Sample records for hydraulic pressure gradient

  1. Modeling of Propagation of Interacting Cracks Under Hydraulic Pressure Gradient

    Huang, Hai [Idaho National Laboratory; Mattson, Earl Douglas [Idaho National Laboratory; Podgorney, Robert Karl [Idaho National Laboratory


    A robust and reliable numerical model for fracture initiation and propagation, which includes the interactions among propagating fractures and the coupling between deformation, fracturing and fluid flow in fracture apertures and in the permeable rock matrix, would be an important tool for developing a better understanding of fracturing behaviors of crystalline brittle rocks driven by thermal and (or) hydraulic pressure gradients. In this paper, we present a physics-based hydraulic fracturing simulator based on coupling a quasi-static discrete element model (DEM) for deformation and fracturing with conjugate lattice network flow model for fluid flow in both fractures and porous matrix. Fracturing is represented explicitly by removing broken bonds from the network to represent microcracks. Initiation of new microfractures and growth and coalescence of the microcracks leads to the formation of macroscopic fractures when external and/or internal loads are applied. The coupled DEM-network flow model reproduces realistic growth pattern of hydraulic fractures. In particular, simulation results of perforated horizontal wellbore clearly demonstrate that elastic interactions among multiple propagating fractures, fluid viscosity, strong coupling between fluid pressure fluctuations within fractures and fracturing, and lower length scale heterogeneities, collectively lead to complicated fracturing patterns.

  2. Towards improved estimation of the unsaturated soil hydraulic conductivity in the near saturated range by a fully automated, pressure controlled unit gradient experiment.

    Werisch, Stefan; Müller, Marius


    Determination of soil hydraulic properties has always been an important part of soil physical research and model applications. While several experiments are available to measure the water retention of soil samples, the determination of the unsaturated hydraulic conductivity is often more complicated, bound to strong assumption and time consuming. Although, the application of unit gradient experiments is recommended since the middle of the last century, as one method towards a (assumption free) direct measurement of the unsaturated hydraulic conductivity, data from unit gradient experiments is seldom to never reported in literature. We developed and build a fully automated, pressure controlled, unit gradient experiment, which allows a precise determination of the unsaturated soil hydraulic conductivity K(h) and water retention VWC(h), especially in the highly dynamic near saturated range. The measurement apparatus applies the concept of hanging water columns and imposes the required soil water pressure by dual porous plates. This concepts allows the simultaneous and direct measurement of water retention and hydraulic conductivity. Moreover, this approach results in a technically less demanding experiment than related flux controlled experiments, and virtually any flux can be measured. Thus, both soil properties can be measured in mm resolution, for wetting and drying processes, between saturation and field capacity for all soil types. Our results show, that it is important to establish separate measurements of the unsaturated hydraulic conductivity in the near saturated range, as the shape of the retention function and hydraulic conductivity curve do not necessarily match. Consequently, the prediction of the hydraulic conductivity curve from measurements of the water retention behavior in combination with a value for the saturated hydraulic conductivity can be misleading. Thus, separate parameterizations of the individual functions might be necessary and are

  3. Constant-Pressure Hydraulic Pump

    Galloway, C. W.


    Constant output pressure in gas-driven hydraulic pump would be assured in new design for gas-to-hydraulic power converter. With a force-multiplying ring attached to gas piston, expanding gas would apply constant force on hydraulic piston even though gas pressure drops. As a result, pressure of hydraulic fluid remains steady, and power output of the pump does not vary.

  4. Variation of hydraulic gradient in nonlinear finite strain consolidation

    谢新宇; 黄杰卿; 王文军; 李金柱


    In the research field of ground water, hydraulic gradient is studied for decades. In the consolidation field, hydraulic gradient is yet to be investigated as an important hydraulic variable. So, the variation of hydraulic gradient in nonlinear finite strain consolidation was focused on in this work. Based on lab tests, the nonlinear compressibility and nonlinear permeability of Ningbo soft clay were obtained. Then, a strongly nonlinear governing equation was derived and it was solved with the finite element method. Afterwards, the numerical analysis was performed and it was verified with the existing experiment for Hong Kong marine clay. It can be found that the variation of hydraulic gradient is closely related to the magnitude of external load and the depth in soils. It is interesting that the absolute value of hydraulic gradient (AVHG) increases rapidly first and then decreases gradually after reaching the maximum at different depths of soils. Furthermore, the changing curves of AVHG can be roughly divided into five phases. This five-phase model can be employed to study the migration of pore water during consolidation.

  5. Vertebrate pressure-gradient receivers

    Christensen-Dalsgaard, Jakob


    The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum and stro......The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum....... Recent vertebrates form a continuum from perfect interaural transmission (0 dB in a certain frequency band) and pronounced eardrum directionality (30-40 dB) in the lizards, over somewhat attenuated transmission and limited directionality in birds and frogs, to the strongly attenuated interaural...

  6. High Pressure Hydraulic Distribution System


    to 500 0 F. 5 cycles. 5000 F room temperature to 50001F; 45 ______________ Icycles The tesis planned for the distribution system demonstrator were...American Society for Testing and Materials ASTM D412 - Tension Testing of Vulcanized Rubber ASTM D571 - Testing Automotive Hydraulic Brake Hose Society of

  7. Heavy Metal Diffusion through Soft Clay under High Hydraulic Gradients

    Zaheer Ahmed Almani


    Full Text Available This study was focused on the determination of contaminant transport parameters of heavy metal Zinc moving through saturated soft Bangkok undisturbed clay under high hydraulic gradients. These parameters were compared with contaminant transport determined under concentration gradient alone (pure diffusion. In total fifteen column tests were conducted and a mathematical model was applied to determine the coefficients. Two different source concentrations conditions, constant and decreasing, were applied. Testing periods were ranged from 15-60 days while hydraulic gradients were ranged from 0-500. The curves between relative concentration and time and pore volume were developed for the constant source condition whereas curves between source reservoirs concentrations and time were developed for decreasing source condition. The effective diffusion and distribution coefficients, De and Kd, were determined by curve fitting using the computer code POLLUTE v 6.3. The results showed that diffusion coefficient increases and distribution coefficient decreases as hydraulic gradient increases from 0 to high value of 500 due to contribution of dispersion and additional molecular diffusion at high advective velocity. Thus, testing at high gradients ensures the safe performance of earthen barriers under worse conditions.

  8. Assimilation of temperature and hydraulic gradients for quantifying the spatial variability of streambed hydraulics

    Huang, Xiang; Andrews, Charles B.; Liu, Jie; Yao, Yingying; Liu, Chuankun; Tyler, Scott W.; Selker, John S.; Zheng, Chunmiao


    Understanding the spatial and temporal characteristics of water flux into or out of shallow aquifers is imperative for water resources management and eco-environmental conservation. In this study, the spatial variability in the vertical specific fluxes and hydraulic conductivities in a streambed were evaluated by integrating distributed temperature sensing (DTS) data and vertical hydraulic gradients into an ensemble Kalman filter (EnKF) and smoother (EnKS) and an empirical thermal-mixing model. The formulation of the EnKF/EnKS assimilation scheme is based on a discretized 1D advection-conduction equation of heat transfer in the streambed. We first systematically tested a synthetic case and performed quantitative and statistical analyses to evaluate the performance of the assimilation schemes. Then a real-world case was evaluated to calculate assimilated specific flux. An initial estimate of the spatial distributions of the vertical hydraulic gradients was obtained from an empirical thermal-mixing model under steady-state conditions using a constant vertical hydraulic conductivity. Then, this initial estimate was updated by repeatedly dividing the assimilated specific flux by estimates of the vertical hydraulic gradients to obtain a refined spatial distribution of vertical hydraulic gradients and vertical hydraulic conductivities. Our results indicate that optimal parameters can be derived with fewer iterations but greater simulation effort using the EnKS compared with the EnKF. For the field application in a stream segment of the Heihe River Basin in northwest China, the average vertical hydraulic conductivities in the streambed varied over three orders of magnitude (5 × 10-1 to 5 × 102 m/d). The specific fluxes ranged from near zero (qz < ±0.05 m/d) to ±1.0 m/d, while the vertical hydraulic gradients were within the range of -0.2 to 0.15 m/m. The highest and most variable fluxes occurred adjacent to a debris-dam and bridge pier. This phenomenon is very likely

  9. Controlling a negative loaded hydraulic cylinder using pressure feedback

    Hansen, M.R.; Andersen, T.O.


    the high pass filtered pressure gradient equal tozero is introduced. It yields lead compensation with a markedly improved performance. The sizing of the filter is described taking into account the bandwidth of the directional control valve. The suggested control scheme is implemented and examined......This paper is concerned with the inherent oscillatory nature of pressure compensated velocity control of a hydraulic cylinder subjected to a negative load and suspended by means of an over-center valve. Initially, a linearized stability analysis of such a hydraulic circuit is carried out clearly...... showing that without extra measures such a system will be unstable in a substantial part of the cylinder stroke. The stability criterion is expressed in hard quantities: Cylinder volumes, cylinder area ratio and overcenter valve pilot area ratio. A pressure feed back scheme that has as target to maintain...

  10. Vertebrate pressure-gradient receivers.

    Christensen-Dalsgaard, Jakob


    The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum and strongly dependent on interaural transmission attenuation. Even though the tympanic middle ear has originated independently in the major tetrapod groups, in each group the ancestral condition probably was that the two middle ears were exposed in the mouth cavity with relatively high interaural transmission. Recent vertebrates form a continuum from perfect interaural transmission (0 dB in a certain frequency band) and pronounced eardrum directionality (30-40 dB) in the lizards, over somewhat attenuated transmission and limited directionality in birds and frogs, to the strongly attenuated interaural transmission and functionally isolated pressure receiver ears in the mammals. Since some of the binaural interaction already takes place at the eardrum in animals with strongly coupled ears, producing enhanced interaural time and level differences, the subsequent neural processing may be simpler. In robotic simulations of lizards, simple binaural subtraction (EI cells, found in brainstem nuclei of both frogs and lizards) produces strongly lateralized responses that are sufficient for steering the animal robustly to sound sources.

  11. Effects of hydraulic pressure on the performance of single chamber air-cathode microbial fuel cells.

    Cheng, Shaoan; Liu, Weifeng; Guo, Jian; Sun, Dan; Pan, Bin; Ye, Yaoli; Ding, Weijun; Huang, Haobin; Li, Fujian


    Scaling up of microbial fuel cells (MFCs) without losing power density requires a thorough understanding of the effect of hydraulic pressure on MFC performance. In this work, the performance of an activated carbon air-cathode MFC was evaluated under different hydraulic pressures. The MFC under 100 mmH2O hydraulic pressure produced a maximum power density of 1260 ± 24 mW m(-2), while the power density decreased by 24.4% and 44.7% as the hydraulic pressure increased to 500 mmH2O and 2000 mmH2O, respectively. Notably, the performance of both the anode and the cathode had decreased under high hydraulic pressures. Electrochemical impedance spectroscopy tests of the cathode indicated that both charge transfer resistance and diffusion transfer resistance increased with the increase in hydraulic pressure. Denaturing gradient gel electrophoresis of PCR-amplified partial 16S rRNA genes demonstrated that the similarity among anodic biofilm communities under different hydraulic pressures was ≥ 90%, and the communities of all MFCs were dominated by Geobacter sp. These results suggested that the reduction in power output of the single chamber air-cathode MFC under high hydraulic pressures can be attributed to water flooding of the cathode and suppression the metabolism of anodic exoelectrogenic bacteria.

  12. Discussion of liquid threshold pressure gradient

    Xiukun Wang


    The correct interpretation is that there are two flow regimes: nonlinear flow regime (non-Darcy flow regime when the pressure gradients are low, and linear flow regime (Darcy flow regime when the pressure gradient is intermediate or high. The nonlinear flow regime starts from the origin point. As the pressure gradient is increased, the curve becomes a straight line demonstrating the linear flow regime. We have verified our views by first analyzing the causes of non-Darcy flow, and then systematically analyzed typical experimental data and correlations in the literature. We conclude that TPG does not exist. We also use several counter examples to support our conclusion.

  13. Pressure Characteristic Analysis of a Hydraulic System

    Cho, H. Y.; Yang, H. J.


    EPPR(ElectroProportional Pressure Reducing) valve control the MCV(Main Control Valve) built on the mobile heavy machine. The EPPR valve was tested in the experimental setup and the performance of the valve was compared with that of the existing EPPR valve. On thisstudy, electromagnetic properties analysis using AMESim program was performed to optimize the designing of EPPR Valve (Electric Proportional Pressure Reducing Valve) and by applying its results to the hydraulic system analytical model, performance of the valve could be predicted. Also by comparing the results of the actual experiment and the simulation, The results of thisstudy is that the 3 factor(cone angle, tip width, clearance between sleeve and plunger) have much effectiveness than other components in the EPPR valve.

  14. Pressure Gradient Evolution and Substorm Onset

    Zhonghua, Y.; Pu, Z.; Cao, X.; Nishimura, T.; Zhang, H.; Fu, S.; Xie, L.; Guo, R.


    Near-Earth current disruption (NECD) and substorm current wedge (SCW) formation are two related key phenomena for substorm onset. They are believed to be in close association with evolution of pressure gradient near the inner edge of plasma sheet. In the past, a few attempts have been made to investigate the pressure gradient in the late growth phase based on one- or two-spacecraft observations (e.g. , Korth et al., 1991; Pu et al., 1992; Shiokawa et al., 1998; Xing et al., 2010, 2011,etc). In this paper, with linearization assumption in the inner-probe region, we use THEMIS three-probe measurements to estimate the pressure gradient near the inner edge of the equatorward and duskward (dawnward) plasma sheet where pressure gradient in the Z-direction is almost vanished. We therefore can roughly get the two-dimensional pressure gradient in the X- and Y-direction simultaneously. Our observations indicate that the pressure gradients in both the X- and Y-direction enhance right after (within one minute) substorm onset. The enhanced pressure gradient in the Y-direction is duskward (dawnward) when the probes are in the duskside (dawnside) of the enhanced earthward flow in the growth phase. The enhanced dawn-dusk pressure gradients can drive downward field-aligned current (FAC) on the dawnside and upward FAC on the duskside, thus make contributions to the NECD and formation of SCW. THEMIS in situ data and all-sky auroral images for two events are presented, followed by a brief discussion.


    Wang Qingfeng; Li Yanmin; Zhong Tianyu; Xu Guohua


    Based on the analysis of the-state-of-the-art of pressure compensation of underwater hydraulic systems (UHSs), a new method of pressure compensation of UHSs, whose hydraulic power unit is in the atmospheric circumstance, is proposed. And a pilot-operated relief valve with pressure compensation is realized. The pressure compensation precision is guaranteed by direct detection. Its dynamic performance and stability are improved by a dynamic feedback. Theoretical study, simulation and experiment show that the pilot-operated relief valve with pressure compensation has a fine property of tracking underwater ambient pressure and meet the requirement of underwater ambient pressure compensation.

  16. Effect of pressure gradients on Gortler instability

    Ragab, S. A.; Nayfeh, A. H.


    Gortler instability for boundary-layer flows over generally curved walls is considered. The full linearized disturbance equations are obtained in an orthogonal curvilinear coordinate system. A perturbation procedure to account for second-order effects is used to determine the effects of the displacement thickness and the variation of the streamline curvature on the neutral stability of the Blasius flow. The pressure gradient in the mean flow is accounted for by solving the nonsimilar boundary-layer equations. Growth rates are obtained for the actual mean flow and the Falkner-Skan flows. The results demonstrate the strong influence of the pressure gradient and the nonsimilarity of the basic flow on the stability characteristics.

  17. Hydraulic integration and shrub growth form linked across continental aridity gradients.

    Schenk, H Jochen; Espino, Susana; Goedhart, Christine M; Nordenstahl, Marisa; Cabrera, Hugo I Martinez; Jones, Cynthia S


    Both engineered hydraulic systems and plant hydraulic systems are protected against failure by resistance, reparability, and redundancy. A basic rule of reliability engineering is that the level of independent redundancy should increase with increasing risk of fatal system failure. Here we show that hydraulic systems of plants function as predicted by this engineering rule. Hydraulic systems of shrubs sampled along two transcontinental aridity gradients changed with increasing aridity from highly integrated to independently redundant modular designs. Shrubs in humid environments tend to be hydraulically integrated, with single, round basal stems, whereas dryland shrubs typically have modular hydraulic systems and multiple, segmented basal stems. Modularity is achieved anatomically at the vessel-network scale or developmentally at the whole-plant scale through asymmetric secondary growth, which results in a semiclonal or clonal shrub growth form that appears to be ubiquitous in global deserts.

  18. FAST TRACK PAPER: The creation of an asymmetric hydraulic fracture as a result of driving stress gradients

    Fischer, T.; Hainzl, S.; Dahm, T.


    Hydraulic fracture stimulation is frequently performed in hydrocarbon reservoirs and geothermal systems to increase the permeability of the rock formation. These hydraulic fractures are often mapped by hypocentres of induced microearthquakes. In some cases microseismicity exhibits asymmetry relative to the injection well, which can be interpreted by unequal conditions for fracture growth at opposite sides of the well or by observation effects. Here we investigate the role of the lateral change of the minimum compressive stress. We use a simple model to describe the relation among the lateral stress gradient, the mean viscous pressure gradients in the fracture wings, the fracture geometry, and the net pressure in the fracture. Our model predicts a faster fracture growth in the direction of decreasing stress and a limited growth in the opposite direction. We derive a simple relationship to estimate the lateral stress gradient from the injection pressure and the shape of the seismic hypocentre cloud. The model is tested by microseismic data obtained during stimulation of a Canyon Sands gas field in West Texas. Using a maximum likelihood method we fit the parameters of the asymmetric fracture model to the space-time pattern of hypocentres. The estimated stress gradients per metre are in the range from 0.008 to 0.010 times the bottom-hole injection overpressure (8-10 kPam-1 assuming the net pressure of 1 MPa). Such large horizontal gradients in the order of the hydrostatic gradient could be caused by the inhomogeneous extraction of gas resulting in a lateral change of the effective normal stress acting normal to the fracture wall.

  19. Hydrologic connectivity responses to thermally-controlled changes in hydraulic gradients on Arctic hillslopes

    Rushlow, C. R.; Godsey, S.


    Active layer freeze and thaw exerts a first-order control on Arctic hillslope hydrology, and thus the weathering and transport of material within Arctic watersheds. We investigate how changes in active layer thaw depth over the summer warm season affect the storage and flux of water, especially in response to snowmelt and storm events. We focus our investigation on six water tracks -linear regions of preferential, but unchannelized flow- draining the hillslopes of the Upper Kuparuk River basin in northern Alaska. Water tracks form a slight topographic depression on the hillslope, and snow depth surveys from before spring snowmelt indicate that snow depths are deeper in the water tracks than on the surrounding hillslope. Thermocouples installed at ten intervals up to 35 cm below ground on the inside, edge and outside of each water track monitored ground temperatures as the active layer expanded throughout the summer. In general, the amplitude of diurnal temperature variability decreases with increasing depth, and the amplitude increases over the course of the season at all depths. Temperatures inside the water track have a muted diurnal cyclicity relative to the temperatures on the edge and outside the water track. Furthermore, surface soil moisture content inside the water tracks is consistently higher than outside. Both of these observations reflect that water moderates subsurface temperatures. Thaw depth surveys perpendicular to the water track show that over the course of the season, thaw depth becomes greater within the water track, increasing the hydraulic gradient from the surrounding hillslope to the water track. Thus, during annual late May snowmelt the surface topography is the main control on water flow paths, but as temperatures continue to warm, the topography of the active layer dominates. Thirty pressure transducers deployed in shallow groundwater wells along perpendicular transects of one water track measure changes in water table elevation during

  20. Sugarcane Tandem Mills Operation at Two Hydraulic Pressure Levels

    Jorge Michel Corrales-Suárez


    Full Text Available Among the areas with more energy consumption in a sugar factory is the tandem of mills. The applied hydraulic pressure on the superior mace is one of the variables that have influence on this energy consumption. Hydraulic pressures were decreased in a value that did not affect the extraction process efficiency to determine the possibilities of decreasing this energy consumption. The research was carried out in two sugar cane tandems of six mills. The pressures were only varied in the extraction mills in humid according to a statistical design of experiments in random blocks. The results were analyzed by means of the analysis of variance of double classification. The independent variables were the hydraulic pressures in the intermediate mills while the dependent variables were the % pol and % humidity of the final bagasse. The hydraulic pressures of the intermediate mills were reduced 3.45 MPa in the Tandem 1 and 2.07 MPa in the Tandem 2. It was demonstrated that under the conditions of the experiment, the employment of working hydraulic pressures smaller than the usually established ones for each tandem did not affect the extraction process of the sugar cane sucrose significantly, but decreased 11.75% the power demand on tandem 1 and 8.17% on tandem 2.

  1. Use of Plant Hydraulic Theory to Predict Ecosystem Fluxes Across Mountainous Gradients in Environmental Controls and Insect Disturbances

    Ewers, B. E.; Pendall, E.; Reed, D. E.; Barnard, H. R.; Whitehouse, F.; Frank, J. M.; Massman, W. J.; Brooks, P. D.; Biederman, J. A.; Harpold, A. A.; Naithani, K. J.; Mitra, B.; Mackay, D. S.; Norton, U.; Borkhuu, B.


    While mountainous areas are critical for providing numerous ecosystem benefits at the regional scale, the strong gradients in environmental controls make predictions difficult. A key part of the problem is quantifying and predicting the feedback between mountain gradients and plant function which then controls ecosystem cycling. The emerging theory of plant hydraulics provides a rigorous yet simple platform from which to generate testable hypotheses and predictions of ecosystem pools and fluxes. Plant hydraulic theory predicts that plant controls over carbon, water, energy and nutrient fluxes can be derived from the limitation of plant water transport from the soil through xylem and out of stomata. In addition, the limit to plant water transport can be predicted by combining plant structure (e.g. xylem diameters or root-to-shoot ratios) and plant function (response of stomatal conductance to vapor pressure deficit or root vulnerability to cavitation). We evaluate the predictions of the plant hydraulic theory by testing it against data from a mountain gradient encompassing sagebrush steppe through subalpine forests (2700 to 3400 m). We further test the theory by predicting the carbon, water and nutrient exchanges from several coniferous trees in the same gradient that are dying from xylem dysfunction caused by blue-stain fungi carried by bark beetles. The common theme of both of these data sets is a change in water limitation caused by either changing precipitation along the mountainous gradient or lack of access to soil water from xylem-occluding fungi. Across all of the data sets which range in scale from individual plants to hillslopes, the data fit the predictions of plant hydraulic theory. Namely, there was a proportional tradeoff between the reference canopy stomatal conductance to water vapor and the sensitivity of that conductance to vapor pressure deficit that quantitatively fits the predictions of plant hydraulic theory. Incorporating this result into

  2. Role of the vertical pressure gradient in wave boundary layers

    Jensen, Karsten Lindegård; Sumer, B. Mutlu; Vittori, Giovanna


    By direct numerical simulation (DNS) of the flow in an oscillatory boundary layer, it is possible to obtain the pressure field. From the latter, the vertical pressure gradient is determined. Turbulent spots are detected by a criterion involving the vertical pressure gradient. The vertical pressure...... gradient is also treated as any other turbulence quantity like velocity fluctuations and statistical properties of the vertical pressure gradient are calculated from the DNS data. The presence of a vertical pressure gradient in the near bed region has significant implications for sediment transport....

  3. Servo Controlled Variable Pressure Modification to Space Shuttle Hydraulic Pump

    Kouns, H. H.


    Engineering drawings show modifications made to the constant pressure control of the model AP27V-7 hydraulic pump to an electrically controlled variable pressure setting compensator. A hanger position indicator was included for continuously monitoring hanger angle. A simplex servo driver was furnished for controlling the pressure setting servovalve. Calibration of the rotary variable displacement transducer is described as well as pump performance and response characteristics.

  4. Thermal Hydraulic Integral Effect Tests for Pressurized Water Reactors

    Baek, W. P.; Song, C. H.; Kim, Y. S. and others


    The objectives of the project are to construct a thermal-hydraulic integral effect test facility and to perform various integral effect tests for design, operation, and safety regulation of pressurized water reactors. During the first phase of this project (1997.8{approx}2002.3), the basic technology for thermal-hydraulic integral effect tests was established and the basic design of the test facility was accomplished: a full-height, 1/300-volume-scaled full pressure facility for APR1400, an evolutionary pressurized water reactor that was developed by Korean industry. Main objectives of the present phase (2002.4{approx}2005.2), was to optimize the facility design and to construct the experimental facility. We have performed following researches: 1) Optimization of the basic design of the thermal-hydraulic integral effect test facility for PWRs - ATLAS (Advanced Thermal-hydraulic Test Loop for Accident Simulation) - Reduced height design for APR1400 (+ specific design features of KSNP safety injection systems) - Thermal-hydraulic scaling based on three-level scaling methodology by Ishii et al. 2) Construction of the ATLAS facility - Detailed design of the test facility - Manufacturing and procurement of components - Installation of the facility 3) Development of supporting technology for integral effect tests - Development and application of advanced instrumentation technology - Preliminary analysis of test scenarios - Development of experimental procedures - Establishment and implementation of QA system/procedure.

  5. Analysis and control of flows in pressurized hydraulic networks

    Gupta, R.K.


    Analysis, design and flow control problems in pressurized hydraulic networks such as water transmission and distribution systems consisting of pipes and other appurtenant components such as reservoirs, pumps, valves and surge devices are dealt with from the prospective of network synthesis aiming at

  6. Quantized pressure control in large-scale nonlinear hydraulic networks

    Persis, Claudio De; Kallesøe, Carsten Skovmose; Jensen, Tom Nørgaard


    It was shown previously that semi-global practical pressure regulation at designated points of a large-scale nonlinear hydraulic network is guaranteed by distributed proportional controllers. For a correct implementation of the control laws, each controller, which is located at these designated poin

  7. Analysis and control of flows in pressurized hydraulic networks

    Gupta, R.K.


    Analysis, design and flow control problems in pressurized hydraulic networks such as water transmission and distribution systems consisting of pipes and other appurtenant components such as reservoirs, pumps, valves and surge devices are dealt with from the prospective of network synthesis aiming at

  8. Hydraulic and biochemical gradients limit wetland mercury supply to an Adirondack stream

    Bradley, Paul M.; Burns, Douglas A.; Harvey, Judson; Journey, Celeste A.; Brigham, Mark E.; Murray, Karen


    Net fluxes (change between upstream and downstream margins) for water, methylmercury (MeHg), total mercury (THg), dissolved organic carbon (DOC), and chloride (Cl) were assessed twice in an Adirondack stream reach (Sixmile Brook, USA), to test the hypothesized importance of wetland-stream hydraulic and chemical gradients as fundamental controls on fluvial mercury (Hg) supply. The 500 m study reach represented less than 4% of total upstream basin area. During a snowmelt high-flow event in May 2009 surface water, DOC, and chloride fluxes increased by 7.1±1.3%, 8.0±1.3%, and 9.0±1.3%, respectively, within the reach, demonstrating that the adjacent wetlands are important sources of water and solutes to the stream. However, shallow groundwater Hg concentrations lower than in the surface water limited groundwater-surface water Hg exchange and no significant changes in Hg (filtered MeHg and THg) fluxes were observed within the reach despite the favorable hydraulic gradient. In August 2009, the lack of significant wetland-stream hydraulic gradient resulted in no net flux of water or solutes (MeHg, THg, DOC, or Cl) within the reach. The results are consistent with the wetland-Hg-source hypothesis and indicate that hydraulic and chemical gradient (direction and magnitude) interactions are fundamental controls on the supply of wetland Hg to the stream.

  9. Effects of shifting time on pressure impact in hydraulic systems

    ZHU Zhen-cai; CHEN Guo-an


    The limitations in existing measures for absorbing pressure impact in hydraulic systems were summarized in this paper. Based on the forming principle of the oil in a hydrostatic closed pressure chamber, the underlying reasons of the pressure impact were analyzed theoretically, the intrinsic laws that the extent of the pressure impact in hydraulic oil lines are affected by some factors, such as oil elastic modulus, oil line's geometrical volume, and changing rate of oil volume versus time etc, were discussed. Experimental investigations into pressure impact in all pressure chambers because of shifting were conducted under different working conditions by employing a special experimental system. The effects of shifting time on pressure impact were studied. A new concept with universal meaning, i.e. optimal shifting time, and its characterizing parameter and the methods of shifting at optimal shifting time were also proposed. The results show that shifting time lag △t is of rationality and maneuverablility. The higher the working pressure, the shorter the shifting time.

  10. Time-Varying Hydraulic Gradient Model of Paste-Like Tailings in Long-Distance Pipeline Transportation

    Li Yang


    Full Text Available Paste-like tailings slurry (PTLS is always simplified as a Bingham plastic fluid, leading to excessive computational errors in the calculation of the hydraulic gradient. In the case of paste-like tailings in long-distance pipeline transportation, to explore a high-precision and reliable hydraulic gradient formula, the rheological behavior of paste-like tailings slurry was analyzed, a time-varying hydraulic gradient model was constructed, and a series of laboratory shear tests were conducted. The results indicate that the PTLS shows noticeable shear-thinning characteristics in constant shear tests; the calculated hydraulic gradient declined by about 56%, from 4.44 MPa·km−1 to 1.95 MPa·km−1 within 253 s, and remained constant for the next four hours during the pipeline transportation. Comparing with the balance hydraulic gradient obtained in a semi-industrial loop test, the computational errors of those calculated by using the time-varying hydraulic gradient model, Jinchuan formula, and Shanxi formula are 15%, 78%, and 130%, respectively. Therefore, our model is a feasible and high-precision solution for the calculation of the hydraulic gradient of paste-like tailings in long-distance pipeline transportation.

  11. Hydraulic forces caused by annular pressure seals in centrifugal pumps

    Iino, T.; Kaneko, H.


    The hydraulic forces caused by annular pressure seals were investigated. The measured inlet and exit loss coefficients of the flow through the seals were much smaller than the conventional values. The results indicate that the damping coefficient and the inertia coefficient of the fluid film in the seal are not affected much by the rotational speed or the eccentricity of the rotor, though the stiffness coefficient seemed to be influenced by the eccentricity.

  12. Changes in entrapped gas content and hydraulic conductivity with pressure.

    Marinas, Maricris; Roy, James W; Smith, James E


    Water table fluctuations continuously introduce entrapped air bubbles into the otherwise saturated capillary fringe and groundwater zone, which reduces the effective (quasi-saturated) hydraulic conductivity, K(quasi), thus impacting groundwater flow, aquifer recharge and solute and contaminant transport. These entrapped gases will be susceptible to compression or expansion with changes in water pressure, as would be expected with water table (and barometric pressure) fluctuations. Here we undertake laboratory experiments using sand-packed columns to quantify the effect of water table changes of up to 250 cm on the entrapped gas content and the quasi-saturated hydraulic conductivity, and discuss our ability to account for these mechanisms in ground water models. Initial entrapped air contents ranged between 0.080 and 0.158, with a corresponding K(quasi) ranging between 2 and 6 times lower compared to the K(s) value. The application of 250 cm of water pressure caused an 18% to 26% reduction in the entrapped air content, resulting in an increase in K(quasi) by 1.16 to 1.57 times compared to its initial (0 cm water pressure) value. The change in entrapped air content measured at pressure step intervals of 50 cm, was essentially linear, and could be modeled according to the ideal gas law. Meanwhile, the changes in K(quasi) with compression-expansion of the bubbles because of pressure changes could be adequately captured with several current hydraulic conductivity models. © Ground Water 2012 and © Her Majesty the Queen in Right of Canada 2012. Ground Water © 2012, National Ground Water Association.

  13. Hydraulic High Pressure Valve Controller Using the In-Situ Pressure Difference

    Bao, Xiaoqi (Inventor); Sherrit, Stewart (Inventor); Badescu, Mircea (Inventor); Bar-Cohen, Yoseph (Inventor); Hall, Jeffery L. (Inventor)


    A hydraulic valve controller that uses an existing pressure differential as some or all of the power source for valve operation. In a high pressure environment, such as downhole in an oil or gas well, the pressure differential between the inside of a pipe and the outside of the pipe may be adequately large to drive a linear slide valve. The valve is operated hydraulically by a piston in a bore. When a higher pressure is applied to one end of the bore and a lower pressure to the other end, the piston moves in response to the pressure differential and drives a valve attached to it. If the pressure differential is too small to drive the piston at a sufficiently high speed, a pump is provided to generate a larger pressure differential to be applied. The apparatus is conveniently constructed using multiport valves, which can be rotary valves.

  14. Validation of NIS 500 MPa hydraulic pressure measurement

    Eltawil Alaaeldin A.


    Full Text Available 500 MPa pressure is considered as the common maximum pressure in most of the National Metrology Institutes worldwide; however, validation of the uncertainty in that range required a lot of work. NIS when recognized on, 2008 guaranteed big uncertainty value above 200 MPa due to the absence of international comparison at that time. This paper summarizes the results of a validation of 500 MPa range of hydraulic gauge pressure measurements carried out at NIS. The study covers the calibration through direct comparison and through using of a pressure sensor. The paper summarized the technical work carried out at the results of measurements and the effect of these results on NIS Calibration Measurements Capability. The validation also includes the comparison between the obtained results and pervious calibration of the same piston-cylinder assembly that calibrated against the NIST primary standard.

  15. Hazards and Safeguards of High Pressure Hydraulic Fatigue Testing


    rew e I&64aN neem mde tliF by block mumber) The creation and transfer of hydraulic pressure at the 690-MPa (100,000-psi) level is in itself hazardous...than alloy steel, we have found that it is more notch sensitive to fatigue and drastically degrades with small constituent variations. To avoid this...I ATTN: SMCWV-PP DIRECTOR, PRODUCT ASSURANCE DIRECTORATE 1 ATTN: SMCWV-QA NOTE: PLEASE NOTIFY DIRECTOR, BENET LABORATORIES, ATTN: SMCAR-CCB-TL, OF ANY

  16. Constraining key hydraulic parameters of Scots Pine through sapflow data assimilation along a climatic gradient

    Sus, O.; Martínez-Vilalta, J.; Poyatos, R.; Williams, M.


    In order to model the water balance of a forest ecosystem and predict its response to environmental changes, the response of tree transpiration to environmental conditions needs to be simulated. The plant hydraulic system can be conceptualised as a series of hydraulic resistances. The flow of water between any two locations of this system is proportional to the hydraulic conductivity and the water potential gradient linking them. The different components of the plant hydraulic system can change during drought as a result of varying stomatal conductance, xylem hydraulics and the regulation of leaf and root area. However, within this soil-plant-atmosphere continuum (SPAC), physical processes of water flow are better understood than plant hydraulics. For example, the effects of leaf microclimate on stomatal regulation of transpiration are not well understood. Moreover, little is known about how key hydraulic traits vary seasonally or as a function of environmental conditions. Within corresponding models, empirical parameters are introduced as surrogates for a range of complex and/or unknown mechanisms. Data assimilation (DA) methodology has shown to be a useful technique for model parameter estimation in various disciplines of the geosciences. However, few studies have applied DA to constrain parameter values within the SPAC in forest transpiration models. DA could prove to be particularly useful in quantifying these parameters, which are often not directly measurable. Sapflow data are highly appropriate for this purpose, as they are the measurable end-product of water transport through the SPAC in response to environmental conditions. Accordingly, these data provide temporally highly resolved, direct constraints on associated key parameters within models. In this study, we assimilated sapflow data from three different Scots Pine sites - following a climatic gradient from the southern dry limit of its distribution (southern Catalunya, Spain) up to the northern

  17. Hydraulics.

    Decker, Robert L.; Kirby, Klane

    This curriculum guide contains a course in hydraulics to train entry-level workers for automotive mechanics and other fields that utilize hydraulics. The module contains 14 instructional units that cover the following topics: (1) introduction to hydraulics; (2) fundamentals of hydraulics; (3) reservoirs; (4) lines, fittings, and couplers; (5)…

  18. Pressure Gradient Estimation Based on Ultrasonic Blood Flow Measurement

    Nitta, Naotaka; Homma, Kazuhiro; Shiina, Tsuyoshi


    Mechanical load to the blood vessel wall, such as shear stress and pressure, which occurs in blood flow dynamics, contribute greatly to plaque rupture in arteriosclerosis and to biochemical activation of endothelial cells. Therefore, noninvasive estimations of these mechanical loads are able to provide useful information for the prevention of vascular diseases. Although the pressure is the dominant component of mechanical load, for practical purposes, the pressure gradient is also often important. So far, we have investigated the estimation of the kinematic viscosity coefficient using a combination of the Navier-Stokes equations and ultrasonic velocity measurement. In this paper, a method for pressure gradient estimation using the estimated kinematic viscosity coefficient is proposed. The validity of the proposed method was investigated on the basis of the analysis with the data obtained by computer simulation and a flow phantom experiment. These results revealed that the proposed method can provide a valid estimation of the pressure gradient.

  19. Experimental Investigation on the Basic Law of Hydraulic Fracturing After Water Pressure Control Blasting

    Huang, Bingxiang; Li, Pengfeng; Ma, Jian; Chen, Shuliang


    Because of the advantages of integrating water pressure blasting and hydraulic fracturing, the use of hydraulic fracturing after water pressure control blasting is a method that is used to fully transform the structure of a coal-rock mass by increasing the number and range of hydraulic cracks. An experiment to study hydraulic fracturing after water pressure blasting on cement mortar samples (300 × 300 × 300 mm3) was conducted using a large-sized true triaxial hydraulic fracturing experimental system. A traditional hydraulic fracturing experiment was also performed for comparison. The experimental results show that water pressure blasting produces many blasting cracks, and follow-up hydraulic fracturing forces blasting cracks to propagate further and to form numerous multidirectional hydraulic cracks. Four macroscopic main hydraulic cracks in total were noted along the borehole axial and radial directions on the sample surfaces. Axial and radial main failure planes induced by macroscopic main hydraulic cracks split the sample into three big parts. Meanwhile, numerous local hydraulic cracks were formed on the main failure planes, in different directions and of different types. Local hydraulic cracks are mainly of three types: local hydraulic crack bands, local branched hydraulic cracks, and axial layered cracks. Because local hydraulic cracks produce multiple local layered failure planes and lamellar ruptures inside the sample, the integrity of the sample decreases greatly. The formation and propagation process of many multidirectional hydraulic cracks is affected by a combination of water pressure blasting, water pressure of fracturing, and the stress field of the surrounding rock. To a certain degree, the stress field of surrounding rock guides the formation and propagation process of the blasting crack and the follow-up hydraulic crack. Following hydraulic fracturing that has been conducted after water pressure blasting, the integrity of the sample is found to

  20. Groundwater Flow and Thermal Modeling to Support a Preferred Conceptual Model for the Large Hydraulic Gradient North of Yucca Mountain

    McGraw, D.; Oberlander, P.


    The purpose of this study is to report on the results of a preliminary modeling framework to investigate the causes of the large hydraulic gradient north of Yucca Mountain. This study builds on the Saturated Zone Site-Scale Flow and Transport Model (referenced herein as the Site-scale model (Zyvoloski, 2004a), which is a three-dimensional saturated zone model of the Yucca Mountain area. Groundwater flow was simulated under natural conditions. The model framework and grid design describe the geologic layering and the calibration parameters describe the hydrogeology. The Site-scale model is calibrated to hydraulic heads, fluid temperature, and groundwater flowpaths. One area of interest in the Site-scale model represents the large hydraulic gradient north of Yucca Mountain. Nearby water levels suggest over 200 meters of hydraulic head difference in less than 1,000 meters horizontal distance. Given the geologic conceptual models defined by various hydrogeologic reports (Faunt, 2000, 2001; Zyvoloski, 2004b), no definitive explanation has been found for the cause of the large hydraulic gradient. Luckey et al. (1996) presents several possible explanations for the large hydraulic gradient as provided below: The gradient is simply the result of flow through the upper volcanic confining unit, which is nearly 300 meters thick near the large gradient. The gradient represents a semi-perched system in which flow in the upper and lower aquifers is predominantly horizontal, whereas flow in the upper confining unit would be predominantly vertical. The gradient represents a drain down a buried fault from the volcanic aquifers to the lower Carbonate Aquifer. The gradient represents a spillway in which a fault marks the effective northern limit of the lower volcanic aquifer. The large gradient results from the presence at depth of the Eleana Formation, a part of the Paleozoic upper confining unit, which overlies the lower Carbonate Aquifer in much of the Death Valley region. The

  1. Non-invasive measurement of pressure gradients using ultrasound

    Olesen, Jacob Bjerring; Traberg, Marie Sand; Pihl, Michael Johannes


    A non-invasive method for estimating 2-D pressure gradients from ultrasound vector velocity data is presented. The method relies on in-plane vector velocity fields acquired using the Transverse Oscillation method. The pressure gradients are estimated by applying the Navier-Stokes equations...... Medical 2202 UltraView Pro Focus scanner. The results are validated through finite element simulations of the carotid flow model where the geometry is determined from MR images. This proof of concept study was conducted at nine ultrasound frames per second. Estimated pressure gradients along...... the longitudinal direction of the constriction varied from 0 kPa/m to 10 kPa/m with a normalized bias of -9.1% for the axial component and -7.9% for the lateral component. The relative standard deviation of the estimator, given in reference to the peak gradient, was 28.4% in the axial direction and 64...

  2. Scale analysis of turbulent channel flow with varying pressure gradient

    邱翔; 罗剑平; 黄永祥; 卢志明; 刘宇陆


    In this paper orthogonal wavelet transformations are applied to decompose experimental velocity signals in fully develo-ped channel flows with varying pressure gradient into scales. We analyze the time series from turbulent data, to obtain the statistical characteristics, correlations between the adjacent scales and the principal scale of coherent structures in different scales by wavelet transformations. The results show that, in the counter gradient transport (CGT) region, skewness factors and flatness factors deviate strongly from the corresponding values of Gaussian distribution on certain scales. PDFs on each scale confirm this observation. Scale-scale correlations show further that the fluctuations on some certain special scales are more intermittent than nearby. Principal scale of coherent structure is coincident with the scales on which the statistical properties depart from Gaussian distribution. These features are the same for different families of wavelets, and it also shows some different features in the region between favorable pressure gradient and adverse pressure gradient.

  3. Capture-zone design in an aquifer influenced by cyclic fluctuations in hydraulic gradients

    Zawadzki, Willy; Chorley, Don; Patrick, Guy


    Design of a groundwater pumping and treatment system for a wood-treatment facility adjacent to the tidally influenced Fraser River estuary required the development of methodologies to account for cyclic variations in hydraulic gradients. Design of such systems must consider the effects of these cyclic fluctuations on the capture of dissolved-phase contaminants. When the period of the cyclic fluctuation is much less than the travel time of the dissolved contaminant from the source to the discharge point, the hydraulic-gradient variations resulting from these cycles can be ignored. Capture zones are then designed based on the average hydraulic gradient determined using filter techniques on continuous groundwater-level measurements. When the period of cyclic fluctuation in hydraulic gradient is near to or greater than the contaminant travel time, the resulting hydraulic-gradient variations cannot be ignored. In these instances, procedures are developed to account for these fluctuations in the capture-zone design. These include proper characterization of the groundwater regime, assessment of the average travel time and period of the cyclic fluctuations, and numerical techniques which allow accounting for the cyclic fluctuations in the design of the capture zone. Résumé. L'étude d'un système de pompage et de traitement de l'eau souterraine d'une usine de traitement du bois proche de l'estuaire de la rivière Fraser, influencé par les marées, a nécessité la mise au point de méthodologies pour prendre en compte les variations cycliques de gradients hydrauliques. L'étude de tels systèmes doit considérer les effets de ces variations cycliques sur l'extraction des contaminants en phase dissoute. Lorsque la période des variations cycliques est très inférieure au temps de parcours du contaminant dissous entre la source et le point d'émergence, les variations du gradient hydraulique résultant de ces cycles peuvent être ignorées. Les zones d'extraction sont

  4. 46 CFR 128.240 - Hydraulic or pneumatic power and control-materials and pressure design.


