacts of different regime framings. It is proposed that the ability to cope with framing issues as situated and political processes is at the core of the governance of transitions....

  20. Modeling of dialogue regimes of distance robot control

    Science.gov (United States)

    Larkin, E. V.; Privalov, A. N.

    2017-02-01

    Process of distance control of mobile robots is investigated. Petri-Markov net for modeling of dialogue regime is worked out. It is shown, that sequence of operations of next subjects: a human operator, a dialogue computer and an onboard computer may be simulated with use the theory of semi-Markov processes. From the semi-Markov process of the general form Markov process was obtained, which includes only states of transaction generation. It is shown, that a real transaction flow is the result of «concurrency» in states of Markov process. Iteration procedure for evaluation of transaction flow parameters, which takes into account effect of «concurrency», is proposed.

  1. Characterising the hydrological regime of an ungauged temporary river system: a case study.

    Science.gov (United States)

    D'Ambrosio, Ersilia; De Girolamo, Anna Maria; Barca, Emanuele; Ielpo, Pierina; Rulli, Maria Cristina

    2017-06-01

    Temporary streams are characterised by specific hydrological regimes, which influence ecosystem processes, groundwater and surface water interactions, sediment regime, nutrient delivery, water quality and ecological status. This paper presents a methodology to characterise and classify the regime of a temporary river in Southern Italy based on hydrological indicators (HIs) computed with long-term daily flow records. By using a principal component analysis (PCA), a set of non-redundant indices were identified describing the main characteristics of the hydrological regime in the study area. The indicators identified were the annual maximum 30- and 90-day mean (DH4 and DH5), the number of zero flow days (DL6), flow permanence (MF) and the 6-month seasonal predictability of dry periods (SD6). A methodology was also tested to estimate selected HIs in ungauged river reaches. Watershed characteristics such as catchment area, gauging station elevation, mean watershed slope, mean annual rainfall, land use, soil hydraulic conductivity and available water content were derived for each site. Selected indicators were then linked to the catchment characteristics using a regression analysis. Finally, MF and SD6 were used to classify the river reaches on the basis of their degree of intermittency. The methodology presented in this paper constitutes a useful tool for ecologists and water resource managers in the Water Framework Directive implementation process, which requires a characterisation of the hydrological regime and a 'river type' classification for all water bodies.

  2. The role of the geophysical template and environmental regimes in controlling stream-living trout populations

    Science.gov (United States)

    Penaluna, Brooke E.; Railsback, Steve F.; Dunham, Jason B.; Johnson, S.; Bilby, Richard E.; Skaugset, Arne E.

    2015-01-01

    The importance of multiple processes and instream factors to aquatic biota has been explored extensively, but questions remain about how local spatiotemporal variability of aquatic biota is tied to environmental regimes and the geophysical template of streams. We used an individual-based trout model to explore the relative role of the geophysical template versus environmental regimes on biomass of trout (Oncorhynchus clarkii clarkii). We parameterized the model with observed data from each of the four headwater streams (their local geophysical template and environmental regime) and then ran 12 simulations where we replaced environmental regimes (stream temperature, flow, turbidity) of a given stream with values from each neighboring stream while keeping the geophysical template fixed. We also performed single-parameter sensitivity analyses on the model results from each of the four streams. Although our modeled findings show that trout biomass is most responsive to changes in the geophysical template of streams, they also reveal that biomass is restricted by available habitat during seasonal low flow, which is a product of both the stream’s geophysical template and flow regime. Our modeled results suggest that differences in the geophysical template among streams render trout more or less sensitive to environmental change, emphasizing the importance of local fish–habitat relationships in streams.

  3. Extending the collisional fluid equations into the long mean-free-path regime in toroidal plasmas. IV. Banana regime

    International Nuclear Information System (INIS)

    Shaing, K. C.

    2007-01-01

    In Part I [Phys. Fluids B 2, 1190 (1990)] and Part II [Phys. Plasmas 12, 082508 (2005)], it was emphasized that the equilibrium plasma viscous forces when applied for the magnetohydrodynamic (MHD) modes are only rigorously valid at the mode rational surface where m-nq=0. Here, m is the poloidal mode number, n is the toroidal mode number, and q is the safety factor. This important fact has been demonstrated explicitly by calculating the viscous forces in the plateau regime in Parts I and II. Here, the effective viscous forces in the banana regime are calculated for MHD modes by solving the linear drift kinetic equation that is driven by the plasma flows first derived in Part I. At the mode rational surface, the equilibrium plasma viscous forces are reproduced. However, it is found that away from the mode rational surface, the viscous forces for MHD modes decrease, a behavior similar to that observed in the viscous forces for the plateau regime. The proper form of the momentum equation that is appropriate for the modeling of the MHD modes is also discussed

  4. Heat-transfer regimes in nuclear-reactor-pumped gas lasers

    Energy Technology Data Exchange (ETDEWEB)

    Torczynski, J.R.

    1990-01-01

    The flow induced in nuclear-reactor-pumped gas lasers by the competing effects of spatially nonuniform fission-fragment heating (pumping) and heat transfer to the walls is examined. The equations of motion are acoustically filtered (low Mach number approximation), and the resulting equations are seen to have three timescales: the duration of the heating, the time required by the heating to produce a pressure rise comparable to the initial pressure, and the time for the thermal boundary layer to grow into the center of the laser cell. Three distinct regimes emerge from consideration of the relative magnitudes of these timescales. In the negligible-conduction regime, thermal-conduction effects are small, and the motion is determined by the spatial nonuniformity of the heating. In the dominant-conduction regime, thermal-conduction effects govern the motion. In the mixed regime, the effects of thermal conduction and heating nonuniformity are comparable, but since they are oppositely directed, a complex gas motion results. Analytical solutions to the equations of motion are presented for the negligible-conduction and dominant-conduction regimes, and examples are given for all three regimes. Plots of the second spatial derivative of the density field (a quantity often used in optical analyses) are given for the negligible-conduction and the dominant-conduction regimes as functions of the appropriate similarity parameters. 26 refs., 14 figs.

  5. Investigation of Different Droplet Formation Regimes in a T-junction Microchannel Using the VOF Technique in OpenFOAM

    Science.gov (United States)

    Malekzadeh, Shima; Roohi, Ehsan

    2015-06-01

    Here we aimed to investigate various droplet formation regimes in a two-dimensional T-junction microchannel geometry using the open source software OpenFOAM. Two incompressible fluids, continuous phase in the main channel and dispersed phase in the lateral channel, have been considered. The interFoam solver was used to simulate laminar flow with two incompressible and isothermal phases. We evaluated the capability of "Compressive Interface Capturing Scheme for Arbitrary Meshes (CICSAM)" volume of fluid (VOF) technique of the OpenFOAM for modeling of the droplet formation and movement in different regimes. The flow behavior in the T-junction microchannel over a wide range of capillary numbers (0.006 to 0.12), volume flow rate ratio (0.125, 0.25, 0.5), and contact angle (130° to 180°) in the squeezing, dripping and jetting regimes were examined.The importance of parameters such as contact angle, capillary number, flow rate ratio, and Reynolds number at the time of separation, as well as the formation of droplets, was investigated in different regimes. We found that droplet detachment time increases by increasing the contact angle in the squeezing regime while increasing the contact angle in the dripping regime results in a decrease in the droplet detachment time. We compare the role of pressure gradient and shear stress forces in the droplet formation process in both dripping and squeezing regimes in details. We also provide a classification of two-phase flow regimes in the investigated T-junction microchannel in terms of three main parameters of, e.g., flow rate ratio, contact angle, and capillary number.

  6. Climate change impacts on the fluvial regime in a Mediterranean mountainous area.

    Science.gov (United States)

    José Pérez-Palazón, María; Pimentel, Rafael; Herrero, Javier; José Polo, María

    2016-04-01

    The water flow regime in Mediterranean basins is greatly influenced by the high variability of the meteorological patterns, with recurrent drought periods, and the heterogeneity of both terrain physical properties and land uses. These aspects together with the simultaneous demands of water resources for human consumption, irrigation and energy production make it crucial to have a continuous flow series on control points along the river network. In the current context of Global Warming, mountainous semiarid watersheds, where Mediterranean and alpine climates coexist, constitute singular places to evaluate its effects on the river flow regime. Sierra Nevada Mountain area (SN) (southern Spain), with altitudes ranging from 2000 to 3500 m.a.s.l., is a clear example of snow regions in a semiarid environment. Due to its special climate conditions, SN is part of the global climate change observatories network. The aim of this work is to estimate the influence of climate change on the flow regime over several control points along the main channel of the Guadalfeo River (in the South face of SN), by means of analysing the observed trends and focusing in the occurrence of drought period and extreme flood events. For this, the flow regime at three selected points in the river was simulated by using WiMMed, a physically-based hydrological model developed for Mediterranean regions, which includes flow routing calculations. The model was calibrated and validated from observations at a gauge station point, from which the flow series were obtained at upstream. Precipitation and temperature datasets from the reference period (1960-2000) and two different scenarios (A2, B1) for a future period (2046-2100) proposed by the Fourth Assessment Report of IPCC (Intergovernmental Panel on Climate Change) were used as forcing meteorological variables. The comparison was performed over different flow indicator variables: 1) annual mean daily flow; 2) annual maximum daily flow; 3) annual number

  7. Numerical study of flame structure in the mild combustion regime

    Directory of Open Access Journals (Sweden)

    Mardani Amir

    2015-01-01

    Full Text Available In this paper, turbulent non-premixed CH4+H2 jet flame issuing into a hot and diluted co-flow air is studied numerically. This flame is under condition of the moderate or intense low-oxygen dilution (MILD combustion regime and related to published experimental data. The modelling is carried out using the EDC model to describe turbulence-chemistry interaction. The DRM-22 reduced mechanism and the GRI2.11 full mechanism are used to represent the chemical reactions of H2/methane jet flame. The flame structure for various O2 levels and jet Reynolds numbers are investigated. The results show that the flame entrainment increases by a decrease in O2 concentration at air side or jet Reynolds number. Local extinction is seen in the upstream and close to the fuel injection nozzle at the shear layer. It leads to the higher flame entertainment in MILD regime. The turbulence kinetic energy decay at centre line of jet decreases by an increase in O2 concentration at hot Co-flow. Also, increase in jet Reynolds or O2 level increases the mixing rate and rate of reactions.

  8. The Two Regimes of Postwar Shipping

    DEFF Research Database (Denmark)

    Iversen, Martin Jes; Tenold, Stig

    2014-01-01

    The aim of this article is to illustrate the most important changes in the regulatory framework of the shipping sector from the 1960s to 2010, and to analyse the basis for, and effects of, these changes. In order to explain how the transformation has occurred, we use two traditional maritime...... nations—Denmark and Norway—as case studies. First, we introduce the two regimes of Danish and Norwegian shipping: ‘the national regime’ from the early 1960s to the mid-1970s; and ‘the competitive regime’, which was fully established by the middle of the 1990s and still persists. Then, we briefly sketch...... the bargaining that accompanied the shift from the national regime to the competitive regime. Specifically, we show that the new regime primarily accommodated the interests of private actors such as shipping companies, rather than the interests of the authorities and the trade unions....

  9. The CTBT regime, significance and potential benefits

    International Nuclear Information System (INIS)

    Chang, Hong-Lae

    2002-01-01

    This presentation briefly outlines the CTBT's background, describes the activities of the Preparatory Commission, the verification regime, the role of the National Data Centres and international coopereation. The objectives of the Nairobi workshop are listed

  10. Policy Regime Juxtaposition in Latin America

    Directory of Open Access Journals (Sweden)

    Kent Eaton

    2017-04-01

    Full Text Available This article has three main objectives, each in the spirit of broadening the study of subnational politics to include the juxtaposition of policy regimes and not just political regimes. First, it identifies the causes that help explain why we are seeing more territorial heterogeneity within countries in terms of the pursuit of ideologically disparate development models at different levels of government. Second, the article assesses the importance of this trend by analyzing the chief advantages and disadvantages of policy regime juxtaposition. Third, I turn to the question of why subnational officials are able to defend ideologically deviant policy regimes in some cases, but not in others. Based on the Bolivian, Ecuadorian, and Peruvian cases, my argument emphasizes the importance of two key factors: capacity and coalitions.

  11. The international climate regime: towards consolidation collapse

    International Nuclear Information System (INIS)

    Berthaud, P.; Cavard, D.; Criqui, P.

    2003-10-01

    This article deals with the different modalities that exist to manage a problem of collective action in the field of climate negotiation. It uses two concepts of the International Political Economy (IPE): the concept of International Regime (IR) and the concept of Hegemony and / or Leadership. The course the international negotiation has taken between 1992 (Rio Convention) and march 2001 (the US rejection of the Kyoto Protocol of 1997) leads us, first, to question the conditions of existence as well as the viability of a non-hegemonic International Regime (Part One). Then, we discuss the perspectives for the 'post - Kyoto' era. After having examined the preferences of the three most active actors in the negotiation (USA, Europe, G77 + China) combined with the leadership capacities they possess, we identify three scenarios for the future: i) anarchy, ii) an international regime under the American hegemony, iii) an international regime under the European leadership (Part Two). (author)

  12. Authoritarian Regimes, Domestic Stability, and International Conflict

    OpenAIRE

    Bae, Joonbum

    2015-01-01

    This dissertation addresses the argument that there may not be room for cooperation in relations with (and in between) states with authoritarian systems of rule because international conflicts may strengthen their hold on power. To this end, it asks 1) whether authoritarian regimes benefit in terms of their duration in power from conflict, 2) whether conflicts stabilize domestic politics by moderating the violence involved during regime transitions (in terms of how they fall), and also 3) whe...

  13. Portfolio Selection with Jumps under Regime Switching

    Directory of Open Access Journals (Sweden)

    Lin Zhao

    2010-01-01

    Full Text Available We investigate a continuous-time version of the mean-variance portfolio selection model with jumps under regime switching. The portfolio selection is proposed and analyzed for a market consisting of one bank account and multiple stocks. The random regime switching is assumed to be independent of the underlying Brownian motion and jump processes. A Markov chain modulated diffusion formulation is employed to model the problem.

  14. Improving the taxation regime for electric power

    International Nuclear Information System (INIS)

    Fjermeros, Morten; Ilstad, Kristine

    2003-01-01

    In Norway, the present taxation regime for electric power is very complex. The power companies are currently charged with ordinary tax on profits, tax on economic rent, tax on natural resources and land tax. In addition there are the rules about licence fees, yield of power due to concession conditions, and reversion. The Norwegian Electricity Industry Association (EBL), assisted by a firm of lawyers, has proposed an improvement over the current taxation regime

  15. Brazil in the global anticorruption regime

    Directory of Open Access Journals (Sweden)

    Marcos Tourinho

    2018-03-01

    Full Text Available Abstract Brazilian anticorruption law and institutions were significantly transformed in recent decades. This article traces those transformations and explains how the international anticorruption and money laundering regimes contributed to their development. It argues that those international regimes were internalised in the Brazilian system through three mechanisms: inspiration and legitimation, coercion, and implementation support, and were critical to the transformation of Brazilian institutions.

  16. The Philippines: predatory regime, growing authoritarian features

    OpenAIRE

    Quimpo, Nathan Gilbert

    2009-01-01

    Over the past decade, and especially over the past few years, political corruption, fraud and violence in the Philippines have reached such alarming levels that many Filipinos have grown despondent, even cynical, about their country's political system. Exploring the suitability of the concepts of 'predatory state' and 'patrimonial oligarchic state' to the Philippines, I find that the regime rather than the state is the more appropriate unit of analysis. I argue that the predatory regime, cont...

  17. Welfare state regimes and gender inequalities in the exposure to work-related psychosocial hazards.

    Science.gov (United States)

    Campos-Serna, Javier; Ronda-Pérez, Elena; Moen, Bente E; Artazcoz, Lucia; Benavides, Fernando G

    2013-01-01

    Gender inequalities in the exposure to work-related psychosocial hazards are well established. However, little is known about how welfare state regimes influence these inequalities. To examine the relationship between welfare state regimes and gender inequalities in the exposure to work-related psychosocial hazards in Europe, considering occupational social class. We used a sample of 27, 465 workers from 28 European countries. Dependent variables were high strain, iso-strain, and effort-reward imbalance, and the independent was gender. We calculated the prevalence and prevalence ratio separately for each welfare state regime and occupational social class, using multivariate logistic regression models. More female than male managers/professionals were exposed to: high strain, iso-strain, and effort-reward imbalance in Scandinavian [adjusted prevalence ratio (aPR) = 2·26; 95% confidence interval (95% CI): 1·87-2·75; 2·12: 1·72-2·61; 1·41: 1·15-1·74; respectively] and Continental regimes (1·43: 1·23-1·54; 1·51: 1·23-1·84; 1·40: 1·17-1·67); and to high strain and iso-strain in Anglo-Saxon (1·92: 1·40-2·63; 1·85: 1·30-2·64; respectively), Southern (1·43: 1·14-1·79; 1·60: 1·18-2·18), and Eastern regimes (1·56: 1·35-1·81; 1·53: 1·28-1·83). Gender inequalities in the exposure to work-related psychosocial hazards were not lower in those welfare state regimes with higher levels of universal social protection policies.