    ... 46 Shipping 4 2010-10-01 2010-10-01 false Hydraulic or pneumatic power and control-materials and... Hydraulic or pneumatic power and control—materials and pressure design. (a) Each standard piping component (such as pipe runs, fittings, flanges, and standard valves) for hydraulic or pneumatic power and...

  5. Vertical pressure gradient and particle motions in wave boundary layers

    Jensen, Karsten Lindegård

    The present study covers both a numerical and experimental investigation of the processes in the oscillatory boundary layer. In the first part a direct numerical simulation (DNS) is conducted to study the vertical pressure gradient, and its role in relation to laminar to turbulent transition...... and its role in the fully turbulent boundary layer. The pressure in the flow is obtained from the flow fields of the oscillatory boundary layer. What differs, the vertical pressure gradient, from other turbulent quantities, like e.g. velocity fluctuations is that it can detect newly generated turbulence....... This is in contrast to velocity fluctuations that are diffusive, so they can also contain residual turbulence from the previous half cycle until they are dissipated. Furthermore, the magnitude of the mean value of conditionally averaged vertical pressure gradient (for −∂p∗/∂x∗ 2 > 0) is compared to the submerged...

  6. HydrogeoEstimatorXL: an Excel-based tool for estimating hydraulic gradient magnitude and direction

    Devlin, J. F.; Schillig, P. C.


    HydrogeoEstimatorXL is a free software tool for the interpretation of flow systems based on spatial hydrogeological field data from multi-well networks. It runs on the familiar Excel spreadsheet platform. The program accepts well location coordinates and hydraulic head data, and returns an analysis of the area flow system in two dimensions based on (1) a single best fit plane of the potentiometric surface and (2) three-point estimators, i.e., well triplets assumed to bound planar sections of the potentiometric surface. The software produces graphical outputs including histograms of hydraulic gradient magnitude and direction, groundwater velocity (based on a site average hydraulic properties), as well as mapped renditions of the estimator triangles and the velocity vectors associated with them. Within the software, a transect can be defined and the mass discharge of a groundwater contaminant crossing the transect can be estimated. This kind of analysis is helpful in gaining an overview of a site's hydrogeology, for problem definition, and as a review tool to check the reasonableness of other independent calculations.

  7. Redshift drift in a pressure gradient cosmology

    Balcerzak, Adam


    We derive the redshift drift formula for the inhomogeneous pressure spherically symmetric Stephani universes which are complementary to inhomogeneous density Lema\\^itre-Tolman-Bondi (LTB) models. We show that there is a clear difference between the redshift drift predictions for these two models. The Stephani models have positive drift values at small redshift and behave qualitatively as the $\\Lambda$CDM models while the drift for LTB models is always negative. This prediction can be tested in future space experiments such as E-ELT, TMT, GMT or CODEX.

  8. Analysis of an controller design for an electro-hydraulic servo pressure regulator

    Pedersen, Henrik C.; Andersen, Torben Ole; Madsen, A. M.;


    of the existing hydraulic components there are, however, still a need for being able to generate a hydraulic pilot pressure, as e.g. almost all open-circuit pumps are hydraulically controlled. The focus of the current paper is therefore on the analysis and controller design an electro-hydraulic servo pressure...... regulator, which generates a hydraulic LS-pressure based on an electrical reference, hereby synergistically integrating knowledge from all parts of the mechatronics area. The servo pressure regulator is used to generate the LS-signal for a variable displacement pump, and the paper rst presents...... to generate a controlled leakage  ow that aids in stabilising the system. The robustness of the system is then discussed in relation to dierent pilot line volumes and pump dynamics. Finally experimental results are presented, where the performance is compared to that of a similar hydraulic reference system...

  9. Time-dependent water permeation behavior of concrete under constant hydraulic pressure

    Fang Yonghao; Wang Zhongli; Zhou Yue


    In the present work, a concrete permeability testing setup was designed to study the behavior of hydraulic concrete subjected to constant hydraulic pressure. The results show that when concrete is subjected to high enough constant hydraulic pressure, it will be permeated, and after it reaches its maximum permeation rate, the permeability coefficient will gradually decrease towards a stable value. A time-dependent model of permeability coefficient for concrete subjected to hydraulic pressure is proposed. It is indicated that the decrease of the permeability coefficient with permeation time conforms well to the negative-exponential decrease model.

  10. Nonparallel stability of boundary layers with pressure gradients and suction

    Saric, W. S.; Nayfeh, A. H.


    An analysis is presented for the linear nonparallel stability of boundary layer flows with pressure gradients and suction. The effect of the boundary layer growth is included by using the method of multiple scales. The present analysis is compared with those of Bouthier and Gaster and the roles of the different definitions of the amplification rates are discussed. The results of these theories are compared with experimental data for the Blasius boundary layer. Calculations are presented for stability characteristics of boundary layers with pressure gradients and nonsimilar suction distributions.

  11. Safety estimation of high-pressure hydraulic cylinder using FSI method

    KIM J.H.; HAN S.M.; KIM Y.J.


    Hydraulic cylinder is a primary component of the hydraulic valve systems.The numerical study of hydraulic cylinder to evaluate the stress analysis,the life assessment and the performance of operation characteristics in hydraulic cylinder were described.The calculation of safety factor,fatigue life,piston chamber pressure,rod chamber pressure and the change of velocity of piston with flow time after the beginning of hydraulic cylinder were incorporated.Numerical analysis was performed using the commercial CFD code,ANSYS with unsteady,dynamic mesh model,two-way FSI (fluid-struc-ture interaction)method and k-εturbulent model.The internal pressure in hydraulic cylinder through stress analysis show higher than those of the yield strength.

  12. Luminescence from cavitation bubbles deformed in uniform pressure gradients

    Supponen, Outi; Obreschkow, Danail; Kobel, Philippe; Farhat, Mohamed


    Presented here are observations that demonstrate how the deformation of millimetric cavitation bubbles by a uniform pressure gradient quenches single collapse luminescence. Our innovative measurement system captures a broad luminescence spectrum (wavelength range 300-900 nm) from the individual collapses of laser-induced bubbles in water. By varying the bubble size, driving pressure and the perceived gravity level aboard parabolic flights, we probed the limit from aspherical to highly spheric...

  13. Physically-based approach to analyze rainfall-triggered landslide using hydraulic gradient as slide direction

    Qi-hua RAN; Dan-yang SU; Qun QIAN; Xu-dong FU; Guang-qian WANG; Zhi-guo HE


    An infinite slope stability numerical model driven by the comprehensive physically-based integrated hydrology model (InHM) is presented.In this approach,the failure plane is assumed to be parallel to the hydraulic gradient instead of the slope surface.The method helps with irregularities in complex terrain since depressions and flat areas are allowed in the model.The present model has been tested for two synthetic single slopes and a small catchment in the Mettman Ridge study area in Oregon,United States,to estimate the shallow landslide susceptibility.The results show that the present approach can reduce the simulation error of hydrological factors caused by the rolling topography and depressions,and is capable of estimating spatial-temporal variations for landslide susceptibilities at simple slopes as well as at catchment scale,providing a valuable tool for the prediction of shallow landslides.

  14. Integrating hydraulic conductivity with biogeochemical gradients and microbial activity along river-groundwater exchange zones in a subtropical stream

    Claret, Cécile; Boulton, Andrew J.


    The pervious lateral bars (parafluvial zone) and beds (hyporheic zone), where stream water and groundwater exchange, are dynamic sites of hydrological and biological retention. The significance of these biogeochemical ‘hotspots’ to stream and groundwater metabolism is largely controlled by filtration capacity, defined as the extent to which subsurface flowpaths and matrix hydraulic conductivity modify water characteristics. Where hydraulic conductivity is high, gradients in biogeochemistry and microbial activity along subsurface flowpaths were hypothesized to be less marked than where hydraulic conductivity is low. This hypothesis was tested in two riffles and gravel bars in an Australian subtropical stream. At one site, gradients in chemical and microbial variables along flowpaths were associated with reduced hydraulic conductivity, longer water residence time and reduced filtration capacity compared with the second site where filtration capacity was greater and longitudinal biogeochemical trends were dampened. These results imply that factors affecting the sediment matrix in this subtropical stream can alter filtration capacity, interstitial microbial activity and biogeochemical gradients along subsurface flowpaths. This hydroecological approach also indicates potential for a simple field technique to estimate filtration capacity and predict the prevailing hyporheic gradients in microbial activity and biogeochemical processing efficiency, with significant implications for stream ecosystem function.

  15. Failure Mode of the Water-filled Fractures under Hydraulic Pressure in Karst Tunnels

    Dong, Xin; Lu, Hao; Huang, Houxu; Hao, Yiqing; Xia, Yuanpu


    Water-filled fractures continue to grow after the excavation of karst tunnels, and the hydraulic pressure in these fractures changes along with such growth. This paper simplifies the fractures in the surrounding rock as flat ellipses and then identifies the critical hydraulic pressure values required for the occurrence of tensile-shear and compression-shear failures in water-filled fractures in the case of plane stress. The occurrence of tensile-shear fracture requires a larger critical hydraulic pressure than compression-shear failure in the same fracture. This paper examines the effects of fracture strike and lateral pressure coefficient on critical hydraulic pressure, and identifies compression-shear failure as the main failure mode of water-filled fractures. This paper also analyses the hydraulic pressure distribution in fractures with different extensions, and reveals that hydraulic pressure decreases along with the continuous growth of fractures and cannot completely fill a newly formed fracture with water. Fracture growth may be interrupted under the effect of hydraulic tensile shear.

  16. Failure Mode of the Water-filled Fractures under Hydraulic Pressure in Karst Tunnels

    Dong Xin


    Full Text Available Water-filled fractures continue to grow after the excavation of karst tunnels, and the hydraulic pressure in these fractures changes along with such growth. This paper simplifies the fractures in the surrounding rock as flat ellipses and then identifies the critical hydraulic pressure values required for the occurrence of tensile-shear and compression-shear failures in water-filled fractures in the case of plane stress. The occurrence of tensile-shear fracture requires a larger critical hydraulic pressure than compression-shear failure in the same fracture. This paper examines the effects of fracture strike and lateral pressure coefficient on critical hydraulic pressure, and identifies compression-shear failure as the main failure mode of water-filled fractures. This paper also analyses the hydraulic pressure distribution in fractures with different extensions, and reveals that hydraulic pressure decreases along with the continuous growth of fractures and cannot completely fill a newly formed fracture with water. Fracture growth may be interrupted under the effect of hydraulic tensile shear.

  17. Analysis of and H∞ Controller Design For An Electro-Hydraulic Servo Pressure Regulator

    Stubkier, Søren; Pedersen, Henrik C.; Andersen, Torben Ole;


    -circuit pumps are still hydraulically controlled, there is however still a need for being able to generate a hydraulic pilot pressure. The focus of the current paper is on the analysis and controller design of an electrohydraulic servo pressure regulator, which generates a hydraulic LS-pressure for a variable......Currently mobile hydraulics is in a transition phase, where electronic sensors and digital signal processors are becoming standard on a high number of machines, hereby replacing hydraulic pilot lines and offering new possibilities with regard to both control and feasibility. As most open...... displacement pump based on an electrical reference. The paper first presents the considered system and an experimentally verified model of this. A linearized model and a stability analysis is then presented, based on which an H∞control strategy is selected. A nominal performance and a robustly stable...

  18. Analysis of and H∞ Controller Design For An Electro-Hydraulic Servo Pressure Regulator

    Stubkier, Søren; Pedersen, Henrik C.; Andersen, Torben Ole


    -circuit pumps are still hydraulically controlled, there is however still a need for being able to generate a hydraulic pilot pressure. The focus of the current paper is on the analysis and controller design of an electrohydraulic servo pressure regulator, which generates a hydraulic LS-pressure for a variable...... displacement pump based on an electrical reference. The paper first presents the considered system and an experimentally verified model of this. A linearized model and a stability analysis is then presented, based on which an H∞control strategy is selected. A nominal performance and a robustly stable...

  19. Pressure-gradient-induced Alfven eigenmodes: 2. Kinetic excitation with ion temperature gradient

    Bierwage, Andreas; Zonca, Fulvio


    The kinetic excitation of ideal magnetohydrodynamic (MHD) discrete Alfven eigenmodes in the second MHD ballooning stable domain is studied in the presence of a thermal ion temperature gradient (ITG), using linear gyrokinetic particle-in-cell simulations of a local flux tube in shifted-circle tokamak geometry. The instabilities are identified as alpha-induced toroidal Alfven eigenmodes (alphaTAE); that is, bound states trapped between pressure-gradient-induced potential barriers of the Schroedinger equation for shear Alfven waves. Using numerical tools, we examine in detail the effect of kinetic thermal ion compression on alphaTAEs; both non-resonant coupling to ion sound waves and wave-particle resonances. It is shown that the Alfvenic ITG instability thresholds (e.g., the critical temperature gradient) are determined by two resonant absorption mechanisms: Landau damping and continuum damping. The numerical results are interpreted on the basis of a theoretical framework previously derived from a variational f...

  20. Study of the starting pressure gradient in branching network


    In order to increase the production of oil in low permeability reservoirs with high efficiency,it is necessary to fully understand the properties and special behaviors of the reservoirs and correctly describe the flow in the reservoirs.This paper applies the branching network mode to the study of the starting pressure gradient of nonlinear Newtonian fluid (Bingham fluid) in the reservoirs with low permeability based on the fact that the fractured network may exist in the reservoirs.The proposed model for starting pressure gradient is a function of yield stress,microstructural parameters of the network.The proposed model may have the potential in further exploiting the mechanisms of flow in porous media with fractured network.


    Hennadii Zaionchkovskyi


    Full Text Available In aviation hydraulic drive of high power as a power supply the axial-piston variable displacement pumps became wide spreaded. The pump operational modes with air isolation and cavitation are accompanied by increased noise, delivery reduction and intensive pressure oscillations. The negative results of such phenomena are hydraulic elements erosion, pipeline fatigue failure, working fluid viscosity reduction and its contamination by wear products. The mechanism of cavitation rising in axial-piston pumps is considered, and factors which influence the cavitation rising and working fluid aeration are specified. The features of transient processes in aircraft hydraulic systems with variable displacement pumps are considered. It has been showed that as the pump delivery changes from its minimum to maximum great pressure oscillations in the aircraft pressure pipeline of the hydraulic system takes place, and have a negative influence on the pump service life. The recommendations concerning such pressure oscillation reduction are given.

  2. Interstitial hydraulic conductivity and interstitial fluid pressure for avascular or poorly vascularized tumors.

    Liu, L J; Schlesinger, M


    A correct description of the hydraulic conductivity is essential for determining the actual tumor interstitial fluid pressure (TIFP) distribution. Traditionally, it has been assumed that the hydraulic conductivities both in a tumor and normal tissue are constant, and that a tumor has a much larger interstitial hydraulic conductivity than normal tissue. The abrupt transition of the hydraulic conductivity at the tumor surface leads to non-physical results (the hydraulic conductivity and the slope of the TIFP are not continuous at tumor surface). For the sake of simplicity and the need to represent reality, we focus our analysis on avascular or poorly vascularized tumors, which have a necrosis that is mostly in the center and vascularization that is mostly on the periphery. We suggest that there is an intermediary region between the tumor surface and normal tissue. Through this region, the interstitium (including the structure and composition of solid components and interstitial fluid) transitions from tumor to normal tissue. This process also causes the hydraulic conductivity to do the same. We introduce a continuous variation of the hydraulic conductivity, and show that the interstitial hydraulic conductivity in the intermediary region should be monotonically increasing up to the value of hydraulic conductivity in the normal tissue in order for the model to correspond to the actual TIFP distribution. The value of the hydraulic conductivity at the tumor surface should be the lowest in value.

  3. Design and Analysis of High Pressure Hydraulic Filter for Marine Application

    Momin, Toshin; Chandrasekar, RP; Balasubramanian, S.; Junaid Basha, AM, Dr.


    Filter is a critical component in ahydraulic system for maintaining the cleanliness of the fluid to required class level. InMarine applications very high reliable filter is required to operate continuously in saline environment. Design anddevelopment of high pressure hydraulic filter for Marine application is a challenging task. The design involves selection of special materialsandstringent qualification tests as per International standards. The present paper describes various stages of design and development of high pressure hydraulic filter for Marine application.

  4. Tree shoot bending generates hydraulic pressure pulses: a new long-distance signal?

    Lopez, Rosana; Badel, Eric; Peraudeau, Sebastien; Leblanc-Fournier, Nathalie; Beaujard, François; Julien, Jean-Louis; Cochard, Hervé; Moulia, Bruno


    When tree stems are mechanically stimulated, a rapid long-distance signal is induced that slows down primary growth. An investigation was carried out to determine whether the signal might be borne by a mechanically induced pressure pulse in the xylem. Coupling xylem flow meters and pressure sensors with a mechanical testing device, the hydraulic effects of mechanical deformation of tree stem and branches were measured. Organs of several tree species were studied, including gymnosperms and angiosperms with different wood densities and anatomies. Bending had a negligible effect on xylem conductivity, even when deformations were sustained or were larger than would be encountered in nature. It was found that bending caused transient variation in the hydraulic pressure within the xylem of branch segments. This local transient increase in pressure in the xylem was rapidly propagated along the vascular system in planta to the upper and lower regions of the stem. It was shown that this hydraulic pulse originates from the apoplast. Water that was mobilized in the hydraulic pulses came from the saturated porous material of the conduits and their walls, suggesting that the poroelastic behaviour of xylem might be a key factor. Although likely to be a generic mechanical response, quantitative differences in the hydraulic pulse were found in different species, possibly related to differences in xylem anatomy. Importantly the hydraulic pulse was proportional to the strained volume, similar to known thigmomorphogenetic responses. It is hypothesized that the hydraulic pulse may be the signal that rapidly transmits mechanobiological information to leaves, roots, and apices.

  5. Novel wave power analysis linking pressure-flow waves, wave potential, and the forward and backward components of hydraulic power.

    Mynard, Jonathan P; Smolich, Joseph J


    Wave intensity analysis provides detailed insights into factors influencing hemodynamics. However, wave intensity is not a conserved quantity, so it is sensitive to diameter variations and is not distributed among branches of a junction. Moreover, the fundamental relation between waves and hydraulic power is unclear. We, therefore, propose an alternative to wave intensity called "wave power," calculated via incremental changes in pressure and flow (dPdQ) and a novel time-domain separation of hydraulic pressure power and kinetic power into forward and backward wave-related components (ΠP±and ΠQ±). Wave power has several useful properties:1) it is obtained directly from flow measurements, without requiring further calculation of velocity;2) it is a quasi-conserved quantity that may be used to study the relative distribution of waves at junctions; and3) it has the units of power (Watts). We also uncover a simple relationship between wave power and changes in ΠP±and show that wave reflection reduces transmitted power. Absolute values of ΠP±represent wave potential, a recently introduced concept that unifies steady and pulsatile aspects of hemodynamics. We show that wave potential represents the hydraulic energy potential stored in a compliant pressurized vessel, with spatial gradients producing waves that transfer this energy. These techniques and principles are verified numerically and also experimentally with pressure/flow measurements in all branches of a central bifurcation in sheep, under a wide range of hemodynamic conditions. The proposed "wave power analysis," encompassing wave power, wave potential, and wave separation of hydraulic power provides a potent time-domain approach for analyzing hemodynamics.



    The pressure gradient of the lithosphere is a key to explaining various geological processes, and varies also in time and space similar to the geothermal gradient. In this paper a correlation formula of geothermal gradients and pressure gradients was built with the thermocomprestion coefficients. Based on this formula, the article has studied the relation between the pressure gradients and the geothermal gradients in the lithosphere, and the results indicate that the pressure gradient in the lithosphere is nonlinear, and its minimum value is the lithostatic gradient, and that the pressure gradient of the lithosphere will increase obviously with the contribution of both geothermal and gravity, and could be twice times more than the lithostatic gradient.

  7. Measuring the initial earth pressure of granite using hydraulic fracturing test; Goseong and Yuseong areas

    Park, Byoung Yoon; Bae, Dae Seok; Kim, Chun Soo; Kim, Kyung Su; Koh, Young Kwon; Won, Kyung Sik [Korea Atomic Energy Research Institute, Taejeon (Korea)


    This report provides the initial earth pressure of granitic rocks obtained from Deep Core Drilling Program which is carried out as part of the assessment of deep geological environmental condition. These data are obtained by hydraulic fracturing test in three boreholes drilled up to 350{approx}500 m depth at the Yuseong and Goseong sites. These sites were selected based on the result of preliminary site evaluation study. The boreholes are NX-size (76 mm) and vertical. The procedure of hydraulic fracturing test is as follows: - Selecting the testing positions by preliminary investigation using BHTV logging. - Performing the hydraulic fracturing test at each selected position with depth.- Estimating the shut-in pressure by the bilinear pressure-decay-rate method. - Estimating the fracture reopening pressure from the pressure-time curves.- Estimating the horizontal principal stresses and the direction of principal stresses. 65 refs., 39 figs., 12 tabs. (Author)

  8. Analysis on the Pressure Fluctuation Law of a Hydraulic Exciting System with a Wave-exciter

    WEI Xiu-ye; KOU Zi-ming; LU Zi-rong


    A hydraulic exciting system with a wave exciter has been constructed in order to study the hydraulic vibra- tion law. The system consists of an oil source, wave-exciter and oil cylinder, and is controlled by a wave-exciter. The working principle of the hydraulic exciting system and wave exciter has been analyzed, and its excitation process has been illustrated. The law of every pipe's pressure fluctuation of the system is obtained by experiment. The theo- retical analysis and experimental data prove that the pipeline pressure periodically changes and the pipeline pressure fluctuation frequency is independently controlled by the excitation frequency of the wave-exciter. Every pipelinc's pressure wave is produced by system flow fluctuation and water hammer coupling. The pressure fluctuation rules of the system provide a theoretical basis for the study of the associated liberation system.

  9. Pressure regulation in nonlinear hydraulic networks by positive controls

    De Persis, Claudio; Skovmose Kallesøe, Carsten


    We report on our investigation of an industrial case study of a system distributed over a network, namely a large-scale hydraulic network which underlies a district heating system. The network comprises an arbitrarily large number of end-users and actuators distributed along the network. After intro

  10. Ice Particles Trapped by Temperature Gradients at mbar Pressure

    Kelling, Thorben; Dürmann, Christoph


    In laboratory experiments we observe that ice particles (\\leq100 \\mu m) entrained in a low pressure atmosphere (~1 mbar) get trapped by temperature gradients between three reservoirs at different tempertature. Confining elements are a peltier element at 250 K (bottom), a liquid nitrogen reservoir at 77 K (top) and the surrounding vacuum chamber at 293 K. Particle levitation and trapping is modeled by an interplay of thermophoresis, photophoresis and gravity. A number of ice particles are trapped simultaneously in close spatial distance to each other at least up to minutes and are accessible for further experiments.



    A method of setting up a pressure-stroke characteristic of the working liquid in hydraulic drawing is studied. A pressure-stroke characteristic and software for controlling its forming process are also developed. And a set of pressure controlling devices with PLC as a central processor are designed. It can be got from the relevant experiments that the pressure-stroke characteristic is correct and its control for forming process is available.

  12. Investigation of pressure gradient aware wall modeling in LES

    Thiry, Olivier; Winckelmans, Gregoire; Duponcheel, Matthieu


    This work focuses on the investigation of various wall modeling strategies for the simulation of high Reynolds number wall-bounded turbulent flows with acceleration and/or deceleration. Our code is based on fourth order finite differences, is momentum conserving, and is energy conserving up to fourth order. We here use a ``channel flow'' set-up, with no slip and wall modeling at the bottom, with slip at the top, and with blowing and/or suction at the top in order to generate the desired acceleration-deceleration profile. Two strategies are investigated and compared. Pressure gradient corrected algebraic models are first considered, and we investigate various local averaging techniques so as to avoid imposing mean profile laws pointwise. RANS sub-layer models are then also considered, where the turbulent viscosity is corrected to account for pressure gradient effects and for resolved LES fluctuations effects. A wall-resolved LES was also performed to provide a reference solution. Research fellow (Ph.D. student) at the F.R.S. - FNRS (Belgium).

  13. Influences of hydraulic gradient, surface roughness, intersecting angle, and scale effect on nonlinear flow behavior at single fracture intersections

    Li, Bo; Liu, Richeng; Jiang, Yujing


    Fluid flow tests were conducted on two crossed fracture models for which the geometries of fracture segments and intersections were measured by utilizing a visualization technique using a CCD (charged coupled device) camera. Numerical simulations by solving the Navier-Stokes equations were performed to characterize the fluid flow at fracture intersections. The roles of hydraulic gradient, surface roughness, intersecting angle, and scale effect in the nonlinear fluid flow behavior through single fracture intersections were investigated. The simulation results of flow rate agreed well with the experimental results for both models. The experimental and simulation results showed that with the increment of the hydraulic gradient, the ratio of the flow rate to the hydraulic gradient, Q/J, decreases and the relative difference of Q/J between the calculation results employing the Navier-Stokes equations and the cubic law, δ, increases. When taking into account the fracture surface roughness quantified by Z2 ranging 0-0.42 for J = 1, the value of δ would increase by 0-10.3%. The influences of the intersecting angle on the normalized flow rate that represents the ratio of the flow rate in a segment to the total flow rate, Ra, and the ratio of the hydraulic aperture to the mechanical aperture, e/E, are negligible when J 10-2. Based on the regression analysis on simulation results, a mathematical expression was proposed to quantify e/E, involving variables of J and Rr, where Rr is the radius of truncating circles centered at an intersection. For E/Rr > 10-2, e/E varies significantly and the scale of model has large impacts on the nonlinear flow behavior through intersections, while for E/Rr < 10-3, the scale effect is negligibly small. Finally, a necessary condition to apply the cubic law to fluid flow through fracture intersections is suggested as J < 10-3, E/Rr < 10-3, and Z2 = 0.

  14. Numerical and experimental study of low-frequency pressure pulsations in hydraulic units with Francis turbine

    Platonov, D.; Minakov, A.; Dekterev, D.; Sentyabov, A.; Dekterev, A.


    The paper presents the numerical simulation method of three-dimensional turbulent flows in the hydraulic turbine. This technique was verified by means of experimental data obtained on a water model of the Francis turbines. An aerodynamic stand, which is a miniature copy of the real hydraulic turbine, was designed. A series of experiments have been carried out on this stand and the corresponding calculations were performed. The dependence of the velocity and pressure pulsations profiles for different operation regimes are presented.

  15. Hydraulic Pressure during Fluid Flow Regulates Purinergic Signaling and Cytoskeleton Organization of Osteoblasts.

    Gardinier, Joseph D; Gangadharan, Vimal; Wang, Liyun; Duncan, Randall L


    During physiological activities, osteoblasts experience a variety of mechanical forces that stimulate anabolic responses at the cellular level necessary for the formation of new bone. Previous studies have primarily investigated the osteoblastic response to individual forms of mechanical stimuli. However in this study, we evaluated the response of osteoblasts to two simultaneous, but independently controlled stimuli; fluid flow-induced shear stress (FSS) and static or cyclic hydrostatic pressure (SHP or CHP, respectively). MC3T3-E1 osteoblasts-like cells were subjected to 12dyn/cm(2) FSS along with SHP or CHP of varying magnitudes to determine if pressure enhances the anabolic response of osteoblasts during FSS. For both SHP and CHP, the magnitude of hydraulic pressure that induced the greatest release of ATP during FSS was 15 mmHg. Increasing the hydraulic pressure to 50 mmHg or 100 mmHg during FSS attenuated the ATP release compared to 15 mmHg during FSS. Decreasing the magnitude of pressure during FSS to atmospheric pressure reduced ATP release to that of basal ATP release from static cells and inhibited actin reorganization into stress fibers that normally occurred during FSS with 15 mmHg of pressure. In contrast, translocation of nuclear factor kappa B (NFκB) to the nucleus was independent of the magnitude of hydraulic pressure and was found to be mediated through the activation of phospholipase-C (PLC), but not src kinase. In conclusion, hydraulic pressure during FSS was found to regulate purinergic signaling and actin cytoskeleton reorganization in the osteoblasts in a biphasic manner, while FSS alone appeared to stimulate NFκB translocation. Understanding the effects of hydraulic pressure on the anabolic responses of osteoblasts during FSS may provide much needed insights into the physiologic effects of coupled mechanical stimuli on osteogenesis.

  16. Hydraulic gradient and dust emissivity along a playa to distal fan transect

    Caldwell, T. G.; Sweeney, M.; Bacon, S. N.; McDonald, E.


    Distal alluvial fans along the margins of playas in the desert southwest, as well as the playas themselves, are subjected to severe temporal changes in groundwater levels. Soil moisture decreases with elevation above the playa floor where groundwater levels control both soil moisture and salinity. A series of measurements were conducted along transects of a wet playa (Soda Lake, California) and a dry playa (Silver Lake; California) to quantify changes in PM10) emissions, in addition to soil physical and chemical properties. The relatively high moisture content at the playa surface of Soda Lake is controlled by a perennial shallow ground water system that promotes the precipitation and wicking of evaporates and the formation of soluble salt crusts. In contrast, Silver Lake playa is underlain by a deep ground water system, therefore the playa surface remains dry throughout the year, except for unseasonably wet winters when flooding occurs of the playa surface during inundation events. Measurements were taken along linear transects across a diverse range of playa features ranging from the playa floor to distal fans using the Portable In-Situ Wind Erosion Lab (PI-SWERL), electromagnetic induction, and soil sampling. Results indicate that dust emissivity of undisturbed soils at a friction velocity (u*) of 0.56 m s-1 increases substantially at the playa fringe (3.53 ± 1.44 mg m-2 s-1) compared to the relatively higher distal alluvial fans (0.13 ± 0.08 mg m-2 s-1) and lower emission on the playa surfaces of either the silt crust of Silver Lake playa (fans. The area between these landforms, the silt-rich playa fringe, is subjected to transient groundwater and surface water influx resulting in monovalent bicarbonate (HCO3-) salts which disperse clays and creates an area of high emissivity. As distance to groundwater increases, the hydraulic gradient shifts from the upward evaporation of saline groundwater to downward flushing by dilute precipitation. This shift results in



    Based on an improvement of the Karman-Pohlhausen's method, using nonlinear polynomial fitting and numerical integral, the axial distributions of pressure and its gradient in an axisymmetric rigid vessel with stenosis were obtained, and the distributions related to Reynolds number and the geometry of stenotic vessel were discussed. It shows that with the increasing of stenotic degree or Reynolds number, the fluctuation of pressure and its gradient in stenotic area is intense rapidly, and negative pressure occurs subsequently in the diverging part of stenotic area. Especially when the axial range of stenosis extends, the flow of blood in the diverging part will be more obviously changed.In higher Reynolds number or heavy stenosis, theoretical calculation is mainly in accordance with past experiments.

  18. High Pressure, High Gradient RF Cavities for Muon Beam Cooling

    Johnson, R P


    High intensity, low emittance muon beams are needed for new applications such as muon colliders and neutrino factories based on muon storage rings. Ionization cooling, where muon energy is lost in a low-Z absorber and only the longitudinal component is regenerated using RF cavities, is presently the only known cooling technique that is fast enough to be effective in the short muon lifetime. RF cavities filled with high-pressure hydrogen gas bring two advantages to the ionization technique: the energy absorption and energy regeneration happen simultaneously rather than sequentially, and higher RF gradients and better cavity breakdown behavior are possible than in vacuum due to the Paschen effect. These advantages and some disadvantages and risks will be discussed along with a description of the present and desired RF R&D efforts needed to make accelerators and colliders based on muon beams less futuristic.

  19. Characterizing developing adverse pressure gradient flows subject to surface roughness

    Brzek, Brian; Chao, Donald; Turan, Özden; Castillo, Luciano


    An experimental study was conducted to examine the effects of surface roughness and adverse pressure gradient (APG) on the development of a turbulent boundary layer. Hot-wire anemometry measurements were carried out using single and X-wire probes in all regions of a developing APG flow in an open return wind tunnel test section. The same experimental conditions (i.e., T ∞, U ref, and C p) were maintained for smooth, k + = 0, and rough, k + = 41-60, surfaces with Reynolds number based on momentum thickness, 3,000 carefully designed such that the x-dependence in the flow field was known. Despite this fact, only a very small region of the boundary layer showed a balance of the various terms in the integrated boundary layer equation. The skin friction computed from this technique showed up to a 58% increase due to the surface roughness. Various equilibrium parameters were studied and the effect of roughness was investigated. The generated flow was not in equilibrium according to the Clauser (J Aero Sci 21:91-108, 1954) definition due to its developing nature. After a development region, the flow reached the equilibrium condition as defined by Castillo and George (2001), where Λ = const, is the pressure gradient parameter. Moreover, it was found that this equilibrium condition can be used to classify developing APG flows. Furthermore, the Zagarola and Smits (J Fluid Mech 373:33-79, 1998a) scaling of the mean velocity deficit, U ∞δ*/δ, can also be used as a criteria to classify developing APG flows which supports the equilibrium condition of Castillo and George (2001). With this information a ‘full APG region’ was defined.

  20. Pore pressure migration during hydraulic stimulation due to permeability enhancement by low-pressure subcritical fracture slip

    Mukuhira, Yusuke; Moriya, Hirokazu; Ito, Takatoshi; Asanuma, Hiroshi; Häring, Markus


    Understanding the details of pressure migration during hydraulic stimulation is important for the design of an energy extraction system and reservoir management, as well as for the mitigation of hazardous-induced seismicity. Based on microseismic and regional stress information, we estimated the pore pressure increase required to generate shear slip on an existing fracture during stimulation. Spatiotemporal analysis of pore pressure migration revealed that lower pore pressure migrates farther and faster and that higher pore pressure migrates more slowly. These phenomena can be explained by the relationship between fracture permeability and stress state criticality. Subcritical fractures experience shear slip following smaller increases of pore pressure and promote migration of pore pressure because of their enhanced permeability. The difference in migration rates between lower and higher pore pressures suggests that the optimum wellhead pressure is the one that can stimulate relatively permeable fractures, selectively. Its selection optimizes economic benefits and minimizes seismic risk.


    Wang Xuesheng; Li Peining; Wang Ruzhu


    The mechanically bonded CRA-lined pipe is developed to meet the need for corrosion-resistant alloy steel pipe. Residual contact pressure at the interface of lined pipe is important factor that governs the quality of lined pipe. A simplified theoretical method is presented to predict the residual contact pressure created by hydraulic pressure. The calculating equation related hydro-forming pressure to the residual contact pressure between two metal faces is derived. And the validation of the proposed equation is accomplished by comparing its result to those obtained by experimental investigation.

  2. Characterizing hydraulic fractures in shale gas reservoirs using transient pressure tests

    Cong Wang


    This work presents an unconventional gas reservoir simulator and its application to quantify hydraulic fractures in shale gas reservoirs using transient pressure data. The numerical model incorporates most known physical processes for gas production from unconventional reservoirs, including two-phase flow of liquid and gas, Klinkenberg effect, non-Darcy flow, and nonlinear adsorption. In addition, the model is able to handle various types and scales of fractures or heterogeneity using continuum, discrete or hybrid modeling approaches under different well production conditions of varying rate or pressure. Our modeling studies indicate that the most sensitive parameter of hydraulic fractures to early transient gas flow through extremely low permeability rock is actually the fracture-matrix contacting area, generated by fracturing stimulation. Based on this observation, it is possible to use transient pressure testing data to estimate the area of fractures generated from fracturing operations. We will conduct a series of modeling studies and present a methodology using typical transient pressure responses, simulated by the numerical model, to estimate fracture areas created or to quantity hydraulic fractures with traditional well testing technology. The type curves of pressure transients from this study can be used to quantify hydraulic fractures in field application.

  3. Roughness induced flow separation in adverse pressure gradient

    Joo, Jongwook; Emory, Mike; Bose, Sanjeeb; Medic, Gorazd; Sharma, Om


    Surface roughness does not only increase turbulent mixing, but also thickens boundary-layers, making flows more susceptible to separation. Detailed flow physics related to the separation is not understood well. Bammert and Milsch (1972) demonstrates a clear example of surface roughness induced separation under adverse pressure gradient. In the study, compressor cascades with NACA 65 airfoils are systematically roughened and the flow over suction surface gradually separates early as roughness increases. A set of Large-Eddy Simulations (LES) over the Bammert's case is investigated, since RANS simulations using roughness models suffer from capturing the separation. In the current study, surface roughness is represented in two different approaches; 1) Realistic rough surface represented by stochastically distributed hills and valleys are gridded and solved with unstructured finite volume method, 2) Using block-structured grid, surface roughness is gridded as a staggered array of 3D rectangles, in a similar way of the previous study for roughened low pressure turbine (GT2016-57912). The current LES's capture rich features of the flow phenomena, which will bring comprehensive understanding of the roughness induced separation. This collaboration is made through 2016 CTR Summer Program.

  4. Luminescence from cavitation bubbles deformed in uniform pressure gradients

    Supponen, Outi; Obreschkow, Danail; Kobel, Philippe; Farhat, Mohamed


    Presented here are observations that demonstrate how the deformation of millimetric cavitation bubbles by a uniform pressure gradient quenches single-collapse luminescence. Our innovative measurement system captures a broad luminescence spectrum (wavelength range, 300-900 nm) from the individual collapses of laser-induced bubbles in water. By varying the bubble size, driving pressure, and perceived gravity level aboard parabolic flights, we probed the limit from aspherical to highly spherical bubble collapses. Luminescence was detected for bubbles of maximum radii within the previously uncovered range, R0=1.5 -6 mm, for laser-induced bubbles. The relative luminescence energy was found to rapidly decrease as a function of the bubble asymmetry quantified by the anisotropy parameter ζ , which is the dimensionless equivalent of the Kelvin impulse. As established previously, ζ also dictates the characteristic parameters of bubble-driven microjets. The threshold of ζ beyond which no luminescence is observed in our experiment closely coincides with the threshold where the microjets visibly pierce the bubble and drive a vapor jet during the rebound. The individual fitted blackbody temperatures range between Tlum=7000 and Tlum=11 500 K but do not show any clear trend as a function of ζ . Time-resolved measurements using a high-speed photodetector disclose multiple luminescence events at each bubble collapse. The averaged full width at half-maximum of the pulse is found to scale with R0 and to range between 10 and 20 ns.

  5. Numerical Model of Hydraulic Fracturing Fluid Transport in the Subsurface with Pressure Transient, Density Effects, and Imbibition

    Birdsell, D.; Rajaram, H.; Dempsey, D.; Viswanathan, H.


    Understanding the transport of hydraulic fracturing (HF) fluid that is injected into the deep subsurface for shale gas extraction is important to ensure that shallow drinking water aquifers are not contaminated from an environmental and public health perspective and to understand formation damage from an oil and gas production perspective. Upward pressure gradients, permeable pathways such as faults or improperly abandoned wellbores, and the density contrast of the HF fluid to the surrounding brine encourages upward HF fluid migration. In contrast, the very low shale permeability and the imbibition of water into partially-saturated shale may sequester much of the HF fluid. Using the Finite Element Heat and Mass Transfer Code (FEHM), single-phase flow and transport simulations are performed to quantify how much HF fluid is removed via the wellbore as flowback and produced water and how much reaches overlying aquifers; imbibition is calculated with a semi-analytical one-dimensional solution and treated as a sink term. The travel time for HF fluid to reach the shallow aquifers is highly dependent on the amount of water imbibed and the suction applied to the well. If imbibition rates and suction are small, the pressure transient due to injection and the density contrast allows rapid upward plume migration at early times. The density contrast diminishes considerably within tens to hundreds of years as mixing occurs. We present estimates of HF fluid migration to shallow aquifers during the first 1,000 years after hydraulic fracturing begins for ranges of subsurface properties.

  6. A Study on the Pressure Relief Scope and the Stress Variation of Hydraulic Flushing Borehole

    C. F.Wei


    Full Text Available To study the variation of the pressure relief scope and the stress around hydraulic flushing borehole, the theory of coalrock damage was utilized to distinguish the interaction area of water-jet and coal-rock into the coal-rock crushing area, the water-jet pressure stagnation area, the transition area and the original stress recovery area of coal-rock. Based on the actual occurrence conditions of the coal seam, the pressure variation and relief scope around the hydraulic flushing borehole were analyzed and simulated by RFPA2D-Flow software. The results showed that a relief area with the radius of 5.0 ~ 6.0 m around the borehole formed due to the hydraulic flushing with the pressure relief of 0.038 ~ 6.545 MPa, and the maximum principal stress is 15.85 MPa with a distance of 6.8 m from the inspected hole where stress concentration appeared. After hydraulic flushing test, the diameter (441.8 ~ 1171.6 mm of the hole which can be an expression of coal crushing area size, was calculated based on the examination of the coal amount through the trial process, and it can be drawn that the pressure relief area must be larger than that of the coal-rock crushing area. Meanwhile, the measured pressures relief range(5.96 ~ 6.62 m is basically consistent with the numerical simulation result (5.0 ~ 6.0 m which verified the accuracy of the simulation analysis, according to the distance from the inspection drilling to the hydraulic flushing borehole and the decreased degree of the gas content in the inspection hole by the way of Gas Content.

  7. The effect of pressure gradient on the structure of an equilibrium turbulent boundary layer

    Lei, Ting-Kwo


    Hot-wire anemometry was used to study the effect of adverse pressure gradient on the large-scale structures of equilibrium turbulent boundary layers. A previously existing zero-pressure gradient wind tunnel was modified into an adverse-pressure gradient wind tunnel, which had the capability of creating designated adverse-pressure gradient equilibrium turbulent boundary layer flows. The range of the equilibrium parameter beta was from 0.0 to 1.8 along a 1.50 m long test section of the wind tunnel. Computer programs were developed to predict the geometric shape of the test section for an equilibrium adverse-pressure gradient turbulent boundary layer flow. The numerical prediction of the test section geometry was found to be satisfactory and a substantial effort was saved in the establishment of an equilibrium boundary layer. Three equilibrium boundary layer flows at values of beta = 0.0, 0.8, and 1.8, which respectively represents zero, mild, and strong adverse pressure gradient, were established and were found to be suitable for turbulence structure measurements. Space-time correlation measurements were carried out to determine the convection velocities and inclination angles of the large-scale structures for the three different pressure gradient cases. The convection velocity measurements were performed at various heights which ranged form y(sup +) = 225 to 525 for each beta value. It was found that, within the range of height of the measurements, the convection velocity was independent of height In the case of the strong adverse-pressure gradient flow, the convection velocity was observed to be much lower than the convection velocity observed in the case of zero-pressure gradient. In the case of the mild-pressure gradient flow, it was observed that the pressure gradient effect on the convection velocity was negligible as compared to the zero-pressure gradient case. The inclination angle in the case of strong-pressure gradient case was found to be much greater than



    Hydraulic counter-pressure deep drawing of truncated conical part is numerically simulated with MARK and the nature of increasing the forming limit in this process is searched.The effects of blank holding force and chamber pressure on forming results are investigated by experiments and,as a result,truncated conical parts with large drawing ratio are successfully formed in single step with this drawing method.

  9. Pressure Responses of a Vertically Hydraulic Fractured Well in a Reservoir with Fractal Structure

    Razminia, Kambiz; Torres, Delfim F M


    We obtain an analytical solution for the pressure-transient behavior of a vertically hydraulic fractured well in a heterogeneous reservoir. The heterogeneity of the reservoir is modeled by using the concept of fractal geometry. Such reservoirs are called fractal reservoirs. According to the theory of fractional calculus, a temporal fractional derivative is applied to incorporate the memory properties of the fractal reservoir. The effect of different parameters on the computed wellbore pressure is fully investigated by various synthetic examples.