  18. The initial regime of drop coalescence

    Science.gov (United States)

    Anthony, Christopher; Harris, Michael; Basaran, Osman

    2017-11-01

    Drop coalescence plays a key role in both industry and nature. Consequently, study of the phenomenon has been the focus of numerous experimental, computational and theoretical works to date. In coalescence, two drops come into contact and a liquid bridge forms between them. As time advances, this bridge grows from microscopic to macroscopic scales. Despite the large volume of work dedicated to this problem, currently experiment, theory, and computation are not in perfect agreement with respect to the earliest times following the initial contact of the drops. Experiments report an initial regime where the radius of the connecting bridge grows linearly in time before a transition to either a Stokes regime or an inertial regime where either viscous or inertial forces balance capillary force. In the initial linear regime, referred to as the inertially-limited viscous regime, all three forces are thought to be important. This is in contrast to theory which predicts that all coalescence events begin in the Stokes regime. We use high accuracy numerical simulation to show that the existing discrepancy in the literature can be resolved by paying careful attention to the initial conditions that set the shape and size of the bridge connecting the two drops.

  19. Tomographic multiphase flow measurement

    International Nuclear Information System (INIS)

    Sætre, C.; Johansen, G.A.; Tjugum, S.A.

    2012-01-01

    Measurement of multiphase flow of gas, oil and water is not at all trivial and in spite of considerable achievements over the past two decades, important challenges remain (). These are related to reducing measurement uncertainties arising from variations in the flow regime, improving long term stability and developing new means for calibration, adjustment and verification of the multiphase flow meters. This work focuses on the first two issues using multi gamma beam (MGB) measurements for identification of the type of flow regime. Further gamma ray tomographic measurements are used for reference of the gas/liquid distribution. For the MGB method one Am-241 source with principal emission at 59.5 keV is used because this relatively low energy enables efficient collimation and thereby shaping of the beams, as well as compact detectors. One detector is placed diametrically opposite the source whereas the second is positioned to the side so that this beam is close to the pipe wall. The principle is then straight forward to compare the measured intensities of these detectors and through that identify the flow pattern, i.e. the instantaneous cross-sectional gas-liquid distribution. The measurement setup also includes Compton scattering measurements, which can provide information about the changes in the water salinity for flow segments with high water liquid ratio and low gas fractions. By measuring the transmitted intensity in short time slots (<100ms), rapid regime variations are revealed. From this we can select the time sections suitable for salinity measurements. Since the salinity variations change at the time scale of hours, a running average can be performed to increase the accuracy of the measurements. Recent results of this work will be presented here. - Highlights: ► Multiphase flow gas-fraction and flow regime measurements by multi gamma ray beams. ► High-speed gamma ray tomograph as reference for the flow pattern and gas fraction. ► Dual modality

  20. Movement mechanisms of gross solids in intermittent flow.

    Science.gov (United States)

    Littlewood, K; Butler, D

    2003-01-01

    Gross solids, such as used tampons, sanitary towels and faecal stools, are introduced into the sewer network via the WC. Although small diameter pipes (< or = 150mm diameter) make up a large proportion of most sewer networks, the transport behaviour of gross solids in these smaller pipes is not fully established. In particular, there are concerns about the effect of water conservation measures on the transport of gross solids in the intermittent flow regime prevalent in small pipes. This paper introduces a study carried out on the movement of solids in this flow regime. An extensive series of experiments has been carried out to investigate the movement mechanisms and behaviour in detail. It was found that there are three different mechanisms of movement, and photographic evidence is provided in the paper. The concept and implications of the "limiting solid transport distance" is also introduced. It is argued that solid movement is dependent on factors other than just WC flush volume and that increased blockage potential is not inevitable.

  1. Ecosystem regime shifts disrupt trophic structure.

    Science.gov (United States)

    Hempson, Tessa N; Graham, Nicholas A J; MacNeil, M Aaron; Hoey, Andrew S; Wilson, Shaun K

    2018-01-01

    Regime shifts between alternative stable ecosystem states are becoming commonplace due to the combined effects of local stressors and global climate change. Alternative states are characterized as substantially different in form and function from pre-disturbance states, disrupting the delivery of ecosystem services and functions. On coral reefs, regime shifts are typically characterized by a change in the benthic composition from coral to macroalgal dominance. Such fundamental shifts in the benthos are anticipated to impact associated fish communities that are reliant on the reef for food and shelter, yet there is limited understanding of how regime shifts propagate through the fish community over time, relative to initial or recovery conditions. This study addresses this knowledge gap using long-term data of coral reef regime shifts and recovery on Seychelles reefs following the 1998 mass bleaching event. It shows how trophic structure of the reef fish community becomes increasingly dissimilar between alternative reef ecosystem states (regime-shifted vs. recovering) with time since disturbance. Regime-shifted reefs developed a concave trophic structure, with increased biomass in base trophic levels as herbivorous species benefitted from increased algal resources. Mid trophic level species, including specialists such as corallivores, declined with loss of coral habitat, while biomass was retained in upper trophic levels by large-bodied, generalist invertivores. Recovering reefs also experienced an initial decline in mid trophic level biomass, but moved toward a bottom-heavy pyramid shape, with a wide range of feeding groups (e.g., planktivores, corallivores, omnivores) represented at mid trophic levels. Given the importance of coral reef fishes in maintaining the ecological function of coral reef ecosystems and their associated fisheries, understanding the effects of regime shifts on these communities is essential to inform decisions that enhance ecological

  2. Multiple Changes in the Hydrologic Regime of the Yangtze River and the Possible Impact of Reservoirs

    Directory of Open Access Journals (Sweden)

    Feng Huang

    2016-09-01

    Full Text Available This paper investigates hydrologic changes in the Yangtze River using long-term daily stream flow records (1955–2013 collected from four flow gauging stations located from the upper to the lower reaches of the river. The hydrologic regime is quantified using the Indicators of Hydrologic Alteration, which statistically characterize hydrologic variation within each year. Scanning t-test is applied to analyze multiple changes in the hydrologic regime at different time scales. Then, coherency analysis is applied to identify common changes among different hydrologic indicators and across different reaches of the Yangtze River. The results point to various change patterns in the five components of hydrologic regime, including the magnitude of monthly water conditions, magnitude and duration of annual extreme water conditions, timing of annual extreme water conditions, frequency and duration of high and low pulses, and rate and frequency of water condition changes. The 32 hydrologic indicators feature multiple temporal-scale changes. Spatial variations can be observed in the hydrologic changes of the upper, middle, and lower reaches of the river. Common changes in different reaches consist of hydrologic indicators including the monthly flow in October and the low-flow indicators. The monthly flow in October is dominated by decreasing trends, while the monthly flows between January and March, the annual minimum 1/3/7/30/90-day flows, and the base flow index are characterized by increasing trends. Low pulse duration and total days of low pulses feature downward trends. The coherency analysis reveals significant relationships between the monthly flow in October and the low-flow indicators, indicating that reservoir regulation is an important factor behind the hydrologic changes.

  3. Assessing water quality trends in catchments with contrasting hydrological regimes

    Science.gov (United States)

    Sherriff, Sophie C.; Shore, Mairead; Mellander, Per-Erik

    2016-04-01

    Environmental resources are under increasing pressure to simultaneously achieve social, economic and ecological aims. Increasing demand for food production, for example, has expanded and intensified agricultural systems globally. In turn, greater risks of diffuse pollutant delivery (suspended sediment (SS) and Phosphorus (P)) from land to water due to higher stocking densities, fertilisation rates and soil erodibility has been attributed to deterioration of chemical and ecological quality of aquatic ecosystems. Development of sustainable and resilient management strategies for agro-ecosystems must detect and consider the impact of land use disturbance on water quality over time. However, assessment of multiple monitoring sites over a region is challenged by hydro-climatic fluctuations and the propagation of events through catchments with contrasting hydrological regimes. Simple water quality metrics, for example, flow-weighted pollutant exports have potential to normalise the impact of catchment hydrology and better identify water quality fluctuations due to land use and short-term climate fluctuations. This paper assesses the utility of flow-weighted water quality metrics to evaluate periods and causes of critical pollutant transfer. Sub-hourly water quality (SS and P) and discharge data were collected from hydrometric monitoring stations at the outlets of five small (~10 km2) agricultural catchments in Ireland. Catchments possess contrasting land uses (predominantly grassland or arable) and soil drainage (poorly, moderately or well drained) characteristics. Flow-weighted water quality metrics were calculated and evaluated according to fluctuations in source pressure and rainfall. Flow-weighted water quality metrics successfully identified fluctuations in pollutant export which could be attributed to land use changes through the agricultural calendar, i.e., groundcover fluctuations. In particular, catchments with predominantly poor or moderate soil drainage

  4. Inequalities in oral impacts and welfare regimes: analysis of 21 European countries.

    Science.gov (United States)

    Guarnizo-Herreño, Carol C; Watt, Richard G; Pikhart, Hynek; Sheiham, Aubrey; Tsakos, Georgios

    2014-12-01

    Very few studies have analysed the relationship between political factors and oral health inequalities, and only one study has compared the magnitude of inequalities in oral health-related quality of life (OHRQoL) across welfare state regimes. This study aimed to compare socioeconomic inequalities in oral impacts on daily life among 21 European countries with different welfare state regimes (Scandinavian, Anglo-Saxon, Bismarckian, Southern, and Eastern). We analysed data from the Eurobarometer 72.3, a survey carried out in 2009 among adults in European countries. Inequalities in oral impacts by education, occupational social class and subjective social status (SSS) were estimated by means of age-standardized prevalence rates, odds ratios (ORs), the relative index of inequality (RII) and the slope index of inequality (SII). Educational inequalities in the form of social gradients were observed in all welfare regimes. The Scandinavian and Southern welfare regimes also showed gradients for all SEP measures. There were not significant differences in the magnitude of relative inequalities (RII) across welfare state regimes. Absolute educational inequalities were largest in the Anglo-Saxon welfare regime (SII = 17.57; 95% CI: 7.80-27.33) and smallest in the Bismarckian (SII = 3.32; 95% CI: -2.18 to 8.83). A significant difference in the magnitude of inequalities across welfare regimes was found for absolute educational inequalities but not for relative inequalities. Welfare state regimes may influence the relationship between knowledge-related resources and oral impacts on daily life. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  5. Two-phase Flow in Micro and Nanofluidic Devices

    NARCIS (Netherlands)

    Shui, Lingling

    2009-01-01

    This thesis provides experimental data and theoretical analysis on two-phase flow in devices with different layouts of micrometer or nanometer-size channels. A full flow diagram is presented for oil and water flow in head-on microfluidic devices. Morphologically different flow regimes (dripping,

  6. Lattice Boltzmann approach for complex nonequilibrium flows.

    Science.gov (United States)

    Montessori, A; Prestininzi, P; La Rocca, M; Succi, S

    2015-10-01

    We present a lattice Boltzmann realization of Grad's extended hydrodynamic approach to nonequilibrium flows. This is achieved by using higher-order isotropic lattices coupled with a higher-order regularization procedure. The method is assessed for flow across parallel plates and three-dimensional flows in porous media, showing excellent agreement of the mass flow with analytical and numerical solutions of the Boltzmann equation across the full range of Knudsen numbers, from the hydrodynamic regime to ballistic motion.

  7. Large amplitude oscillatory elongation flow

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Laillé, Philippe; Yu, Kaijia

    2008-01-01

    A filament stretching rheometer (FSR) was used for measuring the elongation flow with a large amplitude oscillative elongation imposed upon the flow. The large amplitude oscillation imposed upon the elongational flow as a function of the time t was defined as epsilon(t) =(epsilon) over dot(0)t...... with a molecular weight of 145 kg/ mol was subjected to the oscillative flow. The onset of the steady periodic regime is reached at the same Hencky strain as the onset of the steady elongational viscosity ( Lambda = 0). The integral molecular stress function formulation within the 'interchain pressure' concept...

  8. Progress towards a global nuclear liability regime

    International Nuclear Information System (INIS)

    2014-01-01

    During its April 2014 meeting, the Steering Committee for Nuclear Energy held a policy debate on 'Progress towards a Global Nuclear Liability Regime'. The Steering Committee heard presentations from several experts on nuclear liability issues. To prepare the delegates to the Steering Committee for the policy debate, the NEA Secretariat prepared a background note on the status of the nuclear liability regimes, as well as on current issues and challenges in implementing the regimes. This article is based on the background note and is intended to provide basic information on the relevant international conventions and an overview of recent developments to enhance the understanding of the legal framework in which policy-makers and practitioners are engaging to respond to the call for broader adherence to the international liability instruments. (authors)

  9. Multiscale regime shifts and planetary boundaries.

    Science.gov (United States)

    Hughes, Terry P; Carpenter, Stephen; Rockström, Johan; Scheffer, Marten; Walker, Brian

    2013-07-01

    Life on Earth has repeatedly displayed abrupt and massive changes in the past, and there is no reason to expect that comparable planetary-scale regime shifts will not continue in the future. Different lines of evidence indicate that regime shifts occur when the climate or biosphere transgresses a tipping point. Whether human activities will trigger such a global event in the near future is uncertain, due to critical knowledge gaps. In particular, we lack understanding of how regime shifts propagate across scales, and whether local or regional tipping points can lead to global transitions. The ongoing disruption of ecosystems and climate, combined with unprecedented breakdown of isolation by human migration and trade, highlights the need to operate within safe planetary boundaries. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Causas estruturais e consequências dos regimes internacionais: regimes como variáveis intervenientes

    Directory of Open Access Journals (Sweden)

    Stephen D. Krasner

    2012-06-01

    Full Text Available Os regimes internacionais são definidos como princípios, normas, regras e procedimentos de tomada de decisões ao redor dos quais as expectativas dos atores convergem em uma dada área-tema. Como ponto de partida, os regimes são conceituados como variáveis intervenientes, estando entre fatores causais básicos e os resultados e comportamentos relacionados. Há três visões a respeito da importância dos regimes: as orientações estruturais convencionais desvalorizam os regimes como sendo, na melhor das hipóteses, ineficazes; as orientações grocianas vêem os regimes como componentes íntimos do sistema internacional; as perspectivas estruturalistas modificadas vêem os regimes como significativos somente em certas condições restritas. Para os argumentos grociano e estruturalista modificado - que concordam com a visão de que os regimes podem influenciar resultados e comportamentos - , o desenvolvimento de regimes é visto como uma função de cinco variáveis causais básicas: auto-interesse egoísta; poder político; normas e princípios difusos; usos e costumes; conhecimento.

  11. Theoretical and experimental study of inverted annular film boiling and regime transition during reflood transients

    Science.gov (United States)

    Mohanta, Lokanath

    The Loss of Coolant Accident (LOCA) is a design basis accident for light water reactors that usually determines the limits on core power. During a LOCA, film boiling is the dominant mode of heat transfer prior to the quenching of the fuel rods. The study of film boiling is important because this mode of heat transfer determines if the core can be safely cooled. One important film boiling regime is the so-called Inverted Annular Film Boiling (IAFB) regime which is characterized by a liquid core downstream of the quench front enveloped by a vapor film separating it from the fuel rod. Much research have been conducted for IAFB, but these studies have been limited to steady state experiments in single tubes. In the present work, subcooled and saturated IAFB are investigated using high temperature reflood data from the experiments carried out in the Rod Bundle Heat Transfer (RBHT) test facility. Parametric effects of system parameters including the pressure, inlet subcooling, and flooding rate on the heat transfer are investigated. The heat transfer behavior during transition to Inverted Slug Film Boiling (ISFB) regime is studied and is found to be different than that reported in previous studies. The effects of spacer grids on heat transfer in the IAFB and ISFB regimes are also presented. Currently design basis accidents are evaluated with codes in which heat transfer and wall drag must be calculated with local flow parameters. The existing models for heat transfer are applicable up to a void fraction of 0.6, i.e. in the IAFB regime and there is no heat transfer correlation for ISFB. A new semi-empirical heat transfer model is developed covering the IAFB and ISFB regimes which is valid for a void fraction up to 90% using the local flow variables. The mean absolute percentage error in predicting the RBHT data is 11% and root mean square error is 15%. This new semi-empirical model is found to compare well with the reflood data of FLECHT-SEASET experiments as well as data

  12. Analysis of relations for heat transfer at the post-CHF regime

    International Nuclear Information System (INIS)

    Dorokhovich, S. L.; Kirillov, P. L.