  10. Chloride concentration gradients in tank-stored hydraulic fracturing fluids following flowback

    Pamela J. Edwards; Linda L. Tracy; William K. Wilson


    A natural gas well in West Virginia was hydraulically fractured and the flowback was recovered and stored in an 18-foot-deep tank. Both in situ field test kit and laboratory measurements of electrical conductivity and chloride concentrations increased substantially with depth, although the laboratory measurements showed a greater increase. The field test kit also...

  11. Averaging hydraulic head, pressure head, and gravitational head in subsurface hydrology, and implications for averaged fluxes, and hydraulic conductivity

    G. H. de Rooij


    Full Text Available Current theories for water flow in porous media are valid for scales much smaller than those at which problem of public interest manifest themselves. This provides a drive for upscaled flow equations with their associated upscaled parameters. Upscaling is often achieved through volume averaging, but the solution to the resulting closure problem imposes severe restrictions to the flow conditions that limit the practical applicability. Here, the derivation of a closed expression of the effective hydraulic conductivity is forfeited to circumvent the closure problem. Thus, more limited but practical results can be derived. At the Representative Elementary Volume scale and larger scales, the gravitational potential and fluid pressure are treated as additive potentials. The necessary requirement that the superposition be maintained across scales is combined with conservation of energy during volume integration to establish consistent upscaling equations for the various heads. The power of these upscaling equations is demonstrated by the derivation of upscaled water content-matric head relationships and the resolution of an apparent paradox reported in the literature that is shown to have arisen from a violation of the superposition principle. Applying the upscaling procedure to Darcy's Law leads to the general definition of an upscaled hydraulic conductivity. By examining this definition in detail for porous media with different degrees of heterogeneity, a series of criteria is derived that must be satisfied for Darcy's Law to remain valid at a larger scale.

  12. Controlling a negative loaded hydraulic cylinder using pressure feedback

    Hansen, M.R.; Andersen, T.O.


    showing that without extra measures such a system will be unstable in a substantial part of the cylinder stroke. The stability criterion is expressed in hard quantities: Cylinder volumes, cylinder area ratio and overcenter valve pilot area ratio. A pressure feed back scheme that has as target to maintain...

  13. Characteristic analysis of a water hydraulic pilot-operated pressure-reducing valve

    Mao, Xuyao; Hu, Junhua; Wu, Chao; Liu, Yiou; Liu, Yinshui


    Comprehensive characteristics of a seawater hydraulic pilot-operated pressure-reducing valve with constant pressure output were analyzed. A rated pressure of 15MPa and a rated flowrate of 40L/min were offered in the numerical work. Static and dynamic analyses show good behaviors: The settling time is less than 0.2s, the output pressure variation is about 0.3MPa at the maximum when input pressure or flowrate is flucturing, and the steady external leakage is below 0.025L/min. The pilot spring regulates the output pressure and the main spring has an ability to adjust the output pressure variation faintly. The narrow hole diameter of the adjustable damping plugs is negatively related to the respond time. And appropriately raising the spring chamber volume can evidently reduce outlet pressure impact of the valve when input mutations happen.

  14. Measurement of Threshold Pressure Gradient of Microchannels by Static Method

    SONG Fu-Quan; JIANG Ren-Jie; BIAN Shu-Li


    The development of oil fields and laboratory experiment present the threshold pressure gradient (TPG) of liquid flow in low permeability porous media, which is called the micro-size effect in porous media. Some micro-size effects in micro-electro-mechanism systems (MEMS) are not always in agreement with each other. We propose an experiment setup to measure the TPG of microchannels by static method in the microchannels with the diameter ranging from 20-320 μm. The results present the existence of TPG in microchannel, and show an effect that the TPG of microchannel increases with decreasing hydrodynamic diameter. The relation between TPG and diameter is in agreement with single-log normalization. Additionally, the influence of errors in the experiment shows the data of experiment are valid. Finally, the mechanism of micro-size effects is discussed by revealing the facial force between liquid and solid and theory of boundary liquid, but the explanation is still not good, and needs further study.

  15. Hydraulic conductance and water potential gradients in squash leaves showing mycorrhiza-induced increases in stomatal conductance.

    Augé, Robert M; Toler, Heather D; Sams, Carl E; Nasim, Ghazala


    Stomatal conductance (gs) and transpiration rates vary widely across plant species. Leaf hydraulic conductance (k leaf) tends to change with g (s), to maintain hydraulic homeostasis and prevent wide and potentially harmful fluctuations in transpiration-induced water potential gradients across the leaf (Delta Psi leaf). Because arbuscular mycorrhizal (AM) symbiosis often increases gs in the plant host, we tested whether the symbiosis affects leaf hydraulic homeostasis. Specifically, we tested whether k leaf changes with gs to maintain Delta Psi leaf or whether Delta Psi leaf differs when gs differs in AM and non-AM plants. Colonization of squash plants with Glomus intraradices resulted in increased gs relative to non-AM controls, by an average of 27% under amply watered, unstressed conditions. Stomatal conductance was similar in AM and non-AM plants with exposure to NaCl stress. Across all AM and NaCl treatments, k leaf did change in synchrony with gs (positive correlation of gs and k leaf), corroborating leaf tendency toward hydraulic homeostasis under varying rates of transpirational water loss. However, k leaf did not increase in AM plants to compensate for the higher gs of unstressed AM plants relative to non-AM plants. Consequently, Delta Psi leaf did tend to be higher in AM leaves. A trend toward slightly higher Delta Psi leaf has been observed recently in more highly evolved plant taxa having higher productivity. Higher Delta Psi leaf in leaves of mycorrhizal plants would therefore be consistent with the higher rates of gas exchange that often accompany mycorrhizal symbiosis and that are presumed to be necessary to supply the carbon needs of the fungal symbiont.

  16. Abrasion properties of homogenous and blended fill materials during pressure hydraulic transport

    Turchaninov, S.P.


    A description is given of tests conducted to determine the abrasive properties of small and large-grain free-flowing fill materials during hydraulic transport of the materials under pressure. Data are given on the size, density, abrasiveness of various sized varieties of rock, sand, and blends comprising homogenous materials, simple and complex mixtures, and on the physical characteristics of various fill materials in relation to the trafficability and parameters of pipelines. Technical specifications are given for fill steel pipes. The study indicates that the durability of hydraulic fill pipelines largely depends on the abrasiveness of the fill materials. 3 references, 2 figures, 2 tables.

  17. Effect of Hydraulic Accumulator on Pressure Surge of a Hydrostatic Transmission System

    Kumar, Ajit; Das, Jayanta; Dasgupta, Kabir; Barnwal, Manish Kumar


    Hydraulic power system is generally used in off-road vehicles for power transmission such as Heavy Earth Moving Machineries (HEMM). Their energy efficiency and unsubstantial failure becomes an extensive subject of analysis. Various arrangements in the system are compassed along with the utilization of some appropriate components. Application of a hydraulic accumulator is one among them. Benefits of accumulator is its multi-purpose usages like energy saving and pressure surge damping. This paper deals with the control of pressure surges in the hydraulic system and energy saving from the surges by using accumulator. For this purpose, the simulation of the hydraulic system is done in MATLAB/SimulinkR environment and an external disturbance is introduced to generate the pressure surge. The surge absorptivity of the accumulator is studied for different sizes at different pre-charged conditions of the accumulator. The discharge characteristics of different sized accumulators are also analyzed in this paper. It is observed that the ability to absorb the surge and stabilize the system is high in the smaller capacity accumulator. However the energy delivery time of larger sized accumulator is high.

  18. Influence of pore pressure to the development of a hydraulic fracture in poroelastic medium

    Golovin, Sergey V


    In this paper we demonstrate the influence of the pore pressure to the development of a hydraulically-driven fracture in a poroelastic medium. We present a novel numerical model for propagation of a planar hydraulic fracture and prove its correctness by demonstration of the numerical convergence and by comparison with known solutions. The advantage of the algorithm is that it does not require the distinguishing of the fracture's tips and reconstruction of the numerical mesh according to the fracture propagation. Next, we perform a thorough analysis of the interplay of fluid filtration and redistribution of stresses near the fracture. We demonstrate that the fracture length decreases with the increase of the Biot's number (the parameter that determines the contribution of the pore pressure to the stress) and explain this effect by analysing the near-fracture pore pressure, rock deformation and stresses. We conclude, that the correct account for the fluid exchange between the fracture and the rock should be bas...

  19. Multiscale architectured materials with composition and grain size gradients manufactured using high-pressure torsion.

    Kang, Ji Yun; Kim, Jung Gi; Park, Hyo Wook; Kim, Hyoung Seop


    The concept of multiscale architectured materials is established using composition and grain size gradients. Composition-gradient nanostructured materials are produced from coarse grained interstitial free steels via carburization and high-pressure torsion. Quantitative analyses of the dislocation density using X-ray diffraction and microstructural studies clearly demonstrate the gradients of the dislocation density and grain size. The mechanical properties of the gradient materials are compared with homogeneous nanostructured carbon steel without a composition gradient in an effort to investigate the gradient effect. Based on the above observations, the potential of multiscale architecturing to open a new material property is discussed.


    邓松圣; 周绍骑; 廖振方; 邱正阳; 曾顺鹏


    Hydraulic transient,which is resulted from sudden increase of inlet pressure for laminar pipeline flow,is studied.The partial differential equation,initial and boundary conditions for transient pressure were constructed,and the theoretical solution was obtained by variable-separation method.The partial differential equation,initial and boundary conditions for flow rate were obtained in accordance with the constraint correlation between flow rate and pressure while the transient flow rate distribution was also solved by variable-separation method.The theoretical solution conforms to numerical solution obtained by method of characteristics(MOC)very well.

  1. Importance of pressure gradient in solid oxide fuel cell electrodes for modeling study

    Ni, Meng; Leung, Dennis Y. C.; Leung, Michael K. H.

    The pressure gradients in the electrodes of a solid oxide fuel cell (SOFC) are frequently neglected without any justification in calculating the concentration overpotentials of the SOFC electrodes in modeling studies. In this short communication, a comparative study has been conducted to study the effect of pressure gradients on mass transfer and the resulting concentration overpotentials of an SOFC running on methane (CH 4) fuel. It is found that the pressure gradients in both anode and cathode are significant in the fuel cell electrochemical activities. Neglecting the anode pressure gradient in the calculation can lead to underestimation of the concentration overpotential by about 20% at a typical current density of 5000 A m -2 and at a temperature of 1073 K. The deviation can be even larger at a higher temperature. At the cathode, neglecting the pressure gradient can result in overestimation of the concentration overpotential by about 10% under typical working conditions.

  2. Theory and application of rock burst prevention using deep hole high pressure hydraulic fracturing

    Shan-Kun ZHAO; Jun LIU; Xiang-Zhi WEI; Chuan-Hong DING; Yu-Lei LV; Gang-Feng LI


    In order to analyze the mechanism of deep hole high pressure hydraulic fracturing,nonlinear dynamic theory,damage mechanics,elastic-plastic mechanics are used,and the law of crack propagation and stress transfer under two deep hole hydraulic fracturing in tectonic stress areas is studied using seepage-stress coupling models with RFPA simulation software.In addition,the effects of rock burst control are tested using multiple methods,either in the stress field or in the energy field.The research findings show that with two deep holes hydraulic fracturing in tectonic stress areas,the direction of the main crack propagation under shear-tensile stress is parallel to the greatest principal stress direction.High-pressure hydraulic fracturing water seepage can result in the destruction of the coal structure,while also weakening the physical and mechanical properties of coal and rock.Therefore the impact of high stress concentration in hazardous areas will level off,which has an effect on rock burst prevention and control in the region.

  3. Hydraulic Resistance and Liberation of Air in Aviation Kerosene Flow Through Diaphragms at Low Pressure

    Kitanin, É. L.; Kitanina, E. É.; Zherebtsov, V. A.; Peganova, M. M.; Stepanov, S. G.; Bondarenko, D. A.; Morisson, D.


    This paper presents the results of experimental investigations of the liberation of air in gravity flow of aviation fuel through a pipeline with diaphragms. Experiments were carried out in the pressure range 0.2-1.0 bar and temperature range -20 to +20°C. The TC-1 kerosene was preliminarily saturated with air at atmospheric pressure. The liberation of air after the diaphragms with three ratios of the flow area to the cross-sectional area of the pipeline has been investigated. The results of investigations of the two-phase flow in several experimental pipelines containing one or two diaphragms and other local hydraulic resistances have been generalized. The obtained approximation equations permit calculating the hydraulic resistance of the diaphragm in the two-phase flow and the mass gas content of air after the diaphragm in pipelines of complex geometry.

  4. Thermal Hydraulic Analysis of a Passive Residual Heat Removal System for an Integral Pressurized Water Reactor


    A theoretical investigation on the thermal hydraulic characteristics of a new type of passive residual heat removal system (PRHRS), which is connected to the reactor coolant system via the secondary side of the steam generator, for an integral pressurized water reactor is presented in this paper. Three-interknited natural circulation loops are adopted by this PRHRS to remove the residual heat of the reactor core after a reactor trip. Based on the one-dimensional model and a simulation code (S...



    In this article, the three-dimensional unsteady multiphase flow is simulated in the whole passage of Francis hydraulic turbine. The pressure pulsation is predicted and compared with experimental data at positions in the draft tube, in front of runner, guide vanes and at the inlet of the spiral case. The relationship between pressure pulsation in the whole passage and air admission is analyzed. The computational results show: air admission from spindle hole decreases the pressure difference in the horizontal section of draft tube, which in turn decreases the amplitude of low-frequency pressure pulsation in the draft tube; the rotor-stator interaction between the air inlet and the runner increases the blade-frequency pressure pulsation in front of the runner.

  6. Thermally Actuated Hydraulic Pumps

    Jones, Jack; Ross, Ronald; Chao, Yi


    Thermally actuated hydraulic pumps have been proposed for diverse applications in which direct electrical or mechanical actuation is undesirable and the relative slowness of thermal actuation can be tolerated. The proposed pumps would not contain any sliding (wearing) parts in their compressors and, hence, could have long operational lifetimes. The basic principle of a pump according to the proposal is to utilize the thermal expansion and contraction of a wax or other phase-change material in contact with a hydraulic fluid in a rigid chamber. Heating the chamber and its contents from below to above the melting temperature of the phase-change material would cause the material to expand significantly, thus causing a substantial increase in hydraulic pressure and/or a substantial displacement of hydraulic fluid out of the chamber. Similarly, cooling the chamber and its contents from above to below the melting temperature of the phase-change material would cause the material to contract significantly, thus causing a substantial decrease in hydraulic pressure and/or a substantial displacement of hydraulic fluid into the chamber. The displacement of the hydraulic fluid could be used to drive a piston. The figure illustrates a simple example of a hydraulic jack driven by a thermally actuated hydraulic pump. The pump chamber would be a cylinder containing encapsulated wax pellets and containing radial fins to facilitate transfer of heat to and from the wax. The plastic encapsulation would serve as an oil/wax barrier and the remaining interior space could be filled with hydraulic oil. A filter would retain the encapsulated wax particles in the pump chamber while allowing the hydraulic oil to flow into and out of the chamber. In one important class of potential applications, thermally actuated hydraulic pumps, exploiting vertical ocean temperature gradients for heating and cooling as needed, would be used to vary hydraulic pressures to control buoyancy in undersea research

  7. Noninvasive estimation of 2-D pressure gradients in steady flow using ultrasound

    Olesen, Jacob Bjerring; Traberg, Marie Sand; Pihl, Michael Johannes;


    A noninvasive method for estimating 2-D pressure gradients from ultrasound vector velocity data is presented. It relies on vector velocity fields acquired using the transverse oscillation method during steady flow conditions. The pressure gradients are calculated from the velocity fields using...... of -7% for the axial component and -8% for the lateral component. The relative standard deviation of the estimator is 5% (axial component) and 30% (lateral component) when studying the pressure gradient across the constriction using 3 velocity frames per pressure estimate. The study shows that 2-D...... phantom. The geometry of the model is determined from magnetic resonance imaging. The presented study is conducted assuming steady flow using velocity data acquired at 18 frames per second. The proposed method shows pressure gradients at the constricted region from -8 kPa/m to 9 kPa/m, with a maximum bias...

  8. Thermophoresis of dissolved molecules and polymers: Consideration of the temperature-induced macroscopic pressure gradient.

    Semenov, Semen; Schimpf, Martin


    The movement of molecules and homopolymer chains dissolved in a nonelectrolyte solvent in response to a temperature gradient is considered a consequence of temperature-induced pressure gradients in the solvent layer surrounding the solute molecules. Local pressure gradients are produced by nonuniform London-van der Waals interactions, established by gradients in the concentration (density) of solvent molecules. The density gradient is produced by variations in solvent thermal expansion within the nonuniform temperature field. The resulting expression for the velocity of the solute contains the Hamaker constants for solute-solvent and solute-solute interactions, the radius of the solute molecule, and the viscosity and cubic coefficient of thermal expansion of the solvent. In this paper we consider an additional force that arises from directional asymmetry in the interaction between solvent molecules. In a closed cell, the resulting macroscopic pressure gradient gives rise to a volume force that affects the motion of dissolved solutes. An expression for this macroscopic pressure gradient is derived and the resulting force is incorporated into the expression for the solute velocity. The expression is used to calculate thermodiffusion coefficients for polystyrene in several organic solvents. When these values are compared to those measured in the laboratory, the consistency is better than that found in previous reports, which did not consider the macroscopic pressure gradient that arises in a closed thermodiffusion cell. The model also allows for the movement of solute in either direction, depending on the relative values of the solvent and solute Hamaker constants.

  9. Estimating hydraulic conductivity of fractured rocks from high‐pressure packer tests with an Izbash's law‐based empirical model

    Chen, Yi‐Feng; Hu, Shao‐Hua; Hu, Ran; Zhou, Chuang‐Bing


    ...‐pressure groundwater flow conditions. The interpretation of the HPPT data, however, remains difficult due to the transition of flow conditions in the conducting structures and the hydraulic fracturing...

  10. A switched energy saving position controller for variable-pressure electro-hydraulic servo systems.

    Tivay, Ali; Zareinejad, Mohammad; Rezaei, S Mehdi; Baghestan, Keivan


    The electro-hydraulic servo system (EHSS) demonstrates a relatively low level of efficiency compared to other available actuation methods. The objective of this paper is to increase this efficiency by introducing a variable supply pressure into the system and controlling this pressure during the task of position tracking. For this purpose, an EHSS structure with controllable supply pressure is proposed and its dynamic model is derived from the basic laws of physics. A switching control structure is then proposed to control both the supply pressure and the cylinder position at the same time, in a way that reduces the overall energy consumption of the system. The stability of the proposed switching control system is guaranteed by proof, and its performance is verified by experimental testing.

  11. Pressure Control of Electro-Hydraulic Servovalve and Transmission Line Effect

    Ahmed Fouad Mahdi


    Full Text Available The effected of the long transmission line (TL between the actuator and the hydraulic control valve sometimes essentials. The study is concerned with modeling the TL which carries the oil from the electro-hydraulic servovalve to the actuator. The pressure value inside the TL has been controlled by the electro-hydraulic servovalve as a voltage supplied to the servovalve amplifier. The flow rate through the TL has been simulated by using the lumped π element electrical analogy method for laminar flow. The control voltage supplied to servovalve can be achieved by the direct using of the voltage function generator or indirect C++ program connected to the DAP-view program built in the DAP-card data acquisition connected to PC, to control the value of pressure in a selected point in the TL. It has been found that the relation between the voltage value and the output flow rate from the servovalve in most of the path is a linear relation. The MATLAB m-File program is used to create a representation state of the mathematical model to find a good simulation for the experimental open loop control test.

  12. Comparison of Coral Reef Ecosystems along a Fishing Pressure Gradient

    Weijerman, M.W.; Fulton, E.A.; Parrish, F.A.


    Three trophic mass-balance models representing coral reef ecosystems along a fishery gradient were compared to evaluate ecosystem effects of fishing. The majority of the biomass estimates came directly from a large-scale visual survey program; therefore, data were collected in the same way for all t

  13. Method for achieving hydraulic balance in typical Chinese building heating systems by managing differential pressure and flow

    Zhang, Lipeng; Xia, Jianjun; Thorsen, Jan Eric;


    Hydraulic unbalance is a common problem in Chinese district heating (DH) systems. Hydraulic unbalance has resulted in poor flow distribution among heating branches and overheating of apartments. Studies show that nearly 30% of the total heat supply is being wasted in Chinese DH systems due...... to a lack of pressure and flow control. This study investigated using pre-set radiator valves combined with differential pressure (DP) controllers to achieve hydraulic balance in building distribution systems, and consequently save energy and reduce the emissions. We considered a multi-storey building...

  14. On the impact of adverse pressure gradient on the supersonic turbulent boundary layer

    Wang, Qian-Cheng; Wang, Zhen-Guo; Zhao, Yu-Xin


    By employing the particle image velocimetry, the mean and turbulent characteristics of a Mach 2.95 turbulent boundary layer are experimentally investigated without the impact of curvature. The physical mechanism with which the streamwise adverse pressure gradient affects the supersonic boundary layer is revealed. The data are compared to that of the concave boundary layer with similar streamwise distributions of wall static pressure to clarify the separate impacts of the adverse pressure gradient and the concave curvature. The logarithmic law is observed to be well preserved for both of the cases. The dip below the logarithmic law is not observed in present investigation. Theoretical analysis indicates that it could be the result of compromise between the opposite impacts of the compression wave and the increased turbulent intensity. Compared to the zero pressure gradient boundary layer, the principal strain rate and the turbulent intensities are increased by the adverse pressure gradient. The shear layer formed due the hairpin packets could be sharpened by the compression wave, which leads to higher principal strain rate and the associated turbulent level. Due to the additional impact of the centrifugal instability brought by the concave wall, even higher turbulent intensities than that of the adverse pressure gradient case are introduced. The existence of velocity modes within the zero pressure gradient boundary layer suggests that the large scale motions are statistically well organized. The generation of new velocity modes due to the adverse pressure gradient indicates that the turbulent structure is changed by the adverse pressure gradient, through which more turbulence production that cannot be effectively predicted by the Reynolds-stress transport equations could be brought.

  15. Differences in hydraulic pressure producing efficiency of front suspension units for motorcycles due to structural difference

    Kajino, Tsutomu; Namazue, Eitaro; Ueno, Yutaka


    The front suspension unit for motorcycles is one of the functional parts for which continuous engineering improvement is required for advanced driveability. Especially, the ones for off-road motocross racing are frequently required to have their energy absorbing properties, ability to maintain tire-to-ground contact, driving comfort, etc. to be improved to meet the challenges of the racing courses which include many jumps, to exceed the performance of competitors, and to match the ever-improving performance of the engines and frames. To cope with the situation, the operability, rigidity and hydraulic pressure producing mechanism needs to be upgraded. As part of an improvement program, the authors have developed a air-oil separated front suspension which the authors have called the ``twin chamber`` suspension. In this study, the authors compared the hydraulic pressure producing efficiency of the air-oil separated suspension with that of the conventional single chamber construction. The results of the comparison showed that the twin chamber suspension is less affected by the pressure hysteresis by 8% or more at the piston area and 50% or more at the partition area than the conventional suspension. In addition, for the twin chamber suspension, the rise of pressure becomes smoother to give a quicker response as the velocity increases.

  16. Large eddies induced by local impulse at wall of boundary layer with pressure gradients

    Changgen Lu; Weidong Cao; Yanmei Zhang; Jintao Peng


    Large eddies induced by local impulse at the wall with pressure gradients in the boundary layer was studied by direct numerical sim-ulations. The results show that the amplitude evolution, the high and low speed stripes, the formation of streamwise vortices, the ejection and sweeping, inflexions and distortion at the mean velocity profiles, as well as other characteristics, are consistent with the experimental and other numerical results. It is also found that large eddies are easy to be excited with adverse pressure gradient in the boundary layer,and the growth of amplitudes, formation of streamwise vortices and the influencing area etc., are much larger than those with favorable pressure gradient in the boundary layer. In contrast, large eddies are hardly to be induced through local impulse disturbance at the wall with favorable pressure gradients in the boundary layer.

  17. Quantifying dynamic changes in plantar pressure gradient in diabetics with peripheral neuropathy

    Chi-Wen Lung


    Full Text Available Diabetic foot ulcers remain one of the most serious complications of diabetes. Peak plantar pressure (PPP and peak pressure gradient (PPG during walking have been shown to be associated with the development of diabetic foot ulcers. To gain further insight into the mechanical etiology of diabetic foot ulcers, examination of the pressure gradient angle (PGA has been recently proposed. The PGA quantifies directional variation or orientation of the pressure gradient during walking, and provides a measure of whether pressure gradient patterns are concentrated or dispersed along the plantar surface. We hypothesized that diabetics at risk of foot ulceration would have smaller PGA in key plantar regions, suggesting less movement of the pressure gradient over time. A total of 27 participants were studied, including 19 diabetics with peripheral neuropathy and 8 non-diabetic control subjects. A foot pressure measurement system was used to measure plantar pressures during walking. PPP, PPG and PGA were calculated for four foot regions - 1st toe (T1, 1st metatarsal head (M1, 2nd metatarsal head (M2, and heel (HL. Consistent with prior studies, PPP and PPG were significantly larger in the diabetic group compared to non-diabetic controls in the T1 and M1 regions, but not M2 or HL. For example, PPP was 165% (P=0.02 and PPG was 214% (P<0.001 larger in T1. PGA was found to be significantly smaller in the diabetic group in T1 (46%, P=0.04, suggesting a more concentrated pressure gradient pattern under the toe. The proposed PGA may improve our understanding of the role of pressure gradient on the risk of diabetic foot ulcers.

  18. Quantifying Dynamic Changes in Plantar Pressure Gradient in Diabetics with Peripheral Neuropathy

    Lung, Chi-Wen; Hsiao-Wecksler, Elizabeth T.; Burns, Stephanie; Lin, Fang; Jan, Yih-Kuen


    Diabetic foot ulcers remain one of the most serious complications of diabetes. Peak plantar pressure (PPP) and peak pressure gradient (PPG) during walking have been shown to be associated with the development of diabetic foot ulcers. To gain further insight into the mechanical etiology of diabetic foot ulcers, examination of the pressure gradient angle (PGA) has been recently proposed. The PGA quantifies directional variation or orientation of the pressure gradient during walking and provides a measure of whether pressure gradient patterns are concentrated or dispersed along the plantar surface. We hypothesized that diabetics at risk of foot ulceration would have smaller PGA in key plantar regions, suggesting less movement of the pressure gradient over time. A total of 27 participants were studied, including 19 diabetics with peripheral neuropathy and 8 non-diabetic control subjects. A foot pressure measurement system was used to measure plantar pressures during walking. PPP, PPG, and PGA were calculated for four foot regions – first toe (T1), first metatarsal head (M1), second metatarsal head (M2), and heel (HL). Consistent with prior studies, PPP and PPG were significantly larger in the diabetic group compared with non-diabetic controls in the T1 and M1 regions, but not M2 or HL. For example, PPP was 165% (P = 0.02) and PPG was 214% (P < 0.001) larger in T1. PGA was found to be significantly smaller in the diabetic group in T1 (46%, P = 0.04), suggesting a more concentrated pressure gradient pattern under the toe. The proposed PGA may improve our understanding of the role of pressure gradient on the risk of diabetic foot ulcers. PMID:27486576

  19. On determining characteristic length scales in pressure-gradient turbulent boundary layers

    Vinuesa, R.; Bobke, A.; Örlü, R.; Schlatter, P.


    In the present work, we analyze three commonly used methods to determine the edge of pressure gradient turbulent boundary layers: two based on composite profiles, the one by Chauhan et al. ["Criteria for assessing experiments in zero pressure gradient boundary layers," Fluid Dyn. Res. 41, 021404 (2009)] and the one by Nickels ["Inner scaling for wall-bounded flows subject to large pressure gradients," J. Fluid Mech. 521, 217-239 (2004)], and the other one based on the condition of vanishing mean velocity gradient. Additionally, a new method is introduced based on the diagnostic plot concept by Alfredsson et al. ["A new scaling for the streamwise turbulence intensity in wall-bounded turbulent flows and what it tells us about the `outer' peak," Phys. Fluids 23, 041702 (2011)]. The boundary layers developing over the suction and pressure sides of a NACA4412 wing section, extracted from a direct numerical simulation at chord Reynolds number Rec = 400 000, are used as the test case, besides other numerical and experimental data from favorable, zero, and adverse pressure-gradient flat-plate turbulent boundary layers. We find that all the methods produce robust results with mild or moderate pressure gradients, although the composite-profile techniques require data preparation, including initial estimations of fitting parameters and data truncation. Stronger pressure gradients (with a Rotta-Clauser pressure-gradient parameter β larger than around 7) lead to inconsistent results in all the techniques except the diagnostic plot. This method also has the advantage of providing an objective way of defining the point where the mean streamwise velocity is 99% of the edge velocity and shows consistent results in a wide range of pressure gradient conditions, as well as flow histories. Collapse of intermittency factors obtained from a wide range of pressure-gradient and Re conditions on the wing further highlights the robustness of the diagnostic plot method to determine the

  20. Secondary subharmonic instability of boundary layers with pressure gradient and suction

    El-Hady, Nabil M.


    Three-dimensional linear secondary instability is investigated for boundary layers with pressure gradient and suction in the presence of a finite amplitude TS wave. The focus is on principal parametric resonance responsible for a strong growth of subharmonics in a low disturbance environment. Calculations are presented for the effect of pressure gradients and suction on controlling the onset and amplification of the secondary instability.

  1. Nonisothermal turbulent boundary-layer adverse pressure gradient large scale thermal structure measurements

    Bagheri, Nader; White, Bruce R.; Lei, Ting-Kwo


    Hot-wire anemometry measurements in an incompressible turbulent boundary-layer flow over a heated flat plate under equilibrium adverse-pressure-gradient conditions (beta = 1.8) were made for two different temperature difference cases (10 and 15 C) between the wall and the freestream. Space-time correlations of temperature fluctuations (T') were obtained with a pair of subminiature temperature fluctuation probes. The mean convection velocities, the mean inclination angles, and coherence characteristics of the T' large-scale structure were determined. The present temperature structures measurements for a nonisothermal boundary layer are compared to the zero-pressure-gradient case with identical temperature differences previously reported, in which the mean convection velocity of the T' structure was a function of position y(sup +) and independent of the limited temperature-difference cases tested. The three major findings of the present study, as compared to the zero-pressure-gradient case, are (1) the mean convection speed of the T' structure under beta = 1.8 pressure-gradient conditions was found to be substantially lower in the logarithmic core region than the zero-pressure-gradient case. Additionally, the mean convection speed is felt by the authors to be a function of pressure-gradient parameter beta; (2) the mean inclination angle of the T' structure to the wall under the adverse-pressure-gradient flow was 32 deg, which compares favorably to the 30-deg value of the zero-pressure-gradient case; and (3) the limited data suggests that the mean convection velocity of the T' structure is a function of y(sup +) and independent of the limited temperature-difference cases tested.

  2. Estimating Hydraulic Conductivities in a Fractured Shale Formation from Pressure Pulse Testing and 3d Modeling

    Courbet, C.; DICK, P.; Lefevre, M.; Wittebroodt, C.; Matray, J.; Barnichon, J.


    In the framework of its research on the deep disposal of radioactive waste in shale formations, the French Institute for Radiological Protection and Nuclear Safety (IRSN) has developed a large array of in situ programs concerning the confining properties of shales in their underground research laboratory at Tournemire (SW France). One of its aims is to evaluate the occurrence and processes controlling radionuclide migration through the host rock, from the disposal system to the biosphere. Past research programs carried out at Tournemire covered mechanical, hydro-mechanical and physico-chemical properties of the Tournemire shale as well as water chemistry and long-term behaviour of the host rock. Studies show that fluid circulations in the undisturbed matrix are very slow (hydraulic conductivity of 10-14 to 10-15 m.s-1). However, recent work related to the occurrence of small scale fractures and clay-rich fault gouges indicate that fluid circulations may have been significantly modified in the vicinity of such features. To assess the transport properties associated with such faults, IRSN designed a series of in situ and laboratory experiments to evaluate the contribution of both diffusive and advective process on water and solute flux through a clay-rich fault zone (fault core and damaged zone) and in an undisturbed shale formation. As part of these studies, Modular Mini-Packer System (MMPS) hydraulic testing was conducted in multiple boreholes to characterize hydraulic conductivities within the formation. Pressure data collected during the hydraulic tests were analyzed using the nSIGHTS (n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator) code to estimate hydraulic conductivity and formation pressures of the tested intervals. Preliminary results indicate hydraulic conductivities of 5.10-12 m.s-1 in the fault core and damaged zone and 10-14 m.s-1 in the adjacent undisturbed shale. Furthermore, when compared with neutron porosity data from borehole

  3. The design of hydraulic pressure regulators that are stable without the use of sensing line restrictors or frictional dampers

    Gold, H.


    A direct-acting hydraulic pressure regulator design which incorporates stability margin, response and droop margin is developed. The pressure regulator system does not involve a nonlinear sensing line restrictor (which may degrade transient response) or linear damping (which is sensitive to clearance and viscosity). The direct-acting hydraulic pressure regulator makes use of the technique of lead network stabilization (i.e., the tuned stabilizer concept). An analytically derived circuit pressure regulator is tested to study the stability limit under a parallel capacitive plus resistive load and the stabilizing effect of the tuned stabilizer.

  4. Effect of Laser Annealing of Common Solid Pressure Media on Pressure Gradients in a Diamond Anvil Cell

    Uts, I.; Glazyrin, K.; Lee, K. K.


    Advances in experimental techniques allow for the studying of geophysics and planetary science related materials under high pressure and high temperature conditions. With the intrinsic limits of the multianvil apparatus, compression in a diamond anvil cell (DAC) has become the preferred method for creating the extreme conditions of planetary interiors. High pressures up to 1 Mbar can be routinely obtained in laboratories with the use of DACs. Additionally, as in situ laser heating is becoming progressively more affordable for DACs, it is becoming more common to find laser heating setups in many large scale facilities. After the sample material, the pressure medium is the second most important ingredient for a successful high pressure DAC experiment. Not every pressure medium is equally suitable for every experiment. For example, solid pressure media are more persistent than gaseous pressure media if high temperature heating is required. The melting point of the former is much higher, and melting of pressure media may induce undesirable sample shift in the pressure chamber. However, the most important characteristic of a pressure medium is its ability to maintain hydrostaticity in the DAC. The media, particularly solid pressure media, become less effective with increasing pressure. One of the most popular ways of alleviating pressure gradients is through laser annealing of the sample. We explore the effectiveness of this technique in relation to common pressure media, namely, alkali metal halides NaCl, CsCl, KCl, LiF, and oxide MgO. The samples were laser annealed at temperatures above 2000 K. Pressure gradients were determined through the analysis of diamond Raman and ruby fluorescence peaks before and after annealing the sample with a near-infrared laser. We find that the effect of annealing varies for different materials. For some (NaCl and KCl), it reduces pressure gradients considerably, but for the others (MgO), the effect of annealing is less profound.

  5. Percutaneous biliary stones removal using balloon sphincteroplasty and hydraulic pressure as primary therapeutic method

    Kim, Jae Soo; You, Jin Jong [Gyeongsang National University Hospital, Chinju (Korea, Republic of)


    We wanted to report on the efficacy and safety of the percutaneous biliary stone removal technique using hydraulic pressure after balloon sphincteroplasty through the PTBD tract for patients with bile duct stones. The subjects of this study were 85 patients (46 men and 39 women) with bile duct stones who came to hospital over a period of the previous 4 years. All subjects had undergone attempts for with the biliary tree through PTBD. First, an 8-9F sheath was inserted into the biliary tree through the PTBD route by using a balloon catheter prior to sphincteroplasty, and 50cc of hydraulic pressure with contrast-mixed saline solution was then injected via the sheath. Follow-up cholangiogram was performed 1-3 days later to evaluate the results of stone removal. For residual stones, we attempted second, third, and fourth trials to completely remove the stones. The size and number of stones were analyzed. The results were analyzed, together with the complications, after classifying the cases as 'success', 'partial removal' or 'failure' according to the number of remaining stones. Out of 85 patients, 71 (83%) cases had successful results, and 43 (51%) cases resulted in success with the first attempt. The second, third and fourth trials were conducted on 16, 10 and 2 cases, respectively. Out of 14 failure cases, 10 patients had too many intrahepatic duct stones. The complications were abdominal pain (n=21), fever (n=9), and pancreatitis (n=2), and portal vein thrombosis, biloma and sepsis were also found in 1 case each. We report that this percutaneus biliary stone removal technique using hydraulic pressure after balloon sphincteroplasty through the PTBD is safe and effective, and particularly, it achieves good results as the primary therapy for treating only choledocholiths.

  6. A novel high-temperature and high-pressure hydraulic pump based on mononeuron control

    Linhui ZHAO; Xin FANG


    Based on structures and characteristics of traditional hydraulic pumps, this paper proposes a novel high-temperature and high-pressure hydraulic pump (HHHP) that can work under 150℃ and 28MPa to overcome problems of traditional high-temperature plun-ger pumps. The HHHP is designed with the structure of mechanical division and double cylinder parallel. The control signals of two cylinders are two separate triangle waveforms with 90℃ phase difference. Because the output waveforms of two cylinders have the same characteristics as the control signals, the HHHP can obtain a stable output after two separate waveforms are superposed. A mono-neuron self-adaptive PID control algorithm is also improved by modifying parameters K and η. Two improved controllers are used to control the two cylinders,respectively, making two displacements of plungers match each other. Therefore, reduced fluctuations and stable pressure output is obtained. Besides simulation, tests on the built prototype test system are carried out to verify the performance of HHHP. Results show that the improved control approach can limit fluctuations to a lower level and the HHHP system attains good outputs under different signal periods and different pressures.

  7. Little pump that could : hydraulic submersible pump tackles low pressure, low fluid volume gas wells

    Ross, E.


    A new pump designed by Global Energy Services was described. The pump was designed to address problems associated with downhole pumps in coalbed methane (CBM) wells. The hydraulic submersible pump (HSP) was designed to address issues related to artificial lift gas lock and solids. The pump has been installed at 35 CBM wells in western Canada as well as at natural gas wells with low pressures and low rates of water. The HSP technology was designed for use with wells between 0.01 cubic metres and 24 cubic metres per day of water. A single joystick in the surface unit is used to determine the amount of hydraulic oil delivered to the bottomhole pump when then determines the amounts of fluid produced. A 10-slot self-flushing sand screen is used to filter out particles of sand, coal, and cement. The pump also includes a hydraulic flow control valve to control water volumes. The HSP's positive displacement design makes it suitable for use in horizontal and deviated wells. The pump technology is currently being re-designed to handle larger volumes at deeper depths. 2 figs.

  8. Turbulence measurements in axisymmetric supersonic boundary layer flow in adverse pressure gradients

    Gootzait, E.; Childs, M. E.


    Mean flow and turbulence measurements are presented for adiabatic compressible turbulent boundary layer flow in adverse pressure gradients. The gradients were induced on the wall of an axially symmetric wind tunnel by contoured centerbodies mounted on the wind tunnel centerline. The boundary layer turbulence downstream of a boundary layer bleed section in a zero pressure gradient was also examined. The measurements were obtained using a constant temperature hot-wire anemometer. The adverse pressure gradients were found to significantly alter the turbulence properties of the boundary layer. With flow through the bleed holes there was a measureable decrease in the rms longitudinal velocity fluctuations near the wall and the turbulent shear stress in the boundary layer was reduced.

  9. On determining characteristic length scales in pressure gradient turbulent boundary layers

    Vinuesa, Ricardo; Örlü, Ramis; Schlatter, Philipp


    In the present work we analyze three methods used to determine the edge of pressure gradient turbulent boundary layers: two based on composite profiles, the one by Chauhan et al. (Fluid Dyn. Res. 41:021401, 2009) and the one by Nickels (J. Fluid Mech. 521:217-239, 2004), and the other one based on the condition of vanishing mean velocity gradient. Additionally, a new method is introduced based on the diagnostic plot concept by Alfredsson et al. (Phys. Fluids 23:041702, 2011). The boundary layer developing over the suction side of a NACA4412 wing profile, extracted from a direct numerical simulation at Rec = 400,000, is used as the test case. We find that all the methods produce robust results with mild or moderate pressure gradients, but stronger pressure gradients (with β larger than around 7) lead to inconsistent results in all the techniques except the diagnostic plot. This method also has the advantage of providing an objective way of defining the point where the mean streamwise velocity is 99% of the edge velocity, and shows consistent results in a wide range of pressure gradient conditions, as well as flow histories. Therefore, the technique based on the diagnostic plot is a robust method to determine the boundary layer thickness (equivalent to δ99) and edge velocity in pressure gradient turbulent boundary layers.

  10. Portosystemic pressure reduction achieved with TIPPS and impact of portosystemic collaterals for the prediction of the portosystemic-pressure gradient in cirrhotic patients

    Grözinger, Gerd, E-mail: [Department of Diagnostic Radiology, Department of Radiology, University of Tübingen (Germany); Wiesinger, Benjamin; Schmehl, Jörg; Kramer, Ulrich [Department of Diagnostic Radiology, Department of Radiology, University of Tübingen (Germany); Mehra, Tarun [Department of Dermatology, University of Tübingen (Germany); Grosse, Ulrich; König, Claudius [Department of Diagnostic Radiology, Department of Radiology, University of Tübingen (Germany)


    Purpose: The portosystemic pressure gradient is an important factor defining prognosis in hepatic disease. However, noninvasive prediction of the gradient and the possible reduction by establishment of a TIPSS is challenging. A cohort of patients receiving TIPSS was evaluated with regard to imaging features of collaterals in cross-sectional imaging and the achievable reduction of the pressure gradient by establishment of a TIPSS. Methods: In this study 70 consecutive patients with cirrhotic liver disease were retrospectively evaluated. Patients received either CT or MR imaging before invasive pressure measurement during TIPSS procedure. Images were evaluated with regard to esophageal and fundus varices, splenorenal collaterals, short gastric vein and paraumbilical vein. Results were correlated with Child stage, portosystemic pressure gradient and post-TIPSS reduction of the pressure gradient. Results: In 55 of the 70 patients TIPSS reduced the pressure gradient to less than 12 mmHg. The pre-interventional pressure and the pressure reduction were not significantly different between Child stages. Imaging features of varices and portosystemic collaterals did not show significant differences. The only parameter with a significant predictive value for the reduction of the pressure gradient was the pre-TIPSS pressure gradient (r = 0.8, p < 0.001). Conclusions: TIPSS allows a reliable reduction of the pressure gradient even at high pre-interventional pressure levels and a high collateral presence. In patients receiving TIPSS the presence and the characteristics of the collateral vessels seem to be too variable to draw reliable conclusions concerning the portosystemic pressure gradient.

  11. Effects of Loading Paths on Hydrodynamic Deep Drawing with Independent Radial Hydraulic Pressure of Aluminum Alloy Based on Numerical Simulation

    Xiaojing LIU; Yongchao XU; Shijian YUAN


    In order to meet the forming demands for low plasticity materials and large height-diameter ratio parts, a new process of hydrodynamic deep drawing (HDD) with independent radial hydraulic pressure is proposed. To investigate the effects of loading paths on the HDD with independent radial hydraulic pressure, the forming process of 5A06 aluminum alloy cylindrical cup with a hemispherical bottom was studied by numerical simula- tion. By employing the dynamic explicit analytical software ETA/Dynaform based on LS-DYNA3D, the effects of loading paths on the sheet-thickness distribution and surface quality were analyzed. The corresponding relations of the radial hydraulic pressure loading paths and the part's strain status on the forming limit diagram (FLD) were also discussed. The results indicated that a sound match between liquid chamber pressure and independent radial hydraulic pressure could restrain the serious thinning at the hemisphere bottom and that through adjusting radial hydraulic pressure could reduce the radial tensile strain and change the strain paths. Therefore, the drawing limit of the aluminum cylindrical cup with a hemispherical bottom could be increased significantly.

  12. Standard laboratory hydraulic pressure drop characteristics of various solid and I&E fuel elements

    Waters, E.D.; Horn, G.R.


    The purpose of this report is to present a set of standard pressure-drop curves for various fuel elements in process tubes of Hanford reactors. The flow and pressures within a process tube assembly under normal conditions are dependent to a large extent on the magnitude of the pressure drop across the fuel elements. The knowledge of this pressure drop is important in determination of existing thermal conditions within the process tubes and in predicting conditions for new fuel element designs or changes in operating conditions. The pressure-flow relations for the different Hanford fuel element-process tube assemblies have all been determined at one time or another in the 189-D Hydraulics Laboratory but the data had never been collected into a single report. Such a report is presented now in the interest of establishing a set of ``standard curves`` as determined by laboratory investigations. It must be recognized that the pressure drops of fuel elements in actual process tubes in the reactors may be slightly different than those reported here. The data presented here were obtained in new process tubes while reactor process tubes are usually either corroded or filmed, depending on their past history.

  13. A General Pressure Gradient Formulation for Ocean Models - Part II: Energy, Momentum, and Bottom Torque Consistency

    Song, Y.; Wright, D.


    A formulation of the pressure gradient force for use in models with topography-following coordinates is proposed and diagnostically analyzed by Song. We investigate numerical consistency with respect to global energy conservation, depth-integrated momentum changes, and the represent of the bottom pressure torque.

  14. A study of wake development and structure in constant pressure gradients

    Liu, Xiaofeng


    Motivated by the application to high-lift aerodynamics for commercial transport aircraft, a systematic investigation into the response of symmetric/asymmetric planar turbulent wake development to constant adverse, zero and favorable pressure gradients has been conducted. The experiments are performed at a Reynolds number of 2.4 × 106 based on the chord of the wake generator. A unique feature of this wake study is that the pressure gradients imposed on the wake flow field are held constant. The experimental measurements involve both conventional Laser Doppler Velocimetry and Hot Wire Anemometry flow field surveys of mean and turbulent quantities including the turbulent kinetic energy budget. In addition, similarity analysis and numerical simulation have also been conducted for this wake study. A focus of the research has been to isolate the effects of both pressure gradient and initial wake asymmetry on the wake development. Experimental results reveal that the pressure gradient has a tremendous influence on the wake development, despite the relatively modest pressure gradients imposed. For a given pressure gradient, the development of an initially asymmetric wake is different from the initially symmetric wake. An explicit similarity solution for the shape parameters of the symmetric wake is obtained and agrees with the experimental results. The turbulent kinetic energy budget measurements of the symmetric wake demonstrate that except for the convection term, the imposed pressure gradient does not change the fundamental flow physics of turbulent kinetic energy transport. Based on the turbulent kinetic energy budget measurements, an approach to correct the bias error associated with the notoriously difficult dissipation estimate is proposed and validated through the comparison of the experimental estimate with a direct numerical simulation result.

  15. Hydraulic pressure variations of groundwater in the Gran Sasso underground laboratory during Amatrice earthquake of August 24th, 2016

    Gaetano De Luca


    Full Text Available Since May 2015, hydraulic pressure, temperature and electrical conductivity of groundwater are in continuos recording near the deep underground laboratories of Gran Sasso of INFN. We used the S13 borehole that have pressure varying in the range of 24-28 bar during the year; these values mean that we have at least 300 m of water table above. The sampling of these parameters was brought until to 50 Hz using a 3 channels 24-bit ADC. During the period May 2015 – September 2016 (17 months we detected hydraulic pressure signals from 12 earthquakes at different surface distances (from 12.000 to 30 km and different magnitudes (from 8.3 to 4.3 Mw. For the Amatrice mainshock, we present, as first results, the hydroseismograph recorded at the S13 hydraulic pressure device compared to the time history recorded at GIGS station located both in the deep core of the Gran Sasso chain.



    The structure principles under the flow and pressure working conditions are studied, in order to investigate the dynamic characteristics of the electro-hydraulic proportional pressure-flow hybrid valve. According to the structure principles under the two different working conditions, the transfer functions under such conditions are derived. With the transfer functions, some structure elements that may affect its performance, are investigated, afterwards some principles of optimality and effective methods for improving the dynamic performance of the valve are proposed. The conclusions can be used to instruct engineering applications and products designing. The test results conform to the results of the theoretical analysis and simulation, which proves the correctness of the study and simulation works.

  17. Pressure Control for a Hydraulic Cylinder Based on a Self-Tuning PID Controller Optimized by a Hybrid Optimization Algorithm

    Ru Wang


    Full Text Available In order to improve the performance of the hydraulic support electro-hydraulic control system test platform, a self-tuning proportion integration differentiation (PID controller is proposed to imitate the actual pressure of the hydraulic support. To avoid the premature convergence and to improve the convergence velocity for tuning PID parameters, the PID controller is optimized with a hybrid optimization algorithm integrated with the particle swarm algorithm (PSO and genetic algorithm (GA. A selection probability and an adaptive cross probability are introduced into the PSO to enhance the diversity of particles. The proportional overflow valve is installed to control the pressure of the pillar cylinder. The data of the control voltage of the proportional relief valve amplifier and pillar pressure are collected to acquire the system transfer function. Several simulations with different methods are performed on the hydraulic cylinder pressure system. The results demonstrate that the hybrid algorithm for a PID controller has comparatively better global search ability and faster convergence velocity on the pressure control of the hydraulic cylinder. Finally, an experiment is conducted to verify the validity of the proposed method.

  18. Behavior of a horizontal air curtain subjected to a vertical pressure gradient

    Linden, James; Phelps, LeEllen


    We present the details on an experiment to investigate the behavior of an air curtain that is subjected to a transverse pressure gradient. The setup simulates the conditions that will be present in the Advanced Technology Solar Telescope (ATST), a 4-meter solar observatory that will be built on Haleakala, Hawaii. A test rig was built to replicate the region at which the optical path crosses a temperature and pressure boundary between the telescope mount region, which is at the ambient temperature and pressure, and a warmer, pressurized lab space directly below. Use of an air curtain in place of an optically-transmitting window at the interface would allow science observations at a wider range of scientific wavelengths. With the air curtain exhibiting transitional flow behavior across the boundary, and applied pressure gradients of up to 6.5 Pa, we found that the air curtain was able to hold a pressure gradient of 0.25 Pa. As the applied pressure was increased, transient turbulent regions formed at the interface, and predictable flow behavior only occurred in the region closest to the air curtain blower. Computer modeling is used to validate the test data, identify laminar regions of the air curtain where minimal image distortion would occur, and explore the relationship between the applied pressure, effective pressure difference, and air curtain profile.

  19. Non-linear aspects of Görtler instability in boundary layers with pressure gradient

    Rogenski, J. K.; de Souza, L. F.; Floryan, J. M.


    The laminar flow over a concave surface may undergo transition to a turbulent state driven by secondary instabilities initiated by the longitudinal vortices known as Görtler vortices. These vortices distort the boundary layer structure by modifying the streamwise velocity component in both spanwise and wall-normal directions. Numerical simulations have been conducted to identify the role of the external pressure gradients in the development and saturation of the vortices. The results show that flows with adverse pressure gradients reach saturation upstream from the saturation location for neutral and favorable pressure gradients. In the transition region, the mean spanwise shear stress is about three times larger than in the flow without the vortices.

  20. Non-invasive Measurement of Pressure Gradients in Pulsatile Flow using Ultrasound

    Olesen, Jacob Bjerring; Traberg, Marie Sand; Pihl, Michael Johannes


    approach. Pressure gradients are calculated from the measured velocity fields using the Navier-Stokes equation. Velocity fields are measured during constant and pulsating flow on a carotid bifurcation phantom and on a common carotid artery in-vivo. Scanning is performed with a 5 MHz BK8670 linear......This paper demonstrates how pressure gradients in a pulsatile flow environment can be measured non-invasively using ultrasound. The proposed method relies on vector velocity fields acquired from ultrasound data. 2-D flow data are acquired at 18-23 frames/sec using the Transverse Oscillation...... transducer using a BK Medical 2202 UltraView Pro Focus scanner. The calculated pressure gradients are validated through a finite element simulation of the constant flow model. The geometry of the flow simulation model is reproduced using MRI data, thereby providing identical flow domains in measurement...

  1. Pressure Gradient Influence on MHD Flow for Generalized Burgers’ Fluid with Slip Condition

    Ghada H. Ibraheem,


    Full Text Available This paper presents a research for magnetohydrodynamic (MHD flow of an incompressible generalized Burgers' fluid including by an accelerating plate and flowing under the action of pressure gradient. Where the no – slip assumption between the wall and the fluid is no longer valid. The fractional calculus approach is introduced to establish the constitutive relationship of the generalized Burgers' fluid. By using the discrete Laplace transform of the sequential fractional derivatives, a closed form solutions for the velocity and shear stress are obtained in terms of Fox H- function for the following two problems: (i flow due to a constant pressure gradient, and (ii flow due to due to a sinusoidal pressure gradient. The solutions for no – slip condition and no magnetic field, can be derived as special cases of our solutions. Furthermore, the effects of various parameters on the velocity distribution characteristics are analyzed and discussed in detail. Comparison between the two cases is also made.

  2. Coherent structures of a self-similar adverse pressure gradient turbulent boundary layer

    Sekimoto, Atsushi; Kitsios, Vassili; Atkinson, Callum; Jiménez, Javier; Soria, Julio


    The turbulence statistics and structures are studied in direct numerical simulation (DNS) of a self-similar adverse pressure gradient turbulent boundary layer (APG-TBL). The self-similar APG-TBL at the verged of separation is achieved by a modification of the far-field boundary condition to produce the desired pressure gradient. The turbulence statistics in the self-similar region collapse by using the scaling of the external velocity and the displacement thickness. The coherent structures of the APG-TBL are investigated and compared to those of zero-pressure gradient case and homogeneous shear flow. The support of the ARC, NCI and Pawsey SCC funded by the Australian and Western Australian governments as well as the support of PRACE funded by the European Union are gratefully acknowledged.

  3. Semianalytical Solution of the Nonlinear Dual-Porosity Flow Model with the Quadratic Pressure Gradient Term

    Jiang-Tao Li


    Full Text Available The nonlinear dual-porosity flow model, specifically considering the quadratic pressure gradient term, wellbore storage coefficient, well skin factor, and interporosity flow of matrix to natural fractures, was established for well production in a naturally fractured formation and then solved using a semianalytical method, including Laplace transform and a transformation of the pressure function. Analytical solution of the model in Laplace space was converted to numerical solution in real space using Stehfest numerical inversion. Nonlinear flow process for well production in a naturally fractured formation with different external boundaries was simulated and analyzed using standard pressure curves. Influence of the quadratic pressure gradient coefficient on pressure curves was studied qualitatively and quantitatively in conditions of a group of fixed model parameters. The research results show that the semianalytical modelling method is applicable in simulating the nonlinear dual-porosity flow behavior.

  4. The establishment of a new deliverability equation considering threshold pressure gradient

    Li Lezhong; Li Xiangfang; He Dongbo; Xu Hanbing


    The flowing mechanism of a low permeability gas reservoir is different from a conventional gas reservoir, espe-cially for that with higher irreducible water saturation the threshold pressure gradient exists. At present, in all the deliverability equation, the additional pressure drop caused by the threshold pressure gradient is viewed as constant, but this method has big error in the practical application. Based on the non-Darcy steady flow equation, the limited integral of the additional pressure drop is solved in this paper and it is realized that the additional pressure drop is not a constant but has something to do with production data, and a new deliverability equation is derived, with the relevant processing method for modified isochronal test data. The new deliverability equation turns out to be practical through onsite applica-tion.

  5. Numerical Study of Thermal Hydraulic behavior of Pressurizer for PLCS Scenario by CUPID Code

    Lee, Jae Ryong; Yoon, Han Young [KAERI, Daejeon (Korea, Republic of); Yoon, Bo Kam; Kim, Jeong Ju; Park, Jong Cheol; Lee, Gyu Cheon [KEPCO, Daejeon (Korea, Republic of)


    For a malfunction of a pressurizer level control system, a chemical and volume control system (CVCS) charging flowrate becomes a maximum level and a letdown flowrate a minimum level as well. Consequently, a water level and pressure of pressurizer is abnormally increased, which causes a pilot operated relief valve (POSRV) opened. It becomes important to investigate that a mixture from the POSRV becomes single-phase gas or two-phase mixture. In this study, the three-dimensional thermal-hydraulic behavior inside the pressurizer is numerically investigated by the CUPID code. The flow fields highly depend on some parameters such as subcooling of the stored water, interfacial drag model and POSRV opening. Thus, these parameters are examined in this study. These parameters are examined in this study. Less subcooling temperature makes the flow behavior unstable and flashing occur. The two-phase mixture is discharged through the POSRV. Moreover, less flow area delays a discharging flow rate. A sensitivity for the other parameters such critical flow model should be examined for the future work.

  6. Non-invasive Estimation of Pressure Gradients in Pulsatile Flow using Ultrasound

    Olesen, Jacob Bjerring; Villagómez Hoyos, Carlos Armando; Traberg, Marie Sand


    This paper investigates how pressure gradients in a pulsatile flow environment can be measured non-invasively using ultrasound. The presented set-up is based on vector velocity fields measured on a blood mimicking fluid moving at a peak flow rate of 1 ml/s through a constricted vessel. Fields of ...... and standard deviation of 10% and 13%, respectively, relative to peak estimated gradient. The paper concludes that maps of pressure gradients can be measured non-invasively using ultrasound with a precision of more than 85%......This paper investigates how pressure gradients in a pulsatile flow environment can be measured non-invasively using ultrasound. The presented set-up is based on vector velocity fields measured on a blood mimicking fluid moving at a peak flow rate of 1 ml/s through a constricted vessel. Fields...... of pressure gradients are calculated using the Navier-Stokes equations. Flow data are acquired to a depth of 3 cm using directional synthetic aperture flow imaging on a linear array transducer producing 1500 image frames of velocity estimates per second. Scans of a carotid bifurcation phantom with a 70...

  7. Stabilizing effect of ion pressure gradient on magnetic curvature-driven drift modes located at rational surface of tokamak plasma

    Wang Ai-Ke


    In the fluid model, we derive a dispersion relation for the toroidal drift modes of tokamak plasmas, including the ion pressure gradient and the magnetic field gradient and curvature. It is shown that the magnetic field gradient and curvature (MFGC) can cause instabilities at the rational surface, which are of toroidicity-induced (TI) modes. On the other hand, it is discovered that the ion pressure gradient can stabilize the present MFGC instabilities. The critical threshold of ion pressure gradient, which makes the growth rate reduced to zero, is obtained both analytically and numerically.

  8. Energy-saving analysis of hydraulic hybrid excavator based on common pressure rail.

    Shen, Wei; Jiang, Jihai; Su, Xiaoyu; Karimi, Hamid Reza


    Energy-saving research of excavators is becoming one hot topic due to the increasing energy crisis and environmental deterioration recently. Hydraulic hybrid excavator based on common pressure rail (HHEC) provides an alternative with electric hybrid excavator because it has high power density and environment friendly and easy to modify based on the existing manufacture process. This paper is focused on the fuel consumption of HHEC and the actuator dynamic response to assure that the new system can save energy without sacrificing performance. Firstly, we introduce the basic principle of HHEC; then, the sizing process is presented; furthermore, the modeling period which combined mathematical analysis and experiment identification is listed. Finally, simulation results show that HHEC has a fast dynamic response which can be accepted in engineering and the fuel consumption can be reduced 21% to compare the original LS excavator and even 32% after adopting another smaller engine.


    GUO Xin-lei; YANG Kai-lin; GUO Yong-xin


    A pre-filter combined with threshold self-learning wavelet algorithm is proposed for hydraulic pressure signals denoising. The denoising threshold is self-learnt in the steady flow state, and then modified under a given limit to make the mean square errors between reconstruction signals and desirable outputs minimum, so the corresponding optimal denoising threshold in a single operating case can be obtained. These optimal thresholds are used for the whole signal denoising and are different in various cases. Simulation results and comparative studies show that the present approach has an obvious effect of noise suppression and is superior to those of traditional wavelet algorithms and back-propagation neural networks. It also provides the precise data for the next step of pipeline leak detection using transient technique.

  10. Polynomial regularization for robust MRI-based estimation of blood flow velocities and pressure gradients.

    Delles, Michael; Rengier, Fabian; Ley, Sebastian; von Tengg-Kobligk, Hendrik; Kauczor, Hans-Ulrich; Dillmann, Rüdiger; Unterhinninghofen, Roland


    In cardiovascular diagnostics, phase-contrast MRI is a valuable technique for measuring blood flow velocities and computing blood pressure values. Unfortunately, both velocity and pressure data typically suffer from the strong image noise of velocity-encoded MRI. In the past, separate approaches of regularization with physical a-priori knowledge and data representation with continuous functions have been proposed to overcome these drawbacks. In this article, we investigate polynomial regularization as an exemplary specification of combining these two techniques. We perform time-resolved three-dimensional velocity measurements and pressure gradient computations on MRI acquisitions of steady flow in a physical phantom. Results based on the higher quality temporal mean data are used as a reference. Thereby, we investigate the performance of our approach of polynomial regularization, which reduces the root mean squared errors to the reference data by 45% for velocities and 60% for pressure gradients.


    Wiegand, D.E.


    A hydraulic servo is designed in which a small pressure difference produced at two orifices by an electrically operated flapper arm in a constantly flowing hydraulic loop is hydraulically amplified by two constant flow pumps, two additional orifices, and three unconnected ball pistons. Two of the pistons are of one size and operate against the additional orifices, and the third piston is of a different size and operates between and against the first two pistons. (AEC)

  12. Hydraulic redistribution in dwarf Rhizophora mangle trees driven by interstitial soil water salinity gradients: impacts on hydraulic architecture and gas exchange.

    Hao, Guang-You; Jones, Tim J; Luton, Corene; Zhang, Yong-Jiang; Manzane, Eric; Scholz, Fabian G; Bucci, Sandra J; Cao, Kun-Fang; Goldstein, Guillermo


    Rhizophora mangle L. trees of Biscayne National Park (Florida, USA) have two distinct growth forms: tall trees (5-10 m) growing along the coast and dwarf trees (1 m or less) growing in the adjacent inland zone. Sharp decreases in salinity and thus increases in soil water potential from surface soil to about a depth of 1 m were found at the dwarf mangrove site but not at the tall mangrove site. Consistent with our prediction, hydraulic redistribution detected by reverse sap flow in shallow prop roots was observed during nighttime, early morning and late afternoon in dwarf trees, but not in tall trees. In addition, hydraulic redistribution was observed throughout the 24-h period during a low temperature spell. Dwarf trees had significantly lower sapwood-specific hydraulic conductivity, smaller stem vessel diameter, lower leaf area to sapwood area ratio (LA/SA), smaller leaf size and higher leaf mass per area. Leaves of dwarf trees had lower CO(2) assimilation rate and lower stomatal conductance compared to tall trees. Leaf water potentials at midday were more negative in tall trees that are consistent with their substantially higher stomatal conductance and LA/SA. The substantially lower water transport efficiency and the more conservative water use of dwarf trees may be due to a combination of factors such as high salinity in the surface soil, particularly during dry periods, and substantial reverse sap flow in shallow roots that make upper soil layers with high salinity a competing sink of water to the transpiring leaves. There may also be a benefit for the dwarf trees in having hydraulic redistribution because the reverse flow and the release of water to upper soil layers should lead to dilution of the high salinity in the rhizosphere and thus relieve its potential harm to dwarf R. mangle trees.

  13. Can postoperative mean transprosthetic pressure gradient predict survival after aortic valve replacement?

    Koene, Bart M.; Hamad, Mohamed A. Soliman; Bouma, Wobbe; Mariani, Massimo A.; Peels, Kathinka C.; van Dantzig, Jan-Melle; van Straten, Albert H.

    In this study, we sought to determine the effect of the mean transprosthetic pressure gradient (TPG), measured at 6 weeks after aortic valve replacement (AVR) or AVR with coronary artery bypass grafting (CABG) on late all-cause mortality. Between January 1998 and March 2012, 2,276 patients (mean age

  14. The pressure gradient for heterogeneous flow of coal, sand and iron in pipelines

    Yu, X.Q.


    The existing relationships based on Durand's method to predict pressure gradients for slurry flow in pipelines appear to be inadequate when accounting for a wide range of variables such as particle size and relative density as well as concentration. Using the coal, sand and iron ore data collected

  15. A Remark on the Regularity Criterion for the 3D Boussinesq Equations Involving the Pressure Gradient

    Zujin Zhang


    Full Text Available We consider the three-dimensional Boussinesq equations and obtain a regularity criterion involving the pressure gradient in the Morrey-Companato space Mp,q. This extends and improves the result of Gala (Gala 2013 for the Navier-Stokes equations.

  16. Equilibrium turbulent boundary layers with wall suction/blowing and pressure gradients

    Patwardhan, Saurabh; Ramesh, O. N.


    Conditions for the equilibrium conditions in turbulent boundary layers with suction or blowing across a no slip wall and pressure gradients are derived from the governing equations. It is also shown that under these conditions the governing equations show self similarity in the conventional inner co-ordinates as well as ``laminar-like'' co-ordinates. The only turbulent boundary layer in ``perfect equilibrium'' known as sink flow turbulent boundary layer forms a subset of this more general equilibrium concept. Direct numerical simulations were carried out to investigate this hypothesis for the case of favourable pressure gradient with small blowing at the wall. Reynolds number invariance and complete self similarity of mean velocity profile and second order turbulence statistics is observed along the flow direction similar to the sink flow boundary layer. A comparison between the case with wall blowing and imposed favourable pressure gradient and the sink flow case for same value of pressure gradient parameter reveals a shift in log law in mean velocity profile and increase in peak turbulence intensities.

  17. Barrier island breach evolution: Alongshore transport and bay-ocean pressure gradient interactions

    Safak, Ilgar; Warner, John C.; List, Jeffrey H.


    Physical processes controlling repeated openings and closures of a barrier island breach between a bay and the open ocean are studied using aerial photographs and atmospheric and hydrodynamic observations. The breach site is located on Pea Island along the Outer Banks, separating Pamlico Sound from the Atlantic Ocean. Wind direction was a major control on the pressure gradients between the bay and the ocean to drive flows that initiate or maintain the breach opening. Alongshore sediment flux was found to be a major contributor to breach closure. During the analysis period from 2011 to 2016, three hurricanes had major impacts on the breach. First, Hurricane Irene opened the breach with wind-driven flow from bay to ocean in August 2011. Hurricane Sandy in October 2012 quadrupled the channel width from pressure gradient flows due to water levels that were first higher on the ocean side and then higher on the bay side. The breach closed sometime in Spring 2013, most likely due to an event associated with strong alongshore sediment flux but minimal ocean-bay pressure gradients. Then, in July 2014, Hurricane Arthur briefly opened the breach again from the bay side, in a similar fashion to Irene. In summary, opening and closure of breaches are shown to follow a dynamic and episodic balance between along-channel pressure gradient driven flows and alongshore sediment fluxes.

  18. Viscoelastic fluid flow in circular narrow confinements driven by periodic pressure and potential gradients

    Nguyen, T.; Berg, van den A.; Eijkel, J.C.T.


    We present an in-depth analysis and analytical solution for AC hydrodynamic flow (driven by a timedependent pressure gradient and/or electric fields) of viscoelastic fluid through cylindrical micro-, nanochannels. Particularly, for this purpose we solve the linearized Poisson-Boltzmann equation tog

  19. Nozzle design in a fiber spinning process for a maximal pressure gradient

    Yang Zhanping


    Full Text Available The thickness of a spinneret is always a geometrical constraint in nozzle design. The geometrical form of a nozzle has a significant effect on the subsequent spinning characteristics. This paper gives an optimal condition for maximal pressure gradient through the nozzle.

  20. Symmetries and Group-Invariant Solutions for Transonic Pressure-Gradient Equations

    王丽真; 黄晴


    Lie symmetry group method is applied to study the transonic pressure-gradient equations in two-dimensional space. Its symmetry groups and corresponding optimal systems are determined, and several classes of irrotational groupinvariant solutions associated to the symmetries are obtained and special case of one-dimensional rarefaction wave is found.

  1. Relationship among diastolic intraventricular pressure gradients, relaxation, and preload : impact of age and fitness

    Popovic, Z.B.; Prasad, A.; Garcia, M.J.; Arbab-Zadeh, A.; Borowski, A.; Dijk, E.; Greenberg, N.L.; Levine, B.D.; Thomas, J.D.


    Diastolic intraventricular pressure gradients (IVPGs) are a measure of the ability of the ventricle to facilitate its filling using diastolic suction. We assessed 15 healthy young but sedentary subjects, aged <50 yr (young subjects; age, 35 +/- 9 yr); 13 healthy but sedentary seniors, aged >65 yr wi

  2. Alveolar septal patterning during compensatory lung growth: Part II the effect of parenchymal pressure gradients.

    Haber, Shimon; Weisbord, Michal; Mentzer, Steven J; Tsuda, Akira


    In most mammals, compensatory lung growth occurs after the removal of one lung (pneumonectomy). Although the mechanism of alveolar growth is unknown, the patterning of complex alveolar geometry over organ-sized length scales is a central question in regenerative lung biology. Because shear forces appear capable of signaling the differentiation of important cells involved in neoalveolarization (fibroblasts and myofibroblasts), interstitial fluid mechanics provide a potential mechanism for the patterning of alveolar growth. The movement of interstitial fluid is created by two basic mechanisms: 1) the non-uniform motion of the boundary walls, and 2) parenchymal pressure gradients external to the interstitial fluid. In a previous study (Haber et al., Journal of Theoretical Biology 400: 118-128, 2016), we investigated the effects of non-uniform stretching of the primary septum (associated with its heterogeneous mechanical properties) during breathing on generating non-uniform Stokes flow in the interstitial space. In the present study, we analyzed the effect of parenchymal pressure gradients on interstitial flow. Dependent upon lung microarchitecture and physiologic conditions, parenchymal pressure gradients had a significant effect on the shear stress distribution in the interstitial space of primary septa. A dimensionless parameter δ described the ratio between the effects of a pressure gradient and the influence of non-uniform primary septal wall motion. Assuming that secondary septa are formed where shear stresses were the largest, it is shown that the geometry of the newly generated secondary septa was governed by the value of δ. For δ smaller than 0.26, the alveolus size was halved while for higher values its original size was unaltered. We conclude that the movement of interstitial fluid, governed by parenchymal pressure gradients and non-uniform primary septa wall motion, provides a plausible mechanism for the patterning of alveolar growth. Copyright © 2017

  3. Perturbations of the solar wind flow by radial and latitudinal pick-up ion pressure gradients

    H. J. Fahr


    Full Text Available It has been found that pick-up ions at their dynamical incorporation into the solar wind modify the original conditions of the asymptotic solar wind plasma flow. In this respect, it has meanwhile been revealed in many papers that these type of solar wind modifications, i.e. deceleration and decrease of effective Mach number, are not only due to the pick-up ion loading effects, but also to the action of pick-up ion pressure gradients. Up to now only the effects of radial pick-up ion pressure gradients were considered, however, analogously but latitudinal pressure gradients also appear to be important. Here we study the effects of radial and latitudinal pick-up ion pressure gradients, occurring especially during solar minimum conditions at mid-latitude regions where slow solar wind streams change to fast solar wind streams. First, we give estimates of the latitudinal wind components connected with these gradients, and then after revealing its importance, present a more quantitative calculation of solar wind velocity and density perturbations resulting from these pressure forces. It is shown that the relative density perturbations near and in the ecliptic increase with radial distance and thus may well explain the measured non-spherically symmetric density decrease with distance. We also show that the solar wind decelerations actually seen with Voyager-1/2 are in conciliation with interstellar hydrogen densities of nH∞≥0.1cm-3, in contrast to earlier claims for nH∞=0.05cm-3.

  4. 心墙水力劈裂与孔压关系的探讨%The analysis of the relationship between hydraulic fracture and the pore pressure

    张红日; 党发宁; 兰素恋; 魏见海


    基于Biot固结理论的有效应力二维数值模拟方法,研究了堆石坝的粘土心墙水力劈裂过程中孔隙水压力的变化.分析了坝体竣工期粘土心墙中的拱效应,探讨了从竣工固结到蓄水过程和稳定渗流期粘土心墙中孔隙水压力的变化分布特点,并对心墙发生水力劈裂的可能性进行判断.研究结果表明:堆石坝粘土心墙内部孔隙水压力梯度的模拟分析能更加合理地解释水力劈裂发生与蓄水速度和心墙低渗透性的关系,因此,分析考虑水位上升过程中粘土心墙内孔隙水压力分布情况是研究心墙水力劈裂发生机理的重点.%Based on the consolidation theory of Biot effective stress analysis method, two-dimensional numerical simulation is adopted to study the dam from the completion of the dam to the clay core run-time pore pressure changes in the process. Arching effect of the completion period and the changes with the completion of the process of consolidation on the stability of the water flow in the pore water pressure distribution are analyzed based on the analysis of clay core dams, the mechanism of hydraulic fracture on the basis of the core wall of the dam occurred in the hydraulic is determined with the possibility of splitting. The results show that the simulation of gradient internal pore water pressure for the clay core of rockfilled dam core can reasonably explain the occurrence of hydraulic fracturing with water speed, and the low permeability of the core wall has great effects. When hydraulic fracture occurred with the core wall mechanism of the core wall, the distribution of clay pore water pressure must be taken into account.

  5. Doppler echo evaluation of pulmonary venous-left atrial pressure gradients: human and numerical model studies

    Firstenberg, M. S.; Greenberg, N. L.; Smedira, N. G.; Prior, D. L.; Scalia, G. M.; Thomas, J. D.; Garcia, M. J.


    The simplified Bernoulli equation relates fluid convective energy derived from flow velocities to a pressure gradient and is commonly used in clinical echocardiography to determine pressure differences across stenotic orifices. Its application to pulmonary venous flow has not been described in humans. Twelve patients undergoing cardiac surgery had simultaneous high-fidelity pulmonary venous and left atrial pressure measurements and pulmonary venous pulsed Doppler echocardiography performed. Convective gradients for the systolic (S), diastolic (D), and atrial reversal (AR) phases of pulmonary venous flow were determined using the simplified Bernoulli equation and correlated with measured actual pressure differences. A linear relationship was observed between the convective (y) and actual (x) pressure differences for the S (y = 0.23x + 0.0074, r = 0.82) and D (y = 0.22x + 0.092, r = 0.81) waves, but not for the AR wave (y = 0. 030x + 0.13, r = 0.10). Numerical modeling resulted in similar slopes for the S (y = 0.200x - 0.127, r = 0.97), D (y = 0.247x - 0. 354, r = 0.99), and AR (y = 0.087x - 0.083, r = 0.96) waves. Consistent with numerical modeling, the convective term strongly correlates with but significantly underestimates actual gradient because of large inertial forces.

  6. Alternative blade materials for technical and ecological optimization of a hydraulic pressure machine

    Schwyzer, Olivier; Saenger, Nicole


    The Hydraulic Pressure Machine (HPM) is an energy converter to exploit head differences between 0.5 and 2.5 m in small streams and irrigation canals. Previous investigations show that efficiencies above 60% are possible. Several case studies indicate good continuity for aquatic life (e.g. fish) and bed load for the technology. The technology is described as an economically and ecologically viable option for small scale hydropower generation. Primary goal of this research is to improve the HPM blade design regarding its continuity properties by maintaining good efficiency rates. This is done by modifying the blade tip and testing within a large physical model under laboratory condition. Blade tips from steel (conventional - reference case) and a combination of EPDM rubber and steel as sandwich construction (rubber, steel, rubber - adhesive layered) are tested and compared. Both materials reach similar values for hydraulic efficiency (approx. 58%) and mechanical power output (approx. 220 W). The variation of different gap sizes pointed out the importance of small clearance gaps to reach high efficiencies. For assessing the two blade tip materials regarding continuity for aquatic life, fish dummies were led through the wheel. Analysis of slow motion video of dummies hit by the blade show significant advantages for the EPDM blade tip. The EPDM rubber allows to bend and thus reduces the shock and the probability for cuts on the fish dummy. It was shown that blade tips from EPDM have certain advantages regarding continuity compared to standard blade tips from steel. No compromise regarding energy production had to be made. These results from the HPM can be transferred to breast shot water wheel and may be applied for new and retrofitting projects.

  7. The effect of electron thermal conduction on plasma pressure gradient during reconnection of magnetic field lines

    Chu, T.K.


    The interplay of electron cross-field thermal conduction and the reconnection of magnetic field lines around an m = 1 magnetic island prior to a sawtooth crash can generate a large pressure gradient in a boundary layer adjacent to the reconnecting surface, leading to an enhanced gradient of poloidal beta to satisfy the threshold condition for ideal MHD modes. This narrow boundary layer and the short onset time of a sawtooth crash can be supported by fine-grained turbulent processes in a tokamak plasma. 11 refs.

  8. Kinetic performance limits of constant pressure versus constant flow rate gradient elution separations. Part I: theory.

    Broeckhoven, K; Verstraeten, M; Choikhet, K; Dittmann, M; Witt, K; Desmet, G


    We report on a general theoretical assessment of the potential kinetic advantages of running LC gradient elution separations in the constant-pressure mode instead of in the customarily used constant-flow rate mode. Analytical calculations as well as numerical simulation results are presented. It is shown that, provided both modes are run with the same volume-based gradient program, the constant-pressure mode can potentially offer an identical separation selectivity (except from some small differences induced by the difference in pressure and viscous heating trajectory), but in a significantly shorter time. For a gradient running between 5 and 95% of organic modifier, the decrease in analysis time can be expected to be of the order of some 20% for both water-methanol and water-acetonitrile gradients, and only weakly depending on the value of V(G)/V₀ (or equivalently t(G)/t₀). Obviously, the gain will be smaller when the start and end composition lie closer to the viscosity maximum of the considered water-organic modifier system. The assumptions underlying the obtained results (no effects of pressure and temperature on the viscosity or retention coefficient) are critically reviewed, and can be inferred to only have a small effect on the general conclusions. It is also shown that, under the adopted assumptions, the kinetic plot theory also holds for operations where the flow rate varies with the time, as is the case for constant-pressure operation. Comparing both operation modes in a kinetic plot representing the maximal peak capacity versus time, it is theoretically predicted here that both modes can be expected to perform equally well in the fully C-term dominated regime (where H varies linearly with the flow rate), while the constant pressure mode is advantageous for all lower flow rates. Near the optimal flow rate, and for linear gradients running from 5 to 95% organic modifier, time gains of the order of some 20% can be expected (or 25-30% when accounting for

  9. Research on Pressure Shock in Hydraulic System%液压系统中的压力冲击研究



    Based on theoretical calculation and simulation analysis, this paper got the key factor which affect the pressure shock in valve-control hydraulic system. Then concluded how the tube length and valve open-time affect pressure shock in hydraulic system. And the conclusions were verified based on test. It showed that tube length and valve open-time affect pressure shock in hydraulic system directly. The research also showed that shortening tube length and increasing valve open-time properly can reduce pressure shock effectively. All above provide the direction for the layout and design of hydraulic system part/product, and also provide theoretical basis for optimizing hydraulic system.%通过理论计算和仿真分析,研究影响阀控液压系统压力冲击的关键因素,得出阀控液压系统中的压力冲击与管路长度、阀开启时间的关系,并进行试验验证。结果表明,管路长度、阀开启时间直接影响着阀控液压系统中的压力冲击。缩短管路长度和适当延长阀开启时间,都能有效减小阀控系统中的压力冲击。这为飞机液压系统中元部件的布局和设计提供了方向,为飞机液压系统的完善和优化提供了依据。

  10. Two-Dimensional Regular Shock Reflection for the Pressure Gradient System of Conservation Laws

    Yuxi Zheng


    We establish the existence of a global solution to a regular reflection of a shock hitting a ramp for the pressure gradient system of equations. The set-up of the reflection is the same as that of Mach's experiment for the compressible Euler system, i.e., a straight shock hitting a ramp. We assume that the angle of the ramp is close to 90 degrees. The solution has a reflected bow shock wave, called the diffraction of the planar shock at the compressive corner, which is mathematically regarded as a free boundary in the self-similar variable plane.The pressure gradient system of three equations is a subsystem, and an approximation, of the full Euler system,and we offer a couple of derivations.

  11. Experimental Measurements of a High Reynolds Num- ber Adverse Pressure Gradient Turbulent Boundary Layer

    Atkinson, Callum; Amili, Omid; Stanislas, Michel; Cuvier, Christophe; Foucaut, Jean-Marc; Srinath, Sricharan; Laval, Jean-Philippe; Kaehler, Christian; Hain, Rainer; Scharnowski, Sven; Schroeder, Andreas; Geisler, Reinhard; Agocs, Janos; Roese, Anni; Willert, Christian; Klinner, Joachim; Soria, Julio


    The study of adverse pressure gradient turbulent boundary layers is complicated by the need to characterise both the local pressure gradient and it's upstream flow history. It is therefore necessary to measure a significant streamwise domain at a resolution sufficient to resolve the small scales features. To achieve this collaborative particle image velocimetry (PIV) measurements were performed in the large boundary layer wind-tunnel at the Laboratoire de Mecanique de Lille, including: planar measurements spanning a streamwise domain of 3.5m using 16 cameras covering 15 δ spanwise wall-normal stereo-PIV measurements, high-speed micro-PIV of the near wall region and wall shear stress; and streamwise wall-normal PIV in the viscous sub layer. Details of the measurements and preliminary results will be presented.

  12. Thermal Hydraulic Analysis of a Passive Residual Heat Removal System for an Integral Pressurized Water Reactor

    Junli Gou


    Full Text Available A theoretical investigation on the thermal hydraulic characteristics of a new type of passive residual heat removal system (PRHRS, which is connected to the reactor coolant system via the secondary side of the steam generator, for an integral pressurized water reactor is presented in this paper. Three-interknited natural circulation loops are adopted by this PRHRS to remove the residual heat of the reactor core after a reactor trip. Based on the one-dimensional model and a simulation code (SCPRHRS, the transient behaviors of the PRHRS as well as the effects of the height difference between the steam generator and the heat exchanger and the heat transfer area of the heat exchanger are studied in detail. Through the calculation analysis, it is found that the calculated parameter variation trends are reasonable. The higher height difference between the steam generator and the residual heat exchanger and the larger heat transfer area of the residual heat exchanger are favorable to the passive residual heat removal system.

  13. Numerical design and optimization of hydraulic resistance and wall shear stress inside pressure-driven microfluidic networks.

    Damiri, Hazem Salim; Bardaweel, Hamzeh Khalid


    Microfluidic networks represent the milestone of microfluidic devices. Recent advancements in microfluidic technologies mandate complex designs where both hydraulic resistance and pressure drop across the microfluidic network are minimized, while wall shear stress is precisely mapped throughout the network. In this work, a combination of theoretical and modeling techniques is used to construct a microfluidic network that operates under minimum hydraulic resistance and minimum pressure drop while constraining wall shear stress throughout the network. The results show that in order to minimize the hydraulic resistance and pressure drop throughout the network while maintaining constant wall shear stress throughout the network, geometric and shape conditions related to the compactness and aspect ratio of the parent and daughter branches must be followed. Also, results suggest that while a "local" minimum hydraulic resistance can be achieved for a geometry with an arbitrary aspect ratio, a "global" minimum hydraulic resistance occurs only when the aspect ratio of that geometry is set to unity. Thus, it is concluded that square and equilateral triangular cross-sectional area microfluidic networks have the least resistance compared to all rectangular and isosceles triangular cross-sectional microfluidic networks, respectively. Precise control over wall shear stress through the bifurcations of the microfluidic network is demonstrated in this work. Three multi-generation microfluidic network designs are considered. In these three designs, wall shear stress in the microfluidic network is successfully kept constant, increased in the daughter-branch direction, or decreased in the daughter-branch direction, respectively. For the multi-generation microfluidic network with constant wall shear stress, the design guidelines presented in this work result in identical profiles of wall shear stresses not only within a single generation but also through all the generations of the

  14. FFT integration of instantaneous 3D pressure gradient fields measured by Lagrangian particle tracking in turbulent flows

    Huhn, F.; Schanz, D.; Gesemann, S.; Schröder, A.


    Pressure gradient fields in unsteady flows can be estimated through flow measurements of the material acceleration in the fluid and the assumption of the governing momentum equation. In order to derive pressure from its gradient, almost exclusively two numerical methods have been used to spatially integrate the pressure gradient until now: first, direct path integration in the spatial domain, and second, the solution of the Poisson equation for pressure. Instead, we propose an alternative third method that integrates the pressure gradient field in Fourier space. Using a FFT function, the method is fast and easy to implement in programming languages for scientific computing. We demonstrate the accuracy of the integration scheme on a synthetic pressure field and apply it to an experimental example based on time-resolved material acceleration data from high-resolution Lagrangian particle tracking with the Shake-The-Box method.

  15. Validation of the thermal-hydraulic system code ATHLET based on selected pressure drop and void fraction BFBT tests

    Di Marcello, Valentino, E-mail:; Escalante, Javier Jimenez; Espinoza, Victor Sanchez


    Highlights: • Simulation of BFBT-BWR steady-state and transient tests with ATHLET. • Validation of thermal-hydraulic models based on pressure drops and void fraction measurements. • TRACE system code is used for the comparative study. • Predictions result in a good agreement with the experiments. • Discrepancies are smaller or comparable with respect to the measurements uncertainty. - Abstract: Validation and qualification of thermal-hydraulic system codes based on separate effect tests are essential for the reliability of numerical tools when applied to nuclear power plant analyses. To this purpose, the Institute for Neutron Physics and Reactor Technology (INR) at the Karlsruhe Institute of Technology (KIT) is involved in various validation and qualification activities of different CFD, sub-channel and system codes. In this paper, the capabilities of the thermal-hydraulic code ATHLET are assessed based on the experimental results provided within the NUPEC BFBT benchmark related to key Boiling Water Reactors (BWR) phenomena. Void fraction and pressure drops measurements in the BFBT bundle performed under steady-state and transient conditions which are representative for e.g. turbine trip and recirculation pump trip events, are compared with the numerical results of ATHLET. The comparison of code predictions with the BFBT data has shown good agreement given the experimental uncertainty and the results are consistent with the trends obtained with similar thermal-hydraulic codes.

  16. The transpired turbulent boundary layer in various pressure gradients and the blow-off condition

    Georgiou, D. P.; Louis, J. F.


    Experimental data are reported from studies of the cooling effectiveness and conditions leading to blow-off in transpiration cooling (TC). The TC configuration used featured a sintered bronze plate in a hot blowdown wind tunnel. Cooled air was pumped through the plate and data were gathered with calorimeters downstream of a piece of sandpaper which tripped the boundary layer. Pressure taps were also used. Local pressure gradient effects were small, but local accelerations reduced the cooling effectiveness. The downstream Stanton numbers were sensitive to the upstream coolant-injection ratio. Increasing the injection rate had, at best, only a small effect on the local heat flux.

  17. Sound Localization in Lizards: Functioning of a Pressure-Gradient Receiver

    van Hemmen, J. Leo


    Because of their small interaural distance, lizards as well as some other animals have developed a special hearing mechanism, the ``pressure-gradient receiver''. The lizard peripheral auditory system differs from the mammalian one by a coupling of the two eardrums through the internal mouth cavity. We present a three-dimensional analytical model of the pressure-gradient receiver. The central aspect of the coupling of the membranes through the mouth cavity is realized by means of the boundary conditions. Moreover, the lizard's middle ear, a simple lever construction called columella, is asymmetrically attached to the tympanic membrane. This has motivated us to solve the problem of how the middle ear influences the spatial-amplitude profile and the frequency distribution of the tympanic membrane vibration. Finally, we show results from numerical simulations of the eigenfunctions and eigenfrequencies in a lizard's internal mouth cavity bounded by the eardrums. To this end, we have constructed the complex geometry from a cast imprint of the cavity with the help of three-dimensional scans. Our results led to an interesting speculation regarding the neurobiological use of the pressure-gradient system.