    2003-01-01

    Information about heat transfer rates in two-fluid flow at the post-CHF regime is important for analysis of accidents of water-cooled nuclear reactors as well as calculations of steam generators (liquid metal-water). It is complicate to create analytical methods because there is a variety of two-fluid flow regimes dictated by channel size, pressure, mass flow rate, heat flux, droplet spectrum, flow quality, other factors and, finally, by crisis type. At crisis in subcooled liquid or low quality two-phase flows Inverted Annular Film Boiling (IAFB) takes place when liquid flow is separated from the wall by a thin superheated vapor film. For dispersed flow crisis is usually related to drying a liquid film moving along the heated surface (wall). In both cases two-phase flow is thermodynamically nonequilibrium since the temperatures of phases (liquid and vapor) are different. The mean (at the rate of heat content) flow temperature is not the determining parameter. Different boundary conditions of experiment s uniform heat fluxes or 'hot' spots, are able to lead to different relations for the heat transfer coefficient. Last years the great number of semiempirical models were elaborated, that become more and more complicate. It is difficult to examine many parameters of the models. An agreement between final results and separate experimental data is not yet the evidence for the verity of extension while prerequisites taken in the models are often doubtful and hardly examined. Thus the correlations obtained from experimental data, for example, are used in practice. The analysis of relations for heat transfer at the Deteriorated Heat Transfer (DHT) regime, the comparison of relations with the data of look up tables made on the basis of the Institute of Physics and Power Engineering and Chalk River Laboratories experimental data banks are the objective of current report

  13. Fire regimes during the last glacial

    Science.gov (United States)

    Daniau, A.; Harrison, S. P.; Bartlein, P. J.

    2009-12-01

    Fire regimes during the last glacial A.-L. Daniau (1), S.P. Harrison (1) and P.J. Bartlein (2) (1) School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK (2) Department of Geography, University of Oregon, Eugene, OR 97403, USA Sedimentary charcoal records document changes in fire regime. We have identified 67 sites which have records for some part of the last glacial and have used the 30 of these sites with better-than millennial-resolution to analyse changes in global fire regimes. Fire was consistently lower during the glacial than during the Eemian and Holocene. Within the glacial, Marine Isotope Stage (MIS) 3 is characterised globally by more fire than MIS 2. The signal for MIS 4 is less clear: there is more fire in the northern hemisphere and less fire in the southern hemisphere than during MIS 2 and 3. The records, most particularly records from the northern extratropics, show millennial-scale variability in fire regimes corresponding to the rapid climate changes associated with Dansgaard-Oeschger (D-O) cycles. Most of the D-O cycles during the last glacial and all of the Heinrich Stadials are apparent in the composite global record of the high-resolution sites: fire increases during D-O warming events and decreases during intervals of cooling. Our analyses show that fire regimes show a lagged response to rapid climate changes of ca 100-200 years in the case of D-O warming events, ca 0-100 years in the case of D-O cooling events and ca 200 years in the case of Heinrich Stadials. The strong climatic variability experienced during the glacial resulted in important changes in fire regimes even though the base level of biomass burning was less than today.

  14. WELFARE REGIMES IN LATIN AMERICA AND CARIBBEAN

    Directory of Open Access Journals (Sweden)

    Melisa Campana-Alabarce

    2015-06-01

    Full Text Available This article provides a characterization of Latin American and Caribbean Welfare regimes in historiographical perspective. Firstly, it makes a review of the emergence conditions of Welfare States in Western Europe and its core features, with particular emphasis on its role as a method to regulate inequalities in industrial capitalism. Dialoguing with it, then stops in the specific configurations that welfare regimes have taken in Latin America during the course of the twentieth century. Finally, it provides a map of its contemporary features and the major challenges that the States of the region face in his capacity as right guarantors for the future.

  15. The oil tax regime of Azerbaijan

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Gerard

    1998-07-01

    Azerbaijan has a long history in the oil business and a chance of a spectacular future. To understand why the oil tax regime evolved into its present form and how it is likely to develop, it is necessary to know something of the country's history and the commercial environment. Consequently the presentation begins by discussing these items. It then outlines the Production Sharing Agreement regime in Azerbaijan and then deals with the Kazakh and Georgian Tax Codes, as these are likely to be the basis of a new general tax law in Azerbaijan from 1999. The presentation includes comments on the New Draft Tax Code of 1998.

  16. Legal Regimes of Official Information in Ukraine

    Directory of Open Access Journals (Sweden)

    Serhii Yesimov

    2018-04-01

    Full Text Available In the article on the basis of the methodology of system analysis the legal nature and sources of legal regulation of the legal regime of official information in Ukraine in the conditions of adaptation of Ukrainian legislation to the legislation of the European Union are considered. A comparative legal analysis of official information in the public-law and private-law spheres in the context of legal regimes of restricted information, confidential information and information classified as state secrets has been conducted.

  17. Statistical regimes of random laser fluctuations

    International Nuclear Information System (INIS)

    Lepri, Stefano; Cavalieri, Stefano; Oppo, Gian-Luca; Wiersma, Diederik S.

    2007-01-01

    Statistical fluctuations of the light emitted from amplifying random media are studied theoretically and numerically. The characteristic scales of the diffusive motion of light lead to Gaussian or power-law (Levy) distributed fluctuations depending on external control parameters. In the Levy regime, the output pulse is highly irregular leading to huge deviations from a mean-field description. Monte Carlo simulations of a simplified model which includes the population of the medium demonstrate the two statistical regimes and provide a comparison with dynamical rate equations. Different statistics of the fluctuations helps to explain recent experimental observations reported in the literature

  18. Towards a Global Regime of Higher Education

    Directory of Open Access Journals (Sweden)

    Paolo Do

    2015-12-01

    Full Text Available This paper rethinks the spatialization of educational institutions at the global level, scaling and rescaling the space of the university as an inclusive process that makes academic knowledge production something heterogeneous, complex and composite, and proposing a regime for the higher education system based on a stratified relationship that is asymmetrical and geographically displaced. Moreover it outlines the “new” political economy of knowledge, which is a particular mechanism in contemporary capitalist production, capable of creating an artificial scarcity of knowledge by means of hierarchies, and reproducing the classical law of value in a regime based on abundance instead of scarcity.

  19. Flocking regimes in a simple lattice model.

    Science.gov (United States)

    Raymond, J R; Evans, M R

    2006-03-01

    We study a one-dimensional lattice flocking model incorporating all three of the flocking criteria proposed by Reynolds [Computer Graphics 21, 4 (1987)]: alignment, centering, and separation. The model generalizes that introduced by O. J. O'Loan and M. R. Evans [J. Phys. A. 32, L99 (1999)]. We motivate the dynamical rules by microscopic sampling considerations. The model exhibits various flocking regimes: the alternating flock, the homogeneous flock, and dipole structures. We investigate these regimes numerically and within a continuum mean-field theory.

  20. Effect on Heat Transfer Characteristics of Nanofluids Flowing under Laminar and Turbulent Flow Regime - A Review

    Science.gov (United States)

    Kumar, Prince; Pandey, K. M., Dr.

    2017-08-01

    Heat transfer is a most important phenomenon that influence the performance of working device. To date several attempts have been made by researchers to minimize the size of heat exchangers in order to reduce the cost. Earlier we use some conventional fluids (water, air, engine oil etc.) for cooling of automobile, refrigeration and some other industrial applications. But it is observed here that by using these fluids there is curb and hindrance in heat transfer rate because of very low thermal conductivity. From last ten-years new generation fluid introduced known as nanofluid. To increase the thermal conductivity of base fluid some amount of nanoparticles is added. Nanofluid have combined properties of nanoparticles as well as base fluid. Researcher found that heat transfer rate fully dependent of the thermal conductivity of nanoparticles as well as nanoparticle size diameter and volume concentration. This review paper summarised the recent research on enhancement of heat transfer and thermal performance of nanofluid as coolant for industrial applications.

  1. Boiling flow through diverging microchannel

    Indian Academy of Sciences (India)

    Effect of mass flux (118–1182 kg/m2-s) and heat flux (1.6–19.2 W/cm2) on single and two-phase pressure drop and average heat transfer coefficient has been studied. Concurrently, flow visualization is carried out to document the various flow regimes and to correlate the pressure drop and average heat transfer coefficient ...

  2. Pain prevalence in hospitalized children

    DEFF Research Database (Denmark)

    Walther-Larsen, S; Pedersen, M T; Friis, S M

    2017-01-01

    BACKGROUND: Pain management in hospitalized children is often inadequate. The prevalence and main sources of pain in Danish university hospitals is unknown. METHODS: This prospective mixed-method cross-sectional survey took place at four university hospitals in Denmark. We enrolled 570 pediatric...... patients who we asked to report their pain experience and its management during the previous 24 hours. For patients identified as having moderate to severe pain, patient characteristics and analgesia regimes were reviewed. RESULTS: Two hundred and thirteen children (37%) responded that they had experienced...... pain in the previous 24 hours. One hundred and thirty four (24%) indicated moderate to severe pain and 43% would have preferred an intervention to alleviate the pain. In children hospitalized for more than 24 hours, the prevalence of moderate/severe pain was significantly higher compared to children...

  3. Statistics of exchange rate regimes in Nigeria | Iwueze | Global ...

    African Journals Online (AJOL)

    The three distinct exchange rate regimes of Nigeria were subjected to Autoregressive Integrated Moving Average (ARIMA) modeling in order to compare them with respect to model structure. It was found that the three regimes admit different models. Regime one admits Moving average model of order 2, Regime two admits ...

  4. Method and apparatus for monitoring two-phase flow. [PWR

    Science.gov (United States)

    Sheppard, J.D.; Tong, L.S.

    1975-12-19

    A method and apparatus for monitoring two-phase flow is provided that is particularly related to the monitoring of transient two-phase (liquid-vapor) flow rates such as may occur during a pressurized water reactor core blow-down. The present invention essentially comprises the use of flanged wire screens or similar devices, such as perforated plates, to produce certain desirable effects in the flow regime for monitoring purposes. One desirable effect is a measurable and reproducible pressure drop across the screen. The pressure drop can be characterized for various known flow rates and then used to monitor nonhomogeneous flow regimes. Another useful effect of the use of screens or plates in nonhomogeneous flow is that such apparatus tends to create a uniformly dispersed flow regime in the immediate downstream vicinity. This is a desirable effect because it usually increases the accuracy of flow rate measurements determined by conventional methods.

  5. An emissions trading regime for Canada

    International Nuclear Information System (INIS)

    Smith, S.L.

    2001-01-01

    In 1998, over twelve papers were published on emissions trading regimes in Canada by the National Round Table on the Environment and the Economy (NRTEE), a federal government agency whose members represent stakeholders as varied as business, environmental groups, academics, aboriginal groups and others. One of the recommendations that emerged was for the computer modelling of the possibilities that had been identified for a domestic trading regime in Canada for greenhouse gases. It is unclear whether the modelling was ever performed as the file was taken over by the Finance Department under the umbrella of a special emission trading table that examined Canada's commitment under the Kyoto Protocol. The author examined questions pertaining to whether a domestic trading regime is essential, and what its characteristics should be in case it was deemed essential or advisable to have one. The upstream versus downstream application was looked at, as well as grand-fathering versus auction. Provincial issues were then addressed, followed by meshing with a credit system. International systems were reviewed. Early action was discussed, whereby an emitter seeks credit for action taken toward reductions since the original reference year of 1990. The case of emitters having bought or sold permits since the original reference years will also want those trades recognized under a trading regime. The author indicated that it seems probable that an emission trading system will eventually be implemented and that a debate on the issue should be initiated early

  6. Comprehensive review of the maritime safety regimes.

    NARCIS (Netherlands)

    S. Knapp (Sabine); Ph.H.B.F. Franses (Philip Hans)

    2007-01-01

    textabstractThis report presents a comprehensive review of the maritime safety regimes and provides recommendations on how to improve the system. The results show a complex legal framework which generates a high amount of inspections and overlapping of inspection areas where no cross-recognition is

  7. Radiative effects of global MODIS cloud regimes

    Science.gov (United States)

    Oreopoulos, Lazaros; Cho, Nayeong; Lee, Dongmin; Kato, Seiji

    2018-01-01

    We update previously published MODIS global cloud regimes (CRs) using the latest MODIS cloud retrievals in the Collection 6 dataset. We implement a slightly different derivation method, investigate the composition of the regimes, and then proceed to examine several aspects of CR radiative appearance with the aid of various radiative flux datasets. Our results clearly show the CRs are radiatively distinct in terms of shortwave, longwave and their combined (total) cloud radiative effect. We show that we can clearly distinguish regimes based on whether they radiatively cool or warm the atmosphere, and thanks to radiative heating profiles to discern the vertical distribution of cooling and warming. Terra and Aqua comparisons provide information about the degree to which morning and afternoon occurrences of regimes affect the symmetry of CR radiative contribution. We examine how the radiative discrepancies among multiple irradiance datasets suffering from imperfect spatiotemporal matching depend on CR, and whether they are therefore related to the complexity of cloud structure, its interpretation by different observational systems, and its subsequent representation in radiative transfer calculations. PMID:29619289

  8. Stochastic dynamical models for ecological regime shifts

    DEFF Research Database (Denmark)

    Møller, Jan Kloppenborg; Carstensen, Jacob; Madsen, Henrik

    phytoplankton and benthic vegetation with feedback mechanisms is formulated, and it is demonstrated that bistability can occur for specific parameter settings. When stochastic input and stochastic propagation of the states are applied on the system regime shifts occur more frequently, and the threshold...

  9. European welfare regimes: Political orientations versus poverty

    Directory of Open Access Journals (Sweden)

    Josifidis Kosta

    2011-01-01

    Full Text Available This inquiry analyzes how political orientations shape welfare states and labour market institutions when seeking to reduce poverty. In order to identify effects of these two key variables, we conduct a panel regression analysis that includes two poverty measures: poverty rates before and after social spending. This inquiry considers 14 EU countries, and in the period from 1995 to 2008, which are grouped according to welfare state regimes. We consider Social Democratic, Corporatist, Mediterranean and Liberal welfare state regimes. Panel regression results indicate that political orientation engenders no significant statistically measurable effects on poverty rates before social spending. Effects register, however, as significant when considering poverty rates after social spending. With respect to the first set of results, we advance two key explanations. First, we note a longer period of time is necessary in order to observe actual effects of political orientation on market generated poverty. Second, political parties with their respective programs do not register as influential enough to solve social problems related to income distribution when taken alone. Influences register as indirect and are expressed through changes in employment rates and social spending. The second set of results support the hypothesis that a selected political regime does indeed contribute to poverty reduction. In sum, political orientation and political regime does indeed affect poverty through welfare state institutions, as well as through labour market institutions.

  10. STATISTICS OF EXCHANGE RATE REGIMES IN NIGERIA

    African Journals Online (AJOL)

    Admin

    currency. But since transactions are made in national (domestic) currencies, the former is generally applied for exchange (Mordi, 2006). The main objectives of ... different regimes. In this paper, attempt is made to use Autoregressive Integrated Moving Average. (ARIMA) model to study exchange rate data according to ...

  11. Transitions between risk management regimes in cities

    Directory of Open Access Journals (Sweden)

    William Solecki

    2017-06-01

    Full Text Available Ongoing climate change is encouraging cities to reevaluate their risk management strategies. Urban communities increasingly are being forced to respond to climate shifts with actions that promote resistance, resilience, or even larger scale transformations. Our objective is to present a conceptual framework that facilitates examination of how the transition from one type of risk management strategy or regime to another takes place. The research framework is built around a set of assumptions regarding the process of transition between risk management regimes. The framework includes five basic conceptual elements: (1 risk management regimes, (2 development pathways, (3 activity spheres, (4 activity spaces, and (5 root, contextual, and proximate drivers. The interaction among these elements and the potential for transition between four different possible regime states including resistance, resilience, transformation, and collapse are presented. The framework facilitates and guides analysis on whether and how transition is emergent, constrained, or accelerated in specific contexts. A case study of post-Hurricane Sandy New York is used to illustrate the framework and its overall effectiveness.

  12. Estimation in autoregressive models with Markov regime

    OpenAIRE

    Ríos, Ricardo; Rodríguez, Luis

    2005-01-01

    In this paper we derive the consistency of the penalized likelihood method for the number state of the hidden Markov chain in autoregressive models with Markov regimen. Using a SAEM type algorithm to estimate the models parameters. We test the null hypothesis of hidden Markov Model against an autoregressive process with Markov regime.

  13. EARLY INTERVENTION REGIME UNDER THE BANK ...

    African Journals Online (AJOL)

    OLAWUYI

    2000-03-01

    Mar 1, 2000 ... consumption and investment plans; allocating the savings of households and businesses to ... World Bank Principles and Guidelines for Effective Insolvency and Creditor Rights Systems, IMF's ... February 2009 addressed the immediate need for a special bank resolution regime following the global.

  14. A Comparative Typology of Pension Regimes

    NARCIS (Netherlands)

    Arjan Soede; Cok Vrooman

    2008-01-01

    This report presents an empirical typology of pension regimes in the European Union, the US, Canada, Australia and Norway. The categorisation is based on 34 quantitative and qualitative characteristics of the mandatory parts of the pension systems in these countries. The empirical analysis shows

  15. Yukon's common oil and gas regime

    International Nuclear Information System (INIS)

    Love, B.

    1998-01-01

    The Yukon's common oil and gas regime was developed in partnership with First Nations and it sets out the rules that will apply throughout the Yukon and on Yukon and First Nation lands. While separate and distinct, it conforms with and is compatible with other government systems and regimes. The major elements of the common regime include the Oil and Gas Act, regulations, policies, processes and agreements. The specific opportunities that are available in each phase of oil and gas development in the Yukon are described, with a map showing all basins, reserves and sites of current oil and gas activity. The Yukon has eight potential oil and gas basins: North Coast, Old Crow, Kandik, Eagle Plain, Peel Plateau, Bonnet Plume, Whitehorse Trough, and Liard Plateau. Only three of the eight, the Liard Plateau, Whitehorse Trough and Eagle Plain, have been explored. No wells have been drilled in several of Yukon's basins. Factors influencing economic opportunities in the Territory are also described, including: (1) international events and energy markets, (2) North American gas markets, (3) environmental factors, (4) competitiveness of the Yukon regime, and (5) the commitment of industry resources. 4 figs

  16. The Forex Regime and EMU Expansion

    NARCIS (Netherlands)

    P.W. van Foreest; C.G. de Vries (Casper)

    2002-01-01

    textabstractThis paper provides empirical evidence that, irrespective of the foreign exchange rate regime, countries with high monetary volatility have lower relative output growth rates. It is argued that due to the forward looking nature of the foreign exchange market, exchange rate stability

  17. Early detection of ecosystem regime shifts

    DEFF Research Database (Denmark)

    Lindegren, Martin; Dakos, Vasilis; Groeger, Joachim P.

    2012-01-01

    Critical transitions between alternative stable states have been shown to occur across an array of complex systems. While our ability to identify abrupt regime shifts in natural ecosystems has improved, detection of potential early-warning signals previous to such shifts is still very limited. Us...

  18. [The "specific" liability regime for blood products].

    Science.gov (United States)

    Byk, Christian

    2017-10-13

    Based on the system of liability for defective products as organized by the European Directive of 25 July 1985, responsibility for blood products does not therefore constitute a genuine specific regime. However, European law leaves States a margin of discretion in the implementation of the Directive with regard to health products. This is the case in particular with the exemption for development risk.

  19. STATISTICS OF EXCHANGE RATE REGIMES IN NIGERIA

    African Journals Online (AJOL)

    DJFLEX

    2009-02-11

    Feb 11, 2009 ... KEY WORDS: Exchange Rate Regime; ARIMA Model, Stationarity, Random Walk Model. INTRODUCTION. Exchange rate has been defined as the price of one currency in terms of another. It can be expressed in one of two ways: as units of domestic currency per unit of foreign currency; or units of foreign ...

  20. Searching for an Appropriate Exchange Rate Regime

    Directory of Open Access Journals (Sweden)

    Yunjong Wang

    2001-06-01

    Full Text Available This paper attempts to survey current debates on the choice of exchange rate regime in emerging market economies. The issue of choosing an appropriate exchange rate regime is being actively discussed since the recent Asian crisis. As a lesson from the recent crises, one widely shared conclusion is that soft peg exchange rate regimes are extremely vulnerable in a world of volatile capital movements. Consequently, new orthodoxy based on the impossible trinity hypothesis favours two corner solutions ― greater flexibility or credible institutional assurance, like a currency board system or dollarization. Nevertheless, questions whether such corner solutions are adequate for developing countries are rising of late. "Fear of floating" is still conspicuous in many developing countries having adopted nominally a free-floating exchange rate regime. Developing countries are sensitive to exchange rate fluctuations because the cost of exchange rate volatility is greater than the benefit when compared to developed countries. Monitoring bands is a compromise solution, but it still needs further enhancement of estimation techniques for fundamental equilibrium exchange rates in order to make those estimation results more workable in practice. Other alternatives include the creation of soft peg of the G-3 currencies. Despite counterarguments, the stability of G-3 currencies could prove to be beneficial to emerging market economies.

  1. Regime Shifts and Resilience in Fisheries Management

    NARCIS (Netherlands)

    Li, Chuan Zhong; Villasante, Sebastian; Zhu, Xueqin

    2016-01-01

    We investigate the role of potential regime shifts in Argentinean hake fishery and the inter-linkage between ecological and economic resilience. We develop a theoretical model incorporated with the hazard function for resource management under alternative conditions, and derive the corrective

  2. Negotiating a regime to control global warming

    International Nuclear Information System (INIS)

    Sebenius, J.K.

    1991-01-01

    For purposes of analysis, this paper has uncritically maintained that the prospect of a serious climate problem exists and has only lightly examined the broader advantages and drawbacks of various proposed policy and institutional responses. Crucial as they are to a full treatment of the issues, these underlying substantive and policy questions enter the analysis primarily insofar as they affect the likely outcomes of pending and potential negotiations. To an advocate of a new greenhouse control regime, the fundamental negotiating task is to craft and sustain a meaningful winning coalition of countries backing such a regime. Two centrally necessary conditions for the fundamental task are: (1) that each member of the coalition see enough gain in the regime relative to the alternatives to adhere and (2) the potential and actual blocking coalitions of interests opposed to the regime be prevented from forming and from being acceptably accommodated or otherwise neutralized. The analysis of this paper is organized around key questions whose answers will influence whether and how these two necessary conditions might (or might not) be met

  3. Welfare State Regimes and Caseworkers’ Problem Explanation

    DEFF Research Database (Denmark)

    Møller, Marie Østergaard; Stensöta, Helena Helena Olofsdotter

    2018-01-01

    welfare state regime type. Based on in-depth study of caseworker reasoning in Sweden and Denmark, we find a “structural problem explanation” that sees reasons for clients seeking support as rooted in the structures of society— not in the individual client. We find and present two narratives hitherto...

  4. EUROPEAN INFLUENCE ON ETHIOPIAN ANTITRUST REGIME:

    African Journals Online (AJOL)

    eliasn

    Introduction. Despite a noticeable European influence on the Ethiopian competition legal regime, some aspects of Ethiopia's 2003 Trade Practice Proclamation are still inadequate to appropriately deal with certain competition problems. The limitations of the rules need to be put right since achievement of the very goals of ...

  5. Wage Distributions by Bargaining Regime: Linked Employer-Employee Data Evidence from Germany

    OpenAIRE

    Karsten Kohn; Alexander C. Lembcke

    2007-01-01

    Using linked employer-employee data from the German Structure of Earnings Survey 2001, this paper provides a comprehensive picture of the wage structure in three wage-setting regimes prevalent in the German system of industrial relations. We analyze wage distributions for various labor market subgroups by means of kernel density estimation, variance decompositions, and individual and firm-level wage regressions. Unions' impact through collective and firm-level bargaining mainly works towards ...

  6. Regime of the dissolved oxygen in Iron Gates lakes

    International Nuclear Information System (INIS)

    Gruia, Emil; Marcoci, Simona

    1992-01-01

    During the period 1964-1987, in the dissolved oxygen regime of the Danube water elevate modifications occurred in the Iron Gates I and II area, in comparison with the relative stability of the previous period. The causes of this evolution were the water organic pollution, as a result of the socio-economical development of the riparian countries in the mentioned period, and the modifications of the water flow entailed by the building of the Iron Gates power system. As a result, physical, chemical and biological processes, different as intensity and manifestation from those in the previous period occurred. Consequently, the general ratio between demand and re-aeration processes has been modified. The paper has the following content: 1. Introduction; 2. Physico-chemical aspects; 3. Biological aspects; 4. Conclusions. (authors)

  7. Flow Rounding

    OpenAIRE

    Kang, Donggu; Payor, James

    2015-01-01

    We consider flow rounding: finding an integral flow from a fractional flow. Costed flow rounding asks that we find an integral flow with no worse cost. Randomized flow rounding requires we randomly find an integral flow such that the expected flow along each edge matches the fractional flow. Both problems are reduced to cycle canceling, for which we develop an $O(m \\log(n^2/m))$ algorithm.

  8. The global safety regime - Setting the stage

    International Nuclear Information System (INIS)

    Meserve, R.A.

    2005-01-01

    The existing global safety regime has arisen from the exercise of sovereign authority, with an overlay of voluntary international cooperation from a network of international and regional organizations and intergovernmental agreements. This system has, in the main, served us well. For several reasons, the time is ripe to consider the desired shape of a future global safety regime and to take steps to achieve it. First, every nation's reliance on nuclear power is hostage to some extent to safety performance elsewhere in the world because of the effects on public attitudes and hence there is an interest in ensuring achievement of common standards. Second, the world is increasingly interdependent and the vendors of nuclear power plants seek to market their products throughout the globe. Efficiency would arise from the avoidance of needless differences in approach that require custom modifications from country to country. Finally, we have much to learn from each other and a common effort would strengthen us all. Such an effort might also serve to enhance public confidence. Some possible characteristics of such a regime can be identified. The regime should reflect a global consensus on the level of safety that should be achieved. There should be sufficient standardization of approach so that expertise and equipment can be used everywhere without significant modification. There should be efforts to ensure a fundamental commitment to safety and the encouragement of a safety culture. And there should be efforts to adopt more widely the best regulatory practices, recognizing that some modifications in approach may be necessary to reflect each nation's legal and social culture. At the same type, the regime should have the characteristics of flexibility, transparency, stability, practicality, and encouragement of competence. (author)

  9. Human impacts on river ice regime in the Carpathian Basin

    Science.gov (United States)

    Takács, Katalin; Nagy, Balázs; Kern, Zoltán

    2014-05-01

    River ice is a very important component of the cryosphere, and is especially sensitive to climatic variability. Historical records of appearance or disappearance and timing of ice phenomena are useful indicators for past climatic variations (Williams, 1970). Long-term observations of river ice freeze-up and break-up dates are available for many rivers in the temperate or cold region to detect and analyze the effects of climate change on river ice regime. The ice regime of natural rivers is influenced by climatic, hydrological and morphological factors. Regular ice phenomena observation mostly dates back to the 19th century. During this long-term observation period, the human interventions affecting the hydrological and morphological factors have become more and more intensive (Beltaos and Prowse, 2009). The anthropogenic effects, such as river regulation, hydropower use or water pollution causes different changes in river ice regime (Ashton, 1986). To decrease the occurrence of floods and control the water discharge, nowadays most of the rivers are regulated. River regulation changes the morphological parameters of the river bed: the aim is to create solid and equable bed size and stream gradient to prevent river ice congestion. For the satisfaction of increasing water demands hydropower is also used. River damming results a condition like a lake upstream to the barrage; the flow velocity and the turbulence are low, so this might be favourable for river ice appearance and freeze-up (Starosolsky, 1990). Water pollution affects ice regime in two ways; certain water contaminants change the physical characteristics of the water, e.g. lessens the freezing point of the water. Moreover the thermal stress effect of industrial cooling water and communal wastewater is also important; in winter these water sources are usually warmer, than the water body of the river. These interventions result different changes in the characteristic features of river ice regime. Selected

  10. Internet Censorship Circumvention Tools: Escaping the Control of the Syrian Regime

    Directory of Open Access Journals (Sweden)

    Walid Al-Saqaf

    2016-02-01

    Full Text Available Studies have shown that authoritarian regimes tend to censor the media to limit potential threats to the status quo. While such censorship practices were traditionally aimed at broadcast and print media, the emergence of the Internet and social media in particular, prompted some authoritarian regimes, such as the Assad regime in Syria, to try and exert a similar level of censorship on the Internet as well. During the Arab Spring, the Syrian regime blocked hundreds of websites that provided social networking, news, and other services. Taking Syria as a case study, this paper examines whether Internet censorship succeeded in preventing Internet users from reaching censored online content during 2010−2012. By analyzing the use of Alkasir, a censorship circumvention tool created by the author, the paper provides empirical evidence demonstrating that users were in fact able to bypass censorship and access blocked websites. The findings demonstrate that censorship circumvention tools constituted a threat to the information control systems of authoritarian regimes, highlighting the potential of such tools to promote online freedom of expression in countries where Internet censorship is prevalent.

  11. Transport phenomena in chaotic laminar flows.

    Science.gov (United States)

    Sundararajan, Pavithra; Stroock, Abraham D

    2012-01-01

    In many important chemical processes, the laminar flow regime is inescapable and defines the performance of reactors, separators, and analytical instruments. In the emerging field of microchemical process or lab-on-a-chip, this constraint is particularly rigid. Here, we review developments in the use of chaotic laminar flows to improve common transport processes in this regime. We focus on four: mixing, interfacial transfer, axial dispersion, and spatial sampling. Our coverage demonstrates the potential for chaos to improve these processes if implemented appropriately. Throughout, we emphasize the usefulness of familiar theoretical models of transport for processes occurring in chaotic flows. Finally, we point out open challenges and opportunities in the field.

  12. Unraveling flow patterns through nonlinear manifold learning.

    Science.gov (United States)

    Tauro, Flavia; Grimaldi, Salvatore; Porfiri, Maurizio

    2014-01-01

    From climatology to biofluidics, the characterization of complex flows relies on computationally expensive kinematic and kinetic measurements. In addition, such big data are difficult to handle in real time, thereby hampering advancements in the area of flow control and distributed sensing. Here, we propose a novel framework for unsupervised characterization of flow patterns through nonlinear manifold learning. Specifically, we apply the isometric feature mapping (Isomap) to experimental video data of the wake past a circular cylinder from steady to turbulent flows. Without direct velocity measurements, we show that manifold topology is intrinsically related to flow regime and that Isomap global coordinates can unravel salient flow features.

  13. Hydrologic regime controls pattern and architecture of woody debris in mountain streams

    Science.gov (United States)

    Hempel, L. A.; Grant, G.; Lewis, S.

    2015-12-01

    One question that has received little attention in the literature on wood in rivers is the degree to which the pattern and architecture of woody debris accumulations reflect the hydrologic regime of those rivers. In this study we focus on how patterns of woody debris in mountain streams reflect the underlying flow regime by comparing wood loading, piece orientation, location, and jam architecture in spring- and runoff dominated streams with similar bioclimatic settings in the Cascade Range of the Pacific Northwest. A key aspect of spring-dominated streams is that flows are near constant and vary by less than a factor of 2 over the course of the year, rarely exceeding bankfull. In contrast, flow in highly variable runoff-dominated streams can vary by as much as two orders of magnitude. To compare wood accumulations in these two stream types, we took over 40 measurements for each piece of wood along four reaches in streams of similar size but different hydrologic regime. Differences in woody debris are so great that characteristics of woody debris can actually be a useful field indicator of overall flow regime. Wood in stable, spring-fed streams is largely immobile (83%), found as a single piece (67%) or as part of an open-fabric log jam (33%), and is near perpendicular to channel, indicating little movement since emplacement. In a real sense, wood becomes part of the channel and represents the dominant structural feature in these channels, accounting for a large fraction of total flow resistance and form drag. In contrast, the majority of wood in runoff-dominated streams is mobile (83%), has stripped bark (86%), occurs in densely-packed log jams (84%), and is found parallel or sub-parallel to the channel, all indicators of frequent fluvial transport. In these systems, wood moves through the channel quickly and is a much smaller component of total resistance. We conclude that wood patterning and mobility do reflect the degree of flow variability in a stream, and that

  14. Actual evapotranspiration, root extraction, water regime and productivity in the case of lucerne

    International Nuclear Information System (INIS)

    Rambal, S.; Berger, A.; Parisot, J.M.