  18. DNS of self-similar adverse pressure gradient turbulent boundary layer

    Soria, Julio; Kitsios, Vassili; Sekimoto, Atsushi; Atkinson, Callum; Jiménez, Javier


    A direct numerical simulation (DNS) of a self-similar adverse pressure gradient (APG) turbulent boundary layer (TBL) at the verge of separation has been set-up and carried out. The DNS APG TBL has a displacement thickness based Reynolds number that ranges up to 30,000. The conditions for self-similarity and appropriate scaling will be highlighted, with the first and second order velocity statistical profiles non-dimensionalised using this scaling. The details of the DNS and the required boundary conditions that are necessary to establish this self-similar APG-TBL will be presented. The statistical properties of the self-similar adverse pressure gradient (APG) turbulent boundary layer (TBL) DNS will presented, as will the profiles of the terms in the momentum equation, spanwise/wall-normal kinetic energy spectrum and two-point correlations, which will be compared to those of a zero pressure gradient turbulent boundary layer. NCI and Pawsey SCC funded by the Australian and Western Australian governments as well as the support of PRACE funded by the European Union are gratefully acknowledged.

  19. Influence of pressure gradient on streamwise skewness factor in turbulent boundary layer

    Dróżdż, Artur


    The paper shows an effect of favourable and adverse pressure gradients on turbulent boundary layer. The skewness factor of streamwise velocity component was chosen as a measure of the pressure gradient impact. It appears that skewness factor is an indicator of convection velocity of coherent structures, which is not always equal to the average flow velocity. The analysis has been performed based upon velocity profiles measured with hot-wire technique in turbulent boundary layer with pressure gradient corresponding to turbomachinery conditions. The results show that the skewness factor decreases in the flow region subjected to FPG and increases in the APG conditions. The changes of convection velocity and skewness factor are caused by influence of large-scale motion through the mechanism called amplitude modulation. The large-scale motion is less active in FPG and more active in APG, therefore in FPG the production of vortices is random (there are no high and low speed regions), while in the APG the large-scale motion drives the production of vortices. Namely, the vortices appear only in the high-speed regions, therefore have convection velocity higher than local mean velocity. The convection velocity affects directly the turbulent sweep and ejection events. The more flow is dominated by large-scale motion the higher values takes both the convection velocity of small-scale structures and sweep events induced by them.

  20. A modified nodal pressure method for calculating flow distribution in hydraulic circuits for the case of unconventional closing relations

    Egor M. Mikhailovsky


    Full Text Available We proposed a method for numerically solving the problem of flow distribution in hydraulic circuits with lumped parameters for the case of random closing relations. The conventional and unconventional types of relations for the laws of isothermal steady fluid flow through the individual hydraulic circuit components are studied. The unconventional relations are presented by those given implicitly by the flow rate and dependent on the pressure of the working fluid. In addition to the unconventional relations, the formal conditions of applicability were introduced. These conditions provide a unique solution to the flow distribution problem. A new modified nodal pressure method is suggested. The method is more versatile in terms of the closing relation form as compared to the unmodified one, and has lower computational costs as compared to the known technique of double-loop iteration. The paper presents an analysis of the new method and its algorithm, gives a calculated example of a gas transportation network, and its results.

  1. The Difference in Translaminar Pressure Gradient and Neuroretinal Rim Area in Glaucoma and Healthy Subjects

    Lina Siaudvytyte


    Full Text Available Purpose. To assess differences in translaminar pressure gradient (TPG and neuroretinal rim area (NRA in patients with normal tension glaucoma (NTG, high tension glaucoma (HTG, and healthy controls. Methods. 27 patients with NTG, HTG, and healthy controls were included in the prospective pilot study (each group consisted of 9 patients. Intraocular pressure (IOP, intracranial pressure (ICP, and confocal laser scanning tomography were assessed. TPG was calculated as the difference of IOP minus ICP. ICP was measured using noninvasive two-depth transcranial Doppler device. The level of significance P 0.05. The difference between TPG for healthy (5.4(7.7 mmHg and glaucomatous eyes (NTG 6.3(3.1 mmHg, HTG 15.7(7.7 mmHg was statistically significant (P < 0.001. Higher TPG was correlated with decreased NRA (r = −0.83; P = 0.01 in the NTG group. Conclusion. Translaminar pressure gradient was higher in glaucoma patients. Reduction of NRA was related to higher TPG in NTG patients. Further prospective studies are warranted to investigate the involvement of TPG in glaucoma management.

  2. 一种用于液体静压导轨的高精密液压站设计%Design of the Ultra-precision Hydraulic Station for Hydraulic Static Pressured Guide

    赵午云; 郭勇


    Hydraulic static pressured guide is the important function unit of precision machine tool. Hydraulic station is indispen-sable and supplementary unit for hydraulic static pressured guide in normal operation,and must provide hydraulic static pressured guide with lubricating oil of invariable pressure. An ultra-precision hydraulic station for hydraulic static pressured guide was designed. In this hydraulic station,lubricating oil was provided by precision gear pump driven by variable frequency motor,and pressure export was ensured to be steady by full-closed loop feedback control. The export pressure precision of the hydraulic station can reach ± 0.05%. Good effect is gained in the application of the hydraulic station on the hydraulic static pressured guide of ultra-precision machine tool.%液体静压导轨是精密超精密加工机床的重要功能单元,液压站是液体静压导轨正常工作的必要辅助单元。液体静压导轨要保持高的精度,液压站必须能够为静压导轨提供压力非常稳定的润滑油输入。设计一种用于液体静压导轨的高精密液压站,该液压站利用变频电机驱动精密齿轮泵供给润滑油,利用全闭环反馈调节装置控制润滑油的稳压输出。实际测量证明:该液压站的输出压力稳定精度可达±0.05%,应用于超精密机床上的液体静压导轨取得了良好的效果。

  3. Adaptive Control System of Hydraulic Pressure Based on The Mathematical Modeling

    Pilipenko, A. V.; Pilipenko, A. P.; Kanatnikov, N. V.


    In this paper, the authors highlight the problem of replacing an old heavy industrial equipment, and offer the replacement of obsolete control systems on the modern adaptive control system, which takes into account changes in the hydraulic system of the press and compensates them with a corrective action. The proposed system can reduce a water hammer and thereby increase the durability of the hydraulic system and tools.

  4. Nonconvective Forces: A Critical and Often Ignored Component in the Echocardiographic Assessment of Transvalvular Pressure Gradients

    Michael S. Firstenberg


    Full Text Available Echocardiography is routinely used to assess ventricular and valvular function, particularly in patients with known or suspected cardiac disease and who have evidence of hemodynamic compromise. A cornerstone to the use of echocardiographic imaging is not only the qualitative assessment, but also the quantitative Doppler-derived velocity characteristics of intracardiac blood flow. While simplified equations, such as the modified Bernoulli equation, are used to estimate intracardiac pressure gradients based upon Doppler velocity data, these modified equations are based upon assumptions of the varying contributions of the different forces that contribute to blood flow. Unfortunately, the assumptions can result in significant miscalculations in determining a gradient if not completely understood or they are misapplied. We briefly summarize the principles of fluid dynamics that are used clinically with some of the inherent limitations of routine broad application of the simplified Bernoulli equation.

  5. In vitro comparison of Doppler and catheter-measured pressure gradients in 3D models of mitral valve calcification.

    Herrmann, Tarrah A; Siefert, Andrew W; Pressman, Gregg S; Gollin, Hannah R; Touchton, Steven A; Saikrishnan, Neelakantan; Yoganathan, Ajit P


    Mitral annular calcification (MAC) involves calcium deposition in the fibrous annulus supporting the mitral valve (MV). When calcification extends onto the leaflets, valve opening can be restricted. The influence of MAC MV geometry on Doppler gradients is unknown. This study describes a novel methodology to rapid-prototype subject-specific MAC MVs. Replicated valves were used to assess the effects of distorted annular-leaflet geometry on Doppler-derived, transmitral gradients in comparison to direct pressure measurements and to determine if transmitral gradients vary according to measurement location. Three-dimensional echocardiography data sets were selected for two MAC MVs and one healthy MV. These MVs were segmented and rapid prototyped in their middiastolic configuration for in vitro testing. The effects of MV geometry, measurement modality, and measurement location on transmitral pressure gradient were assessed by Doppler and catheter at three locations along the MV's intercommissural axis. When comparing dimensions of the rapid-prototyped valves to the subject echocardiography data sets, mean relative errors ranged from 6.2% to 35%. For the evaluated MVs, Doppler pressure gradients exhibited good agreement with catheter-measured gradients at a variety of flow rates, though with slight systematic overestimation in the recreated MAC valves. For all of the tested MVs, measuring the transmitral pressure gradient at differing valve orifice positions had minimal impact on observed gradients. Upon the testing of additional normal and calcific MVs, these data may contribute to an improved clinical understanding of MAC-related mitral stenosis. Moreover, they provide the ability to statistically evaluate between measurement locations, flow rates, and valve geometries for Doppler-derived pressure gradients. Determining these end points will contribute to greater clinical understanding for the diagnosis MAC patients and understanding the use and application of Doppler

  6. Analysis of mine's air leakage based on pressure gradient matrix between nodes

    ZHANG Jian-rang; WANG Hong-gang; WU Feng-liang; CHANG Xin-tan


    Air leakage may significantly affect the effectiveness of mine ventilation by in-creasing the cost of ventilation and arousing problems for ventilation management. Fur-thermore, air leakage may accelerate the process of coal spontaneous combustion andcause gas explosion, thus greatly threatens the safety of coat production. The estimationof air leakage, therefore, have great practical significance. For any ventilation system ofcoal mines, there is a defined pattern of pressure gradient which drived the mine air toflow in the network, drives possible air leakage to go shortcut as well. Air leakage mayoccur through ventilation structures such as ventilation doors and fractures of the surroun-dig coal and rock of airways. A concept and the relevent calculation method of the pres-sure gradient matrix was put forward to assist the analysis of potential air leakage routes.A simplified example was used to introduce the application principle of'pressure gradientmatrix in identifying all the potential air leaking routes, which offers a deeper understand-ing over the ventilation system and the prevention of coal spontaneous combustion.

  7. Measurement of the Turbulence Kinetic Energy Budget of a Turbulent Planar Wake Flow in Pressure Gradients

    Liu, Xiao-Feng; Thomas, Flint O.; Nelson, Robert C.


    Turbulence kinetic energy (TKE) is a very important quantity for turbulence modeling and the budget of this quantity in its transport equation can provide insight into the flow physics. Turbulence kinetic energy budget measurements were conducted for a symmetric turbulent wake flow subjected to constant zero, favorable and adverse pressure gradients in year-three of research effort. The purpose of this study is to clarify the flow physics issues underlying the demonstrated influence of pressure gradient on wake development and provide experimental support for turbulence modeling. To ensure the reliability of these notoriously difficult measurements, the experimental procedure was carefully designed on the basis of an uncertainty analysis. Four different approaches, based on an isotropic turbulence assumption, a locally axisymmetric homogeneous turbulence assumption, a semi-isotropy assumption and a forced balance of the TKE equation, were applied for the estimate of the dissipation term. The pressure transport term is obtained from a forced balance of the turbulence kinetic energy equation. This report will present the results of the turbulence kinetic energy budget measurement and discuss their implication on the development of strained turbulent wakes.

  8. Flow Control Device Evaluation for an Internal Flow with an Adverse Pressure Gradient

    Jenkins, Luther N.; Gorton, Susan Althoff; Anders, Scott G.


    The effectiveness of several active and passive devices to control flow in an adverse pressure gradient with secondary flows present was evaluated in the 15 Inch Low Speed Tunnel at NASA Langley Research Center. In this study, passive micro vortex generators, micro bumps, and piezoelectric synthetic jets were evaluated for their flow control characteristics using surface static pressures, flow visualization, and 3D Stereo Digital Particle Image Velocimetry. Data also were acquired for synthetic jet actuators in a zero flow environment. It was found that the micro vortex generator is very effective in controlling the flow environment for an adverse pressure gradient, even in the presence of secondary vortical flow. The mechanism by which the control is effected is a re-energization of the boundary layer through flow mixing. The piezoelectric synthetic jet actuators must have sufficient velocity output to produce strong longitudinal vortices if they are to be effective for flow control. The output of these devices in a laboratory or zero flow environment will be different than the output in a flow environment. In this investigation, the output was higher in the flow environment, but the stroke cycle in the flow did not indicate a positive inflow into the synthetic jet.

  9. Invasive assessment of doubtful aortic stenosis by measuring simultaneous transaortic gradient with a pressure wire.

    Chopard, Romain; Meneveau, Nicolas; Plastaras, Philoktimon; Janin, Sebastien; Seronde, Marie-France; Ecarnot, Fiona; Schiele, Francois


    Two-dimensional transthoracic echocardiography (2D-TTE) is the reference technique for evaluating aortic stenosis (AS) but may be unreliable in some cases. We aimed to assess whether the use of a pressure wire to measure simultaneous transaortic gradient and aortic valve area (AVA) could be helpful in patients in whom initial noninvasive evaluations were considered doubtful for AS. Fifty-seven patients (mean age 76 years; 39 men) underwent cardiac catheterization with single arterial access for assessment of AVA with the Gorlin and Gorlin formula. Transaortic pressure was obtained by 2 invasive methods: (1) conventional pullback method (PM) from the left ventricle toward the aorta and (2) simultaneous method (SM) with transaortic pressure simultaneously recorded with a 0.014-inch pressure wire introduced into the left ventricle and with a diagnostic catheter placed in the ascending aorta. Reasons for inaccurate assessment by 2D-TTE were low flow states (88%) and/or atrial fibrillation (79%). Agreement for severe AS defined by AVA <0.6 cm²/m² between SM and 2D-TTE and between SM and PM was fair, with kappa coefficients of 0.38 (95% confidence interval [CI] 0.14-0.75) and 0.36 (95% CI 0.22-0.7) respectively; agreement was poor between 2D-TTE and PM (kappa: 0.23; 95% CI 0.002-0.36). SM led to a reclassification of the severity of AS in 9 patients (15.8%) compared with 2D-TTE and in 11 patients (19.3%) compared with PM. In conclusion, invasive evaluation of doubtful AS by measuring simultaneous transaortic gradient using a pressure wire may provide an attractive method that can lead to a change in therapeutic strategy in a substantial proportion of patients.

  10. Performance limiting effects in power generation from salinity gradients by pressure retarded osmosis.

    Yip, Ngai Yin; Elimelech, Menachem


    Pressure retarded osmosis has the potential to utilize the free energy of mixing when fresh river water flows into the sea for clean and renewable power generation. Here, we present a systematic investigation of the performance limiting phenomena in pressure retarded osmosis--external concentration polarization, internal concentration polarization, and reverse draw salt flux--and offer insights on the design criteria of a high performance pressure retarded osmosis power generation system. Thin-film composite polyamide membranes were chemically modified to produce a range of membrane transport properties, and the water and salt permeabilities were characterized to determine the underlying permeability-selectivity trade-off relationship. We show that power density is constrained by the trade-off between permeability and selectivity of the membrane active layer. This behavior is attributed to the opposing influence of the beneficial effect of membrane water permeability and the detrimental impact of reverse salt flux coupled with internal concentration polarization. Our analysis reveals the intricate influence of active and support layer properties on power density and demonstrates that membrane performance is maximized by tailoring the water and salt permeabilities to the structural parameters. An analytical parameter that quantifies the relative influence of each performance limiting phenomena is employed to identify the dominant effect restricting productivity. External concentration polarization is shown to be the main factor limiting performance at high power densities. Enhancement of the hydrodynamic flow conditions in the membrane feed channel reduces external concentration polarization and thus, yields improved power density. However, doing so will also incur additional operating costs due to the accompanying hydraulic pressure loss. This study demonstrates that by thoughtful selection of the membrane properties and hydrodynamic conditions, the detrimental

  11. Performance Limiting Effects in Power Generation from Salinity Gradients by Pressure Retarded Osmosis

    Yip, Ngai Yin


    Pressure retarded osmosis has the potential to utilize the free energy of mixing when fresh river water flows into the sea for clean and renewable power generation. Here, we present a systematic investigation of the performance limiting phenomena in pressure retarded osmosis-external concentration polarization, internal concentration polarization, and reverse draw salt flux-and offer insights on the design criteria of a high performance pressure retarded osmosis power generation system. Thin-film composite polyamide membranes were chemically modified to produce a range of membrane transport properties, and the water and salt permeabilities were characterized to determine the underlying permeability-selectivity trade-off relationship. We show that power density is constrained by the trade-off between permeability and selectivity of the membrane active layer. This behavior is attributed to the opposing influence of the beneficial effect of membrane water permeability and the detrimental impact of reverse salt flux coupled with internal concentration polarization. Our analysis reveals the intricate influence of active and support layer properties on power density and demonstrates that membrane performance is maximized by tailoring the water and salt permeabilities to the structural parameters. An analytical parameter that quantifies the relative influence of each performance limiting phenomena is employed to identify the dominant effect restricting productivity. External concentration polarization is shown to be the main factor limiting performance at high power densities. Enhancement of the hydrodynamic flow conditions in the membrane feed channel reduces external concentration polarization and thus, yields improved power density. However, doing so will also incur additional operating costs due to the accompanying hydraulic pressure loss. This study demonstrates that by thoughtful selection of the membrane properties and hydrodynamic conditions, the detrimental

  12. Local pressure gradients due to incipience of boiling in subcooled flows

    Ruggles, A.E.; McDuffee, J.L. [Univ. of Tennessee, Knoxville, TN (United States)


    Models for vapor bubble behavior and nucleation site density during subcooled boiling are integrated with boundary layer theory in order to predict the local pressure gradient and heat transfer coefficient. Models for bubble growth rate and bubble departure diameter are used to scale the movement of displaced liquid in the laminar sublayer. An added shear stress, analogous to a turbulent shear stress, is derived by considering the liquid movement normal to the heated surface. The resulting mechanistic model has plausible functional dependence on wall superheat, mass flow, and heat flux and agrees well with data available in the literature.

  13. Exact solution of unsteady flow generated by sinusoidal pressure gradient in a capillary tube

    M. Abdulhameed


    Full Text Available In this paper, the mathematical modeling of unsteady second grade fluid in a capillary tube with sinusoidal pressure gradient is developed with non-homogenous boundary conditions. Exact analytical solutions for the velocity profiles have been obtained in explicit forms. These solutions are written as the sum of the steady and transient solutions for small and large times. For growing times, the starting solution reduces to the well-known periodic solution that coincides with the corresponding solution of a Newtonian fluid. Graphs representing the solutions are discussed.

  14. Ion slip effect on unsteady Hartmann flow with heat transfer under exponential decaying pressure gradient

    Hazem A. Attia


    Full Text Available The unsteady Hartmann flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel nonconducting porous plates is studied with heat transfer taking the ion slip into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates, while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.

  15. Coherent structures in a zero-pressure-gradient and a strongly decelerated boundary layer

    Simens, Mark P.; Gungor, Ayse G.; Maciel, Yvan


    Coherent structures in a strongly decelerated large-velocity-defect turbulent boundary layer (TBL) and a zero pressure gradient (ZPG) boundary layer are analysed by direct numerical simulation (DNS). The characteristics of the one-point velocity stastistics are also considered. The adverse pressure gradient (APG) TBL simulation is a new one carried out by the present authors. The APG TBL begins as a zero pressure gradient boundary layer, decelerates under a strong adverse pressure gradient, and separates near the end of the domain in the form of a very thin separation bubble. The one-point velocity statistics in the outer region of this large-defect boundary layer are compared to those of two other large-velocity-defect APG TBLs (one in dynamic equilibrium, the other in disequilibrium) and a mixing layer. In the upper half of the large-defect boundary layers, the velocity statistics are similar to those of the mixing layer. The dominant peaks of turbulence production and Reynolds stresses are located in the middle of the boundary layers. Three-dimensional spatial correlations of (u, u) and (u, v) show that coherence is lost in the streamwise and spanwise directions as the velocity defect increases. Near-wall streaks tend to disappear in the large-defect zone of the flow to be replaced by more disorganized u motions. Near-wall sweeps and ejections are also less numerous. In the outer region, the u structures tend to be shorter, less streaky, and more inclined with respect to the wall than in the ZPG TBL. The sweeps and ejections are generally bigger with respect to the boundary layer thickness in the large-defect boundary layer, even if the biggest structures are found in the ZPG TBL. Large sweeps and ejections that reach the wall region (wall-attached) are less streamwise elongated and they occupy less space than in the ZPG boundary layer. The distinction between wall-attached and wall-detached structures is not as pronounced in the large-defect TBL.

  16. Gap heating with pressure gradients. [for Shuttle Orbiter thermal protection system tiles

    Scott, C. D.; Maraia, R. J.


    The heating rate distribution and temperature response on the gap walls of insulating tiles is analyzed to determine significant phenomena and parameters in flows where there is an external surface pressure gradient. Convective heating due to gap flow, modeled as fully developed pipe flow, is coupled with a two-dimensional thermal model of the tiles that includes conduction and radiative heat transfer. To account for geometry and important environmental parameters, scale factors are obtained by curve-fitting measured temperatures to analytical solutions. These scale factors are then used to predict the time-dependent gap heat flux and temperature response of tile gaps on the Space Shuttle Orbiter during entry.

  17. Comparative study of Thermal Hydraulic Analysis Codes for Pressurized Water Reactors

    Kim, Yang Hoon; Jang, Mi Suk; Han, Kee Soo [Nuclear Engineering Service and Solution Co. Ltd., Daejeon (Korea, Republic of)


    Various codes are used for the thermal hydraulic analysis of nuclear reactors. The use of some codes among these is limited by user and some codes are not even open to general person. Thus, the use of alternative code is considered for some analysis. In this study, simple thermal hydraulic behaviors are analyzed using three codes to show that alternative codes are possible for the analysis of nuclear reactors. We established three models of the simple u-tube manometer using three different codes. RELAP5 (Reactor Excursion and Leak Analysis Program), SPACE (Safety and Performance Analysis CodE for nuclear power Plants), GOTHIC (Generation of Thermal Hydraulic Information for Containments) are selected for this analysis. RELAP5 is widely used codes for the analysis of system behavior of PWRs. SPACE has been developed based on RELAP5 for the analysis of system behavior of PWRs and licensing of the code is in progress. And GOTHIC code also has been widely used for the analysis of thermal hydraulic behavior in the containment system. The internal behavior of u-tube manometer was analyzed by RELAP5, SPACE and GOTHIC codes. The general transient behavior was similar among 3 codes. However, the stabilized status of the transient period analyzed by REPAP5 was different from the other codes. It would be resulted from the different physical models used in the other codes, which is specialized for the multi-phase thermal hydraulic behavior analysis.

  18. Final report of supplementary comparison SIM.M.P-S7: Hydraulic pressure comparison from 7 MPa to 70 MPa

    Gil Romero, Juan Carlos; Catalina Neira, María; Torres Guzmán, Jorge C.


    This report presents the final results of supplementary comparison SIM.M.P-S7 in the field of hydraulic pressure up to 70 MPa, within the PTB-ANDIMET-PLUS project. Seven national pressure reference laboratories participated in this comparison, which started with an opening meeting in November 2011 at the city of Lima; the closing meeting was held at the National Metrology Institute of Colombia INM, at Bogota, on 27-28 November 2012. Each participating laboratory used for the comparison its best hydraulic pressure balance standard in the range from 7 MPa to 70 MPa. The transfer standard for the comparison was a digital manometer DH Instruments Fluke RPM-4 with an accuracy of 0.008% of the reading. The reference laboratory and advisor for the comparison was CENAM, Mexico. The comparison protocol and results analysis was made by the pressure laboratory of National Metrology Institute INM (Colombia) who participated in the comparison as well. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database The final report has been peer-reviewed and approved for publication by SIM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  19. Effect of Favorable Pressure Gradients on Turbine Blade Pressure Surface Heat Transfer

    Boyle, Robert J.; Giel, P. W.


    Recent measurements on a turbine rotor showed significant relaminarization effects. These effects were evident on the pressure surface heat transfer measurements. The character of the heat transfer varied with Reynolds number. Data were obtained for exit Reynolds numbers between 500,000 and 880,000. Tests were done with a high level of inlet turbulence, 7.5%. At lower Reynolds numbers the heat transfer was similar to that for laminar flow, but at a level higher than for laminar flow. At higher Reynolds numbers the heat transfer was similar to turbulent flow, when the acceleration parameter, K, was sufficiently small. The proposed paper discusses the experimental results, and also discusses approaches to calculating the surface heat transfer for the blade surface. Calculations were done using a three-dimensional Navier-Stokes CFD analysis. The results of these tests, when compared with previous blade tests in the same facility, illustrate modeling difficulties that were encountered in CFD predictions. The two blades were in many ways similar. However, the degree of agreement between the same analysis and the experimental data was significantly different. These differences are highlighted to illustrate where improvements in modeling approaches are needed for transitional flows.

  20. Observations of wave-induced pore pressure gradients and bed level response on a surf zone sandbar

    Anderson, Dylan; Cox, Dan; Mieras, Ryan; Puleo, Jack A.; Hsu, Tian-Jian


    Horizontal and vertical pressure gradients may be important physical mechanisms contributing to onshore sediment transport beneath steep, near-breaking waves in the surf zone. A barred beach was constructed in a large-scale laboratory wave flume with a fixed profile containing a mobile sediment layer on the crest of the sandbar. Horizontal and vertical pore pressure gradients were obtained by finite differences of measurements from an array of pressure transducers buried within the upper several centimeters of the bed. Colocated observations of erosion depth were made during asymmetric wave trials with wave heights between 0.10 and 0.98 m, consistently resulting in onshore sheet flow sediment transport. The pore pressure gradient vector within the bed exhibited temporal rotations during each wave cycle, directed predominantly upward under the trough and then rapidly rotating onshore and downward as the wavefront passed. The magnitude of the pore pressure gradient during each phase of rotation was correlated with local wave steepness and relative depth. Momentary bed failures as deep as 20 grain diameters were coincident with sharp increases in the onshore-directed pore pressure gradients, but occurred at horizontal pressure gradients less than theoretical critical values for initiation of the motion for compact beds. An expression combining the effects of both horizontal and vertical pore pressure gradients with bed shear stress and soil stability is used to determine that failure of the bed is initiated at nonnegligible values of both forces.Plain Language SummaryThe pressure gradient present within the seabed beneath breaking waves may be an important physical mechanism transporting sediment. A large-scale laboratory was used to replicate realistic surfzone conditions in controlled tests, allowing for horizontal and vertical pressure gradient magnitudes and the resulting sediment bed response to be observed with precise instruments. Contrary to previous studies


    G.C. Sharma; Madhu Jain; Mahesh Chandra


    The oscillating natural convection in the presence of transverse magnetic field with time depending pressure gradient is studied. The analysis of the problem is carried out by assuming that the fluid is flowing in a parallel plate configuration. The emphasis is on low frequency oscillating convective flows induced by g-jitter associated with micro gravity because of their importance to the space processing materials. A general solution for an oscillating flow in the presence of transverse magnetic field is carried out. Some special cases of the oscillating flow and its response to an applied magnetic field are performed. It was observed that the behavior of oscillating free convective flows depends on frequency, amplitude of the driving buoyancy forces, temperature gradient, magnetic field and the electric conditions of the channel walls. In the absence of magnetic field, buoyancy force plays a predominant role in driving the oscillatory flow pattern, and velocity magnitude is also affected by temperature gradients. To suppress the oscillating flow external magnetic field can be used. It is also found that the reduction of the velocity is inversely proportional to the square of the applied magnetic field with conducting wall but directly proportional to the inverse of the magnetic field with insulating wall. Detailed calculations and computational results are also carried out to depict the real situation.

  2. Staging of liver fibrosis or cirrhosis: The role of hepaticvenous pressure gradient measurement

    Ki Tae Suk; Dong Joon Kim


    Liver fibrosis is a common histological change ofchronic liver injury and it is closely related with portalhypertension which is hemodynamic complication ofchronic liver disease. Currently, liver fibrosis has beenknown as a reversible dynamic process in previousliteratures. Although liver biopsy is a gold standardfor assessing the stage of liver fibrosis, it may notcompletely represent the stage of liver fibrosis becauseof sampling error or semi-quantative measurement.Recent evidences suggested that histologic, clinical,hemodynamic, and biologic features are closelyassociated in patients with chronic liver disease. Hepaticvenous pressure gradient (HVPG) measurement has beenknown as a modality to evaluate the portal pressure.The HVPG measurement has been used clinicallyfor fibrosis diagnosis, risk stratification, preoperativescreening for liver resection, monitoring the efficacy ofmedical treatments, and assessing the prognosis of liverfibrosis. Therefore, the HVPG measurement can be usedto monitor areas the chronic liver disease but also otherimportant areas of chronic liver disease.

  3. Phenomenon of methane driven caused by hydraulic fracturing in methane-bearing coal seams

    Huang Bingxiang; Cheng Qingying; Chen Shuliang


    The methane concentration of the return current will always be enhanced to a certain degree when hydraulic fracturing with bedding drilling is implemented to a gassy coal seam in an underground coal mine. The methane in coal seam is driven out by hydraulic fracturing. Thus, the phenomenon is named as methane driven effect of hydraulic fracturing. After deep-hole hydraulic fracturing at the tunneling face of the gassy coal seam, the coal methane content exhibits a‘low-high-low”distribution along exca-vation direction in the following advancing process, verifying the existence of methane driven caused by hydraulic fracturing in methane-bearing coal seam. Hydraulic fracturing causes the change of pore-water and methane pressure in surrounding coal. The uneven distribution of the pore pressure forms a pore pressure gradient. The free methane migrates from the position of high pore (methane) pressure to the position of low pore (methane) pressure. The methane pressure gradient is the fundamental driving force for methane-driven coal seam hydraulic fracturing. The uneven hydraulic crack propagation and the effect of time (as some processes need time to complete and are not completed instantaneously) will result in uneven methane driven. Therefore, an even hydraulic fracturing technique should be used to avoid the negative effects of methane driven; on the other hand, by taking fully advantage of methane driven, two technologies are presented.

  4. The hydraulics of the pressurized water reactors; L'hydraulique des reacteurs a eau pressurisee

    Bouchter, J.C. [CEA Cadarache, SMET, 13 - Saint-Paul-lez-Durance (France); Barbier, D. [CEA/Grenoble, Dept. de Thermohydraulique et de Physique, DTP/SH2C, 38 (France); Caruso, A. [Electricite de France, Service Etudes et Projets Thermiques et Nucleaires, 75 - Paris (France)] [and others


    The SFEN organized, the 10 june 1999 at Paris, a meeting in the domain of the PWR hydraulics and in particular the hydraulic phenomena concerning the vessel and the vapor generators. The papers presented showed the importance of the industrial stakes with their associated phenomena: cores performance and safety with the more homogenous cooling system, the rods and the control rods wear, the temperature control, the fluid-structure interactions. A great part was also devoted to the progresses in the domain of the numerical simulation and the models and algorithms qualification. (A.L.B.)

  5. Beyond Pressure Gradients: The Effects of Intervention on Heart Power in Aortic Coarctation

    Brüning, Jan; Hellmeier, Florian; Nordmeyer, Sarah; da Silva, Tiago Ferreira; Schubert, Stephan; Berger, Felix; Kuehne, Titus; Kelm, Marcus


    Background In aortic coarctation, current guidelines recommend reducing pressure gradients that exceed given thresholds. From a physiological standpoint this should ideally improve the energy expenditure of the heart and thus prevent long term organ damage. Objectives The aim was to assess the effects of interventional treatment on external and internal heart power (EHP, IHP) in patients with aortic coarctation and to explore the correlation of these parameters to pressure gradients obtained from heart catheterization. Methods In a collective of 52 patients with aortic coarctation 25 patients received stenting and/or balloon angioplasty, and 20 patients underwent MRI before and after an interventional treatment procedure. EHP and IHP were computed based on catheterization and MRI measurements. Along with the power efficiency these were combined in a cardiac energy profile. Results By intervention, the catheter gradient was significantly reduced from 21.8±9.4 to 6.2±6.1mmHg (p<0.001). IHP was significantly reduced after intervention, from 8.03±5.2 to 4.37±2.13W (p < 0.001). EHP was 1.1±0.3 W before and 1.0±0.3W after intervention, p = 0.044. In patients initially presenting with IHP above 5W intervention resulted in a significant reduction in IHP from 10.99±4.74 W to 4.94±2.45W (p<0.001), and a subsequent increase in power efficiency from 14 to 26% (p = 0.005). No significant changes in IHP, EHP or power efficiency were observed in patients initially presenting with IHP < 5W. Conclusion It was demonstrated that interventional treatment of coarctation resulted in a decrease in IHP. Pressure gradients, as the most widespread clinical parameters in coarctation, did not show any correlation to changes in EHP or IHP. This raises the question of whether they should be the main focus in coarctation interventions. Only patients with high IHP of above 5W showed improvement in IHP and power efficiency after the treatment procedure. Trial Registration clinicaltrials

  6. Pressure Regulation in Nonlinear Hydraulic Networks by Positive and Quantized Controls

    Persis, Claudio De; Kallesøe, Carsten Skovmose


    We investigate an industrial case study of a system distributed over a network, namely, a large-scale hydraulic network which underlies a district heating system. The network comprises an arbitrarily large number of components (valves, pipes, and pumps). After introducing the model for this class of

  7. Critical hydraulic pressure forecasting of water inrush in coal seam floors based on a genetic algorithm-neural network

    Zhong, M.; Shi, C.; Liu, T. [China Academy of Safety Science and Technology, Beijing (China); Fu, T. [Tsinghua Univ., Beijing (China). Dept. of Thermal Engineering


    This paper presented a method of forecasting water inrush in coal seam floors. The theoretical forecasting method used a combined genetic algorithm-neural network method to analyze the relationships between the critical pressure of water inrush and the different conditions in coal seam floors. Actual measurement data from Chinese coal mines were used to train the multi-layer feedforward neural network. Genetic algorithms were used to train the neural networks and optimize the neural network topology. The topology structure of the network was selected by considering population size, mutation rate, and crossing rates. The critical hydraulic pressure of water inrush was then predicted, and predictions were compared with measurements taken to validate the method. Results of the study showed that the forecasting method improved learning efficiency and the prediction capacity of the network. It was concluded that the combined method can be used to accurately predict the critical hydraulic pressure of water inrush on coal seam floors. 28 refs., 1 tab., 7 figs.

  8. Pick-up ion pressure gradients modulating the solar wind dynamics

    Fahr, Hans J.; Fichtner, Horst


    Neutral interstellar atoms penetrate deeply into the inner heliosphere before they become ionized by various processes. As ions they are picked-up by the frozen-in magnetic fields and are convected outwards with the solar wind plasma. Thereby the primary plasma flow is mass, momentum, and energy-loaded. The dynamics of the distant multi-constituent solar wind is, however, not solely determined by these loading processes, but is also affected by the wave-mediated pick-up ion pressure gradients derivable from the pick-up ion distribution function. The action of the radial components of these pressures essentially counter balances the decelerating effect of the solar wind momentum loading, diminishing strongly the deceleration of the distant solar wind. Furthermore the latitudinal components of the pick-up ion pressures induce latitudinal forces acting on the multiconstituent solar plasma outflow and inducing nonradial bulk flow components. The enforced nonradial outflow geometry on the upwind hemisphere may partly be responsible for the magnetic flux deficit which was claimed since several years in the PIONEER-10 magnetic flux data.

  9. A Simple Method for Noninvasive Quantification of Pressure Gradient Across the Pulmonary Valve.

    Zhou, Xueying; Xing, Changyang; Feng, Yang; Duan, Yunyou; Zheng, Qiangsun; Wang, Zuojun; Liu, Jie; Cao, Tiesheng; Yuan, Lijun


    Pressure gradient across the pulmonary valve (PVPG) is an important hemodynamic variable used in the management of patients with cardiovascular and pulmonary disease. However, a reliable noninvasive method is unavailable. We hypothesized that a progressive Muller maneuver would elicit the pulmonary valve premature opening (PVPO) in diastole and that this event would be detectable by Doppler echocardiography. The intrathoracic pressure (ITP) decrease during this maneuver equals PVPG, which may be assessed with a custom airway pressure measurement device. A total of 102 subjects were enrolled in the study. At the earliest appearance of PVPO, the ITP decrease was recorded as the PVPG. PVPG was also simultaneously measured and compared by other two methods: right heart catheterization in 43 subjects, and routine Doppler echocardiography (pulmonary regurgitation jet) in the other 59 subjects. The results measured by different approaches were compared using the Bland-Altman analysis. PVPG assessed via PVPO showed strong agreement with PVPG measured by catheterization or routine Doppler echocardiography methods, with Lin concordance correlation coefficients of 0.91 and 0.70, respectively. In conclusion, PVPO provides a new noninvasive method of quantification of PVPG.

  10. Implicit Large-Eddy Simulations of Zero-Pressure Gradient, Turbulent Boundary Layer

    Sekhar, Susheel; Mansour, Nagi N.


    A set of direct simulations of zero-pressure gradient, turbulent boundary layer flows are conducted using various span widths (62-630 wall units), to document their influence on the generated turbulence. The FDL3DI code that solves compressible Navier-Stokes equations using high-order compact-difference scheme and filter, with the standard recycling/rescaling method of turbulence generation, is used. Results are analyzed at two different Re values (500 and 1,400), and compared with spectral DNS data. They show that a minimum span width is required for the mere initiation of numerical turbulence. Narrower domains ((is) less than 100 w.u.) result in relaminarization. Wider spans ((is) greater than 600 w.u.) are required for the turbulent statistics to match reference DNS. The upper-wall boundary condition for this setup spawns marginal deviations in the mean velocity and Reynolds stress profiles, particularly in the buffer region.

  11. Developments in the theory of trapped particle pressure gradient-driven turbulence in tokamaks and stellarators

    Diamond, P.H.; Biglari, H.; Gang, F.Y.; Kim, Y.B.; Rosenbluth, M.N.; Wang, X.H.; Xu, X.Q. (California Univ., San Diego, La Jolla, CA (USA). Dept. of Physics); Dominguez, N.; Carreras, B.A.; Leboeuf, J.N.; Lynch, V.E.; Charlton, L.A.; Garcia, L. (Oak Ridge National Lab., TN (USA)); Terry, P.W.; Newman, D.E. (Wisconsin Univ., Madison, WI (USA). Dept. of Physics); Koniges, A.E.; Crotinger, J.; Dannevik, W. (Lawre


    Recent advances in the theory of trapped particle pressure gradient driven turbulence are summarized. A novel theory of trapped ion convective cell turbulence is presented. It is shown that nonlinear transfer to small scales occurs, and that saturation levels are not unphysically large, as previously thought. As the virulent saturation mechanism of ion Compton scattering is shown to result in weak turbulence at higher frequencies, it is thus likely that trapped ion convective cells are the major agent of tokamak transport. Fluid-like trapped electron modes at short wavelengths (k{sub {theta}} {rho}{sub i} > 1) are shown to drive an inward particle pinch. The characteristics of convective cell turbulence in flat density discharges are described, as is the stability of dissipative trapped electron modes in stellarators, with flexible magnetic field structure. The role of cross-correlations in the dynamics of multi-field models of drift wave turbulence is discussed. 32 refs., 7 figs., 1 tab.

  12. Direct Numerical Simulation and Theories of Wall Turbulence with a Range of Pressure Gradients

    Coleman, G. N.; Garbaruk, A.; Spalart, P. R.


    A new Direct Numerical Simulation (DNS) of Couette-Poiseuille flow at a higher Reynolds number is presented and compared with DNS of other wall-bounded flows. It is analyzed in terms of testing semi-theoretical proposals for universal behavior of the velocity, mixing length, or eddy viscosity in pressure gradients, and in terms of assessing the accuracy of two turbulence models. These models are used in two modes, the traditional one with only a dependence on the wall-normal coordinate y, and a newer one in which a lateral dependence on z is added. For pure Couette flow and the Couette-Poiseuille case considered here, this z-dependence allows some models to generate steady streamwise vortices, which generally improves the agreement with DNS and experiment. On the other hand, it complicates the comparison between DNS and models.

  13. Wall mass transfer and pressure gradient effects on turbulent skin friction

    Watson, R. D.; Balasubramanian, R.


    The effects of mass injection and pressure gradients on the drag of surfaces were studied theoretically with the aid of boundary-layer and Navier-Stokes codes. The present investigation is concerned with the effects of spatially varying the injection in the case of flat-plate drag. Effects of suction and injection on wavy wall surfaces are also explored. Calculations were performed for 1.2 m long surfaces, one flat and the other sinusoidal with a wavelength of 30.5 cm. Attention is given to the study of the effect of various spatial blowing variations on flat-plate skin friction reduction, local skin friction coefficient calculated by finite difference boundary-layer code and Navier-Stokes code, and the effect of phase-shifting sinusoidal mass transfer on the drag of a sinusoidal surface.

  14. Baroclinic pressure gradient difference schemes of subtracting the local averaged density stratification in sigma coordinates models

    ZHU Shouxian; ZHANG Wenjing


    Much has been written of the error in computing the baroclinic pressure gradient (BPG) with sigma coordinates in ocean or atmos- pheric numerical models. The usual way to reduce the error is to subtract area-averaged density stratification of the whole computa- tion region. But if there is great difference between the area-averaged and the local averaged density stratification, the error will be obvious. An example is given to show that the error from this method may be larger than that from no correction sometimes. The definition of local area is put forward. Then, four improved BPG difference schemes of subtracting the local averaged density strat- ification are designed to reduce the error. Two of them are for diagnostic calculation (density field is fixed), and the others are for prognostic calculation (density field is not fixed). The results show that the errors from these schemes all significantly decrease.

  15. Effects of Abscisic Acid and of Hydrostatic Pressure Gradient on Water Movement through Excised Sunflower Roots.

    Glinka, Z


    The effect of abscisic acid on the exudation rate from decapitated roots of sunflower plants (Helianthus annuus L.) was investigated in the presence and absence of an imposed hydrostatic pressure gradient. The magnitude of the abscisic acid effect was constant even when suctions up to 60 cm Hg were applied to the cut stumps.When roots were bathed in a THO-labeled nutrient solution, the course of the appearance of radioactivity in the exudate, expressed as a function of exudate volume, was not affected by abscisic acid treatment but was strongly speeded up by applying suction.The implications of those findings with regard to the water pathway through the root and the location of the abscisic acid effect are discussed.

  16. A Nonlinear k-ε Turbulence Model Applicable to High Pressure Gradient and Large Curvature Flow

    Xiyao Gu


    Full Text Available Most of the RANS turbulence models solve the Reynolds stress by linear hypothesis with isotropic model. They can not capture all kinds of vortexes in the turbomachineries. In this paper, an improved nonlinear k-ε turbulence model is proposed, which is modified from the RNG k-ε turbulence model and Wilcox's k-ω turbulence model. The Reynolds stresses are solved by nonlinear methods. The nonlinear k-ε turbulence model can calculate the near wall region without the use of wall functions. The improved nonlinear k-ε turbulence model is used to simulate the flow field in a curved rectangular duct. The results based on the improved nonlinear k-ε turbulence model agree well with the experimental results. The calculation results prove that the nonlinear k-ε turbulence model is available for high pressure gradient flows and large curvature flows, and it can be used to capture complex vortexes in a turbomachinery.

  17. Turbulent magnetic field amplification driven by cosmic-ray pressure gradients

    Drury, Luke O'C


    Observations of non-thermal emission from several supernova remnants suggest that magnetic fields close to the blastwave are much stronger than would be naively expected from simple shock compression of the field permeating the interstellar medium (ISM). We present a simple model which is capable of achieving sufficient magnetic field amplification to explain the observations. We propose that the cosmic-ray pressure gradient acting on the inhomogeneous ISM upstream of the supernova blastwave induces strong turbulence upstream of the supernova blastwave. The turbulence is generated through the differential acceleration of the upstream ISM which occurs as a result of density inhomogeneities in the ISM. This turbulence then amplifies the pre-existing magnetic field. Numerical simulations are presented which demonstrate that amplification factors of 20 or more are easily achievable by this mechanism when reasonable parameters for the ISM and supernova blastwave are assumed. The length scale over which this amplif...