    1983-01-01

    Measurements were made of the actual evaportranspiration, root extraction and above-ground yield in the case of two varieties of lucerne Medicago sativa L. - Du Puits and Polder - and mixtures of them in equal parts. The daily kinetics of the water potential of the leaves and the collar show that the water regimes of the two varieties are identical in a first approximation. The root systems are different. Polder has the deeper system. The regime of the binary mixture is not simply a juxtaposition of the regimes of the constitutents. Two types of non-linearity were found. The first relates to water flow and the second to productivity. It is postulated that the root systems of the two varieties constituting the mixture undergo plastic deformation, leading to a more efficient resultant system. A system of this type needs, on the other hand, an allocation of photosynthates that would affect its productivity. (author)

  15. Antibody to P. falciparum in pregnancy varies with intermittent preventive treatment regime and bed net use.

    Directory of Open Access Journals (Sweden)

    Elizabeth H Aitken

    Full Text Available Antibodies towards placental-binding P. falciparum are thought to protect against pregnancy malaria; however, environmental factors may affect antibody development.Using plasma from pregnant Malawian women, we measured IgG against placental-binding P. falciparum parasites by flow cytometry, and related results to intermittent preventive treatment (IPTp regime, and bed net use. Bed net use was associated with decreased antibody levels at mid-pregnancy but not at 1 month post partum (1 mpp. At 1 mpp a more intensive IPTp regime was associated with decreased antibody levels in primigravidae, but not multigravidae.Results suggest bed nets and IPTp regime influence acquisition of pregnancy-specific P. falciparum immunity.

  16. Hydrodynamics of multi-sized particles in stable regime of a swirling bed

    Energy Technology Data Exchange (ETDEWEB)

    Miin, Chin Swee; Sulaiman, Shaharin Anwar; Raghavan, Vijay Raj; Heikal, Morgan Raymond; Naz, Muhammad Yasin [Universiti Teknologi PETRONAS, Perak (Malaysia)

    2015-11-15

    Using particle imaging velocimetry (PIV), we observed particle motion within the stable operating regime of a swirling fluidized bed with an annular blade distributor. This paper presents velocity profiles of particle flow in an effort to determine effects from blade angle, particle size and shape and bed weight on characteristics of a swirling fluidized bed. Generally, particle velocity increased with airflow rate and shallow bed height, but decreased with bed weight. A 3 .deg. increase in blade angle reduced particle velocity by approximately 18%. In addition, particle shape, size and bed weight affected various characteristics of the swirling regime. Swirling began soon after incipience in the form of a supra-linear curve, which is the characteristic of a swirling regime. The relationship between particle and gas velocities enabled us to predict heat and mass transfer rates between gas and particles.

  17. Sediment regime constraints on river restoration - An example from the lower Missouri river

    Science.gov (United States)

    Jacobson, R.B.; Blevins, D.W.; Bitner, C.J.

    2009-01-01

    Dammed rivers are subject to changes in their flow, water-quality, and sediment regimes. Each of these changes may contribute to diminished aquatic habitat quality and quantity. Of the three factors, an altered sediment regime is a particularly unyielding challenge on many dammed rivers. The magnitude of the challenge is illustrated on the Lower Missouri River, where the largest water storage system in North America has decreased the downriver suspended-sediment load to 0.2%–17% of pre-dam loads. In response to the altered sediment regime, the Lower Missouri River channel has incised as much as 3.5 m just downstream of Gavins Point Dam, although the bed has been stable to slightly aggrading at other locations farther downstream. Effects of channel engineering and commercial dredging are superimposed on the broad-scale adjustments to the altered sediment regime.The altered sediment regime and geomorphic adjustments constrain restoration and management opportunities. Incision and aggradation limit some objectives of flow-regime management: In incising river segments, ecologically desirable reconnection of the floodplain requires discharges that are beyond operational limits, whereas in aggrading river segments, small spring pulses may inundate or saturate low-lying farmlands. Lack of sediment in the incising river segment downstream of Gavins Point Dam also limits sustainable restoration of sand-bar habitat for bird species listed under the Endangered Species Act. Creation of new shallow-water habitat for native fishes involves taking sediment out of floodplain storage and reintroducing most or all of it to the river, raising concerns about increased sediment, nutrient, and contaminant loads. Calculations indicate that effects of individual restoration projects are small relative to background loads, but cumulative effects may depend on sequence and locations of projects. An understanding of current and historical sediment fluxes, and how they vary along the river

  18. Choice of exchange rate regimes for African countries: Fixed or Flexible Exchange rate regimes?

    OpenAIRE

    Simwaka, Kisu

    2010-01-01

    The choice of an appropriate exchange rate regime has been a subject of ongoing debate in international economics. The majority of African countries are small open economies and thus where the choice of the exchange rate regime is an important policy issue. Aside from factors such as interest rates and inflation, the exchange rate is one of the most important determinants of a country’s relative level of economic health. For this reason, exchange rates are among the most watched analyzed and ...

  19. The optomechanical instability in the quantum regime

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, Max; Kubala, Bjoern; Marquardt, Florian [Department fuer Physik, Arnold Sommerfeld Center for Theoretical Physics, and Center for NanoScience, Ludwig-Maximilians-Universitaet Muenchen, Theresienstr 37, D-80333 Muenchen (Germany)], E-mail: max.ludwig@physik.lmu.de

    2008-09-15

    We consider a generic optomechanical system, consisting of a driven optical cavity and a movable mirror attached to a cantilever. Systems of this kind (and analogues) have been realized in many recent experiments. It is well known that these systems can exhibit an instability towards a regime where the cantilever settles into self-sustained oscillations. In this paper, we briefly review the classical theory of the optomechanical instability, and then discuss the features arising in the quantum regime. We solve numerically a full quantum master equation for the coupled system, and use it to analyze the photon number, the cantilever's mechanical energy, the phonon probability distribution and the mechanical Wigner density, as a function of experimentally accessible control parameters. When a suitable dimensionless 'quantum parameter' is sent to zero, the results of the quantum mechanical model converge towards the classical predictions. We discuss this quantum-to-classical transition in some detail.

  20. Steady and transient regimes in hydropower plants

    Science.gov (United States)

    Gajic, A.

    2013-12-01

    Hydropower plant that has been in operation for about 30 years has to be reconstructed. They have already installed 12 Kaplan turbines, the largest in the world at that time. The existing CAM relationship was determined based on hydraulic model tests and checked by efficiency on-site tests. It was also tested based on turbine bearing vibrations. In order to discover vibrations and long cracks on stay vanes detailed on-site measurements were performed. Influence of the modification of the trailing edges on the dynamic stresses of the stay vanes is also shown. In order to improve power output transient regimes were analyzed, both experimentally and numerically. Reversible hydropower plant, a pioneer in Europe since it was the first Pump storage power plant constructed with the highest head pump-turbines in the world. Analyses of transient regimes discover some problems with S-shaped characteristics coupled with non-symmetrical penstock.

  1. Coulomb drag in the mesoscopic regime

    DEFF Research Database (Denmark)

    Mortensen, N. Asger; Flensberg, Karsten; Jauho, Antti-Pekka

    2002-01-01

    We present a theory for Coulomb drug between two mesoscopic systems which expresses the drag in terms of scattering matrices and wave functions. The formalism can be applied to both ballistic and disordered systems and the consequences can be studied either by numerical simulations or analytic...... means such as perturbation theory or random matrix theory. The physics of Coulomb drag in the mesoscopic regime is very different from Coulomb drag between extended electron systems. In the mesoscopic regime we in general find fluctuations of the drag comparable to the mean value. Examples are vanishing...... average drag for chaotic 2D-systems and dominating fluctuations of drag between quasi-ballistic wires with almost ideal transmission....

  2. Coulomb drag in the mesoscopic regime

    DEFF Research Database (Denmark)

    Mortensen, N.A.; Flensberg, Karsten; Jauho, Antti-Pekka

    2002-01-01

    We present a theory for Coulomb drag between two mesoscopic systems which expresses the drag in terms of scattering matrices and wave functions. The formalism can be applied to both ballistic and disordered systems and the consequences can be studied either by numerical simulations or analytic...... means such as perturbation theory or random matrix theory. The physics of Coulomb drag in the mesoscopic regime is very different from Coulomb drag between extended electron systems. In the mesoscopic regime we in general find fluctuations of the drag comparable to the mean value. Examples are vanishing...... average drag for chaotic 2D-systems and dominating fluctuations of drag between quasi-ballistic wires with almost ideal transmission....

  3. Regimes de espaço

    Directory of Open Access Journals (Sweden)

    Eric Landowski

    2015-06-01

    Full Text Available Space Regimes - Based on a general model of interaction, the present analysis attempts to account for the diversity of the ways space may be apprehended in lived experience. It leads to the definition of four configurations that correspond to as many regimes of relation with the environing world. The conventional space of the circulation of values takes the archetypical shape of the net (incarnated today by Internet. The operational space is that of our dealing with objects within a material environment seen as a tissue of stable and intelligible relations. The experienced space of bodies’ movement, to which one may give as an emblem the spiral, expresses the dynamics of sensitive relationships between the self and the other. The existential space is that of our presence in a universe without boundaries, which no one can properly represent oneself but that nonetheless haunts art and thought: its figure is the abyss.

  4. Mesoscopic effects in the quantum Hall regime

    Indian Academy of Sciences (India)

    creases, while at the critical point the Thouless number goes to a universal value. In the scaling regime, the dimensionless quantity depends on system size only through the ratio. L/ξ(E): gL(E) = ˜g(L/ξ) =g(L1 ν. E Ec ),. (9) where the localization length ξ diverges at the critical energy Ec, in a power law fashion ξ(E) E Ec ν.

  5. Dynamic Regime of Ignition of Solid Propellant

    Directory of Open Access Journals (Sweden)

    Zolotorev Nikolay

    2016-01-01

    Full Text Available This article presents a dynamic regime of exposure of the radiant flux on the sample of gun-cotton. Obtained time the ignition of gun-cotton in the heating conditions of increasing heat flux in the range from 0.2 W/cm2 to 22 W/cm2. A comparison of the delay times of the ignition when heated variable and constant heat flux.

  6. Deuteron structure in the deep inelastic regime

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Canal, C.A.; Tarutina, T. [Universidad Nacional de La Plata, IFLP/CONICET y Departamento de Fisica, La Plata (Argentina); Vento, V. [Universidad de Valencia-CSIC, Departamento de Fisica Teorica-IFIC, Burjassot (Valencia) (Spain)

    2017-06-15

    We study nuclear effects in the deuteron in the deep inelastic regime using the newest available data. We put special emphasis on their Q{sup 2} dependence. The study is carried out using a scheme which parameterizes, in a simple manner, these effects by changing the proton and neutron stucture functions in medium. The result of our analysis is compared with other recent proposals. We conclude that precise EMC ratios cannot be obtained without considering the nuclear effects in the deuteron. (orig.)

  7. Supersonic free jet, molecular free regime

    International Nuclear Information System (INIS)

    Sanna, G.; Tomassetti, G.

    1999-01-01

    The structure of the free jet emitted by a converging nozzle as obtained by the method of characteristics by Ashkenas and Sherman is described in details. In particular the dependence of the field variable by the distance from the nozzle is given. The transition from continuum to molecular free regime is then considered and the sudden freeze approximation is introduced. The processing of monoatomic and polyatomic gasses is also considered [it

  8. Tax compliance under tax regime changes

    OpenAIRE

    Heinemann, Friedrich; Kocher, Martin G.

    2010-01-01

    In this paper we focus on the compliance effects of tax regime changes. According to the economic model of tax evasion, a tax reform should affect compliance through its impact on tax rates and incentives. Our findings demonstrate the importance of at least two further effects not covered by the traditional model: First, reform losers tend to evade more taxes after the reform. Second, a reform from a proportionate to a progressive system decreases compliance compared to a switch in the revers...

  9. Experimental Study on Boiling Regime During Quenching Process in Heated Rod Bundle Queen

    International Nuclear Information System (INIS)

    J, Mulya; Antariksawan, A.R.; PW, Joko; S, Edy; H, Khairul; H, Ismu; Kiswanta; Giarno

    2003-01-01

    Following loss-of-coolant accident in light water reactor, the emergency core cooling must be injected. During flooding the core, the fuel cladding quenching occurred. The fuel quenching velocity is key factor for reactor safety. Various parameter influence the quenching velocity. It can also be related to the boiling regime change during transient. Current experimental study is performed to observe and apprehend boiling regime during quenching process and to measure its velocity. Experiment is conducted using Queen heated rod bundle. The quenching occurred from bottom flooding with flow rate of 0.0417 kg/s. The initial temperature of heated rod varies from 334 o C at zero point and 499 o C at top of heated zone. The visual observation method and rod surface temperature measurements is used to discus the change of boiling regime and quench front velocity. From the observation, it is obvious that at a one defined point, the boiling regime change from film boiling to single phase convection. On the other hand, the quench front velocity was affected by surface temperature and boiling regime. At the heated zone and at the beginning of quench, the quench front velocity was relatively low. While the surface temperature decreases, the quench front velocity was increase until all vapor film collapse. The average quench front velocity is about 11.5 mm/s

  10. Critical slowing down associated with regime shifts in the US housing market

    Science.gov (United States)

    Tan, James Peng Lung; Cheong, Siew Siew Ann

    2014-02-01

    Complex systems are described by a large number of variables with strong and nonlinear interactions. Such systems frequently undergo regime shifts. Combining insights from bifurcation theory in nonlinear dynamics and the theory of critical transitions in statistical physics, we know that critical slowing down and critical fluctuations occur close to such regime shifts. In this paper, we show how universal precursors expected from such critical transitions can be used to forecast regime shifts in the US housing market. In the housing permit, volume of homes sold and percentage of homes sold for gain data, we detected strong early warning signals associated with a sequence of coupled regime shifts, starting from a Subprime Mortgage Loans transition in 2003-2004 and ending with the Subprime Crisis in 2007-2008. Weaker signals of critical slowing down were also detected in the US housing market data during the 1997-1998 Asian Financial Crisis and the 2000-2001 Technology Bubble Crisis. Backed by various macroeconomic data, we propose a scenario whereby hot money flowing back into the US during the Asian Financial Crisis fueled the Technology Bubble. When the Technology Bubble collapsed in 2000-2001, the hot money then flowed into the US housing market, triggering the Subprime Mortgage Loans transition in 2003-2004 and an ensuing sequence of transitions. We showed how this sequence of couple transitions unfolded in space and in time over the whole of US.

  11. Free-surface non-Newtonian fluid flow in a round pipe

    Science.gov (United States)

    Borzenko, E. I.; Schrager, G. R.; Yakutenok, V. A.

    2012-03-01

    Free-surface pseudoplastic and viscoplastic fluid flows in a round pipe were studied for the case where the direction of motion coincides with the direction of gravity. Numerical modeling was performed using a technique based on a combination of the SIMPLE algorithm and the method of invariants. Three characteristic filling regimes were found to exist: a complete filling regime, a regime characterized by air-cavity formation on the solid wall, and a jet regime. Critical parameter values separating the regions of existence of these regimes were calculated. The evolution of quasisolid cores was studied for flow of a fluid with an yield point.

  12. ACCESSORIES OF FISCAL OBLIGATION. LEGAL REGIME

    Directory of Open Access Journals (Sweden)

    RADA POSTOLACHE

    2012-05-01

    Full Text Available The interest – which is an institution typical to private law, has been taken over by the fiscal field and adapted to the specific features of fiscal obligation – being defined by its imperative legal regime, which has at the least the following characteristic elements: unitary character, imposed legal percentage, compulsory demand of interest, automatic application. In order to render responsible fiscal debtors, the lawmaker has reintroduced, as an accessory of fiscal obligation, delayed payment penalties, which have a distinct nature and legal regime, but without the principle non bis in idem being transgressed. Our study aims to establish the legal regime ofaccessories typical to fiscal obligation, from the perspective of special normative acts, but also of the common law within the field – Civil Code and Government Ordinance No. 13/2011 – by pointing out at the same time both the particular circumstances and procedural ones regulated by the Fiscal Procedure Code, shedding light upon the controversial legal nature of accessories.

  13. Detecting spatial regimes in ecosystems | Science Inventory ...

    Science.gov (United States)

    Research on early warning indicators has generally focused on assessing temporal transitions with limited application of these methods to detecting spatial regimes. Traditional spatial boundary detection procedures that result in ecoregion maps are typically based on ecological potential (i.e. potential vegetation), and often fail to account for ongoing changes due to stressors such as land use change and climate change and their effects on plant and animal communities. We use Fisher information, an information theory based method, on both terrestrial and aquatic animal data (US Breeding Bird Survey and marine zooplankton) to identify ecological boundaries, and compare our results to traditional early warning indicators, conventional ecoregion maps, and multivariate analysis such as nMDS (non-metric Multidimensional Scaling) and cluster analysis. We successfully detect spatial regimes and transitions in both terrestrial and aquatic systems using Fisher information. Furthermore, Fisher information provided explicit spatial information about community change that is absent from other multivariate approaches. Our results suggest that defining spatial regimes based on animal communities may better reflect ecological reality than do traditional ecoregion maps, especially in our current era of rapid and unpredictable ecological change. Use an information theory based method to identify ecological boundaries and compare our results to traditional early warning

  14. Particle optics in the Rayleigh regime.

    Science.gov (United States)

    Moosmüller, Hans; Arnott, W Patrick

    2009-09-01

    Light scattering and absorption by particles suspended in the atmosphere modifies the transfer of solar energy in the atmosphere, thereby influencing global and regional climate change and atmospheric visibility. Of particular interest are the optical properties of particles in the Rayleigh regime, where particles are small compared with the wavelength of the scattered or absorbed light, because these particles experience little gravitational settlement and may have long atmospheric lifetimes. Optical properties of particles in the Rayleigh regime are commonly derived from electromagnetic theory using Maxwell's equations and appropriate boundary conditions. The size dependence of particle scattering and absorption are derived here from the most basic principles for coherent processes such as Rayleigh scattering (i.e., add amplitudes if in phase) and incoherent processes such as absorption (i.e., add cross sections), at the same time yielding understanding of the upper particle size limit for the Rayleigh regime. The wavelength dependence of Rayleigh scattering and absorption are also obtained by adding a basic scale invariance for particle optics. Simple consequences for particle single-scattering albedo ("whiteness") and the optical measurement of particle mass densities are explained. These alternative derivations complement the conventional understanding obtained from electromagnetic theory.

  15. "International regime for advancing lunar development"

    Science.gov (United States)

    Beldavs, VZ

    2017-09-01

    A specific concern regarding the Moon Treaty is the provision for sharing the wealth gained from space with developing countries that have not invested and taken risks in making possible space materials utilization. Article 11, par. 7 states "The main purposes of the international regime to be established shall include: (a) The orderly and safe development of the natural resources of the moon; (b) The rational management of those resources; (c) The expansion of opportunities in the use of those resources; (d) An equitable sharing by all States Parties in the benefits derived from those resources, whereby the interests and needs of the developing countries, as well as the efforts of those countries which have contributed either directly or indirectly to the exploration of the moon, shall be given special consideration." Whether the Moon Treaty in its present form or modified to be acceptable to more parties or the Moon Treaty is ignored, the language of Article 11, paragraph 7 can be used to construct an international regime for lunar development that can meet the requirements of commercial business as well as of states that provide support for lunar development as well as developing countries that may have played a modest role in making lunar development possible. This paper will consider options for constructing an international regime for lunar development.

  16. Modal Decomposition of Synthetic Jet Flow Based on CFD Computation

    Directory of Open Access Journals (Sweden)

    Hyhlík Tomáš

    2015-01-01

    Full Text Available The article analyzes results of numerical simulation of synthetic jet flow using modal decomposition. The analyzes are based on the numerical simulation of axisymmetric unsteady laminar flow obtained using ANSYS Fluent CFD code. Three typical laminar regimes are compared from the point of view of modal decomposition. The first regime is without synthetic jet creation with Reynolds number Re = 76 and Stokes number S = 19.7. The second studied regime is defined by Re = 145 and S = 19.7. The third regime of synthetic jet work is regime with Re = 329 and S = 19.7. Modal decomposition of obtained flow fields is done using proper orthogonal decomposition (POD where energetically most important modes are identified. The structure of POD modes is discussed together with classical approach based on phase averaged velocities.

  17. analysis of flow in a concentric annulus using finite element method

    African Journals Online (AJOL)

    user

    Annular flow is a flow regime of two-phase gas-liquid. It is characterized by the presence of liquid fluid flowing on an annulus shaped channel. Annular flow is important in drilling and production in deviated and horizontal wells [2]. Concentric annular flows of fluids in pipes have had a number of engineering applications.

  18. Effects of a diversion hydropower facility on the hydrological regime of the Correntes River, a tributary to the Pantanal floodplain, Brazil

    Science.gov (United States)

    Fantin-Cruz, Ibraim; Pedrollo, Olavo; Girard, Pierre; Zeilhofer, Peter; Hamilton, Stephen K.

    2015-12-01

    Facilities that produce hydroelectricity by diversion of part of the river's flow, which are often considered to have lower environmental impact than conventional hydropower dams, are being built in large numbers on river systems throughout the world, yet their cumulative impacts are not well understood. This study evaluated the hydrological effects of operation of a diversion hydropower facility on the Correntes River in Brazil (mean discharge 73 m3 s-1), which is potentially important because of the ecological implications for the floodplains of the Pantanal into which it flows. Many similar dams are built or proposed on rivers feeding the Pantanal. The 210-MW facility known as Ponte de Pedra diverts part of the river flow into a diversion channel in a nearly "run-of-river" design. The natural (reconstructed) and regulated (observed) flow regimes were characterized using Indicators of Hydrologic Alteration (IHA) and Flow Duration Curves (FDC). Seven parameters of IHA were significantly altered by the reservoir formation (magnitude of lowest monthly flow, minimum flows of 1, 3 and 7 days, maximum flow of 90 days and counts of high and low pulses). Among these, Principal Components Analysis identified the maximum flow of 90 days and the count of high flow pulses as integrators of hydrological alterations. The FDC showed that the reservoir also changed the seasonal regime of the flows, with greater changes in the lowest flow season. The reduction of river-floodplain connectivity and loss of associated ecosystem services are the major downstream ecological implications of this altered flow regime. To maintain the seasonal flooding regime while meeting the requirements for hydroelectric production, proposed limits for flow regime alterations are up to ±18% in low flow, ±24% in the rising limb and ±22% in high flow and the falling limb, relative to the natural flow. Operational changes to maintain flows with these limits could easily be implemented because the

  19. Experimental identification of dynamic coefficients of lightly loaded tilting-pad bearings under several lubrication regimes

    DEFF Research Database (Denmark)

    Salazar, Jorge G.; Santos, Ilmar F.

    2016-01-01

    This paper presents the identified dynamic coefficients of a lightly loaded actively lubricated bearing under three lubrication regimes: passive, hybrid and feedback-controlled. The goal is to experimentally demonstrate the feasibility of modifying the bearing dynamic properties via active...... lubrication. Dominated by the latest two regimes, the bearing properties become adjustable or controllable due to the injection of either a constant or variable pressurized oil flow. Such a flow is regulated by a hydraulic control system composed of (a) a high-pressure oil supply unit, (b) servovalves, (c......) radial injection nozzles, (d) displacement sensors and (e) well-tuned digital controllers. A scaled-down industrial rotor featuring active lubrication, composed of a flexible rotor supported by a four-rocker load-between-pads tilting-pad bearing under light load condition, is used for this objective...

  20. A Regime Diagram for Autoignition of Homogeneous Reactant Mixtures with Turbulent Velocity and Temperature Fluctuations

    KAUST Repository

    Im, Hong G.

    2015-04-02

    A theoretical scaling analysis is conducted to propose a diagram to predict weak and strong ignition regimes for a compositionally homogeneous reactant mixture with turbulent velocity and temperature fluctuations. The diagram provides guidance on expected ignition behavior based on the thermo-chemical properties of the mixture and the flow/scalar field conditions. The analysis is an extension of the original Zeldovich’s analysis by combining the turbulent flow and scalar characteristics in terms of the characteristic Damköhler and Reynolds numbers of the system, thereby providing unified and comprehensive understanding of the physical and chemical mechanisms controlling ignition characteristics. Estimated parameters for existing experimental measurements in a rapid compression facility show that the regime diagram predicts the observed ignition characteristics with good fidelity.

  1. Big River Benthos: Linking Year Round Biological Response to Altered Hydrological Regimes

    Science.gov (United States)

    2017-04-02

    ecological response to altered flow regimes and help document benefits of restoring connectivity between secondary channels and the Mississippi River main...term ecological response to this temporary loss of habitat connectivity, or the mitigation thereof, is unknown. 3 Figure 1. Aerial photographs...of (a) Prairie Point Secondary Channel dike field, and (b) Ludlow Secondary Channel dike field; both dikes with environmental notches constructed

  2. Numerical-Model Investigation of the Hydrothermal Regime of a Straight-Through Shallow Cooling Pond

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, A. S. [JSC ' VNIIG im. B. E. Vedeneeva' (Russian Federation)

    2013-11-15

    A mathematic model based on solution of hydrodynamics and heat-transfer equations by the finite-element method is constructed to predict the hydrothermal regime of a straight-through shallow cooling pond, which provides cooling circulating water to a repository of spent nuclear fuel. Numerical experiments made it possible to evaluate the influence exerted by wind conditions and flow rate of water in the river on the temperature of the circulating water.

  3. Transport of a multiple ion species plasma in the Pfirsch--Schluter regime

    International Nuclear Information System (INIS)

    Hirshman, S.P.

    1976-10-01

    The classical parallel friction coefficients, which relate the collisional friction forces to the flow of particles and heat along the magnetic field, are calculated for a multiple ion species plasma. In the short mean free path regime, the neoclassical Pfirsch--Schlueter transport coefficients for a toroidally confined multispecies plasma are computed in terms of the classical friction coefficients. The dependence of the neoclassical cross-field transport on the equilibration of the parallel ion temperature profiles is determined

  4. Global hydrological droughts in the 21st century under a changing hydrological regime

    Directory of Open Access Journals (Sweden)

    N. Wanders

    2015-01-01

    Full Text Available Climate change very likely impacts future hydrological drought characteristics across the world. Here, we quantify the impact of climate change on future low flows and associated hydrological drought characteristics on a global scale using an alternative drought identification approach that considers adaptation to future changes in hydrological regime. The global hydrological model PCR-GLOBWB was used to simulate daily discharge at 0.5° globally for 1971–2099. The model was forced with CMIP5 climate projections taken from five global circulation models (GCMs and four emission scenarios (representative concentration pathways, RCPs, from the Inter-Sectoral Impact Model Intercomparison Project. Drought events occur when discharge is below a threshold. The conventional variable threshold (VTM was calculated by deriving the threshold from the period 1971–2000. The transient variable threshold (VTMt is a non-stationary approach, where the threshold is based on the discharge values of the previous 30 years implying the threshold to vary every year during the 21st century. The VTMt adjusts to gradual changes in the hydrological regime as response to climate change. Results show a significant negative trend in the low flow regime over the 21st century for large parts of South America, southern Africa, Australia and the Mediterranean. In 40–52% of the world reduced low flows are projected, while increased low flows are found in the snow-dominated climates. In 27% of the global area both the drought duration and the deficit volume are expected to increase when applying the VTMt. However, this area will significantly increase to 62% when the VTM is applied. The mean global area in drought, with the VTMt, remains rather constant (11.7 to 13.4%, compared to the substantial increase when the VTM is applied (11.7 to 20%. The study illustrates that an alternative drought identification that considers adaptation to an altered hydrological regime has a

  5. Flow in Porous Media with Special Reference to Breakwater Structures

    DEFF Research Database (Denmark)

    Andersen, O. Holst

    A literature study concerning porous flow is carried out. For the stationary case, the hydraulic radius theory, for which some justification can be given based on Navier-Stokes equations, appears to be adequate. Three different porous flow regimes are identified and the associated flow resistance...

  6. Synthetic monthly flow duration curves for the Cape Floristic Region ...

    African Journals Online (AJOL)

    A flow duration curve (FDC) provides a valuable planning and management tool since it describes the entire flow regime of a river. Water resource planning in South Africa is often based on monthly river flow data and synthetic FDCs are required for applications in ungauged catchments. The objective of this study was to ...

  7. A geospatial risk assessment model for leprosy in Ethiopia based on environmental thermal-hydrological regime analysis

    Directory of Open Access Journals (Sweden)

    Azeb Tadesse Argaw

    2006-11-01

    Full Text Available Geospatial methods were used to study the associations of the environmental thermal-hydrological regime with leprosy prevalence in the Oromia and Amhara regions of Ethiopia. Prediction models were developed that indicated leprosy prevalence was related to: (i long-term normal climate grid data on temperature and moisture balance (rain/potential evapo-transpiration; (ii satellite surveillance data on the Normalized Difference Vegetation Index (NDVI and daytime earth surface temperature (Tmax from the Advanced Very High Resolution Radiometer (AVHRR; and (iii a Genetic Algorithm Rule-Set Prediction (GARP model based on NDVI and Tmax data in relation to leprosy prevalence data. Our results suggest that vertical transmission is not the only means of acquiring leprosy and support earlier reports that a major factor that governs transmission of leprosy is the viability of Mycobacterium leprae outside the human body which is related to the thermal-hydrologic regime of the environment.

  8. Gender inequalities in mental wellbeing in 26 European countries: do welfare regimes matter?

    Science.gov (United States)

    Dreger, Stefanie; Gerlinger, Thomas; Bolte, Gabriele

    2016-10-01

    Nature and extent of welfare regimes and social policies are important determinants of health and health inequalities. This study examines the association of gender and mental wellbeing in European countries and investigates whether type of welfare regime plays a role in this association. Data of 19 366 women and 14 338 men of the third round of the European Quality of Life Survey (2011-12) was used to analyse mental wellbeing, assessed by the World Health Organization 5-Mental Wellbeing Index. Multilevel logistic regression analyses were performed to analyse the association between gender and good mental wellbeing first at country-level, and secondly the between country variation was analysed and welfare regimes were included as explanatory variables. We observed cross-national variation in good mental wellbeing. At country levels gender inequalities in good mental wellbeing were observed in 7 out of 26 countries. In analyses considering all countries together gender inequalities in good mental wellbeing were identified independent of further individual socio-demographic variables and independent of the welfare regimes that people lived in [women vs. men: OR = 0.76; (95% CI = 0.71-0.81)]. Gender inequalities in good mental wellbeing were not modified by welfare regimes. There are cross-national differences in good mental wellbeing between European countries. Gender inequalities with a lower prevalence of good mental wellbeing among women are common in European countries. This study suggests that welfare regimes do not modify these gender inequalities in mental wellbeing. © The Author 2016. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved.

  9. A Comparative Study of Finite Journal Bearing in Laminar and Turbulent Regimes Using CFD (Computational Fluid Dynamic

    Directory of Open Access Journals (Sweden)

    Susilowati

    2016-01-01

    Full Text Available In this paper, an investigation of hydrodynamic performance for journal bearing lubricated by thin film is performed by three-dimensional CFD (computational fluid dynamic. Two regimes, i.e. laminar and turbulent regimes are of main interest. The sliding velocity was varied from 3000, 5000 and 10000. The numerical simulation shows that the velocity magnitude of the journal has a strong effect on the hydrodynamic pressure. In addition, it is found that an appropriate modelling of flow regime affects the predicted lubrication performance. From the overall analysis, both using laminar and turbulent regimes, the distribution of static hydrodynamic pressure shows a similar trend. It is also found that at the beginning of the contact, the static pressure is low, and then, it gradually increases to the highest point, and finally drops significantly.

  10. Convective Flow of a Colloidal Suspension in a Vertical Slot Heated from Side Wall

    Science.gov (United States)

    Cherepanov, I. N.; Smorodin, B. L.

    2018-02-01

    Convective flows and the transport of nanoparticles are numerically investigated in the vertical slot filled with a colloidal suspension and heated from the side. The thermodiffusion and gravitational sedimentation of the nanoparticles are taken into account. Two different regimes of laminar flow are found. The intensity of the first regime is much lower than in molecular liquids (the magnitudes of the convective and diffusion fluxes have the same order). The second regime is more intensive. The transitions between these two regimes are investigated. It is shown that intensive convective flow completely mixes the colloidal suspension to a homogeneous state as a result of the long transient process.

  11. Terms of trade and exchange rate regimes in developing countries

    OpenAIRE

    Christian Broda

    2002-01-01

    Since Friedman (1953), an advantage often attributed to flexible exchange rate regimes over fixed regimes is their ability to insulate more effectively the economy against real shocks. I use a post-Bretton Woods sample (1973-96) of seventy-five developing countries to assess whether the responses of real GDP, real exchange rates, and prices to terms-of-trade shocks differ systematically across exchange rate regimes. I find that responses are significantly different across regimes in a way tha...

  12. Droplet formation in microfluidic T-junction generators operating in the transitional regime. I. Experimental observations.