  18. Mean flow structure of non-equilibrium boundary layers with adverse pressure gradient

    B C Mandal; H P Mazumdar; S S Dutta


    In this paper Spalding’s formulation for the law of the wall with constants modified by Persen is used to describe the inner region (viscous sub-layer and certain portion of logarithmic layer) and a wake law due to Persen is used to describe the wake region (outer region). These two laws are examined in the light of measured data by Marušić and Perry for non-equilibrium adverse pressure gradient layers. It is observed that structure of turbulence for this flow is well-described by these two laws. From the known structure of turbulence eddy viscosity for the flow under consideration is calculated. Self similarity in eddy viscosity is observed in the wall region.

  19. Direct measured systolic pressure gradients across the aorto-iliac segment in multiple-level-obstruction arteriosclerosis

    Noer, Ivan; Praestholm, J; Tønnesen, K H


    to the angiographic findings. A consistent pressure gradient was found in the various types of arterial occlusions. In patients with occlusion of both the aorta and the iliac arteries, the systolic pressure drop was about 60% (range, 50-78%, SD 9%). The various types of iliac artery occlusions resulted in quite...... uniform systolic pressure drops of about 50% (range 35-68%, SD 9%). In contrast, the systolic pressure drop along different types of iliac stenoses showed a wide variation, ranging from a minimal drop to about 60%. The degree of stenosis on the angiogram was correlated significantly with the pressure drop...


    Vitaliy Mamchuk


    Full Text Available Purpose: Mathematical modeling of complex turbulent near-wall flows, that occur during the flow of airfoils, is impossible without understanding the nature of the flow in boundary layer. From a mathematical point of view, the calculation of such flows, because in practical problems they regarded as turbulent, and the characteristics of turbulence are largely dependent on the geometry of the profile of the longitudinal component of the average velocity of the near-wall flow. Based on this, the purpose of this work is studying and mathematical modeling of turbulent near-wall flows in the interaction with the real streamlined surface, that has certain features, such as the curvature, roughness, etc., as well as the study and research of the influence of the pressure gradient on the empirical coefficients, parameters of the flow, velocity profiles and friction stress. Methods: We performed the calculations using numerical finite-difference marching method with algebraic model of turbulent viscosity coefficient. Results: In this paper we present some results of the numerical study of the effect of the positive pressure gradient on the empirical coefficients of the transition zone and the law of the near-wall and the outer-wall areas. Discussion: Comparison of the calculated results with the experimental data shows that the proposed approaches provide an opportunity to simulate the flow as close as possible to their physical properties. Presented mathematical model for the calculation of turbulent boundary layers and near-wall flows makes it possible to calculate such a complex and valuable from a practical point of view type of the flow as the aerodynamic trail behind the streamlined body.

  1. An Experimental Study of Measuring Oscillatory and Transient Pressures in Hydraulic Systems.


    dynamic conditions. One of these computer programs that was of interest in this study was the Hydraulic Systems Frequency Response (HsFR). H- SFR program...reason for that failure is that the model for the hose was not accurate enough. The predicted amplitudes were much lower than measurec’ values except...the line. 6. P(%)- in line - Pclanp on x 100 ( 6 Pin line 7. Span - The distance between two clamps. The trans- ducers were located in the center of the

  2. Sildenafil does not influence hepatic venous pressure gradient in patients with cirrhosis

    Jens Otto Clemmesen; Annamaria Giraldi; Peter Ott; Kim Dalhoff; Bent Adel Hansen; Fin Stolze Larsen


    AIM: To investigate if sildenafil increases splanchnic blood flow and changes the hepatic venous pressure gradient (HVPG) in patients with cirrhosis. Phosphodiesterase type-5 inhibitors are valuable in the treatment of erectile dysfunction and pulmonary hypertension in patients with end-stage liver disease. However, the effect of phosphodiesterase type-5 inhibitors on splanchnic blood flow and portal hypertension remains essentially unknown. METHODS: Ten patients with biopsy proven cirrhosis (five females/five males, mean age 54±8 years) and an HVPG above 12 mmHg were studied after informed consent. Measurement of splanchnic blood flow and the HVPG during liver vein catheterization were done before and 80 min after oral administration of 50 mg sildenafil. Blood flow was estimated by use of indocyanine green clearance technique and Fick's principle, with correction for non-steady state. RESULTS: The plasma concentration of sildenafil was 222±136 ng/mL 80 min after administration. Mean arterial blood pressure decreased from 77±7 mmHg to 66±12 mmHg, P=0.003, while the splanchnic blood flow and oxygen consumption remained unchanged at 1.14±0.71 L/min and 2.3±0.6 mmol/ min, respectively. Also the HVPG remained unchanged (18±2 mmHg vs 16±2 mmHg) with individual changes ranging from-8 mmHg to+2 mmHg. In seven patients, HVPG decreased and in three it increased. CONCLUSION: In spite of arterial blood pressure decreases 80 min after administration of the phosphodiesterase type-5 inhibitor sildenafil, the present study could not demonstrate any clinical relevant influence on splanichnic blood flow, oxygen consumption or the HVPG.

  3. Pressure gradients and boiling as mechanisms for localizing ore in porphyry systems

    Cunningham, Charles G.


    Fluid inclusions in ore zones of porphyry systems indicate that extensive boiling of hydrothermal fluids accompanies deposition of ore and gangue minerals. The boiling commonly accompanied a change from a lithostatic to a hydrostatic environment during evolution of an epizonal stock. Pressure gradients near the margin of the stock can determine whether ore or only a diffuse zone of mineralization is formed. A sharp drop in pressure in an epizonal environment is more likely to cause extensive boiling than a comparable change in a deeper environment, as the slope of the boiling curve steepens with an increase 'in pressure. The drop in pressure causes the hydrothermal fluids to boil and creates a crackle (stockwork) breccia, which hosts the veinlets of gangue quartz and ore minerals. The boiling selectively partitions CO2, H2S, and HCl into the vapor phase, changing the pH, composition, ionic strength, and thus the solubility product of metal complexes in the remaining liquid and causing the ore and gangue to come out of solution. Fluid inclusions trapped from boiling solutions can exhibit several forms, depending on the physical and chemical conditions of the hydrothermal fluid from which they were trapped. In one case, inclusions when heated can homogenize to either liquid or vapor at the same temperature, which is the true boiling temperature. In another case, homogenization of various inclusions can occur through a range of temperatures. The latter case results from the trapping of mixture of liquid and vapor. Variations in salinity can result from boiling of the hydrothermal fluid, or intermittent incorporation of high-salinity fluids from the magma, or trapping of fluids of varying densities at pressure-temperature conditions above the critical point of the fluid. In places, paleopressure-temperature transition zones can be recognized by fluid-inclusion homogenization temperatures and phase relationships and by the presence of anhydrite daughter minerals

  4. Computational evaluation of intraventricular pressure gradients based on a fluid-structure approach.

    Redaelli, A; Montevecchi, F M


    The dynamics of intraventricular blood flow, i.e. its rapid evolution, implies the rise of intraventricular pressure gradients (IPGs) characteristic of the inertia-driven events as experimentally observed by Pasipoularides (1987, 1990) and by Falsetti et al. (1986). The IPG time course is determined by the wall contraction which, in turn, depends on the load applied, namely the intraventricular pressure which is the sum of the aortic pressure (i.e., the systemic net response) and the IPG. Hence the IPGs account, at least in part, for the wall movement. These considerations suggest the necessity of a comprehensive analysis of the ventricular mechanics involving both ventricular wall mechanics and intraventricular fluid dynamics as each domain determines the boundary conditions of the other. This paper presents a computational approach to ventricular ejection mechanics based on a fluid-structure interaction calculation for the evaluation of the IPG time course. An axisymmetric model of the left ventricle is utilized. The intraventricular fluid is assumed to be Newtonian. The ventricle wall is thin and is composed of two sets of counter-rotating fibres which behave according to the modified version of Wong's sarcomere model proposed by Montevecchi and Pietrabissa and Pietrabissa et al. (1987, 1991). The full Navier-Stokes equations describing the fluid domain are solved using Galerkin's weighted residual approach in conjunction with finite element approximation (FIDAP). The wall displacement is solved using the multiplane quasi-Newton method proposed by Buzzi Ferraris and Tronconi (1985). The interaction procedure is performed by means of an external macro which compares the flow fields and the wall displacement and appropriately modifies the boundary conditions to reach the simultaneous and congruous convergence of the two problems. The results refer to a simulation of the ventricular ejection with a heart rate of 72 bpm. In this phase the ventricle ejects 61 cm3

  5. Vaginal pressure during lifting, floor exercises, jogging, and use of hydraulic exercise machines.

    O'Dell, Katharine K; Morse, Abraham N; Crawford, Sybil L; Howard, Allison


    We recorded vaginal pressure in 12 women without risk factors for prolapse during two activity and exercise sessions, compared exercise and cough pressure, and evaluated method reproducibility and patterns of relative pressure. Portable urodynamic equipment, repeated measures descriptive design, and purposeful sampling were used with nonparametric analysis and visual comparison of pressure graphs. Mean participant age was 31.1 years (range 20-51), and mean body mass index was 22.7 (range 18.5-29.3). Mean pressures (in cm H(2)O): cough, 98.0 (48.0-133.7); standing, 24.0 (15.9-28.5); supine exercise, 34.0 (6.3-91.9); exercise machines, 37.0 (20.3-182.3). Repeated measures correlations for selected measures ranged from 0.66 (p pressure patterns were not consistent with patterns of group medians. We concluded that vaginal pressure measurement is reproducible in women without prolapse and that studied exercises generally produced lower pressure than cough, but individuals varied in pressure exerted. Individual variations warrant further study.

  6. Intraoperative evaluation of transmitral pressure gradients after edge-to-edge mitral valve repair.

    Jan N Hilberath

    Full Text Available OBJECTIVE: Edge-to-edge repair of the mitral valve (MV has been described as a viable option used for the surgical management of mitral regurgitation (MR. Based on the significant changes in MV geometry associated with this technique, we hypothesized that edge-to-edge MV repairs are associated with higher intraoperative transmitral pressure gradients (TMPG compared to conventional methods. METHODS: Patient records and intraoperative transesophageal echocardiography (TEE examinations of 552 consecutive patients undergoing MV repair at a single institution over a three year period were assessed. After separation from cardiopulmonary bypass (CPB, peak and mean TMPG were recorded for each patient and subsequently analyzed. RESULTS: 84 patients (15% underwent edge-to-edge MV repair. Peak and mean TMPG were significantly higher compared to gradients in patients undergoing conventional repairs: 10.7 ± 0.5 mmHg vs 7.1 ± 0.2 mmHg; P<0.0001 and 4.3 ± 0.2 mmHg vs 2.8 ± 0.1 mmHg; P<0.0001. Only patients with mean TMPG ≥ 7 mmHg (n = 9 required prompt reoperation for iatrogenic mitral stenosis (MS. No differences in peak and mean TMPG were observed among edge-to-edge repairs performed in isolation, compared to those performed in combination with annuloplasty: 11.0 ± 0.7 mmHg vs 10.3 ± 0.6 mmHg and 4.4 ± 0.3 mmHg vs 4.3 ± 0.3 mmHg. There were no differences in TMPG between various types of annuloplasty techniques used in combination with the edge-to-edge repairs. CONCLUSIONS: Edge-to-edge MV repairs are associated with higher intraoperative peak and mean TMPG after separation from CPB compared to conventional repair techniques. Unless gradients are severely elevated, these findings are not necessarily suggestive of iatrogenic MS. Thus, in the immediate postoperative period mildly elevated TMPG can be expected and tolerated after edge-to-edge mitral repairs.

  7. Nuclear Engineering Computer Modules, Thermal-Hydraulics, TH-1: Pressurized Water Reactors.

    Reihman, Thomas C.

    This learning module is concerned with the temperature field, the heat transfer rates, and the coolant pressure drop in typical pressurized water reactor (PWR) fuel assemblies. As in all of the modules of this series, emphasis is placed on developing the theory and demonstrating its use with a simplified model. The heart of the module is the PWR…

  8. Prediction of pressure fluctuation of a hydraulic turbine at no-load condition

    Chen, T. J.; Wu, X. J.; Liu, J. T.; Wu, Y. L.


    In order to study characteristics of pressure fluctuation of a turbine during the starting period, a turbine with guide vanes device at no-load condition was investigated using RNG k-epsilon turbulence model. The inner flow distribution and pressure fluctuation characteristics were analyzed. Results show that the pressure fluctuations in the region between the runner and guide vanes are different around the runner inlet. The dominant frequency of pressure fluctuation in the vaneless space close to the casing outlet is the blade passing frequency, while the dominant frequency at the rest region is the twice of the blade passing frequency. The increase of amplitude of pressure fluctuation close to the casing outlet can be attribute to the large scale stall at suction side of the runner inlet.

  9. Predictive permeability model of faults in crystalline rocks; verification by joint hydraulic factor (JH) obtained from water pressure tests

    Barani, Hamidreza Rostami; Lashkaripour, Gholamreza; Ghafoori, Mohammad


    In the present study, a new model is proposed to predict the permeability per fracture in the fault zones by a new parameter named joint hydraulic factor (JH). JH is obtained from Water Pressure Test (WPT) and modified by the degree of fracturing. The results of JH correspond with quantitative fault zone descriptions, qualitative fracture, and fault rock properties. In this respect, a case study was done based on the data collected from Seyahoo dam site located in the east of Iran to provide the permeability prediction model of fault zone structures. Datasets including scan-lines, drill cores, and water pressure tests in the terrain of Andesite and Basalt rocks were used to analyse the variability of in-site relative permeability of a range from fault zones to host rocks. The rock mass joint permeability quality, therefore, is defined by the JH. JH data analysis showed that the background sub-zone had commonly core had permeability characteristics nearly as low as the outer damage zone, represented by 8 Lu (1.3 ×10-4 m 3/s) per fracture, with occasional peaks towards 12 Lu (2 ×10-4 m 3/s) per fracture. The maximum JH value belongs to the inner damage zone, marginal to the fault core, with 14-22 Lu (2.3 ×10-4-3.6 ×10-4 m 3/s) per fracture, locally exceeding 25 Lu (4.1 ×10-4 m 3/s) per fracture. This gives a proportional relationship for JH approximately 1:4:2 between the fault core, inner damage zone, and outer damage zone of extensional fault zones in crystalline rocks. The results of the verification exercise revealed that the new approach would be efficient and that the JH parameter is a reliable scale for the fracture permeability change. It can be concluded that using short duration hydraulic tests (WPTs) and fracture frequency (FF) to calculate the JH parameter provides a possibility to describe a complex situation and compare, discuss, and weigh the hydraulic quality to make predictions as to the permeability models and permeation amounts of different

  10. Predictive permeability model of faults in crystalline rocks; verification by joint hydraulic factor (JH) obtained from water pressure tests

    Hamidreza Rostami Barani; Gholamreza Lashkaripour; Mohammad Ghafoori


    In the present study, a new model is proposed to predict the permeability per fracture in the fault zones by a new parameter named joint hydraulic factor (JH). JH is obtained from Water Pressure Test WPT) and modified by the degree of fracturing. The results of JH correspond with quantitative fault zone descriptions, qualitative fracture, and fault rock properties. In this respect, a case study was done based on the data collected from Seyahoo dam site located in the east of Iran to provide the permeability prediction model of fault zone structures. Datasets including scan-lines, drill cores, and water pressure tests in the terrain of Andesite and Basalt rocks were used to analyse the variability of in-site relative permeability of a range from fault zones to host rocks. The rock mass joint permeability quality, therefore, is defined by the JH. JH data analysis showed that the background sub-zone had commonly > 3 Lu (less of 5 × 10−5 m3/s) per fracture, whereas the fault core had permeability characteristics nearly as low as the outer damage zone, represented by 8 Lu (1.3 × 10−4 m3/s) per fracture, with occasional peaks towards 12 Lu (2 × 10−4 m3/s) per fracture. The maximum JH value belongs to the inner damage zone, marginal to the fault core, with 14–22 Lu (2.3 × 10−4 –3.6 × 10−4 m3/s) per fracture, locally exceeding 25 Lu (4.1 × 10−4 m3/s) per fracture. This gives a proportional relationship for JH approximately 1:4:2 between the fault core, inner damage zone, and outer damage zone of extensional fault zones in crystalline rocks. The results of the verification exercise revealed that the new approach would be efficient and that the JH parameter is a reliable scale for the fracture permeability change. It can be concluded that using short duration hydraulic tests (WPTs) and fracture frequency (FF) to calculate the JH parameter provides a possibility to describe a complex situation and compare, discuss, and weigh the hydraulic quality to make

  11. 用L管测定膏体料浆水力坡度试验研究%Experimental Study on Hydraulic Gradient of Paste Slurry by L-pipe

    陈琴瑞; 王洪江; 吴爱祥; 翟永刚; 张仪; 章清涛


    全尾砂膏体料浆的水力坡度是浆体管道输送的关键参数之一.采用自制的L管,结合全尾砂膏体料浆的流态特性来测定其水力坡度,根据水力坡度来计算其流变参数,并用数据证明了膏体料浆的均质流特性.试验结果表明:全尾砂膏体料浆不沉粒径d0>dmax,属均质流;雷诺数Re<2 100,属柱塞流;流变参数为膏体料浆的固有属性,不同管径、不同流速下的水力坡度可根据其流变参数进行计算.%The hydraulic gradient of full-tailings paste slurry is one of the key parameters of pipeline transportation. In this paper, using self-made L-pipe, the hydraulic gradient was measured through the combination of the flow characteristics of full-tailings paste slurry,then slurry rheological parameters was calculated on the basis of hydraulic gradient, and slurry's homogeneous property was proved through data. The results showed that: the full-tailings paste slurry belongs to homogeneous flow because of unsinkable diameter d0 >dmax, plug flow because of Reynolds number Re <2 100; The rheological parameters are intrinsic properties of slurry. The hydraulic gradient with various diameters and various velocities can be calculated in accordance with the rheological parameters.

  12. Scaling properties of the mean wall-normal velocity in zero-pressure-gradient boundary layers

    Wei, Tie; Klewicki, Joseph


    The scaling properties of the mean wall-normal velocity V (x ,y ) in zero-pressure-gradient laminar and turbulent boundary-layer flows are investigated using numerical simulation data, physical experiment data, and integral analyses of the governing equations. The maximum mean wall-normal velocity V∞ and the boundary-layer thickness δ are evidenced to be the proper scaling for V over most if not all of the boundary layer. This is different from the behavior of the mean streamwise velocity U or the turbulent shear stress T =-ρ , which depend on different characteristic length scales in the regions near and away from the surface, respectively. The reason for this apparent difference in scaling behaviors is described physically relative to the downstream development of the U velocity profile and the mechanisms of boundary-layer growth. Insights pertaining to this are further surmised from an analytical relationship for the ratio of the displacement to momentum thickness, i.e., shape factor H . Integral analyses using the continuity and mean momentum equation show that U∞V∞/uτ2=H , where uτ is the friction velocity. Both the laminar similarity solution and direct numerical simulation data in post-transitional flows convincingly support this relation. Over the transitional regime, data of sufficiently high quality are lacking to check if this relation remains valid.

  13. Hepatic venous pressure gradient predicts development of hepatocellular carcinoma independently of severity of cirrhosis☆

    Ripoll, Cristina; Groszmann, Roberto J.; Garcia-Tsao, Guadalupe; Bosch, Jaime; Grace, Norman; Burroughs, Andrew; Planas, Ramon; Escorsell, Angels; Garcia-Pagan, Juan Carlos; Makuch, Robert; Patch, David; Matloff, Daniel S.


    Background/Aims A total of 213 patients with compensated cirrhosis, portal hypertension and no varices were included in a trial evaluating beta-blockers in preventing varices. Predictors of the development of hepatocellular carcinoma (HCC), including hepatic venous pressure gradient (HVPG) were analyzed. Methods Baseline laboratory tests, ultrasound and HVPG measurements were performed. Patients were followed prospectively every three months until development of varices or variceal bleeding or end of the study in 09/02. The endpoint was HCC development according to standard diagnostic criteria. Univariate and multivariate Cox regression models were developed to identify predictors of HCC. Results In a median follow-up of 58 months 26/213 (12.2%) patients developed HCC. Eight patients were transplanted and 28 patients died without HCC. Twenty-one (84%) HCC developed in patients with HCV. On multivariate analysis HVPG (HR 1.18; 95%CI 1.08–1.29), albumin (HR 0.34; 95%CI 0.14–0.83) and viral etiology (HR 4.59; 95%CI 1.51–13.92) were independent predictors of HCC development. ROC curves identified 10 mmHg of HVPG as the best cutoff; those who had an HVPG above this value had a 6-fold increase in the HCC incidence. Conclusions Portal hypertension is an independent predictor of HCC development. An HVPG >10 mmHg is associated with a 6-fold increase of HCC risk. PMID:19303163

  14. Direct Numerical Simulation of Zero-Pressure Gradient and Sink Flow Turbulent Boundary Layers

    Ramesh, O.; Patwardhan, Saurabh


    Direct Numerical Simulations have been performed for the zero pressure gradient (ZPG) (600 < Reθ< 900) and for the sink flow turbulent boundary layers (K = 7.71x10-7). A finite difference code on Cartesian grid was used to perform the simulations. Inflow generation method developed by Lund et al. was used to generate inflow boundary condition for the ZPG case. This method was slightly modified for the case of sink flow in view of self-similarity it possesses in the inner co-ordinates. Hence, there was no need to use empirical relations for the calculation of inlet θ or δ and rescaling in outer co-ordinates. The average statistics obtained from the simulations are in close agreement with the experimental as well as DNS data available in the literature. The intermittency distribution in the case of sink flow approaches zero inside the boundary layer (y = 0.8δ), an observation which is also confirmed by the experiments. This effect could be due to the acceleration near the boundary layer edge which suppresses the turbulent fluctuations near the boundary layer edge.

  15. Heat transfer between two parallel porous plates for Couette flow under pressure gradient and Hall current

    Hazem A Attia; W Abbas; Mostafa A M Abdeen; Ahmed A M Said


    The aim of the present paper is to study the unsteady magneto-hydrodynamic viscous Couette flow with heat transfer in a Darcy porous medium between two infinite parallel porous plates considering Hall effect, and temperature dependent physical properties under constant pressure gradient. The parallel plates are assumed to be porous and subjected to a uniform suction from above and injection from below while the fluid is flowing through a porous medium that is assumed to obey Darcy’s law. A numerical solution for the governing nonlinear partial differential equations coupled with set of momentum equations and the energy equation including the viscous and Joule dissipations is adopted. The effect of the porosity of the medium, the Hall current and the temperature dependent viscosity and thermal conductivity on both the velocity and temperature distributions are investigated. It is found that the porosity numberMhas a marked effect on decreasing the velocity distribution (owing to a simultaneous increase in Darcy porous drag). Also the temperature T is decreased considerably with increasing porosity number.With increasing Hall current parameter m, the velocity component u (x-direction) is considerably increased, whereas velocity component w (z-direction) is reduced. Temperatures are decreased in the early stages of flow but effectively increased in the steady state with increasing m.

  16. Laboratory Hydraulic Fracturing Experiments for Determining Reopening and Closing Pressures of Fractures

    IMAI, Tadao; KAMOSHIDA, Naoto; KATO, Harumi; SUGIMOTO, Fumio


    ... in the borehole wall and the triggering of acoustic emissions.In the experiments, we measured the pressures during the reopening and closing of a fracture caused by elastic restitution in a block of rock not subjected to compressive load...

  17. Thin-Film Composite Pressure Retarded Osmosis Membranes for Sustainable Power Generation from Salinity Gradients

    Yip, Ngai Yin


    Pressure retarded osmosis has the potential to produce renewable energy from natural salinity gradients. This work presents the fabrication of thin-film composite membranes customized for high performance in pressure retarded osmosis. We also present the development of a theoretical model to predict the water flux in pressure retarded osmosis, from which we can predict the power density that can be achieved by a membrane. The model is the first to incorporate external concentration polarization, a performance limiting phenomenon that becomes significant for high-performance membranes. The fabricated membranes consist of a selective polyamide layer formed by interfacial polymerization on top of a polysulfone support layer made by phase separation. The highly porous support layer (structural parameter S = 349 μm), which minimizes internal concentration polarization, allows the transport properties of the active layer to be customized to enhance PRO performance. It is shown that a hand-cast membrane that balances permeability and selectivity (A = 5.81 L m-2 h-1 bar-1, B = 0.88 L m-2 h-1) is projected to achieve the highest potential peak power density of 10.0 W/m2 for a river water feed solution and seawater draw solution. The outstanding performance of this membrane is attributed to the high water permeability of the active layer, coupled with a moderate salt permeability and the ability of the support layer to suppress the undesirable accumulation of leaked salt in the porous support. Membranes with greater selectivity (i.e., lower salt permeability, B = 0.16 L m-2 h-1) suffered from a lower water permeability (A = 1.74 L m-2 h-1 bar-1) and would yield a lower peak power density of 6.1 W/m2, while membranes with a higher permeability and lower selectivity (A = 7.55 L m-2 h-1 bar-1, B = 5.45 L m-2 h-1) performed poorly due to severe reverse salt permeation, resulting in a similar projected peak power density of 6.1 W/m2. © 2011 American Chemical Society.

  18. A new macroscopically anisotropic pressure dependent yield function for metal matrix composite based on strain gradient plasticity for the microstructure

    Azizi, Reza; Legarth, Brian Nyvang; Niordson, Christian Frithiof


    Metal matrix composites with long aligned elastic fibers are studied using an energetic rate independent strain gradient plasticity theory with an isotropic pressure independent yield function at the microscale. The material response is homogenized to obtain a conventional macroscopic model...... that exhibits anisotropic yield properties with a pressure dependence. At the microscale free energy includes both elastic strains and plastic strain gradients, and the theory demands higher order boundary conditions in terms of plastic strain or work conjugate higher order tractions. The mechanical response...... of the composite is inclined compared to a standard pressure independent yield surfaces. The evolution of the macroscopic yield surface is investigated by quantifying both anisotropic hardening (expansion) and kinematic hardening (translation), where the coefficients of anisotropy and the Bauschinger stress...

  19. Investigating patterns and controls of groundwater up-welling in a lowland river by combining Fibre-optic Distributed Temperature Sensing with observations of vertical hydraulic gradients

    S. Krause


    Full Text Available This paper investigates the patterns and controls of aquifer–river exchange in a fast-flowing lowland river by the conjunctive use of streambed temperature anomalies identified with Fibre-optic Distributed Temperature Sensing (FO-DTS and observations of vertical hydraulic gradients (VHG.

    FO-DTS temperature traces along this lowland river reach reveal discrete patterns with "cold spots" indicating groundwater up-welling. In contrast to previous studies using FO-DTS for investigation of groundwater–surface water exchange, the fibre-optic cable in this study was buried in the streambed sediments, ensuring clear signals despite fast flow and high discharges. During the observed summer baseflow period, streambed temperatures in groundwater up-welling locations were found to be up to 1.5 °C lower than ambient streambed temperatures. Due to the high river flows, the cold spots were sharp and distinctly localized without measurable impact on down-stream surface water temperature.

    VHG patterns along the stream reach were highly variable in space, revealing strong differences even at small scales. VHG patterns alone are indicators of both, structural heterogeneity of the stream bed as well as of the spatial heterogeneity of the groundwater–surface water exchange fluxes and are thus not conclusive in their interpretation. However, in combination with the high spatial resolution FO-DTS data we were able to separate these two influences and clearly identify locations of enhanced exchange, while also obtaining information on the complex small-scale streambed transmissivity patterns responsible for the very discrete exchange patterns. The validation of the combined VHG and FO-DTS approach provides an effective strategy for analysing drivers and controls of groundwater–surface water exchange, with implications for the quantification of biogeochemical cycling and contaminant transport at aquifer–river interfaces.

  20. On axial temperature gradients due to large pressure drops in dense fluid chromatography.

    Colgate, Sam O; Berger, Terry A


    The effect of energy degradation (Degradation is the creation of net entropy resulting from irreversibility.) accompanying pressure drops across chromatographic columns is examined with regard to explaining axial temperature gradients in both high performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). The observed effects of warming and cooling can be explained equally well in the language of thermodynamics or fluid dynamics. The necessary equivalence of these treatments is reviewed here to show the legitimacy of using whichever one supports the simpler determination of features of interest. The determination of temperature profiles in columns by direct application of the laws of thermodynamics is somewhat simpler than applying them indirectly by solving the Navier-Stokes (NS) equations. Both disciplines show that the preferred strategy for minimizing the reduction in peak quality caused by temperature gradients is to operate columns as nearly adiabatically as possible (i.e. as Joule-Thomson expansions). This useful fact, however, is not widely familiar or appreciated in the chromatography community due to some misunderstanding of the meaning of certain terms and expressions used in these disciplines. In fluid dynamics, the terms "resistive heating" or "frictional heating" have been widely used as synonyms for the dissipation function, Φ, in the NS energy equation. These terms have been widely used by chromatographers as well, but often misinterpreted as due to friction between the mobile phase and the column packing, when in fact Φ describes the increase in entropy of the system (dissipation, ∫TdSuniv>0) due to the irreversible decompression of the mobile phase. Two distinctly different contributions to the irreversibility are identified; (1) ΔSext, viscous dissipation of work done by the external surroundings driving the flow (the pump) contributing to its warming, and (2) ΔSint, entropy change accompanying decompression of

  1. On the application of reynolds theory to thermo-piezo-viscous lubrication in oil hydraulics

    Johansen, Per; Roemer, Daniel Beck; Andersen, Torben O.


    . In this paper the derivation of Reynolds equation from the continuum assumption is reviewed and it is shown that the validity of Reynolds theory based pressure field solutions in oil hydraulic thermo-piezo-viscous lubrication models are subject to maximum bounds on the pressure and temperature field gradients...

  2. Simplification of hydraulic balance without differential pressure regulators; Vereinfachung des hydraulischen Abgleichs. Wegfall der Differenzdruckregler

    Gebauer, Marc [W. Baelz und Sohn GmbH und Co., Heilbronn (Germany)


    In many heating systems, it would be possible to reduce the number of armatures to save energy. The author presents an example to show the shortcomings of systems with differential pressure controllers and recirculation pumps and points out the advantages of jet pump control. (orig.)

  3. The numerical simulation based on CFD of hydraulic turbine pump

    Duan, X. H.; Kong, F. Y.; Liu, Y. Y.; Zhao, R. J.; Hu, Q. L.


    As the functions of hydraulic turbine pump including self-adjusting and compensation with each other, it is far-reaching to analyze its internal flow by the numerical simulation based on CFD, mainly including the pressure field and the velocity field in hydraulic turbine and pump.The three-dimensional models of hydraulic turbine pump are made by Pro/Engineer software;the internal flow fields in hydraulic turbine and pump are simulated numerically by CFX ANSYS software. According to the results of the numerical simulation in design condition, the pressure field and the velocity field in hydraulic turbine and pump are analyzed respectively .The findings show that the static pressure decreases systematically and the pressure gradient is obvious in flow area of hydraulic turbine; the static pressure increases gradually in pump. The flow trace is regular in suction chamber and flume without spiral trace. However, there are irregular traces in the turbine runner channels which contrary to that in flow area of impeller. Most of traces in the flow area of draft tube are spiral.

  4. Calculation of turbulent boundary layers with heat transfer and pressure gradient utilizing a compressibility transformation. Part 2: Constant property turbulent boundary layer flow with simultaneous mass transfer and pressure gradient

    Boccio, J.; Economos, C.


    An analysis of the incompressible turbulent boundary layer, developing under the combined effects of mass transfer and pressure gradient, is presented in this paper. A strip-integral method is employed whereby two of the three governing equations are obtained by integrating the combined momentum and continuity equation to 50 percent and 100 percent, respectively, of the boundary-layer height. The latter equation is the usual momentum-integral equation; the former equation requires specification of shear. Accordingly, Clauser's equilibrium eddy-viscosity law is assumed valid at this point. The third and final equation is obtained by specifying that Stevenson's velocity profiles apply throughout the domain of interest, from which a skin-friction law can be derived. Comparisons of the numerical results with the experiments of McQuaid, which include combined effects of variable pressure gradient and mass transfer, show good agreement.

  5. High-order accurate finite-volume formulations for the pressure gradient force in layered ocean models

    Engwirda, Darren; Kelley, Maxwell; Marshall, John


    Discretisation of the horizontal pressure gradient force in layered ocean models is a challenging task, with non-trivial interactions between the thermodynamics of the fluid and the geometry of the layers often leading to numerical difficulties. We present two new finite-volume schemes for the pressure gradient operator designed to address these issues. In each case, the horizontal acceleration is computed as an integration of the contact pressure force that acts along the perimeter of an associated momentum control-volume. A pair of new schemes are developed by exploring different control-volume geometries. Non-linearities in the underlying equation-of-state definitions and thermodynamic profiles are treated using a high-order accurate numerical integration framework, designed to preserve hydrostatic balance in a non-linear manner. Numerical experiments show that the new methods achieve high levels of consistency, maintaining hydrostatic and thermobaric equilibrium in the presence of strongly-sloping layer geometries, non-linear equations-of-state and non-uniform vertical stratification profiles. These results suggest that the new pressure gradient formulations may be appropriate for general circulation models that employ hybrid vertical coordinates and/or terrain-following representations.

  6. Stability Verification for Energy-Aware Hydraulic Pressure Control via Simplicial Subdivision

    Sloth, Christoffer; Wisniewski, Rafael


    This paper presents a linear programming-based method for finding Lyapunov functions of dynamical systems with polynomial vector fields. We propose to utilize a certificate of positivity in the Bernstein basis based on subdivisioning to find a Lyapunov function. The subdivision-based method...... is proposed since it has better degree bounds than similar methods based on degree elevation. The proposed method is successfully applied to find a Lyapunov function for a pressure controlled water distribution system....

  7. Thermal-hydraulic behaviors of vapor-liquid interface due to arrival of a pressure wave

    Inoue, Akira; Fujii, Yoshifumi; Matsuzaki, Mitsuo [Tokyo Institute of Technology (Japan)


    In the vapor explosion, a pressure wave (shock wave) plays a fundamental role for triggering, propagation and enhancement of the explosion. Energy of the explosion is related to the magnitude of heat transfer rate from hot liquid to cold volatile one. This is related to an increasing rate of interface area and to an amount of transient heat flux between the liquids. In this study, the characteristics of transient heat transfer and behaviors of vapor film both on the platinum tube and on the hot melt tin drop, under same boundary conditions have been investigated. It is considered that there exists a fundamental mechanism of the explosion in the initial expansion process of the hot liquid drop immediately after arrival of pressure wave. The growth rate of the vapor film is much faster on the hot liquid than that on the solid surface. Two kinds of roughness were observed, one due to the Taylor instability, by rapid growth of the explosion bubble, and another, nucleation sites were observed at the vapor-liquid interface. Based on detailed observation of early stage interface behaviors after arrival of a pressure wave, the thermal fragmentation mechanism is proposed.

  8. A practical approach for predicting retention time shifts due to pressure and temperature gradients in ultra-high-pressure liquid chromatography.

    Åsberg, Dennis; Chutkowski, Marcin; Leśko, Marek; Samuelsson, Jörgen; Kaczmarski, Krzysztof; Fornstedt, Torgny


    Large pressure gradients are generated in ultra-high-pressure liquid chromatography (UHPLC) using sub-2μm particles causing significant temperature gradients over the column due to viscous heating. These pressure and temperature gradients affect retention and ultimately result in important selectivity shifts. In this study, we developed an approach for predicting the retention time shifts due to these gradients. The approach is presented as a step-by-step procedure and it is based on empirical linear relationships describing how retention varies as a function of temperature and pressure and how the average column temperature increases with the flow rate. It requires only four experiments on standard equipment, is based on straightforward calculations, and is therefore easy to use in method development. The approach was rigorously validated against experimental data obtained with a quality control method for the active pharmaceutical ingredient omeprazole. The accuracy of retention time predictions was very good with relative errors always less than 1% and in many cases around 0.5% (n=32). Selectivity shifts observed between omeprazole and the related impurities when changing the flow rate could also be accurately predicted resulting in good estimates of the resolution between critical peak pairs. The approximations which the presented approach are based on were all justified. The retention factor as a function of pressure and temperature was studied in an experimental design while the temperature distribution in the column was obtained by solving the fundamental heat and mass balance equations for the different experimental conditions. We strongly believe that this approach is sufficiently accurate and experimentally feasible for this separation to be a valuable tool when developing a UHPLC method. After further validation with other separation systems, it could become a useful approach in UHPLC method development, especially in the pharmaceutical industry where

  9. Inelastic compression legging produces gradient compression and significantly higher skin surface pressures compared with an elastic compression stocking.

    Kline, Cassie N; Macias, Brandon R; Kraus, Emily; Neuschwander, Timothy B; Angle, Niren; Bergan, John; Hargens, Alan R


    The purposes of this study were to (1) investigate compression levels beneath an inelastic legging equipped with a new pressure-adjustment system, (2) compare the inelastic compression levels with those provided by a well-known elastic stocking, and (3) evaluate each support's gradient compression production. Eighteen subjects without venous reflux and 12 patients with previously documented venous reflux received elastic and inelastic compression supports sized for the individual. Skin surface pressures under the elastic (Sigvaris 500, 30-40 mm Hg range, Sigvaris, Inc., Peachtree City, GA) and inelastic (CircAid C3 with Built-in-Pressure System [BPS], CircAid Medical Products, San Diego, CA) supports were measured using a calibrated Tekscan I-Scan device (Tekscan, Inc., Boston, MA). The elastic stocking produced significantly lower skin surface pressures than the inelastic legging. Mean pressures (+/- standard error) beneath the elastic stocking were 26 +/- 2 and 23 +/- 1 mm Hg at the ankle and below-knee regions, respectively. Mean pressures (+/- standard error) beneath the inelastic legging with the BPS were 50 +/- 3 and 38 +/- 2 mm Hg at the ankle and below-knee regions, respectively. Importantly, our study indicates that only the inelastic legging with the BPS produces significant ankle to knee gradient compression (p = .001).

  10. Characteristics and performance analysis report of the major thermal hydraulic components in the high temperature/high pressure thermal hydraulic test facility (VISTA)

    Choi, Ki Yong; Park, Hyun Sik; Cho, Seok; Lee, Sung Jae; Song, Chul Hwa; Park, Chun Kyong; Chung, Moon Ki


    The VISTA (Experimental Verification by Integral Simulation of Transients and Accidents) is an experimental facility to verify the performance and safety issues of the SMART-P (Pilot plant of the System-integrated Modular Advanced Reactor). The basic design of the SMART-P has been completed by KAERI. The present report describes the characteristics and performance of the major thermal hydraulic components in the VISTA Facility.

  11. Intimal and medial contributions to the hydraulic resistance of the arterial wall at different pressures: a combined computational and experimental study.

    Chooi, K Y; Comerford, A; Sherwin, S J; Weinberg, P D


    The hydraulic resistances of the intima and media determine water flux and the advection of macromolecules into and across the arterial wall. Despite several experimental and computational studies, these transport processes and their dependence on transmural pressure remain incompletely understood. Here, we use a combination of experimental and computational methods to ascertain how the hydraulic permeability of the rat abdominal aorta depends on these two layers and how it is affected by structural rearrangement of the media under pressure. Ex vivo experiments determined the conductance of the whole wall, the thickness of the media and the geometry of medial smooth muscle cells (SMCs) and extracellular matrix (ECM). Numerical methods were used to compute water flux through the media. Intimal values were obtained by subtraction. A mechanism was identified that modulates pressure-induced changes in medial transport properties: compaction of the ECM leading to spatial reorganization of SMCs. This is summarized in an empirical constitutive law for permeability and volumetric strain. It led to the physiologically interesting observation that, as a consequence of the changes in medial microstructure, the relative contributions of the intima and media to the hydraulic resistance of the wall depend on the applied pressure; medial resistance dominated at pressures above approximately 93 mmHg in this vessel.



    Conventional models for fluid flow in well tests have not been consistent with material balance. According to the slightly compressible fluid assumption, the quadratic gradient term in the nonlinear partial differential equation has been usually neglected. This approach is questionable for live oil and low permeability reservoirs. We have already known that linearization by neglecting quadratic gradient terms may lead to errors for large values of well-test time. In this paper, a method that is consistent with material balance was proposed on the spherical flow system. All terms in the nonlinear partial eqiation were retained. Exact solution for the resulting nonlinear partial differential equation in an infinite reservoir was obtained by using the Laplace transform considering wellbore storage. Analytical solution for nonlinear partial differential equation are resulted by using orthogonal transforms under both closed and constant-pressure outer boundary conditions. The law of pressure changes for a fluid compressibility α and a storage coefficient CD were discussed.

  13. An experimental study on laminar-turbulent transition at high free-stream turbulence in boundary layers with pressure gradients

    Chernoray Valery


    Full Text Available We report here the results of a study on measurements and prediction of laminar-turbulent transition at high free-stream turbulence in boundary layers of the airfoil-like geometries with presence of the external pressure gradient changeover. The experiments are performed for a number of flow cases with different flow Reynolds number, turbulence intensity and pressure gradient distributions. The results were then compared to numerical calculations for same geometries and flow conditions. The experiments and computations are performed for the flow parameters which are typical for turbomachinery applications and the major idea of the current study is the validation of the turbulence model which can be used for such engineering applications.

  14. Estimation of the fluid excess pressure of hydraulic fractures in paleo geothermal reservoirs; Abschaetzung des Fluidueberdrucks von hydraulischen Bruechen in palaeogeothermischen Reservoiren

    Philipp, Sonja L. [Goettingen Univ. (Germany). Geowissenschaftliches Zentrum


    In many geothermal reservoirs to low natural permeabilities have to be enhanced by opening or shearing the existing fractures or by generating artificial hydraulic fractures (reservoir stimulation). Such hydraulic fractures can also occur naturally and will remain in paleo geothermal reservoirs. Using the example of calcite passages in a Jurassic limestone-marl alternations in southwest England the author of the contribution under consideration shows that the fault zones (mainly normal faults) were used as fluid transport pathways for calcium carbonate containing water which was injected as hydraulic fractures in the host rock. Overall, in consensus with isotopic studies it was shown that geothermal waters with relatively local origin were within the sedimentary basin and did not come from great depths. The pore fluid pressure within the limestone beds is not sufficient as a reason for the formation of calcite passages.

  15. Intrinsic advantages of packed capillaries over narrow-bore columns in very high-pressure gradient liquid chromatography.

    Gritti, Fabrice; McDonald, Thomas; Gilar, Martin


    250μm×100mm fused silica glass capillaries were packed with 1.8μm high-strength silica (HSS) fully porous particles. They were prepared without bulky stainless steel endfittings and metal frits, which both generate significant sample dispersion. The isocratic efficiencies and gradient peak capacities of these prototype capillary columns were measured for small molecules (n-alkanophenones) using a home-made ultra-low dispersive micro-HPLC instrument. Their resolution power was compared to that of standard 2.1mm×100mm very high-pressure liquid chromatography (vHPLC) narrow-bore columns packed with the same particles. The results show that, for the same column efficiency (25000 plates) and gradient steepness (0.04min(-1)), the peak capacity of the 250μm i.d. capillary columns is systematically 15-20% higher than that of the 2.1mm i.d. narrow-bore columns. A validated model of gradient chromatography enabled one to predict accurately the observed peak capacities of the capillary columns for non-linear solvation strength retention behavior and under isothermal conditions. Thermodynamics applied to the eluent quantified the temperature difference for the thermal gradients in both capillary and narrow-bore columns. Experimental data revealed that the gradient peak capacity is more affected by viscous heating than the column efficiency. Unlike across 2.1mm i.d. columns, the changes in eluent composition across the 250μm i.d. columns during the gradient is rapidly relaxed by transverse dispersion. The combination of (1) the absence of viscous heating and (2) the high uniformity of the eluent composition across the diameter of capillary columns explains the intrinsic advantage of capillary over narrow-bore columns in gradient vHPLC.