    Science.gov (United States)

    Glawdel, Tomasz; Elbuken, Caglar; Ren, Carolyn L

    2012-01-01

    This is the first part of a two-part study on the generation of droplets at a microfluidic T-junction operating in the transition regime where confinement of the droplet creates a large squeezing pressure that influences droplet formation. In this regime, the operation of the T-junction depends on the geometry of the intersection (height-to-width ratio, inlet width ratio), capillary number, flow ratio, and viscosity ratio of the two phases. Here in paper I we presented our experimental observations through the analysis of high-speed videos of the droplet formation process. Various parameters are tracked during the formation cycle such as the shape of the droplet (penetration depth and neck), interdroplet spacing, production rate, and flow of both phases across several T-junction designs and flow conditions. Generally, the formation process is defined by a two-stage model consisting of an initial filling stage followed by a necking stage. However, video evidence suggests the inclusion of a third stage, which we term the lag stage, at the beginning of the formation process that accounts for the retraction of the interface back into the injection channel after detachment. Based on the observations made in this paper, a model is developed to describe the formation process in paper II, which can be used to understand the design and operation of T-junction generators in the transition regime.

  13. Natural convection in rectangular porous cavity under non-Darcian regime; Conveccao natural numa cavidade porosa retangular no regime nao Darciano

    Energy Technology Data Exchange (ETDEWEB)

    Medeiros, Jesus; Gurgel, Jose Mauricio [Paraiba Univ., Joao Pessoa, PB (Brazil). Centro Tecnologico; Marcondes, Francisco [Paraiba Univ., Joao Pessoa, PB (Brazil). Dept. de Engenharia Mecanica

    1998-07-01

    This paper presents an numerical investigation of natural convection heat transfer in a saturated porous media under non-Darcian regime using a generalized model. The generalized model employees a Navier-Stokes equation and added the Brinkman and Forchheimer terms to represent the linear and non-linear porous medium drag, respectively. The boundary conditions were: Two isothermal vertical walls and two adiabatic horizontal walls. The governing equations in terms of the primitive variables are solved numerically by the finite volume method employing a staggered grids. The results of the generalized model have been compared with various Darcy and non-Darcy porous media model predictions reported in literature. It has been observed that the average Nusselt number is significantly affected by porosity in the non Darcy flow regime. (author)

  14. Unifying Suspension and Granular flows near Jamming

    Directory of Open Access Journals (Sweden)

    DeGiuli Eric

    2017-01-01

    Full Text Available Rheological properties of dense flows of hard particles are singular as one approaches the jamming threshold where flow ceases, both for granular flows dominated by inertia, and for over-damped suspensions. Concomitantly, the lengthscale characterizing velocity correlations appears to diverge at jamming. Here we review a theoretical framework that gives a scaling description of stationary flows of frictionless particles. Our analysis applies both to suspensions and inertial flows of hard particles. We report numerical results in support of the theory, and show the phase diagram that results when friction is added, delineating the regime of validity of the frictionless theory.

  15. Drying regimes in homogeneous porous media from macro- to nanoscale

    Science.gov (United States)

    Thiery, J.; Rodts, S.; Weitz, D. A.; Coussot, P.

    2017-07-01

    Magnetic resonance imaging visualization down to nanometric liquid films in model porous media with pore sizes from micro- to nanometers enables one to fully characterize the physical mechanisms of drying. For pore size larger than a few tens of nanometers, we identify an initial constant drying rate period, probing homogeneous desaturation, followed by a falling drying rate period. This second period is associated with the development of a gradient in saturation underneath the sample free surface that initiates the inward recession of the contact line. During this latter stage, the drying rate varies in accordance with vapor diffusion through the dry porous region, possibly affected by the Knudsen effect for small pore size. However, we show that for sufficiently small pore size and/or saturation the drying rate is increasingly reduced by the Kelvin effect. Subsequently, we demonstrate that this effect governs the kinetics of evaporation in nanopores as a homogeneous desaturation occurs. Eventually, under our experimental conditions, we show that the saturation unceasingly decreases in a homogeneous manner throughout the wet regions of the medium regardless of pore size or drying regime considered. This finding suggests the existence of continuous liquid flow towards the interface of higher evaporation, down to very low saturation or very small pore size. Paradoxically, even if this net flow is unidirectional and capillary driven, it corresponds to a series of diffused local capillary equilibrations over the full height of the sample, which might explain that a simple Darcy's law model does not predict the effect of scaling of the net flow rate on the pore size observed in our tests.

  16. Annular flow film characteristics in variable gravity.

    Science.gov (United States)

    MacGillivray, Ryan M; Gabriel, Kamiel S

    2002-10-01

    Annular flow is a frequently occurring flow regime in many industrial applications. The need for a better understanding of this flow regime is driven by the desire to improve the design of many terrestrial and space systems. Annular two-phase flow occurs in the mining and transportation of oil and natural gas, petrochemical processes, and boilers and condensers in heating and refrigeration systems. The flow regime is also anticipated during the refueling of space vehicles, and thermal management systems for space use. Annular flow is mainly inertia driven with little effect of buoyancy. However, the study of this flow regime is still desirable in a microgravity environment. The influence of gravity can create an unstable, chaotic film. The absence of gravity, therefore, allows for a more stable and axisymmetric film. Such conditions allow for the film characteristics to be easily studied at low gas flow rates. Previous studies conducted by the Microgravity Research Group dealt with varying the gas or liquid mass fluxes at a reduced gravitational acceleration.(1,2) The study described here continues this work by examining the effect of changing the gravitational acceleration (hypergravity) on the film characteristics. In particular, the film thickness and the associated pressure drops are examined. The film thickness was measured using a pair of two-wire conductance probes. Experimental data was collected over a range of annular flow set points by changing the liquid and gas mass flow rates, the liquid-to-gas density ratio and the gravitational acceleration. The liquid-to-gas density ratio was varied by collecting data with helium-water and air-water at the same flow rates. The gravitational effect was examined by collecting data during the microgravity and pull-up (hypergravity) portions of the parabolic flights.

  17. Pool scrubbing and hydrodynamic experiments on jet injection regime

    International Nuclear Information System (INIS)

    Peyres, V.; Espigares, M.M.; Polo, J.; Escudero, M.J.; Herranz, L.E.; Lopez-Jimenez, J.

    1995-01-01

    Plant analyses have shown that pool scrubbing can play an important role in source term during PWR risk dominant sequences. An examination ofboundary conditions governing fission products and aerosols transport through aqueous beds revealed that most of radioactivity is discharged into the pool under jet injection regime. This fact and the lack of experimental data under such conditions pointed the need of setting out an experimental programme which provided reliable experimental data to validate code models. In this report the major results of a pool scrubbing experimental programme carried out in PECA facility are presented. One of the major findings was that a remarkable fraction of particle absorption was not a function of the residence time of bubbles rising through the pool. Such a contribution was assumed to be associated to aerosol removal mechanisms acting at the pool entrance. As a consequence, a hydrodynamic experimental plan was launched to examine the gas behaviour during the initial stages in the pool. Size and shape of gas nuclei the pool were measured and fitted to a long normal distribution. Particularly, size was found to be quite sensitive to inletgas flow and at minor extent to gas composition and pool temperature. SPARC90 and BUSCA-AUG92 were used to simulate the retention tests. Whereas SPARC90 showed a pretty good agreement with experimental data, BUSCA-AUG92 results were far away from measurements in all the cases. SPARC90consistency apparently pointed out the important role of fission products and aerosols retention at the injection zone; nonetheless, a peer examination of pool scrubbing phenomenology at the pool entrance should be carried out to test both hydrodynamic and removal models. Hence, one of the major highlights drawn from this work was the need of further research under representative severe accident conditions (i.e., saturated pools, jet injection regimes, etc.), as well as separate effect tests to validate, improve and

  18. Evolution of the Greek national regime for water resources

    NARCIS (Netherlands)

    Kampa, Eleftheria; Bressers, Johannes T.A.

    2008-01-01

    This paper characterizes and explains the development of the Greek national water regime, based on a framework from institutional resource regime theory. The specific framework combines public resource policies with property rights and operationalizes the concept of integration for resource regimes.

  19. Level-ARCH Short Rate Models with Regime Switching

    DEFF Research Database (Denmark)

    Christiansen, Charlotte

    This paper introduces regime switching volatility into level- ARCH models for the short rates of the US, the UK, and Germany. Once regime switching and level effects are included there are no gains from including ARCH effects. It is of secondary importance exactly how the regime switching is spec...

  20. The global nuclear safety regime and its impact in Brazil

    International Nuclear Information System (INIS)

    Almeida, C.

    2004-01-01

    This work describes the Global Nuclear Safety Regime that was established worldwide after the accident at the Tchernobyl nuclear power plant. This regime is composed of biding international safety conventions, globally accepted safety standard, and a voluntary peer review system. The impact of this Global Regime in Brazil is also discussed. (Author)

  1. Enduring ambiguity: Sunni community-Syrian regime dynamics

    NARCIS (Netherlands)

    Donker, T.H.

    2010-01-01

    The paper's central thesis is that authoritarian regimes can benefit from the presence of domestic (Sunni) civil activism; through a social dynamic that creates an incentive for Sunni activists to actively approach regime actors. The article poses that they thereby imply a subservience to the regime

  2. Convective Replica-Exchange in Ergodic Regimes.

    Science.gov (United States)

    Signorini, Giorgio F; Giovannelli, Edoardo; Spill, Yannick G; Nilges, Michael; Chelli, Riccardo

    2014-03-11

    In a recent article (J. Comput. Chem. 2013, 34, 132-140), convective replica-exchange (convective-RE) has been presented as an alternative to the standard even-odd transition scheme. Computations on systems of various complexity have shown that convective-RE may increase the number of replica round-trips in temperature space with respect to the standard exchange scheme, leading to a more effective sampling of energy basins. Moreover, it has been shown that the method may prevent the formation of bottlenecks in the diffusive walk of replicas through the space of temperature states. By using an ideal temperature-RE model and a classical harmonic-oscillator RE scheme, we study the performances of convective-RE when ergodicity is not broken and convergence of acceptance probabilities is attained. In this dynamic regime, the round-trip ratio between convective and standard-RE is at maximum ∼ 1.5, a value much smaller than that observed in nonergodic simulations. For large acceptance probabilities, the standard-RE outperforms convective-RE. Our observations suggest that convective-RE can safely be used in either ergodic or non-ergodic regimes; however, convective-RE is advantageous only when bottlenecks occur in the state-space diffusion of replicas, or when acceptance probabilities are globally low. We also show that decoupling of the state-space dynamics of the stick replica from the dynamics of the remaining replicas improves the efficiency of convective-RE at low acceptance probability regimes.

  3. Transport in the quantum critical regime

    Science.gov (United States)

    Enss, Tilman

    2014-05-01

    In this talk I will explain the relevance of the quantum critical point for the phase diagram of the unitary Fermi gas, briefly review theoretical approaches, and present results for the shear viscosity and spin diffusion in strongly interacting Fermi gases. The unitary Fermi gas describes strongly interacting fermions ranging from ultracold atoms near a Feshbach resonance to dilute neutron matter, which share a common universal phase diagram. The behavior at finite temperature is governed by a quantum critical point (QCP) at zero temperature and zero density, and observables can be expressed by universal scaling functions of the distance from the critical point. In the quantum critical regime above the QCP, thermal and quantum fluctuations are equally important, and the absence of a small parameter makes the computation of critical properties demanding. I will mention two theoretical approaches to transport properties in this regime: the large-N expansion in the number of fermion flavors allows for a systematic and controlled expansion even at strong coupling and elucidates the importance of medium effects on scattering. Second, the Luttinger-Ward, or self-consistent T-matrix approach goes beyond the quasiparticle picture and also explains universal high-energy tails. I will present results on the shear viscosity, or internal friction, for mass transport and show that the strongly interacting Fermi gas is an almost perfect quantum fluid. On the other hand, if particles of different spin move in opposite directions, the dynamics are governed by spin diffusion. One can distinguish longitudinal diffusion, when atomic clouds of different spin collide, and transverse diffusion, when the magnetization is wound up in a helix in a spin-echo experiment. Medium scattering and spin rotation have a strong effect on spin diffusion, and I will discuss how spin transport becomes very slow at strong coupling in the quantum degenerate regime and reaches a quantum limit of

  4. The trade regime and the climate regime. Institutional evolution and adaptation

    International Nuclear Information System (INIS)

    Brewer, Thomas L.

    2003-01-01

    This article addresses concerns that the multilateral trade regime centered in the WTO and the emerging climate regime may conflict in ways that could be damaging to either or both. The article discusses the institutional and diplomatic context of these concerns, and it identifies the kinds of issues that are in question. The analysis suggests that there are opportunities for win-win outcomes in the interactions of the two regimes, for instance in the possibility of reducing fossil fuel subsidies. However, there are also problematic areas where they intersect. A core issue-and as yet an unresolved one-is whether and how emission credit trading and other activities envisioned by the Kyoto Protocol would be subject to WTO rules. The resolution of this issue will affect many other issues as well. Additional specific issues about the interactions of particular provisions in WTO agreements and the Kyoto Protocol are analyzed in a subsequent companion article in Climate Policy

  5. Electron acceleration in the bubble regime

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, Oliver

    2014-02-03

    The bubble regime of laser-wakefield acceleration has been studied over the recent years as an important alternative to classical accelerators. Several models and theories have been published, in particular a theory which provides scaling laws for acceleration parameters such as energy gain and acceleration length. This thesis deals with numerical simulations within the bubble regime, their comparison to these scaling laws and data obtained from experiments, as well as some specific phenomenona. With a comparison of the scaling laws with numerical results a parameter scan was able to show a large parameter space in which simulation and theory agree. An investigation of the limits of this parameter space revealed boundaries to other regimes, especially at very high (a{sub 0} > 100) and very low laser amplitudes (a{sub 0} < 4). Comparing simulation data with data from experiments concerning laser pulse development and electron energies, it was found that experimental results can be adequately reproduced using the Virtual-Laser-Plasma-Laboratory code. In collaboration with the Institut fuer Optik und Quantenelektronik at the Friedrich-Schiller University Jena synchrotron radiation emitted from the inside of the bubble was investigated. A simulation of the movement of the electrons inside the bubble together with time dependent histograms of the emitted radiation helped to prove that the majority of radiation created during a bubble acceleration originates from the inside of the bubble. This radiation can be used to diagnose the amplitude of oscillation of the trapped electrons. During a further study it was proven that the polarisation of synchrotron radiation from a bubble contains information about the exact oscillation direction. This oscillation was successfully controlled by using either a laser pulse with a tilted pulse front or an asymmetric laser pulse. First results of ongoing studies concerning injecting electrons into an existing bubble and a scheme called

  6. Operation regimes of a dielectric laser accelerator

    Science.gov (United States)

    Hanuka, Adi; Schächter, Levi

    2018-04-01

    We investigate three operation regimes in dielectric laser driven accelerators: maximum efficiency, maximum charge, and maximum loaded gradient. We demonstrate, using a self-consistent approach, that loaded gradients of the order of 1 to 6 [GV/m], efficiencies of 20% to 80%, and electrons flux of 1014 [el/s] are feasible, without significant concerns regarding damage threshold fluence. The latter imposes that the total charge per squared wavelength is constant (a total of 106 per μm2). We conceive this configuration as a zero-order design that should be considered for the road map of future accelerators.

  7. Random nanolasing in the Anderson localized regime

    DEFF Research Database (Denmark)

    Liu, Jin; Garcia, P. D.; Ek, Sara

    2014-01-01

    multiple scattering. The applicability of random lasers has been limited due to multidirectional emission, lack of tunability, and strong mode competition with chaotic fluctuations due to a weak mode confinement. The regime of Anderson localization of light has been proposed for obtaining stable multimode...... random lasing, and initial work concerned macroscopic one-dimensional layered media. Here, we demonstrate on-chip random nanolasers where the cavity feedback is provided by the intrinsic disorder. The strong confinement achieved by Anderson localization reduces the spatial overlap between lasing modes...

  8. Change of secondary water regime of Paks NPP. Change of secondary water regime at Unit 2

    International Nuclear Information System (INIS)

    Doma, A.; Patek, G.; Pinter, T.; Bajari, M.; Tilky, P.

    2001-01-01

    The installation of high pH water regime during the 17th cycle of Unit 2 aimed to decrease the amount of transportation inlet of erosion-corrosion products (magnitude) in feedwater to SGs. The resolution of OAH-NBI permitting the installation ordained to make an evaluation of the process. The main conclusions and results are discussed. The high pH water regime proved to be adequate in the case of Unit 2 as well, similarly to Units 3, 4 and 1. (R.P.)

  9. TREHS: An open-access software tool for investigating and evaluating temporary river regimes as a first step for their ecological status assessment.

    Science.gov (United States)

    Gallart, Francesc; Cid, Núria; Latron, Jérôme; Llorens, Pilar; Bonada, Núria; Jeuffroy, Justin; Jiménez-Argudo, Sara-María; Vega, Rosa-María; Solà, Carolina; Soria, Maria; Bardina, Mònica; Hernández-Casahuga, Antoni-Josep; Fidalgo, Aránzazu; Estrela, Teodoro; Munné, Antoni; Prat, Narcís

    2017-12-31

    When the regime of a river is not perennial, there are four main difficulties with the use of hydrographs for assessing hydrological alteration: i) the main hydrological features relevant for biological communities are not quantitative (discharges) but qualitative (phases such as flowing water, stagnant pools or lack of surface water), ii) stream flow records do not inform on the temporal occurrence of stagnant pools, iii) as most of the temporary streams are ungauged, their regime has to be evaluated by alternative methods such as remote sensing or citizen science, and iv) the biological quality assessment of the ecological status of a temporary stream must follow a sampling schedule and references adapted to the flow- pool-dry regime. To overcome these challenges within an operational approach, the freely available software tool TREHS has been developed within the EU LIFE TRIVERS project. This software permits the input of information from flow simulations obtained with any rainfall-runoff model (to set an unimpacted reference stream regime) and compares this with the information obtained from flow gauging records (if available) and interviews with local people, as well as instantaneous observations by individuals and interpretation of ground-level or aerial photographs. Up to six metrics defining the permanence of water flow, the presence of stagnant pools and their temporal patterns of occurrence are used to determine natural and observed river regimes and to assess the degree of hydrological alteration. A new regime classification specifically designed for temporary rivers was developed using the metrics that measure the relative permanence of the three main phases: flow, disconnected pools and dry stream bed. Finally, the software characterizes the differences between the natural and actual regimes, diagnoses the hydrological status (degree of hydrological alteration), assesses the significance and robustness of the diagnosis and recommends the best periods

  10. Precipitation regimes over central Greenland inferred from 5 years of ICECAPS observations

    Directory of Open Access Journals (Sweden)

    C. Pettersen

    2018-04-01

    Full Text Available A novel method for classifying Arctic precipitation using ground based remote sensors is presented. Using differences in the spectral variation of microwave absorption and scattering properties of cloud liquid water and ice, this method can distinguish between different types of snowfall events depending on the presence or absence of condensed liquid water in the clouds that generate the precipitation. The classification reveals two distinct, primary regimes of precipitation over the Greenland Ice Sheet (GIS: one originating from fully glaciated ice clouds and the other from mixed-phase clouds. Five years of co-located, multi-instrument data from the Integrated Characterization of Energy, Clouds, Atmospheric state, and Precipitation at Summit (ICECAPS are used to examine cloud and meteorological properties and patterns associated with each precipitation regime. The occurrence and accumulation of the precipitation regimes are identified and quantified. Cloud and precipitation observations from additional ICECAPS instruments illustrate distinct characteristics for each regime. Additionally, reanalysis products and back-trajectory analysis show different synoptic-scale forcings associated with each regime. Precipitation over the central GIS exhibits unique microphysical characteristics due to the high surface elevations as well as connections to specific large-scale flow patterns. Snowfall originating from the ice clouds is coupled to deep, frontal cloud systems advecting up and over the southeast Greenland coast to the central GIS. These events appear to be associated with individual storm systems generated by low pressure over Baffin Bay and Greenland lee cyclogenesis. Snowfall originating from mixed-phase clouds is shallower and has characteristics typical of supercooled cloud liquid water layers, and slowly propagates from the south and southwest of Greenland along a quiescent flow above the GIS.

  11. THE WIND OF ROTATING B SUPERGIANTS. I. DOMAINS OF SLOW AND FAST SOLUTION REGIMES

    Energy Technology Data Exchange (ETDEWEB)

    Venero, R. O. J.; Cidale, L. S. [Departamento de Espectroscopía, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata (UNLP), and Instituto de Astrofísica La Plata, CCT La Plata, CONICET-UNLP, Paseo del Bosque S/N, 1900 La Plata (Argentina); Curé, M.; Araya, I., E-mail: roberto@fcaglp.unlp.edu.ar [Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso Av. Gran Bretaña 1111, Casilla 5030, Valparaíso (Chile)

    2016-05-01

    In the scenario of rotating radiation-driven wind theory for massive stars, three types of stationary hydrodynamic solutions are currently known: the classical ( fast ) m-CAK solution, the Ω- slow solution that arises for fast rotators, and the so-called δ - slow solution if high values of the δ line-force parameter are allowed independently of the rotation speed. Compared to the fast solution, both “ slow solutions” have lower terminal velocities. As the study of the parameter domain for the slow solution is still incomplete, we perform a comprehensive analysis of the distinctive flow regimes for B supergiants that emerge from a fine grid of rotation values, Ω, and various ionization conditions in the wind ( δ ) parameter. The wind ionization defines two domains: one for fast outflowing winds and the other for slow expanding flows. Both domains are clear-cut by a gap, where a kink/plateau structure of the velocity law could exist for a finite interval of δ . The location and width of the gap depend on T {sub eff} and Ω. There is a smooth and continuous transition between the Ω- slow and δ - slow regimes, a single Ω δ - slow regime. We discuss different situations where the slow solutions can be found and the possibility of a switch between fast and slow solutions in B supergiant winds. We compare the theoretical terminal velocity with observations of B and A supergiants and find that the fast regime prevails mostly for early B supergiants while the slow wind regime matches better for A and B mid- and late-type supergiants.

  12. Computational characterization of ignition regimes in a syngas/air mixture with temperature fluctuations

    KAUST Repository

    Pal, Pinaki

    2016-07-27

    Auto-ignition characteristics of compositionally homogeneous reactant mixtures in the presence of thermal non-uniformities and turbulent velocity fluctuations were computationally investigated. The main objectives were to quantify the observed ignition characteristics and numerically validate the theory of the turbulent ignition regime diagram recently proposed by Im et al. 2015 [29] that provides a framework to predict ignition behavior . a priori based on the thermo-chemical properties of the reactant mixture and initial flow and scalar field conditions. Ignition regimes were classified into three categories: . weak (where deflagration is the dominant mode of fuel consumption), . reaction-dominant strong, and . mixing-dominant strong (where volumetric ignition is the dominant mode of fuel consumption). Two-dimensional (2D) direct numerical simulations (DNS) of auto-ignition in a lean syngas/air mixture with uniform mixture composition at high-pressure, low-temperature conditions were performed in a fixed volume. The initial conditions considered two-dimensional isotropic velocity spectrums, temperature fluctuations and localized thermal hot spots. A number of parametric test cases, by varying the characteristic turbulent Damköhler and Reynolds numbers, were investigated. The evolution of the auto-ignition phenomena, pressure rise, and heat release rate were analyzed. In addition, combustion mode analysis based on front propagation speed and computational singular perturbation (CSP) was applied to characterize the auto-ignition phenomena. All results supported that the observed ignition behaviors were consistent with the expected ignition regimes predicted by the theory of the regime diagram. This work provides new high-fidelity data on syngas ignition characteristics over a broad range of conditions and demonstrates that the regime diagram serves as a predictive guidance in the understanding of various physical and chemical mechanisms controlling auto

  13. Managing Disagreement: A Defense of "Regime Bias"

    Science.gov (United States)

    Sabl, Andrew

    2011-02-01

    Stein Ringen's theory of democratic purpose cannot do the work expected of it. Ringen's own criteria oscillate between being too vague to be useful (i.e. "freedom") or, when specified more fully, conflicting, so that almost all democracies will seem to be potentially at cross-purposes with themselves rather than their purposes or sub-purposes being mutually reinforcing. This reflects a bigger and more theoretical problem. Disagreement about the purpose of democracy is built into democracy itself. The whole point of many (perhaps all) of our democratic institutions is to arrive at conditionally legitimate decisions in spite of such disagreement. So-called regime bias, i.e. the tendency to assess democracies according to the form and stability of their institutions rather than their results or their ability to serve certain purposes, does not in fact arise from bias. It arises on the contrary from a determination to avoid the bias inherent in giving some-inevitably partisan-ideals of what democracies should do pride of place over others in a scheme of measurement or evaluation. And even a regime-based definition of democracy must itself make simplifying assumptions that elide possible normative controversies over how the democratic game is best played. Vindicating one's preferred set of democratic ideals against alternatives is a completely legitimate enterprise and lends richness to debates within and across democracies. But it is an inherently ideological and political enterprise, not a neutral or scholarly one.

  14. Legal framework of the environmental regulatory regime

    International Nuclear Information System (INIS)

    Black, D.

    1992-01-01

    The growing concern regarding environmental issues has presented a number of new challenges to those exploring and developing the hydrocarbon reserves located on the Newfoundland continental shelf. Not the least of these challenges is the development of new technologies in the harsh environment of the North Atlantic; in addition, these new technologies must be implemented in an existing and ever-changing regulatory regime. The legal framework of the environmental regulatory regime relating to offshore development in Canada is reviewed along with some of the more important legislation involved in regulating environmental issues in the offshore area. The legal basis for exploration, development, and management of resources located on the Newfoundland continental shelf is the Canada-Newfoundland Accord on Joint Management of Offshore Oil and Gas Resources off Newfoundland and Labrador. Administration of the Accord is the responsibility of the Canada-Newfoundland Offshore Petroleum Board. To be able to apply Canadian laws to the continental shelf, legislation was passed including the Canadian Laws Offshore Application Act as well as the Act implementing the Accord. The latter gives the Offshore Petroleum Board authority to regulate all stages involved in bringing an oil pool to production, such as granting of licenses and work authorizations. Granting of such licenses and authorizations is subject to compliance with environmental requirements, and there are provisions against certain environmental offenses such as spills. Other federal legislation applicable to the offshore includes the Canada Shipping Act and the Canadian Environmental Protection Act

  15. Characterizing multistationarity regimes in biochemical reaction networks.

    Directory of Open Access Journals (Sweden)

    Irene Otero-Muras

    Full Text Available Switch like responses appear as common strategies in the regulation of cellular systems. Here we present a method to characterize bistable regimes in biochemical reaction networks that can be of use to both direct and reverse engineering of biological switches. In the design of a synthetic biological switch, it is important to study the capability for bistability of the underlying biochemical network structure. Chemical Reaction Network Theory (CRNT may help at this level to decide whether a given network has the capacity for multiple positive equilibria, based on their structural properties. However, in order to build a working switch, we also need to ensure that the bistability property is robust, by studying the conditions leading to the existence of two different steady states. In the reverse engineering of biological switches, knowledge collected about the bistable regimes of the underlying potential model structures can contribute at the model identification stage to a drastic reduction of the feasible region in the parameter space of search. In this work, we make use and extend previous results of the CRNT, aiming not only to discriminate whether a biochemical reaction network can exhibit multiple steady states, but also to determine the regions within the whole space of parameters capable of producing multistationarity. To that purpose we present and justify a condition on the parameters of biochemical networks for the appearance of multistationarity, and propose an efficient and reliable computational method to check its satisfaction through the parameter space.

  16. Tlatelolco regime and nonproliferation in Latin America

    International Nuclear Information System (INIS)

    Redick, J.R.

    1981-01-01

    The regime established by the Treaty of Tlatelolco supports peace and security in the Latin American region and global nonproliferation efforts. Circumstances leading to the creation of the nuclear-weapon-free zone include careful preparations and negotiations, individual leadership, existence of certain shared cultural and legal traditions of Latin American countries, and the temporary stimulus of the Cuban missile crisis. The lack of overt superpower pressure on Latin America, compared with more turbulent regions, has permitted continued progress toward full realization of the zone. Tlatelolco's negotiating process, as well as the substance of the Treaty, deserve careful consideration relative to other areas. The Treaty enjoys wide international approval, but full support by certain Latin American States (Argentina, Brazil, Chile, Cuba) has been negatively affected by the failure of the US Senate to ratify Tlatelolco's Protocol I. Nuclear programs of Argentina, Brazil, and Mexico are expanding rapidly and these nations are forming linkages with West European countries, rather than the United States. The May 1980 Argentine-Brazilian nuclear agreement foresees significant cooperation between the two nation's nuclear energy commissions and more coordinated resistance to the nuclear supplier countries. Argentine-Brazilian nuclear convergence and the response accorded to it by the United States will have significant implications for the future of the Tlatelolco regime and nonproliferation in Latin America. 52 references

  17. Elastic regimes of subisostatic athermal fiber networks

    Science.gov (United States)

    Licup, A. J.; Sharma, A.; MacKintosh, F. C.

    2016-01-01

    Athermal models of disordered fibrous networks are highly useful for studying the mechanics of elastic networks composed of stiff biopolymers. The underlying network architecture is a key aspect that can affect the elastic properties of these systems, which include rich linear and nonlinear elasticity. Existing computational approaches have focused on both lattice-based and off-lattice networks obtained from the random placement of rods. It is not obvious, a priori, whether the two architectures have fundamentally similar or different mechanics. If they are different, it is not clear which of these represents a better model for biological networks. Here, we show that both approaches are essentially equivalent for the same network connectivity, provided the networks are subisostatic with respect to central force interactions. Moreover, for a given subisostatic connectivity, we even find that lattice-based networks in both two and three dimensions exhibit nearly identical nonlinear elastic response. We provide a description of the linear mechanics for both architectures in terms of a scaling function. We also show that the nonlinear regime is dominated by fiber bending and that stiffening originates from the stabilization of subisostatic networks by stress. We propose a generalized relation for this regime in terms of the self-generated normal stresses that develop under deformation. Different network architectures have different susceptibilities to the normal stress but essentially exhibit the same nonlinear mechanics. Such a stiffening mechanism has been shown to successfully capture the nonlinear mechanics of collagen networks.

  18. Strengthening the non proliferation regime: French views

    International Nuclear Information System (INIS)

    Delaune, P.

    2013-01-01

    3 main issues can be identified in the French policy concerning the backing of non proliferation: 1) responding resolutely to proliferation crises, 2) reinforcing substantive efforts to prevent and impede proliferation, and 3) strengthening the non-proliferation regime. The first issue is very important because combating proliferation is vital to the security of all. Concerning the second issue, France attaches particular importance to strengthening specific measures to prevent and check proliferation. Let me mention a few proposals that we put forward: exports need to be controlled more effectively, proliferation activities have to be criminalized, or the development of proliferation-resistant technologies should be supported. Concerning the third issue it means the strengthening of the non-proliferation regime, France proposes several means: -) aiming at the universalization of the additional protocol; -) ensuring that the Agency continues to have sufficient human, financial and technical resources to fulfill its verification mission effectively; -) encouraging the IAEA to make full use of the authority available to it; -) enhancing the use of information relevant to the delivery of the IAEA mandate; and -) sharing more accurate information concerning the breaches of commitments that happen. The paper is followed by the slides of the presentation. (A.C.)

  19. The thermal regime around buried submarine high-voltage cables

    Science.gov (United States)

    Emeana, C. J.; Hughes, T. J.; Dix, J. K.; Gernon, T. M.; Henstock, T. J.; Thompson, C. E. L.; Pilgrim, J. A.

    2016-08-01

    The expansion of offshore renewable energy infrastructure and the need for trans-continental shelf power transmission require the use of submarine high-voltage (HV) cables. These cables have maximum operating surface temperatures of up to 70 °C and are typically buried 1-2 m beneath the seabed, within the wide range of substrates found on the continental shelf. However, the heat flow pattern and potential effects on the sedimentary environments around such anomalously high heat sources in the near-surface sediments are poorly understood. We present temperature measurements from a 2-D laboratory experiment representing a buried submarine HV cable, and identify the thermal regimes generated within typical unconsolidated shelf sediments—coarse silt, fine sand and very coarse sand. We used a large (2 × 2.5 m2) tank filled with water-saturated spherical glass beads (ballotini) and instrumented with a buried heat source and 120 thermocouples to measure the time-dependent 2-D temperature distributions. The observed and corresponding Finite Element Method simulations of the steady state heat flow regimes and normalized radial temperature distributions were assessed. Our results show that the heat transfer and thus temperature fields generated from submarine HV cables buried within a range of sediments are highly variable. Coarse silts are shown to be purely conductive, producing temperature increases of >10 °C up to 40 cm from the source of 60 °C above ambient; fine sands demonstrate a transition from conductive to convective heat transfer between cf. 20 and 36 °C above ambient, with >10 °C heat increases occurring over a metre from the source of 55 °C above ambient; and very coarse sands exhibit dominantly convective heat transfer even at very low (cf. 7 °C) operating temperatures and reaching temperatures of up to 18 °C above ambient at a metre from the source at surface temperature