  16. Effect of spanwise pressure gradient on flow and heat transfer characteristics of longitudinal vortices embedded in a turbulent boundary layer

    Lee, Jeong Min; Moon, Joo Hyun; Park, Jae Yong; Kim, Dae Yun; Lee, Seong Hyuk [Chung-Ang University, Seoul (Korea, Republic of)


    This study numerically investigated the influence of spanwise pressure gradient on heat transfer of a 3D turbulent boundary layer with longitudinal vortices. A 30° bend in the passage provided the spanwise pressure gradient. The longitudinal pair vortices were generated using a pair of delta winglets. The Reynolds-averaged Navier-Stokes and energy equations based on the conventional Reynolds stress model were used. The predictions agreed well with the experimental data for the straight plate. The turbulent boundary layer was significantly perturbed with the longitudinal vortices. The spanwise pressure gradient contributed to faster degradation of the longitudinal vortices and widened the perturbed flow region. The local Stanton number distributions were asymmetric because of the difference in the evolution of the longitudinal vortices in the curved region. Moreover, comparison showed that the local Stanton number in the downstream of the straight channel increased near the surface because of the secondary re-circulating vortex. The thickness of the thermal boundary layers increased in the streamwise direction because of the significant flow mixing and heat transfer.

  17. Marked discrepancy in pressure gradient between Doppler and catheter examinations on Medtronic Mosaic valve in aortic position.

    Ito, Toshiaki; Maekawa, Atsuo; Fujii, Genyo; Sawaki, Sadanari; Hoshino, Satoshi; Hayashi, Yasunari


    A 71-year-old woman underwent aortic valve replacement with 23 mm Medtronic Mosaic Ultra valve 4 years ago because of aortic stenosis. Although she had been asymptomatic since the operation, echocardiography showed 4 m/s of transprosthetic valve flow that implied early prosthetic valve failure. Catheter examination revealed that the mean transvalvular pressure gradient during systole was 15.1 mmHg on simultaneous pressure recording, and calculated valve area 1.82 cm(2). Her body surface area was 1.56 m(2). Prosthetic valve failure and prosthesis-patient mismatch were both denied. The discrepancy between Doppler study data and catheter data seemed to be due to fluid dynamical pressure recovery phenomenon. Net pressure difference between the left ventricle and the aorta may be significantly smaller than that estimated using Bernoulli's equation from transvalvular flow speed in some patients after aortic valve replacement.

  18. Experimental and Parametric Design of Petroleum Back-pressured Hydraulic Impactor

    YUAN Guang-jie; YAO Zhen-qiang; CHEN Ping; HUANG Wan-zhi


    Percussive-rotary drilling technology was considered many years ago as one of the best approaches for hard rock drilling. It is a key for popularizing this technology on a large scale to design and make an impactor with excellent performance. This paper presents a suit of method to design the percussive parameters for the oil or gas field by introducing the working principle of back-pressured impactor, dividing the working periods of impactor into three phases and establishing the computer emulational model of percussive parameters. It draws a comparison between the results of model calculation and experiment on the basis of analyzing the experiment results of impactor.The conclude provides credible foundation for designing and further ameliorating the impactor.

  19. The diastolic flow velocity-pressure gradient relation and dpv50 to assess the hemodynamic significance of coronary stenoses.

    Marques, Koen M J; van Eenige, Machiel J; Spruijt, Hugo J; Westerhof, Nico; Twisk, Jos; Visser, Cees A; Visser, Frans C


    To evaluate the hemodynamic impact of coronary stenoses, the fractional (FFR) or coronary flow velocity reserve (CFVR) usually is measured. The combined measurement of instantaneous flow velocity and pressure gradient (v-dp relation) is rarely used in humans. We derived from the v-dp relation a new index, dp(v50) (pressure gradient at flow velocity of 50 cm/s), and compared the diagnostic performance of dp(v50), CFVR, and FFR. Before coronary angiography was performed, patients underwent noninvasive stress testing. In all coronary vessels with an intermediate or severe stenosis, the flow velocity, aortic, and distal coronary pressure were measured simultaneously with a Doppler and pressure guidewire after induction of hyperemia. After regression analysis of all middiastolic flow velocity and pressure gradient data, the dp(v50) was calculated. With the use of the results of noninvasive stress testing, the dp(v50) cutoff value was established at 22.4 mmHg. In 77 patients, 124 coronary vessels with a mean 39% (SD 19) diameter stenosis were analyzed. In 43 stenoses, ischemia was detected. We found a sensitivity, specificity, and accuracy of 56%, 86%, and 76% for CFVR; 77%, 99%, and 91% for FFR; and 95%, 95%, and 95% for dp(v50). To establish that dp(v50) is not dependent on maximal hyperemia, dp(v50) was recalculated after omission of the highest quartile of flow velocity data, showing a difference of 3%. We found that dp(v50) provided the highest sensitivity and accuracy compared with FFR and CFVR in the assessment of coronary stenoses. In contrast to CFVR and FFR, assessment of dp(v50) is not dependent on maximal hyperemia.

  20. 3D Numerical Simulation versus Experimental Assessment of Pressure Pulsations Using a Passive Method for Swirling Flow Control in Conical Diffusers of Hydraulic Turbines



    The hydraulic turbines operated at partial discharge (especially hydraulic turbines with fixed blades, i.e. Francis turbine), developing a swirling flow in the conical diffuser of draft tube. As a result, the helical vortex breakdown, also known in the literature as “precessing vortex rope” is developed. A passive method to mitigate the pressure pulsations associated to the vortex rope in the draft tube cone of hydraulic turbines is presented in this paper. The method involves the development of a progressive and controlled throttling (shutter), of the flow cross section at the bottom of the conical diffuser. The adjustable cross section is made on the basis of the shutter-opening of circular diaphragms, while maintaining in all positions the circular cross-sectional shape, centred on the axis of the turbine. The stagnant region and the pressure pulsations associated to the vortex rope are mitigated when it is controlled with the turbine operating regime. Consequently, the severe flow deceleration and corresponding central stagnant are diminished with an efficient mitigation of the precessing helical vortex. Four cases (one without diaphragm and three with diaphragm), are numerically and experimentally investigated, respectively. The present paper focuses on a 3D turbulent swirling flow simulation in order to evaluate the control method. Numerical results are compared against measured pressure recovery coefficient and Fourier spectra. The results prove the vortex rope mitigation and its associated pressure pulsations when employing the diaphragm.

  1. Thermal-hydraulic instabilities in pressure tube graphite - moderated boiling water reactors

    Tsiklauri, G.; Schmitt, B.


    Thermally induced two-phase instabilities in non-uniformly heated boiling channels in RBMK-1000 reactor have been analyzed using RELAP5/MOD3 code. The RELAP5 model of a RBMK-1000 reactor was developed to investigate low flow in a distribution group header (DGH) supplying 44 fuel pressure tubes. The model was evaluated against experimental data. The results of the calculations indicate that the period of oscillation for the high power tube varied from 3.1s to 2.6s, over the power range of 2.0 MW to 3.0 MW, respectively. The amplitude of the flow oscillation for the high powered tube varied from +100% to -150% of the tube average flow. Reverse flow did not occur in the lower power tubes. The amplitude of oscillation in the subcooled region at the inlet to the fuel region is higher than in the saturated region at the outlet. In the upper fuel region and outlet connectors the flow oscillations are dissipated. The threshold of flow instability for the high powered tubes of a RBMK reactor is compared to Japanese data and appears to be in good agreement.

  2. Application of RELAP5/MOD3.3 to Calculate Thermal Hydraulic Behavior of the Pressurizer Safety Valve Performance Test Facility

    Kim, Chang Hyun; Kim, Young Ae; Oh, Seung Jong; Park, Jong Woon [Korea Hydro and Nuclear Power Co., Ltd., Daejeon (Korea, Republic of)


    The increase of the acceptance tolerance of Pressurizer Safety Valve (PSV) test is vital for the safe operation of nuclear power plants because the frequent tests may make the valves decrepit and become a cause of leak. Recently, Korea Hydro and Nuclear Power Company (KHNP) is building a PSV performance test facility to provide the technical background data for the relaxation of the acceptance tolerance of PSV including the valve pop-up characteristics and the loop seal dynamics (if the plant has the loop seal in the upstream of PSV). The discharge piping and supports must be designed to withstand severe transient hydrodynamic loads when the safety valve actuates. The evaluation of hydrodynamic loads is a two-step process: first the thermal hydraulic behavior in the piping must be defined, and then the hydrodynamic loads are calculated from the thermal hydraulic parameters such as pressure and mass flow. The hydrodynamic loads are used as input to the structural analysis.

  3. Analysis of pressure-strain and pressure gradient-scalar covariances in cloud-topped boundary layers: A large-eddy simulation study

    Heinze, Rieke; Mironov, Dmitrii; Raasch, Siegfried


    A detailed analysis of the pressure-scrambling terms (i.e., the pressure-strain and pressure gradient-scalar covariances) in the Reynolds-stress and scalar-flux budgets for cloud-topped boundary layers (CTBLs) is performed using high-resolution large-eddy simulation (LES). Two CTBLs are simulated — one with trade wind shallow cumuli, and the other with nocturnal marine stratocumuli. The pressure-scrambling terms are decomposed into contributions due to turbulence-turbulence interactions, mean velocity shear, buoyancy, and Coriolis effects. Commonly used models of these contributions, including a simple linear model most often used in geophysical applications and a more sophisticated two-component-limit (TCL) nonlinear model, are tested against the LES data. The decomposition of the pressure-scrambling terms shows that the turbulence-turbulence and buoyancy contributions are most significant for cloud-topped boundary layers. The Coriolis contribution is negligible. The shear contribution is generally of minor importance inside the cloudy layers, but it is the leading-order contribution near the surface. A comparison of models of the pressure-scrambling terms with the LES data suggests that the more complex TCL model is superior to the simple linear model only for a few contributions. The linear model is able to reproduce the principal features of the pressure-scrambling terms reasonably well. It can be applied in the second-order turbulence modeling of cloud-topped boundary layer flows, provided some uncertainties are tolerated.

  4. Improvement of pressure text procedure for outside pour type hydraulic prop%外注式单体液压支柱试压工序的改进



    This paper introduces the improving process of outside pour type hydraulic prop.It can reduce labour strength,raise pressure text safety and work efficiency.%介绍了外注式单体液压支柱试压头的改造过程,对其进行改进可以降低劳动强度,提高试压安全性能和劳动效率。

  5. Reducing leaks in water distribution networks. Controlling pressure by means of automatic hydraulic valves; Reduccion de fugas en redes de distribucion de agua. Control de la presion mediante valvulas hidraulicas automaticas

    Singla Font, S.


    Any water distribution network, bet it of drinking water or irrigation water, always loses an inevitable amount. One of the main ways to reduce leaks is to optimise the pressure in the network by means of hydraulic valves with different types of control devices. These can be either completely hydraulic or supplemented by electronic systems. (Author)

  6. Inclusion of biotic stress (consumer pressure) alters predictions from the stress gradient hypothesis

    Smit, Christian; Rietkerk, Max; Wassen, Martin J.


    The stress gradient hypothesis (SGH) predicts a shift from net negative interactions in benign environments towards net positive in harsh environments in ecological communities. While several studies found support for the SGH, others found evidence against it, leading to a debate on how nature and s

  7. Microstructural and hardness gradients in Cu processed by high pressure surface rolling

    He, Q. Y.; Zhu, X.-M.; Mei, Q. S.


    in the topmost surface to the microscale in the bulk. The hardness varies from 1.37 GPa at the topmost surface to about 0.6 GPa in the coarse-grained matrix. The results of the investigation demonstrate that the HPSR process shows good potential for the generation of thick gradient microstructures on the surface...

  8. Inclusion of biotic stress (consumer pressure) alters predictions from the stress gradient hypothesis

    Smit, Christian; Rietkerk, Max; Wassen, Martin J.


    The stress gradient hypothesis (SGH) predicts a shift from net negative interactions in benign environments towards net positive in harsh environments in ecological communities. While several studies found support for the SGH, others found evidence against it, leading to a debate on how nature and

  9. Dependence of transcutaneous oxygen tension on local arteriovenous pressure gradient in normal subjects.

    Wyss, C R; Matsen, F A; King, R V; Simmons, C W; Burgess, E M


    1. We studied the relationship between transcutaneous oxygen tension at the foot and local arteriovenous pressure difference in 15 normal men and women; arteriovenous pressure difference was varied by changing the height of the foot with respect to the heart and by applying external pressure to the foot. 2. Control transcutaneous oxygen tension was 67 +/- 9 SD mmHg (8.9 +/- 1.2 kPa) at a control arteriovenous pressure difference of 80 +/- 6 SD mmHg (10.6 +/- 0.8 kPa). 3. In every subject transcutaneous oxygen tension fell non-linearly with a decrease in arteriovenous pressure difference; transcutaneous oxygen tension was relatively insensitive to changes in arteriovenous pressure difference when arteriovenous pressure difference was high, but always fell sharply to zero at some positive arteriovenous pressure difference [range 13-34 mmHg (1.7-4.5 kPa)]. 4. An analysis of the data indicated that transcutaneous oxygen tension varied with arteriovenous pressure difference approximately as the oxygen tension of cutaneous venous blood under the sensor varied (in the absence of changes in cutaneous vascular resistance and oxygen consumption). 5. This analysis was supported by studies in three subjects in whom the oxygen tension of superficial venous drainage from a warmed hand or foot was measured along with transcutaneous oxygen tension while arteriovenous pressure difference was varied.

  10. A comparison of methods for computing the sigma-coordinate pressure gradient force for flow over sloped terrain in a hybrid theta-sigma model

    Johnson, D. R.; Uccellini, L. W.


    In connection with the employment of the sigma coordinates introduced by Phillips (1957), problems can arise regarding an accurate finite-difference computation of the pressure gradient force. Over steeply sloped terrain, the calculation of the sigma-coordinate pressure gradient force involves computing the difference between two large terms of opposite sign which results in large truncation error. To reduce the truncation error, several finite-difference methods have been designed and implemented. The present investigation has the objective to provide another method of computing the sigma-coordinate pressure gradient force. Phillips' method is applied for the elimination of a hydrostatic component to a flux formulation. The new technique is compared with four other methods for computing the pressure gradient force. The work is motivated by the desire to use an isentropic and sigma-coordinate hybrid model for experiments designed to study flow near mountainous terrain.

  11. A General Pressure Gradient Formulation for Ocean Models, Part 1: Scheme Design and Diagnostic Analysis, Part II: Energy, Momentum, and Bottom Torque Consistency

    Song, Y. T.


    A Jacobian formulation of the pressure gradient force for use in models with topography following coordinates is proposed. It can be used in conjunction with any vertical coordinate system and is easily implemented.

  12. Experimental studies on dynamic system characteristics of the high temperature/high pressure thermal-hydraulic test facility(VISTA) for the power variation

    Choi, K. Y.; Park, H. S.; Joe, S.; Park, C. K.; Lee, S. J.; Song, C. W.; Jeong, M. K. [KAERI, Taejon (Korea, Republic of)


    Dynamic system characteristics tests were carried out for the power variation by using the high temperature/high pressure thermal-hydraulic test facility, VISTA(Experimental Verification by Integral Simulation of Transient and Accidents), which had been constructed to simulate the SMART-P by KAERI. Experimental tests have been performed to investigate the thermal-hydraulic dynamic characteristics of the primary and the secondary systems in the range of 5% to 85% power. Automatic PID control logics were developed and installed to the VISTA facility to control the major thermal hydraulic parameters. Power was changed with either a step or a ramp changing method from the reference power of 10%, 25%, 50% and 75% to 5% or 10% higher power. It was found that there is no noticeable difference in the responses between a step and a ramp changing method. When unique constants of P, I, and D were used in the range of 5% to 85% power, it was found to be liable to lose the system control. Further studies are required to quantify the controllability and the time constants of the major thermal hydraulic parameters.

  13. A Study of the Development of Steady and Periodic Unsteady Turbulent Wakes Through Curved Channels at Positive, Zero, and Negative Streamwise Pressure Gradients, Part 1

    Schobeiri, M. T.; John, J.


    The turbomachinery wake flow development is largely influenced by streamline curvature and streamwise pressure gradient. The objective of this investigation is to study the development of the wake under the influence of streamline curvature and streamwise pressure gradient. The experimental investigation is carried out in two phases. The first phase involves the study of the wake behind a stationary circular cylinder (steady wake) in curved channels at positive, zero, and negative streamwise pressure gradients. The mean velocity and Reynolds stress components are measured using a X-hot-film probe. The measured quantities obtained in probe coordinates are transformed to a curvilinear coordinate system along the wake centerline and are presented in similarity coordinates. The results of the steady wakes suggest strong asymmetry in velocity and Reynolds stress components. However, the velocity defect profiles in similarity coordinates are almost symmetrical and follow the same distribution as the zero pressure gradient straight wake. The results of Reynolds stress distributions show higher values on the inner side of the wake than the outer side. Other quantities, including the decay of maximum velocity defect, growth of wake width, and wake integral parameters, are also presented for the three different pressure gradient cases of steady wake. The decay rate of velocity defect is fastest for the negative streamwise pressure gradient case and slowest for the positive pressure gradient case. Conversely, the growth of the wake width is fastest for the positive streamwise pressure gradient case and slowest for the negative streamwise pressure gradient. The second phase studies the development of periodic unsteady wakes generated by the circular cylinders of the rotating wake generator in a curved channel at zero streamwise pressure gradient. Instantaneous velocity components of the periodic unsteady wakes, measured with a stationary X-hot-film probe, are analyzed by the

  14. Calculation and analysis of velocity and viscous drag in an artery with a periodic pressure gradient

    Alizadeh, M.; Seyedpour, S. M.; Mozafari, V.; Babazadeh, Shayan S.


    Blood as a fluid that human and other living creatures are dependent on has been always considered by scientists and researchers. Any changes in blood pressure and its normal velocity can be a sign of a disease. Whatever significant in blood fluid's mechanics is Constitutive equations and finding some relations for analysis and description of drag, velocity and periodic blood pressure in vessels. In this paper, by considering available experimental quantities, for blood pressure and velocity in periodic time of a thigh artery of a living dog, at first it is written into Fourier series, then by solving Navier-Stokes equations, a relation for curve drawing of vessel blood pressure with rigid wall is obtained. Likewise in another part of this paper, vessel wall is taken in to consideration that vessel wall is elastic and its pressure and velocity are written into complex Fourier series. In this case, by solving Navier-Stokes equations, some relations for blood velocity, viscous drag on vessel wall and blood pressure are obtained. In this study by noting that vessel diameter is almost is large (3.7 mm), and blood is considered as a Newtonian fluid. Finally, available experimental quantities of pressure with obtained curve of solving Navier-Stokes equations are compared. In blood analysis in rigid vessel, existence of 48% variance in pressure curve systole peak caused vessel blood flow analysis with elastic wall, results in new relations for blood flow description. The Resultant curve is obtained from new relations holding 10% variance in systole peak.

  15. Limit analysis of viscoplastic thick-walled cylinder and spherical shell under internal pressure using a strain gradient plasticity theory


    Plastic limit load of viscoplastic thick-walled cylinder and spherical shell subjected to internal pressure is investigated analytically using a strain gradient plastic-itv theory. As a result, the current solutions can capture the size effect at the micron scale. Numerical results show that the smaller the inner radius of the cylinder or spherical shell, the more significant the scale effects. Results also show that the size effect is more evident with increasing strain or strain-rate sensitivity index. The classical plastic-based solutions of the same problems are shown to be a special case of the present solution.

  16. Discussion on Methods of Proportional Pressure Control in Hydraulic System of Hydraulic Press%液压机液压系统比例压力控制方法探讨

    李贵闪; 翟华


    Three methods of proportional pressure control on hydraulic presses were introduced and compared, which were open-loop control, closed-loop control based on PID and PID control with addition of initial signals. Results of comparison showe that the closed-loop control algorithm which is added with initial signals has many advantages such as simple control structure, easy debugging operations, stable system and high precision, and etc. The requirements of this hydraulic press on pressure control can be fully satisfied.%介绍了液压机比例压力控制的3种方法,即开环控制、基于PID的闭环控制、加入初始信号的PID控制.并对3种控制方法进行了比较.结果表明:采取的加入初始信号的闭环控制算法具有控制结构简单、调试方便、系统稳定、精度高等优点,完全满足该液压机对压力控制的要求.

  17. Aerodynamic pressure and heating-rate distributions in tile gaps around chine regions with pressure gradients at a Mach number of 6.6

    Hunt, L. Roane; Notestine, Kristopher K.


    Surface and gap pressures and heating-rate distributions were obtained for simulated Thermal Protection System (TPS) tile arrays on the curved surface test apparatus of the Langley 8-Foot High Temperature Tunnel at Mach 6.6. The results indicated that the chine gap pressures varied inversely with gap width because larger gap widths allowed greater venting from the gap to the lower model side pressures. Lower gap pressures caused greater flow ingress from the surface and increased gap heating. Generally, gap heating was greater in the longitudinal gaps than in the circumferential gaps. Gap heating decreased with increasing gap depth. Circumferential gap heating at the mid-depth was generally less than about 10 percent of the external surface value. Gap heating was most severe at local T-gap junctions and tile-to-tile forward-facing steps that caused the greatest heating from flow impingement. The use of flow stoppers at discrete locations reduced heating from flow impingement. The use of flow stoppers at discrete locations reduced heating in most gaps but increased heating in others. Limited use of flow stoppers or gap filler in longitudinal gaps could reduce gap heating in open circumferential gaps in regions of high surface pressure gradients.

  18. Analysis report of the thermal-hydraulic characteristics of the high temperature/high pressure thermal-hydraulic test facility (VISTA) in steady state conditions

    Park, Hyun Sik; Choi, Ki Yong; Cho, Seok; Lee, Sung Jae; Song, Chul Hwa; Park, Chun Kyong; Chung, Moon Ki


    The VISTA (Experimental Verification by Integral Simulation of Transients and Accidents) is an experimental facility to verify the performance and safety issues of the SMART-P (Pilot plant of the system-integrated modular advanced reactor). The basic design of the SMART-P has been completed by KAERI. The present report describes the experimental results on the water inventory distribution, the pressure distribution, and the differential pressure characteristics of the VISTA facility and on the heat transfer characteristics of the core simulating heater and the steam generator of the VISTA facility. There were little differences of their water inventories between the designed and the measured data. The pressure of the VISTA primary system kept near the steady-state operating pressure of 147 bar, and the differential pressures through the primary and secondary systems increased with the increase of their flow rates. Also the surface temperatures of core simulating heaters were measured, and the overall heat transfer coefficient of the VISTA steam generator was calculated to show a little higher values than that of the SMART-P.

  19. Validation of pressure gradient and peripheral fractional flow reserve measured by a pressure wire for diagnosis of iliofemoral artery disease with intermediate stenosis

    Murata N


    Full Text Available Naotaka Murata,1 Hideaki Aihara,2 Yoshimitsu Soga,1 Yusuke Tomoi,1 Seiichi Hiramori,1 Yohei Kobayashi,1 Kei Ichihashi,1 Nobuhiro Tanaka3 1Department of Cardiology, Kokura Memorial Hospital, Kitakyushu, 2Department of Cardiology, Tsukuba Medical Center Hospital, Ibaraki, 3Department of Cardiology, Tokyo Medical University, Tokyo, Japan Objective: To examine the pressure gradient and peripheral fractional flow reserve (pFFR measured by a pressure wire as indicators of hemodynamic significance in iliofemoral angiographic intermediate stenosis. Background: The utility of pressure measurements using a pressure wire with vasodilators is unclear in cases with intermediate iliofemoral stenosis. Methods: The mean pressure gradient (MPG and mean pressure ratio (MPR were measured at baseline and after injection of isosorbide dinitrate in 23 lesions with angiographically intermediate iliofemoral stenosis. Patients with complex lesions, infrapopliteal artery lesions, chronic total occlusion, and surgical bypass grafts were excluded. Hyperemic MPR was considered equivalent to pFFR. Changes in parameters in response to vasodilators were assessed and correlations of peak systolic velocity ratio (PSVR with hyperemic MPG and pFFR were examined using duplex ultrasound. Results: After injection of isosorbide dinitrate, hyperemic MPG increased significantly (from 9.0±5.7 to 16.3±6.2 mmHg; P<0.05 and hyperemic MPR (pFFR decreased significantly (from 0.92±0.06 to 0.81±0.07; P<0.05. PSVR was significantly correlated with hyperemic MPG (R=0.52; P<0.05 and pFFR (R=–0.50; P<0.05. The optimal cut-off value of pFFR as an indicator of significant hemodynamic stenosis (PSVR >2.5 was 0.85 (area under the curve 0.72; sensitivity 94%; specificity 50%, P<0.05. Conclusion: pFFR measured using a pressure wire is reliable for prediction of hemodynamic significance in iliofemoral intermediate stenosis. Keywords: endovascular therapy, peripheral artery disease, pressure

  20. High-order accurate finite-volume formulations for the pressure gradient force in layered ocean models

    Engwirda, Darren; Marshall, John


    The development of a set of high-order accurate finite-volume formulations for evaluation of the pressure gradient force in layered ocean models is described. A pair of new schemes are presented, both based on an integration of the contact pressure force about the perimeter of an associated momentum control-volume. The two proposed methods differ in their choice of control-volume geometries. High-order accurate numerical integration techniques are employed in both schemes to account for non-linearities in the underlying equation-of-state definitions and thermodynamic profiles, and details of an associated vertical interpolation and quadrature scheme are discussed in detail. Numerical experiments are used to confirm the consistency of the two formulations, and it is demonstrated that the new methods maintain hydrostatic and thermobaric equilibrium in the presence of strongly-sloping layer-wise geometry, non-linear equation-of-state definitions and non-uniform vertical stratification profiles. Additionally, one...

  1. Computation of Flow in a Circular Cylinder Driven by Coaxial Screw Rotation and an Opposing Pressure Gradient.

    Cotrell, David L.; Pearlstein, Arne J.


    We report computations of the velocity field for flows driven by rotation of a screw in a circular cylinder with an applied opposing pressure gradient. Use of a helical coordinate system in a frame rotating with the screw reduces the flow calculation to a steady one, which is taken to be fully-developed in the helical direction. The full incompressible Navier-Stokes equations in primitive-variables form are solved numerically using a finite-element method employing quadrilateral elements with quadratic velocity and linear pressure interpolation. A consistent penalty method is used to satisfy incompressibility. The screw cross-section is rectangular. The effect of screw clearance and other geometric parameters on the velocity field will be discussed for low and intermediate Reynolds numbers and compared to the Stokes flow case.

  2. Social class-related gradient in the association of skeletal growth with blood pressure among adolescent boys in India.

    Rao, Shobha; Apte, Priti


    In view of the fact that height differences between socio-economic groups are apparent early in childhood, it is of interest to examine whether skeletal growth is reflective of the social class gradient in CVD risk. The present study examined blood pressure levels, adiposity and growth of adolescent boys from high and low social classes. In a cross-sectional study, skeletal growth (height and sitting height), adiposity (weight, BMI and body fat) and blood pressure levels of the adolescents were measured. Pune, India. Adolescent schoolboys (9-16 years) from high socio-economic (HSE; n 1146) and low socio-economic (LSE; n 932) class. LSE boys were thin, short and undernourished (mean BMI: 15.5 kg/m2 v. 19.3 kg/m2 in HSE boys, P = 0.00). Social gradient was revealed in differing health risks. The prevalence of high systolic blood pressure (HSBP) was high in HSE class (10.5 % v. 2.7 % in LSE class, P = 0.00) and was associated with adiposity, while the prevalence of high diastolic blood pressure (HDBP) was high in LSE class (9.8 % v. 7.0 % in HSE class, P = 0.00) and had only a weak association with adiposity. Despite this, lower ratio of leg length to height was associated with significantly higher respective health risks, i.e. for HDBP in LSE class (OR = 1.99, 95 % CI 1.14, 3.47) and for HSBP in HSE class (OR = 1.69, 95 % CI 1.02, 2.77). As stunting in childhood is a major problem in India and Asia, the leg length to height indicator needs to be validated in different populations to understand CVD risks.

  3. A paradigm shift in predicting stormflow responses in an active tectonic region through a similarity analysis of pressure propagation in a hydraulic continuum

    Makoto Tani


    Full Text Available Soil layers on hillslopes acts as systems in quasi-steady states generating rainfall-stormflow responses that are controlled by pressure propagation in a hydraulic continuum established when the rainfall volume is sufficiently large. A similarity analysis for quantifying the sensitivity of the stormflow response and recession limb to topographic and soil properties in a sloping permeable domain showed that the deviation of stormflow responses in the hydraulic continuum decreases due to the macropore effect. The rapid responses seem to be naturally derived from the evolution of the soil layer with the assistance of the vegetation-root system and effective drainage systems in zero-order catchments in active tectonic regions with heavy storms. To predict stormflow responses using distributed runoff models, a paradigm shift to consider this evolution process is needed because the simple stormflow responses and complex and heterogeneous catchment properties are poorly related, but may be mainly determined by soil evolution processes.

  4. Experimental studies on heat transfer characteristics and natural circulation performance of PRHRS of the high temperature and high pressure thermal-hydraulic test facility

    Park, H. S.; Choi, K. Y.; Joe, S.; Park, C. K.; Lee, S. J.; Song, C. W.; Jeong, M. K. [KAERI, Taejon (Korea, Republic of)


    Several experiments are performed to investigate the heat transfer characteristics and natural circulation performance of passive residual removal system (PRHRS) of the high temperature and high pressure thermal-hydraulic test facility. Especially the natural circulation performance of PRHRS, the heat transfer characteristics of PRHRS heat exchangers and emergency cooldown tank (ECT), and the thermal-hydraulic behavior of the primary loop are investigated in detail. The coolant flows steadily in the natural circulation loop which is composed of the steam generator (SG) primary side, the secondary system, and the PRHRS. The heat transfers through the PRHRS heat exchanger and ECT are sufficient enough to enable the natural circulation of the coolant. Also the experimental results show that the core decay heat are sufficiently removed with the operation of the PRHRS.

  5. End-tidal arterial CO2 partial pressure gradient in patients with severe hypercapnia undergoing noninvasive ventilation

    Defilippis V


    Full Text Available Vito Defilippis,1 Davide D’Antini,2 Gilda Cinnella,2 Michele Dambrosio,2 Fernando Schiraldi,3 Vito Procacci1 1Emergency Department, Riuniti Hospital, 2Department of Anaesthesiology and Intensive Care, University of Foggia, Foggia, 3Emergency Department, San Paolo Hospital, Naples, Italy Background: Patients with severe hypercapnia represent a particularly serious condition in an emergency department (ED, requiring immediate attention. Noninvasive ventilation (NIV is an integral part of the treatment for acute respiratory failure. The present study aimed to validate the measurement of end-tidal CO2 (EtCO2 as a noninvasive technique to evaluate the effectiveness of NIV in acute hypercapnic respiratory failure. Methods: Twenty consecutive patients admitted to the ED with severe dyspnea were enrolled in the study. NIV by means of bilevel positive airway pressure, was applied to the patients simultaneously with standard medical therapy and continued for 12 hours; the arterial blood gases and side-stream nasal/oral EtCO2 were measured at subsequent times: T0 (admission to the ED, T1h (after 1 hour, T6h (after 6 hours, and T12h (after 12 hours during NIV treatment. Results: The arterial CO2 partial pressure (PaCO2–EtCO2 gradient decreased progressively, reaching at T6h and T12h values lower than baseline (P < 0.001, while arterial pH increased during the observation period (P < 0.001. A positive correlation was found between EtCO2 and PaCO2 values (r = 0.89, P < 0.001 at the end of the observation period. Conclusion: In our hypercapnic patients, the effectiveness of the NIV was evidenced by the progressive reduction of the PaCO2–EtCO2 gradient. The measurement of the CO2 gradient could be a reliable method in monitoring the effectiveness of NIV in acute hypercapnic respiratory failure in the ED. Keywords: arterial end-tidal CO2 gradient, noninvasive ventilation, bilevel positive airway pressure, acute respiratory failure

  6. Fountain streaming contributes to fast tip-growth through regulating the gradients of turgor pressure and concentration in pollen tubes.

    Liu, ShaoBao; Liu, Han; Feng, ShangSheng; Lin, Min; Xu, Feng; Lu, Tian Jian


    Fountain streaming is a typical microfluidic pattern in plant cells, especially for cells with a high aspect ratio such as pollen tubes. Although it has been found that fountain streaming plays crucial roles in the transport of nutrients and metabolites, the positioning of organelles and the mixing of cytoplasms, its implications for the fast tip growth of pollen tubes remain a mystery. To address this, based on the observations of asiatic lily Lilium Casablanca, we developed physical models for reverse fountain streaming in pollen tubes and solved the hydrodynamics and advection-diffusion dynamics of viscous Stokes flow in the shank and apical region of pollen tubes. Theoretical and numerical results demonstrated that the gradients of turgor pressure and concentration of wall materials along the length of pollen tubes provide undamped driving force and high-efficiency materials supply, which are supposed to contribute to the fast tip-growth of pollen tubes. The sample experimental results show that the tip-growth will be abnormal when the gradients of turgor pressure change under osmotic stress induced by different concentrations of PEG-6000 (a dehydrant).

  7. Rationale, design and methodology for Intraventricular Pressure Gradients Study: a novel approach for ventricular filling assessment in normal and falling hearts

    Vouga Luís


    Full Text Available Abstract Background Intraventricular pressure gradients have been described between the base and the apex of the left ventricle during early diastolic ventricular filling, as well as, their increase after systolic and diastolic function improvement. Although, systolic gradients have also been observed, data are lacking on their magnitude and modulation during cardiac dysfunction. Furthermore, we know that segmental dysfunction interferes with the normal sequence of regional contraction and might be expected to alter the physiological intraventricular pressure gradients. The study hypothesis is that systolic and diastolic gradients, a marker of normal left ventricular function, may be related to physiological asynchrony between basal and apical myocardial segments and they can be attenuated, lost entirely, or even reversed when ventricular filling/emptying is impaired by regional acute ischemia or severe aortic stenosis. Methods/Design Animal Studies: Six rabbits will be completely instrumented to measuring apex to outflow-tract pressure gradient and apical and basal myocardial segments lengthening changes at basal, afterloaded and ischemic conditions. Afterload increase will be performed by abruptly narrowing or occluding the ascending aorta during the diastole and myocardial ischemia will be induced by left coronary artery ligation, after the first diagonal branch. Patient Studies: Patients between 65-80 years old (n = 12, both genders, with severe aortic stenosis referred for aortic valve replacement will be selected as eligible subjects. A high-fidelity pressure-volume catheter will be positioned through the ascending aorta across the aortic valve to measure apical and outflow-tract pressure before and after aortic valve replacement with a bioprosthesis. Peak and average intraventricular pressure gradients will be recorded as apical minus outflow-tract pressure and calculated during all diastolic and systolic phases of cardiac cycle

  8. Combined effect of salt concentration and pressure gradients across charged membranes

    Benavente, Juana; Jonsson, Gunnar Eigil


    The combined effect of both concentration and pressure differences on electrical potential (Deltaphi) for two ion-exchanger membranes, one positively charged (AE) and another negatively charged (CE), measured with the membranes in contact with NaCl solutions was studied. Results show a linear...... dependence between Deltaphi and pressure, independently if DeltaC and DeltaP have the same or opposite directions. The ratio of the streaming potential for cation/anion exchange membranes is r = (2.1+/-0.4). A "bipolar" membrane (BM) was obtained by joining together both ion-exchanger membranes. In order...... to correlate the behaviour of the BP membrane with that corresponding to each sublayer, the same kind of measurements was carried out for both opposite external conditions, this means, applying the pressure on the cation exchanger (CABM) or on the anion exchanger membrane (ACBM), respectively. From values...

  9. Prediction of Pressure Gradient and Holdup in Small E(o)tv(o)s Number Liquid-Liquid Segregated Flow%预测小E(o)tv(o)s数液-液分离流的压力梯度和平均界面含水率

    刘夷平; 张华; 王淑华; 王经


    The segregated flow pattern, which occurs in a 26.1 mm diameter, horizontal, stainless steel test section,is investigated. Pressure gradient and in situ phase distribution data were obtained for different combinations of system (E0D=4.77), the dominant effect of interracial tension and wall-wetting properties of the liquids over the gravity is considered. The approach introduces the closure relationship for the case of turbulent flow in a rough pipe,and attempts to modify the two-fluid model to account for the curved interface. In present flow rates range, wave amplitudes were found small, while interfacial mixing was observed. An adjustable definition for hydraulic diame-ters of two fluids and interfacial friction factor is adopted. The predicted pressure gradient and in situ phase distri-bution data have been compared with present experimental data and those reported in the literature.

  10. Salinity-gradient power : Evaluation of pressure-retarded osmosis and reverse electrodialysis

    Post, Jan W.; Veerman, Joost; Hamelers, Hubertus V.M.; Euverink, Gerrit J.W.; Metz, Sybrand J.; Nymeijer, Kitty; Buisman, Cees J.N.


    A huge potential to obtain clean energy exists from mixing water streams with different salt concentrations. Two membrane-based energy conversion techniques are evaluated: pressure-retarded osmosis and reverse electrodialysis. From the literature, a comparison is not possible since the reported perf

  11. Estimates of pressure gradients in PEMFC gas channels due to blockage by static liquid drops

    Venkatraman, M.; Shimpalee, S.; Van Zee, J.W. [Department of Chemical Engineering, University of South Carolina, 301 Main St., Columbia, SC 29208 (United States); Moon, Sung In; Extrand, C.W. [Entegris, Inc., 3500 Lyman Boulevard, Chaska, MN 55318 (United States)


    Numerical analyses are presented to explain the effect of drop size and contact angle on local pressures inside small channels. These pressures and channel characteristics are of interest when water condenses in the gas channels of Proton Exchange Membrane Fuel Cells and hence the study uses Reynolds numbers consistent with as typical utilization of reacting gases in 200 cm{sup 2} flow fields (i.e., 200 < Re < 1500 and stoichiometries of 1.2-2.0 at 1.0 A/cm{sup 2}). The analyses were performed using three-dimensional computational fluid dynamic techniques and the results show that pressure drops are minimal until the blockage was greater than 50%. As blockage increased further, due to larger drops or increased hydrophobicity, pressure drop increased. The results of a stagnant drop are supported by visualization experiments, which show minimal distortion of the drop for these low flow rates, small ratios, and hydrophobic contact angles. Proper scaling parameters and design criteria for microchannels validation experiments are presented. (author)

  12. Salinity-gradient power: Evaluation of pressure-retarded osmosis and reverse electrodialysis

    Post, J.W.; Veerman, J.; Hamelers, H.V.M.; Euverink, G.J.W.; Metz, S.J.; Nymeijer, K.; Buisman, C.J.N.


    A huge potential to obtain clean energy exists from mixing water streams with different salt concentrations. Two membrane-based energy conversion techniques are evaluated: pressure-retarded osmosis and reverse electrodialysis. From the literature, a comparison is not possible since the reported perf

  13. Thermal studies of a high gradient quadrupole magnet cooled with pressurized, stagnant superfluid

    Chiesa, L; Kerby, J S; Lamm, M J; Novitski, I; Orris, D; Ozelis, J P; Peterson, Thomas J; Tartaglia, M; Zlobin, A V


    A 2-m long superconducting model of an LHC Interaction Region quadrupole magnet was wound with stabrite coated cable. The resulting low interstrand resistance and high AC losses presented the opportunity to measure magnet quench performance in superfluid as a function of helium temperature and heat deposition in the coil. Our motivation was to duplicate the high radiation heat loads predicted for the inner triplet quadrupoles at LHC and study the coil cooling conditions in the magnet. At the Magnet Test Facility in Fermilab's Technical Division, the magnet quench performance was tested as a function of bulk helium temperature and current ramp rate near the planned high luminosity interaction region field gradient of 205 T/m. AC loss measurements provided a correlation between current ramp rate and heat deposition in the coil. Analysis indicates that the results are consistent with there being little participation of superfluid helium in the small channels inside the inner layer in the heat removal from the co...

  14. 46 CFR 28.405 - Hydraulic equipment.


    ... 46 Shipping 1 2010-10-01 2010-10-01 false Hydraulic equipment. 28.405 Section 28.405 Shipping... Operate With More Than 16 Individuals on Board § 28.405 Hydraulic equipment. (a) Each hydraulic system... than four times the system maximum operating pressure. (c) Each hydraulic system must be equipped...

  15. Evanescent pressure gradient response in the upper ocean to subinertial wind stress forcing of finite wavelength

    White, Warren B.; Mcnally, Gerard


    A schematic model is used to interpret field observations related to the mixed layer response to wind stress at subinertial frequencies. It is shown that subinertial density and pressure fluctuations can arise locally from the finite wavelength character of the wind stress forcing as a fundamental part of the upper ocean transient, wind-driven response on time scales of 2-10 pendulum days. Evanescent vertical motions arise which alter the density field of the pycnocline, and hence the pressure field over the entire upper ocean. It is thus found that in the real ocean driven by wind stress, a transient geostrophic response exists which can be as large or larger than the transient Eckman response.

  16. Literature survey of heat transfer and hydraulic resistance of water, carbon dioxide, helium and other fluids at supercritical and near-critical pressures

    Pioro, I.L.; Duffey, R.B


    This survey consists of 430 references, including 269 Russian publications and 161 Western publications devoted to the problems of heat transfer and hydraulic resistance of a fluid at near-critical and supercritical pressures. The objective of the literature survey is to compile and summarize findings in the area of heat transfer and hydraulic resistance at supercritical pressures for various fluids for the last fifty years published in the open Russian and Western literature. The analysis of the publications showed that the majority of the papers were devoted to the heat transfer of fluids at near-critical and supercritical pressures flowing inside a circular tube. Three major working fluids are involved: water, carbon dioxide, and helium. The main objective of these studies was the development and design of supercritical steam generators for power stations (utilizing water as a working fluid) in the 1950s, 1960s, and 1970s. Carbon dioxide was usually used as the modeling fluid due to lower values of the critical parameters. Helium, and sometimes carbon dioxide, were considered as possible working fluids in some special designs of nuclear reactors. (author)

  17. Control of Separation for Turbulent Boundary Layers Subjected to Wall Curvature and Streamwise Pressure Gradients


    the pressure side were studied. The same case, at the higher Reynolds number of 148,000, was also studied by Xiaohua and Durbin (2001). They used a...with the Boussinesq- assumption or the explicit algebraic Reynolds stress model (EASM) by Gatski (Gatski and Sepziale 1993, Gatski and Jongen 2000...approximation is employed for computing the Reynolds stresses. When the Explicit Algebraic Stress Model (EASM) is used, the turbulence equations are

  18. Vibration of hydraulic machinery

    Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong


    Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...

  19. Transport efficiency and dynamics of hydraulic fracture networks

    Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique


    Intermittent fluid pulses in the Earth's crust can explain a variety of geological phenomena, for instance the occurrence of hydraulic breccia. Fluid transport in the crust is usually modeled as continuous darcian flow, ignoring that sufficient fluid overpressure can cause hydraulic fractures as fluid pathways with very dynamic behavior. Resulting hydraulic fracture networks are largely self-organized: opening and healing of hydraulic fractures depends on local fluid pressure, which is, in turn, largely controlled by the fracture network. We develop a crustal-scale 2D computer model designed to simulate this process. To focus on the dynamics of the process we chose a setup as simple as possible. Control factors are constant overpressure at a basal fluid source and a constant 'viscous' parameter controlling fracture-healing. Our results indicate that at large healing rates hydraulic fractures are mobile, transporting fluid in intermittent pulses to the surface and displaying a 1/fα behavior. Low healing rates result in stable networks and constant flow. The efficiency of the fluid transport is independent from the closure dynamics of veins or fractures. More important than preexisting fracture networks is the distribution of fluid pressure. A key requirement for dynamic fracture networks is the presence of a fluid pressure gradient.

  20. Transport efficiency and dynamics of hydraulic fracture networks

    Till eSachau


    Full Text Available Intermittent fluid pulses in the Earth's crust can explain a variety of geological phenomena, for instance the occurrence of hydraulic breccia. Fluid transport in the crust is usually modeled as continuous darcian flow, ignoring that sufficient fluid overpressure can cause hydraulic fractures as fluid pathways with very dynamic behavior. Resulting hydraulic fracture networks are largely self-organized: opening and healing of hydraulic fractures depends on local fluid pressure, which is, in turn, largely controlled by the fracture network. We develop a crustal-scale 2D computer model designed to simulate this process. To focus on the dynamics of the process we chose a setup as simple as possible. Control factors are constant overpressure at a basal fluid source and a constant 'viscous' parameter controlling fracture-healing. Our results indicate that at large healing rates hydraulic fractures are mobile, transporting fluid in intermittent pulses to the surface and displaying a 1/fα behavior. Low healing rates result in stable networks and constant flow. The efficiency of the fluid transport is independent from the closure dynamics of veins or fractures. More important than preexisting fracture networks is the distribution of fluid pressure. A key requirement for dynamic fracture networks is the presence of a fluid pressure gradient.

  1. Scrape-off Layer Flows With Pressure Gradient Scale Length ~ {rho}{sub p}

    Robert J. Goldston


    A heuristic model for the plasma scrape-off width balances magnetic drifts against parallel loss at c{sub s} /2, resulting in a SOL width ~ {rho}{sub p}. T{sub sep} is calculated from Spitzer–Härm parallel thermal conduction. This results in a prediction for the power scrape-off width in quantitative agreement both in magnitude and scaling with recent experimental data. To achieve the ~ c{sub s} /2 flow assumed in this model and measured experimentally sets requirements on the ratio of upstream to total SOL particle sources, relative to the square-root of the ratio of target to upstream temperature. The Pfisch-Schlüter model for equilibrium flows has been modified to allow near-sonic flows, appropriate for gradient scale lengths of order {rho}{sub p}, resulting in a new quadrupole radial flow pattern. The strong parallel flows and plasma charging implied by this model suggest a mechanism for H-mode transition, consistent with many observations

  2. Scrape-off layer flows with pressure gradient scale length ∼ρ{sub p}

    Goldston, Robert J., E-mail: [Princeton Plasma Physics Laboratory, MS-41, Princeton, NJ 08543 (United States)


    A heuristic model for the plasma scrape-off width balances magnetic drifts against parallel loss at c{sub s}/2, resulting in a SOL width ∼ρ{sub p}. T{sub sep} is calculated from Spitzer–Härm parallel thermal conduction. This results in a prediction for the power scrape-off width in quantitative agreement both in magnitude and scaling with recent experimental data. To achieve the ∼c{sub s}/2 flow assumed in this model and measured experimentally sets requirements on the ratio of upstream to total SOL particle sources, relative to the square-root of the ratio of target to upstream temperature. The Pfisch–Schlüter model for equilibrium flows has been modified to allow near-sonic flows, appropriate for gradient scale lengths of order ρ{sub p}, resulting in a new quadrupole radial flow pattern. The strong parallel flows and plasma charging implied by this model suggest a mechanism for H-mode transition, consistent with many observations.

  3. Effects of predation pressure on species packing on a resource gradient: insights from nonlinear dynamics.

    Vandermeer, John; Liere, Heidi; Lin, Brenda


    The classical case of three competitors arranged on a resource gradient such that the central competitor will be excluded due to competition from the other two is studied from the point of view of the effects of added predators. The basic formulation is motivated by a desire to understand the effects of asymmetries in multidimensional Lotka-Volterra systems. We first study the effects of perfectly specialist predators and find a rich collection of possible behaviors of the system including (1) extinction of all predators and subsequent extinction of the subordinate competitor, (2) dominant competitors and their predators coexist but the subdominant competitor goes extinct, (3) all species except the predator of the subordinate competitor coexist in coordinated phase-reversed chaos, (4) exclusion of one or more species occurs through an expanding heteroclinic cycle, and (5) all species coexist in an uncoordinated chaos. We then study the effects of five qualitatively distinct forms of polyphagy. In one case, corresponding to the well-known vulnerability to predation versus competitive ability trade-off, it is possible to have the subordinate competitor be the only survivor in the system. The other three cases of polyphagy lead to distortions in the basic pattern seen in the previously analyzed specialist case. Studying this case of ecologically motivated asymmetries in the basic Lotka-Volterra formulation is a step in the direction of fully understanding interacting populations.

  4. Remotely Adjustable Hydraulic Pump

    Kouns, H. H.; Gardner, L. D.


    Outlet pressure adjusted to match varying loads. Electrohydraulic servo has positioned sleeve in leftmost position, adjusting outlet pressure to maximum value. Sleeve in equilibrium position, with control land covering control port. For lowest pressure setting, sleeve shifted toward right by increased pressure on sleeve shoulder from servovalve. Pump used in aircraft and robots, where hydraulic actuators repeatedly turned on and off, changing pump load frequently and over wide range.

  5. Avoidance of transmission line pressure oscillations in discrete hydraulic systems – by shaping of valve opening characteristics

    Hansen, Anders Hedegaard; Pedersen, Henrik C.; Bech, Michael Møller


    The architecture of multi pressure line discrete fluid power force systems imposes rapid pressure shifts in the actuator volumes. These fast shifts between pressure levels often introduce pressure oscillations in the actuator chamber and connecting pipes. The topic of this paper is to perform...... pressure shifts by changing the connection between various fixed pressure lines without introducing significant pressure oscillation. As a case study a discrete force system is utilised is a Power Take Off(PTO) system of a wave energy converter. Four pressure shifting algorithms are proposed...

  6. Two layer dielectric-electrolyte micro-flow with pressure gradient

    Ganchenko Georgy


    Full Text Available The present work considers stability of two-phase dielectric/electrolyte system, consisting of two immiscible liquids in microchannel. The system is set in motion by the constant external electric field, which causes the electroosmotic flow in the electrolyte, and by the pressure driving force. The investigation of its linear stability has shown that there are two types of instability in the system: short-wave and long-wave instability. The short-wave instability occurs for a stronger external field than the long-wave instability but the growth rate of the short-wave instability is much higher than that of the long-wave instability.

  7. A dynamic response model for pressure sensors in continuum and high Knudsen number flows with large temperature gradients

    Whitmore, Stephen A.; Petersen, Brian J.; Scott, David D.


    This paper develops a dynamic model for pressure sensors in continuum and rarefied flows with longitudinal temperature gradients. The model was developed from the unsteady Navier-Stokes momentum, energy, and continuity equations and was linearized using small perturbations. The energy equation was decoupled from momentum and continuity assuming a polytropic flow process. Rarefied flow conditions were accounted for using a slip flow boundary condition at the tubing wall. The equations were radially averaged and solved assuming gas properties remain constant along a small tubing element. This fundamental solution was used as a building block for arbitrary geometries where fluid properties may also vary longitudinally in the tube. The problem was solved recursively starting at the transducer and working upstream in the tube. Dynamic frequency response tests were performed for continuum flow conditions in the presence of temperature gradients. These tests validated the recursive formulation of the model. Model steady-state behavior was analyzed using the final value theorem. Tests were performed for rarefied flow conditions and compared to the model steady-state response to evaluate the regime of applicability. Model comparisons were excellent for Knudsen numbers up to 0.6. Beyond this point, molecular affects caused model analyses to become inaccurate.

  8. Spatial variation patterns of subtidal seaweed assemblages along a subtropical oceanic archipelago: Thermal gradient vs herbivore pressure

    Sangil, Carlos; Sansón, Marta; Afonso-Carrillo, Julio


    The structure and composition of subtidal rocky seaweed assemblages were studied at 69 sites on the Canary Islands (northeastern Atlantic). This group of islands are situated at the southern boundary of the warm temperate region and adjacent to the cold waters from the northwest African coastal upwelling, which creates a difference of almost 2 °C in surface seawater temperature from the eastern to the western islands. This thermal variation allows an examination of the transition between the warm temperate and the tropical regions along this longitudinal gradient together with the hypothesised Fucales-dominated assemblages towards the eastern islands in contrast to the Dictyotales-dominated assemblages towards the western ones. Environmental and biological parameters were considered in order to investigate which were the main factors explaining spatial variation along the gradient in a multi-scaled approach. Although seventy-nine macroalgae were identified, 87.63% of the total mean cover was due to six taxa ( Lobophora variegata, nongeniculate corallines, Canistrocarpus cervicornis, Jania adhaerens, Cystoseira abies-marina and Pseudolithoderma adriaticum). At a large scale, sea urchin density explained the highest variation in seaweed assemblages (26.94%), and its pattern of distribution across the islands. The expected pattern of distribution according to the upwelling distance only occurred in restricted areas of the Canarian Archipelago in absence of herbivore pressure and habitat degradation. Spatial variations within islands (medium scale) were mainly related to wave exposure, while at a small scale these were mostly due to the degree of sedimentation.

  9. Two-phase boundary layer flow and heat transfer with temperature-dependent viscosity and nonzero pressure gradient

    Randelia, R.R.; Sahai, V.


    A numerical analysis of a two-phase, laminar boundary layer is carried out using the Keller Box method. The two phases are assumed to be immiscible. The problem considered involves the boundary layer flow of a compressible gas with variable properties over a flat surface in the presence of a thin liquid film with power law temperature dependent viscosity. Both zero and nonzero pressure gradients are considered. The main purpose of the study was to investigate the effect of the presence of the liquid layer on the velocity and temperature distributions. A limited set of results are presented in terms of varying liquid Prandtl numbers, film thickness, and viscosity exponents on these distributions as well as the shear stress and heat transfer parameters at the wall and at the interface between the two fluids.

  10. Final report on supplementary comparison APMP.M.P-S7.TRI in hydraulic gauge pressure from 40 MPa to 200 MPa

    Kobata, Tokihiko; Olson, Douglas A.; Eltawil, Alaaeldin A.


    This report describes the results of a supplementary comparison of hydraulic high-pressure standards at three national metrology institutes (NMIs); National Metrology Institute of Japan, AIST (NMIJ/AIST), National Institute of Standards and Technology (NIST), USA and National Institute for Standards (NIS), Egypt, which was carried out at NIST during the period May 2001 to September 2001 within the framework of the Asia-Pacific Metrology Programme (APMP) in order to evaluate their degrees of equivalence at pressures in the range 40 MPa to 200 MPa for gauge mode. The pilot institute was NMIJ/AIST. Three working pressure standards from the institutes, in the form of piston-cylinder assemblies, were used for the comparison. The comparison and calculation methods used are discussed in this report. From the cross-float measurements, the differences between the working pressure standards of each institute were examined through an evaluation of the effective area of each piston-cylinder assembly with its uncertainty. From the comparison results, it was revealed that the values claimed by the participating institutes, NMIJ, NIST, and NIS, agree within the expanded (k = 2) uncertainties. The hydraulic pressure standards in the range 40 MPa to 200 MPa for gauge mode of the three participating NMIs were found to be equivalent within their claimed uncertainties. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  11. Quantifying predation pressure along an urbanisation gradient in Denmark using artificial caterpillars

    Ferrante, Marco; Lo Cacciato, Alessandro; Lövei, Gabor L


    Urbanisation results in a marked modification of habitats and influences several ecological processes, some of which give rise to beneficial ecological services. Natural pest control, the effect of predators on prey is one of such services. We quantified changes in the incidence of predation with.......3% in suburban and 16.4% in urban forest fragments. Mammals exerted the highest predation pressure in suburban habitats (22.2% vs. 4.9% in forest, and 8.1% in urban forest fragments).......Urbanisation results in a marked modification of habitats and influences several ecological processes, some of which give rise to beneficial ecological services. Natural pest control, the effect of predators on prey is one of such services. We quantified changes in the incidence of predation...... of these to carabids, the most common group of ground-active arthropods. Chewing insects exerted the greatest predation pressure in the original forest (52.1%), with lower values recorded in the suburban (10.1%) and urban (16.4%) forest fragments. Ants were responsible for only 4.7% of the attacks in forest, 11...

  12. Trace element concentrations along a gradient of urban pressure in forest and lawn soils of the Paris region (France).

    Foti, Ludovic; Dubs, Florence; Gignoux, Jacques; Lata, Jean-Christophe; Lerch, Thomas Z; Mathieu, Jérôme; Nold, François; Nunan, Naoise; Raynaud, Xavier; Abbadie, Luc; Barot, Sébastien


    The concentration, degree of contamination and pollution of 7 trace elements (TEs) along an urban pressure gradient were measured in 180 lawn and wood soils of the Paris region (France). Iron (Fe), a major element, was used as reference element. Copper (Cu), cadmium (Cd), lead (Pb) and zinc (Zn) were of anthropogenic origin, while arsenic (As), chromium (Cr) and nickel (Ni) were of natural origin. Road traffic was identified as the main source of anthropogenic TEs. In addition, the industrial activity of the Paris region, especially cement plants, was identified as secondary source of Cd. Soil characteristics (such as texture, organic carbon (OC) and total nitrogen (tot N) contents) tell the story of the soil origins and legacies along the urban pressure gradient and often can explain TE concentrations. The history of the land-use types was identified as a factor that allowed understanding the contamination and pollution by TEs. Urban wood soils were found to be more contaminated and polluted than urban lawns, probably because woods are much older than lawns and because of the legacy of the historical management of soils in the Paris region (Haussmann period). Lawn soils are similar to the fertile agricultural soils and relatively recently (mostly from the 1950s onwards) imported from the surrounding of Paris, so that they may be less influenced by urban conditions in terms of TE concentrations. Urban wood soils are heavily polluted by Cd, posing a high risk to the biological communities. The concentration of anthropogenic TEs increased from the rural to the urban areas, and the concentrations of most anthropogenic TEs in urban areas were equivalent to or above the regulatory reference values, raising the question of longer-term monitoring. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Stem Hydraulic Conductivity depends on the Pressure at Which It Is Measured and How This Dependence Can Be Used to Assess the Tempo of Bubble Pressurization in Recently Cavitated Vessels1[OPEN

    Liu, Jinyu; Tyree, Melvin T.


    Cavitation of water in xylem vessels followed by embolism formation has been authenticated for more than 40 years. Embolism formation involves the gradual buildup of bubble pressure (air) to atmospheric pressure as demanded by Henry’s law of equilibrium between gaseous and liquid phases. However, the tempo of pressure increase has not been quantified. In this report, we show that the rate of pressurization of embolized vessels is controlled by both fast and slow kinetics, where both tempos are controlled by diffusion but over different spatial scales. The fast tempo involves a localized diffusion from endogenous sources: over a distance of about 0.05 mm from water-filled wood to the nearest embolized vessels; this process, in theory, should take 17 h, with complete equilibrium requiring 1 to 2 d. The implications of these timescales for the standard methods of measuring percentage loss of hydraulic conductivity are discussed in theory and deserve more research in future. PMID:26468516

  14. Evaluation of the effects of pressure gradients on four Brazilian freshwater fish species

    Paulo dos Santos Pompeu


    Full Text Available This work aimed to experimentally evaluate the behavior of Brazilian freshwater fish species when submitted to a gradual increase in pressure, as well as sudden decompression's effects simulating the passage through a hydroelectric turbine. Four species from the São Francisco river basin were tested: Astyanax bimaculatus, Hypostomus sp., Leporinus reinhardti and Prochilodus costatus. For all of them mortality rates due to decompression were extremely low. However, the symptoms related to decompression, such as bulged eyes and hemorrhage, were not observed only in Hypostomus sp., and were more frequent the larger the pressure values were, considering the values from which decompression was performed. All these symptoms decreased significantly after 24 h of observation. With the increase in pressure inside the apparatus, the four tested species moved towards the upper levels. This behavior could make possoble the implementation of bypass downstream fish passages in dams constructed in Brazil.Este trabalho teve como objetivo avaliar experimentalmente o comportamento de espécies brasileiras quando submetidas a um aumento gradual na pressão, bem como os efeitos de uma descompressão rápida simulando a passagem por uma turbina hidrelétrica. Quatro espécies da bacia do rio São Francisco foram testadas: Astyanax bimaculatus, Hypostomus sp., Leporinus reinhardti e Prochilodus costatus. Para todas elas as taxas de mortalidade devido à descompressão foram extremamente baixas. No entanto, sintomas relacionados à descompressão, como exoftalmia e hemorragia só não foram observados em Hypostomus sp., sendo mais freqüentes quanto maior o valor de pressão a partir do qual realizou-se a descompressão. Todos estes sintomas diminuíram significativamente após 24 horas de observação. Com o aumento da pressão no aparato, as espécies testadas se movimentaram em direção aos níveis superiores. Este comportamento sugere a possibilidade de se


    UTILI Stefano; 尹振宇; 蒋明镜


    着重研究一个典型的混凝土重力坝的坝底水浮力对大坝稳定性的影响,此大坝位于意大利的Cumbidanovu岛.大坝的基础由含有高度开裂的岩石所构成.首先,通过把大坝视为自由体的平衡分析法来评价大坝破坏前的最大水压力和有效排水系统对大坝稳定性的影响.然后,使用离散元方法来进一步评价开裂基岩中的水流状态,得到该水流产生的浮托力的分布,最终得到此水浮力对大坝稳定性的影响.对设计而言,上述分析考虑了岩基渗透,运用离散元方法进行模拟.研究结果表面,相比保守的平衡分析法,此模型可以得到更大的水浮力荷载.%A study of the influences of the hydraulic uplift pressures underneath the base of a typical concrete gravity dam on its stability is presented. The dam is located at Cumbidanovu(Sardegna,Italy). The foundation of the dam is made of heavily fractured rock. Firstly,analytical calculations about the equilibrium of the dam as a free body have been employed to evaluate the maximum hydraulic pressure before collapsing and to assess the impact of an effective drainage system on the stability of the dam in a simple way. Secondly,numerical analyses by the distinct element method(DEM) using the code UDEC have been carried out to evaluate the hydraulic flow taking place within the fractured rock foundation,the uplift pressure distribution generated by the calculated flow,and its influence on the stability of the dam. For design purposes,it emerges that availability of reliable data on the hydraulic permeability of rock foundations and a computationally advanced distinct element modeling might lead to the acceptance of loads significantly higher than the more conservative estimations obtained from equilibrium analyses.

  16. Sildenafil does not influence hepatic venous pressure gradient in patients with cirrhosis

    Clemmesen, Jens-Otto; Giraldi, Annamaria; Ott, Peter


    disease. However, the effect of phosphodiesterase type-5 inhibitors on splanchnic blood flow and portal hypertension remains essentially unknown. METHODS: Ten patients with biopsy proven cirrhosis (five females/five males, mean age 54 +/- 8 years) and an HVPG above 12 mmHg were studied after informed...... consent. Measurement of splanchnic blood flow and the HVPG during liver vein catheterization were done before and 80 min after oral administration of 50 mg sildenafil. Blood flow was estimated by use of indocyanine green clearance technique and Fick's principle, with correction for non-steady state....... RESULTS: The plasma concentration of sildenafil was 222 +/- 136 ng/mL 80 min after administration. Mean arterial blood pressure decreased from 77 +/- 7 mmHg to 66 +/- 12 mmHg, P = 0.003, while the splanchnic blood flow and oxygen consumption remained unchanged at 1.14 +/- 0.71 L/min and 2.3 +/- 0.6 mmol...

  17. Gender difference and economic gradients in the secular trend of population systolic blood pressure

    Andersen, Ulla; Jensen, Gorm B


    To a large extent population blood pressure (PBP) affects morbidity and mortality in the society. Reports indicated that PBP decreased in many western countries. The associations between the main cardiovascular risk factors and the changing PBP have been described. The aim of this study....... In addition, there was a trend towards a lowering of risk-factor adjusted SBP in the high income women with time. The mechanism that lies behind the associations between trend in SBP and income is not known but data suggest that poor lifestyle may explain some of the differences. The treated hypertensives...... was to investigate association between income factors and trends in population BP and hypertension. Copenhagen City Heart Study is a prospective longitudinal epidemiological study on almost 20000 individuals through four surveys from 1976 to 2003. The BP measurement was fully standardised. Questionnaires...

  18. Viscosity bio reducer Influence in a non-Newtonian fluid horizontal pipeline pressure gradient

    Edgardo Jonathan Suarez-Dominguez


    Full Text Available Due to increased production of heavy and extra heavy crude in Mexico, it has led to the necessity touse chemicals to facilitate the transport in the pipe of our country. Experimental study was conductedto analyze the influence of a viscosity reducer of biological origin (BRV, on the rheological behaviorof heavy oil in the northern region of Mexico, finding that it exhibits a non-Newtonian viscoelasticbehavior, where a concentration increase of BRV leads to a consistency decrease and an increasedflow order, where dilatant behavior was observed in high temperatures. From these results it wasestimated the pressure losses by friction in a horizontal pipe for single phase and two phase flow. Wefound that in all cases the increase in the concentration of BRV reduces these losses.

  19. Convective heat transfer studies at high temperatures with pressure gradient for inlet flow Mach number of 0.45

    Pedrosa, A. C. F.; Nagamatsu, H. T.; Hinckel, J. A.


    Heat transfer measurements were determined for a flat plate with and without pressure gradient for various free stream temperatures, wall temperature ratios, and Reynolds numbers for an inlet flow Mach number of 0.45, which is a representative inlet Mach number for gas turbine rotor blades. A shock tube generated the high temperature and pressure air flow, and a variable geometry test section was used to produce inlet flow Mach number of 0.45 and accelerate the flow over the plate to sonic velocity. Thin-film platinum heat gages recorded the local heat flux for laminar, transition, and turbulent boundary layers. The free stream temperatures varied from 611 R (339 K) to 3840 R (2133 K) for a T(w)/T(r,g) temperature ratio of 0.87 to 0.14. The Reynolds number over the heat gages varied from 3000 to 690,000. The experimental heat transfer data were correlated with laminar and turbulent boundary layer theories for the range of temperatures and Reynolds numbers and the transition phenomenon was examined.

  20. Simplified modeling of liquid sodium medium with temperature and velocity gradient using real thermal-hydraulic data. Application to ultrasonic thermometry in sodium fast reactor

    Massacret, N.; Moysan, J.; Ploix, M. A.; Jeannot, J. P.; Corneloup, G.


    In the framework of the French R&D program for the Generation IV reactors and specifically for the sodium cooled fast reactors (SFR), studies are carried out on innovative instrumentation methods in order to improve safety and to simplify the monitoring of fundamental physical parameters during reactor operation. The aim of the present work is to develop an acoustic thermometry method to follow up the sodium temperature at the outlet of subassemblies. The medium is a turbulent flow of liquid sodium at 550 °C with temperature inhomogeneities. To understand the effect of disturbance created by this medium, numerical simulations are proposed. A ray tracing code has been developed with Matlabin order to predict acoustic paths in this medium. This complex medium is accurately described by thermal-hydraulic data which are issued from a simulation of a real experiment in Japan. The analysis of these results allows understanding the effects of medium inhomogeneities on the further thermometric acoustic measurement.

  1. Final report on key comparison APMP.M.P-K13 in hydraulic gauge pressure from 50 MPa to 500 MPa

    Kajikawa, Hiroaki; Kobata, Tokihiko; Yadav, Sanjay; Jian, Wu; Changpan, Tawat; Owen, Neville; Yanhua, Li; Hung, Chen-Chuan; Ginanjar, Gigin; Choi, In-Mook


    This report describes the results of a key comparison of hydraulic high-pressure standards at nine National Metrology Institutes (NMIs: NMIJ/AIST, NPLI, NMC/A*STAR, NIMT, NMIA, NIM, CMS/ITRI, KIM-LIPI, and KRISS) within the framework of the Asia-Pacific Metrology Programme (APMP) in order to determine their degrees of equivalence in the pressure range from 50 MPa to 500 MPa in gauge mode. The pilot institute was the National Metrology Institute of Japan (NMIJ/AIST). All participating institutes used hydraulic pressure balances as their pressure standards. A set of pressure balance with a free-deformational piston-cylinder assembly was used as the transfer standard. Three piston-cylinder assemblies, only one at a time, were used to complete the measurements in the period from November 2010 to January 2013. Ten participants completed their measurements and reported the pressure-dependent effective areas of the transfer standard at specified pressures with the associated uncertainties. Since one of the participants withdrew its results, the measurement results of the nine participants were finally compared. The results were linked to the CCM.P-K13 reference values through the results of two linking laboratories, NMIJ/AIST and NPLI. The degrees of equivalence were evaluated by the relative deviations of the participants' results from the CCM.P-K13 key comparison reference values, and their associated combined expanded (k=2) uncertainties. The results of all the nine participating NMIs agree with the CCM.P-K13 reference values within their expanded (k=2) uncertainties in the entire pressure range from 50 MPa to 500 MPa. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database The final report has been peer-reviewed and approved for publication by CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  2. Experimental study on the flow regimes and pressure gradients of air-oil-water three-phase flow in horizontal pipes.

    Al-Hadhrami, Luai M; Shaahid, S M; Tunde, Lukman O; Al-Sarkhi, A


    An experimental investigation has been carried out to study the flow regimes and pressure gradients of air-oil-water three-phase flows in 2.25 ID horizontal pipe at different flow conditions. The effects of water cuts, liquid and gas velocities on flow patterns and pressure gradients have been studied. The experiments have been conducted at 20 °C using low viscosity Safrasol D80 oil, tap water and air. Superficial water and oil velocities were varied from 0.3 m/s to 3 m/s and air velocity varied from 0.29 m/s to 52.5 m/s to cover wide range of flow patterns. The experiments were performed for 10% to 90% water cuts. The flow patterns were observed and recorded using high speed video camera while the pressure drops were measured using pressure transducers and U-tube manometers. The flow patterns show strong dependence on water fraction, gas velocities, and liquid velocities. The observed flow patterns are stratified (smooth and wavy), elongated bubble, slug, dispersed bubble, and annular flow patterns. The pressure gradients have been found to increase with the increase in gas flow rates. Also, for a given superficial gas velocity, the pressure gradients increased with the increase in the superficial liquid velocity. The pressure gradient first increases and then decreases with increasing water cut. In general, phase inversion was observed with increase in the water cut. The experimental results have been compared with the existing unified Model and a good agreement has been noticed.

  3. Investigation of the effects of pressure gradient, temperature and wall temperature ratio on the stagnation point heat transfer for circular cylinders and gas turbine vanes

    Nagamatsu, H. T.; Duffy, R. E.


    Low and high pressure shock tubes were designed and constructed for the purpose of obtaining heat transfer data over a temperature range of 390 to 2500 K, pressures of 0.3 to 42 atm, and Mach numbers of 0.15 to 1.5 with and without pressure gradient. A square test section with adjustable top and bottom walls was constructed to produce the favorable and adverse pressure gradient over the flat plate with heat gages. A water cooled gas turbine nozzle cascade which is attached to the high pressure shock tube was obtained to measuse the heat flux over pressure and suction surfaces. Thin-film platinum heat gages with a response time of a few microseconds were developed and used to measure the heat flux for laminar, transition, and turbulent boundary layers. The laminar boundary heat flux on the shock tube wall agreed with Mirel's flat plate theory. Stagnation point heat transfer for circular cylinders at low temperature compared with the theoretical prediction, but for a gas temperature of 922 K the heat fluxes were higher than the predicted values. Preliminary flat plate heat transfer data were measured for laminar, transition, and turbulent boundary layers with and without pressure gradients for free-stream temperatures of 350 to 2575 K and flow Mach numbers of 0.11 to 1.9. The experimental heat flux data were correlated with the laminar and turbulent theories and the agreement was good at low temperatures which was not the case for higher temperatures.

  4. Urban tree species show the same hydraulic response to vapor pressure deficit across varying tree size and environmental conditions.

    Chen, Lixin; Zhang, Zhiqiang; Ewers, Brent E


    The functional convergence of tree transpiration has rarely been tested for tree species growing under urban conditions even though it is of significance to elucidate the relationship between functional convergence and species differences of urban trees for establishing sustainable urban forests in the context of forest water relations. We measured sap flux of four urban tree species including Cedrus deodara, Zelkova schneideriana, Euonymus bungeanus and Metasequoia glyptostroboides in an urban park by using thermal dissipation probes (TDP). The concurrent microclimate conditions and soil moisture content were also measured. Our objectives were to examine 1) the influence of tree species and size on transpiration, and 2) the hydraulic control of urban trees under different environmental conditions over the transpiration in response to VPD as represented by canopy conductance. The results showed that the functional convergence between tree diameter at breast height (DBH) and tree canopy transpiration amount (E(c)) was not reliable to predict stand transpiration and there were species differences within same DBH class. Species differed in transpiration patterns to seasonal weather progression and soil water stress as a result of varied sensitivity to water availability. Species differences were also found in their potential maximum transpiration rate and reaction to light. However, a same theoretical hydraulic relationship between G(c) at VPD = 1 kPa (G(cref)) and the G(c) sensitivity to VPD (-dG(c)/dlnVPD) across studied species as well as under contrasting soil water and R(s) conditions in the urban area. We concluded that urban trees show the same hydraulic regulation over response to VPD across varying tree size and environmental conditions and thus tree transpiration could be predicted with appropriate assessment of G(cref).

  5. 10 MW高温气冷堆反应堆压力容器的出厂水压试验%Hydraulic Pressure Test of Pressure Vessel of 10 MW High Temperature Gas-cooled Reactor

    刘俊杰; 张征明; 何树延; 王金海


    The hydraulic pressure test of 10MW Hight Temperature Gas-cooled Reactorc(HTR-10) pressure vessel was successfully performed according to the requirement of the section NB-6200, ASME Ⅲ code. The test requirement, the test results and the test evaluations are described in detail. The test tension was effectively and rationally done through an hydraulic tensionor, which was developed at institue of nuclear energy technology of Tsinghua University. The strain and deformation of the HTR-10 pressure vessel were also measured.%根据ASME规范第Ⅲ卷NB-6200节的规定,对10MW高温气冷堆压力容器的水压试验要求、试验过程,试验结果及评价进行了叙述。用清华大学核能技术设计研究院研制的液压张拉机对主螺栓实施了合理及有效的张拉,对压力容器进行了应变和变形测量,取得了反应堆压力容器水压试验的圆满成功。

  6. Multiphase Transport in Porous Media: Gas-Liquid Separation Using Capillary Pressure Gradients International Space Station (ISS) Flight Experiment Development

    Wheeler, Richard R., Jr.; Holtsnider, John T.; Dahl, Roger W.; Deeks, Dalton; Javanovic, Goran N.; Parker, James M.; Ehlert, Jim


    Advances in the understanding of multiphase flow characteristics under variable gravity conditions will ultimately lead to improved and as of yet unknown process designs for advanced space missions. Such novel processes will be of paramount importance to the success of future manned space exploration as we venture into our solar system and beyond. In addition, because of the ubiquitous nature and vital importance of biological and environmental processes involving airwater mixtures, knowledge gained about fundamental interactions and the governing properties of these mixtures will clearly benefit the quality of life here on our home planet. The techniques addressed in the current research involving multiphase transport in porous media and gas-liquid phase separation using capillary pressure gradients are also a logical candidate for a future International Space Station (ISS) flight experiment. Importantly, the novel and potentially very accurate Lattice-Boltzmann (LB) modeling of multiphase transport in porous media developed in this work offers significantly improved predictions of real world fluid physics phenomena, thereby promoting advanced process designs for both space and terrestrial applications.This 3-year research effort has culminated in the design and testing of a zero-g demonstration prototype. Both the hydrophilic (glass) and hydrophobic (Teflon) media Capillary Pressure Gradient (CPG) cartridges prepared during the second years work were evaluated. Results obtained from ground testing at 1-g were compared to those obtained at reduced gravities spanning Martian (13-g), Lunar (16-g) and zero-g. These comparisons clearly demonstrate the relative strength of the CPG phenomena and the efficacy of its application to meet NASAs unique gas-liquid separation (GLS) requirements in non-terrestrial environments.LB modeling software, developed concurrently with the zero-g test effort, was shown to accurately reproduce observed CPG driven gas-liquid separation

  7. Climatic gradients and human development pressure determine spatial patterns of forest fragmentation in the Great Lakes basin, USA

    Currie, W. S.; Hart, S.


    Over half of temperate forest area globally has been fragmented or deforested by human activities. Our objective was to gain insight into the combination of climatic, ecological, and social factors that control complex spatial patterns of forest cover and fragmentation at the regional scale. Our study area was the US portion of the land area of the Laurentian Great Lakes basin (USGL basin) of the Upper Midwest, USA, covering ca. 300,000 km2 and home to 25 million people. While this region was historically forested, today there are regional gradients in forest cover as well as complex spatial patterns of agriculture, human settlements, and tree cover. This includes large expanses of fragmented forests in the wildland-urban interface or the forest transition zone. We used structural equation modeling to test models of social and climatic-ecological factors to explain spatial patterns of forest cover and fragmentation. This is a model-driven approach to statistical analysis that is used to test proposed causal "structures" of direct and indirect relationships among variables. It is an innovative approach that makes use of large spatial datasets to test understanding. We assembled numerous spatial data layers at 1 km2 resolution across the USGL basin. We found that 64% to 75% of variance in tree cover and forest connectivity was explained through a relatively simple model combining climatic gradients and human development pressure. Human development pressure was best represented as a measurement model that explained 45% of variance in road density and 87% of housing unit density, while significantly explaining patterns of forest fragmentation. Climate could be represented by a single variable, temperature: where temperature was higher, tree cover and forest connectivity was lower due to human land use. Temperatures did not help to explain patterns of human development as roads and housing, but did affect forest fragmentation through land use as cropland. This suggests

  8. Intraperitoneal and retroperitoneal carbon dioxide insufflation evoke different effects on caval vein pressure gradients in humans: evidence for the starling resistor concept of abdominal venous return.

    Giebler, R M; Behrends, M; Steffens, T; Walz, M K; Peitgen, K; Peters, J


    The authors hypothesized that intraperitoneal and retroperitoneal carbon dioxide insufflation during surgical procedures evoke markedly different effects on the venous low-pressure system, induce different inferior caval vein pressure gradients at similar insufflation pressures, and may provide evidence for the Starling resistor concept of abdominal venous return. Intra- and extrathoracic caval vein pressures were measured using micromanometers during carbon dioxide insufflation at six cavity pressures (baseline and 10, 15, 20, and 24 mmHg and desufflation) in 20 anesthetized patients undergoing laparoscopic (supine, n = 8) or left (n = 6) or right (n = 6) retroperitoneoscopic (prone position) surgery. Intracavital, esophageal, and gastric pressures also were assessed. Data were analyzed for insufflation pressure-dependent and group effects by one-way and two-way analysis of variance for repeated measurements, respectively, followed by the Newman-Keuls post hoc test (P < 0.05). Intraperitoneal, unlike retroperitoneal, insufflation markedly increased, in an insufflation pressure-dependent fashion, the inferior-to-superior caval vein pressure gradient (P < 0.00001) at the level of the diaphragm. In contrast to what was observed with retroperitoneal insufflation, transmural intrathoracic caval vein pressure increased at 10 mmHg insufflation pressure, but the increase flattened with an insufflation pressure of more than 10 mmHg, and pressure decreased with an inflation pressure of 20 mmHg (P = 0.0397). These data are consistent with a zone 2 or 3 abdominal vascular condition during intraperitoneal and a zone 3 abdominal vascular condition during retroperitoneal insufflation. Intraperitoneal but not retroperitoneal carbon dioxide insufflation evokes a transition of the abdominal venous compartment from a zone 3 to a zone 2 condition, presumably impairing venous return, supporting the Starling resistor concept of abdominal venous return in humans.

  9. Simplified modeling of liquid sodium medium with temperature and velocity gradient using real thermal-hydraulic data. Application to ultrasonic thermometry in sodium fast reactor

    Massacret, N.; Jeannot, J. P. [DEN/DTN/STPA/LIET, CEA Cadarache, Saint Paul Lez Durance (France); Moysan, J.; Ploix, M. A.; Corneloup, G. [Aix-Marseille Univ, LMA UPR 7051 CNRS, site LCND, 13625 Aix-en-Provence (France)


    In the framework of the French R and D program for the Generation IV reactors and specifically for the sodium cooled fast reactors (SFR), studies are carried out on innovative instrumentation methods in order to improve safety and to simplify the monitoring of fundamental physical parameters during reactor operation. The aim of the present work is to develop an acoustic thermometry method to follow up the sodium temperature at the outlet of subassemblies. The medium is a turbulent flow of liquid sodium at 550 Degree-Sign C with temperature inhomogeneities. To understand the effect of disturbance created by this medium, numerical simulations are proposed. A ray tracing code has been developed with Matlab Copyright-Sign in order to predict acoustic paths in this medium. This complex medium is accurately described by thermal-hydraulic data which are issued from a simulation of a real experiment in Japan. The analysis of these results allows understanding the effects of medium inhomogeneities on the further thermometric acoustic measurement.

  10. An experimental investigation of heat transfer to reusable surface insulation tile array gaps in a turbulent boundary layer with pressure gradient. M.S. Thesis

    Throckmorton, D. A.


    An experimental investigation was performed to determine the effect of pressure gradient on the heat transfer to space shuttle reusable surface insulation (RSI) tile array gaps under thick, turbulent boundary layer conditions. Heat transfer and pressure measurements were obtained on a curved array of full-scale simulated RSI tiles in a tunnel wall boundary layer at a nominal freestream Mach number of 10.3 and freestream unit Reynolds numbers of 1.6, 3.3, and and 6.1 million per meter. Transverse pressure gradients were induced over the model surface by rotating the curved array with respect to the flow. Definition of the tunnel wall boundary layer flow was obtained by measurement of boundary layer pitot pressure profiles, and flat plate wall pressure and heat transfer. Flat plate wall heat transfer data were correlated and a method was derived for prediction of smooth, curved array heat transfer in the highly three-dimensional tunnel wall boundary layer flow and simulation of full-scale space shuttle vehicle pressure gradient levels was assessed.



    This is the second communication of a series dealing with an experimental and modelling study on propane catalytic combustion in a membrane reactor with separate feed of reactants. In paper I the behaviour of the reactor in the absence of trans-membrane pressure gradients was presented and

  12. Catalytic combustion of propane in a membrane reactor with separate feed of reactants—II. Operation in presence of trans-membrane pressure gradients

    Saracco, Guido; Veldsink, Jan Willem; Versteeg, Geert F.; Swaaij, Wim P.M. van


    This is the second communication of a series dealing with an experimental and modelling study on propane catalytic combustion in a membrane reactor with separate feed of reactants. In paper I the behaviour of the reactor in the absence of trans-membrane pressure gradients was presented and

  13. Catalytic combustion of propane in a membrane reactor with separate feed of reactants II. Operation in presence of transmembrane pressure gradients

    Saracco, Guido; Veldsink, J.W.; Veldsink, Jan Willem; Versteeg, Geert; van Swaaij, Willibrordus Petrus Maria


    This is the second communication of a series dealing with an experimental and modelling study on propane catalytic combustion in a membrane reactor with separate feed of reactants. In paper I the behaviour of the reactor in the absence of trans-membrane pressure gradients was presented and

  14. Control arrangement for the actuation of hydraulic consumers

    Kussel, W.; Dettmers, M.; Weirich, W.


    An arrangement for controlling the actuation of hydraulic consumers, by selectively connecting the consumers to hydraulic pressure and return lines; the control arrangement comprising a respective hydraulically operated directional control valve associated with each of the hydraulic consumers, a respective electro-magnetically operated pre-control valve associated with each of the hydraulic directional control valves, and further electro-magnetically operated directional control valve means associated with the pre-control valves, each of the hydraulic consumers being connectible to the hydraulic pressure or return lines via the associated hydraulically operated directional control valve which is actuatable by a hydraulic control line leading from the output of the associated pre-control valve, wherein the inputs of the pre-control valves are connected directly to the hydraulic return line and indirectly, via the further control valve means, to the hydraulic return line or to a hydraulic control pressure line.

  15. Hydraulic structures

    Chen, Sheng-Hong


    This book discusses in detail the planning, design, construction and management of hydraulic structures, covering dams, spillways, tunnels, cut slopes, sluices, water intake and measuring works, ship locks and lifts, as well as fish ways. Particular attention is paid to considerations concerning the environment, hydrology, geology and materials etc. in the planning and design of hydraulic projects. It also considers the type selection, profile configuration, stress/stability calibration and engineering countermeasures, flood releasing arrangements and scouring protection, operation and maintenance etc. for a variety of specific hydraulic structures. The book is primarily intended for engineers, undergraduate and graduate students in the field of civil and hydraulic engineering who are faced with the challenges of extending our understanding of hydraulic structures ranging from traditional to groundbreaking, as well as designing, constructing and managing safe, durable hydraulic structures that are economical ...

  16. An experimental investigation of a low Reynolds number turbulent boundary layer subject to an adverse pressure gradient

    Watmuff, Jonathan H.


    A very low Reynolds number turbulent boundary layer subject to an adverse pressure gradient is studied. The aim is to obtain highly accurate mean-flow and turbulence measurements under conditions that can be closely related to the numerical simulations of Philippe Spalart for the purposes of CFD validation. Much of the Boundary Layer Wind Tunnel was completely rebuilt with a new wider contraction and working section which will improve compatibility with the simulations. A unique sophisticated high-speed computer controlled 3-D probe traversing mechanism was integrated into the test section. Construction of the tunnel and traverse is discussed in some detail. The hardware is now complete, and measurements are in progress. The mean-flow data indicate that a suitably two-dimensional base flow was established. Automation of the probe positioning and data acquistion have led to a decreased running time for total pressure measurements. However, the most significant benefits are expected to occur when using hot-wire probes. Calibrations can be performed automatically and there is no need to handle fragile probes when moving between measuring stations. Techniques are being developed which require sampling of the signals from moving hot-wire probes on the basis of their position in the flow. Measurements can be made in high intensity turbulence by flying probes upstream at high speed so that the relative magnitude of the turbulent velocity fluctuations are reduced. In regions, where the turbulence intensity is not too large, the probe can also be repetitively scanned across very dense spatial grids in other directions. With this technique, a complete profile can be measured in about 1/3 the time and with a spatial density about 50 times that obtainable using a stationary probe.

  17. The Role of Postintervention Pullback Pressure Gradient in Percutaneous Transluminal Angioplasty for Central Vein Stenosis in Dialysis Patients

    Lin, Yu-Sheng, E-mail: [Chang Gung Memorial Hospital, Chiayi, Chang Gung Institute of Technology, Division of Cardiology (China); Yang, Cheng-Hsu, E-mail: [Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Division of Cardiology and Department of Internal Medicine (China); Chu, Chi-Ming, E-mail: [National Defense Medical Center and University, Section of Health Informatics, Institute of Public Health (China); Fang, Chi-Yung, E-mail:; Chen, Chien-Jen, E-mail: [Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Division of Cardiology and Department of Internal Medicine (China); Hsu, Jen-Te, E-mail:; Yang, Teng-Yao, E-mail: [Chang Gung Memorial Hospital, Chiayi, Chang Gung Institute of Technology, Division of Cardiology (China); Hang, Chi-Ling, E-mail:; Wu, Chiung-Jen, E-mail: [Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Division of Cardiology and Department of Internal Medicine (China)


    Purpose: The severity of residual stenosis (RS) sometimes cannot be accurately measured by angiography during central vein intervention. This study evaluated the role of pullback pressure measurement during central vein stenosis (CVS) intervention. Methods: A retrospective review enrolled 94 consecutive dialysis patients who underwent CVS interventions but not stenting procedures. Patients were classified into 2 groups by either angiography or pressure gradient (PG) criteria, respectively. Groups divided by angiographic result were successful group (RS {<=}30 %) and acceptable group (50 % {>=} RS > 30 %), while groups divided by PG were low PG group (PG {<=}5 mmHg) and high PG group (PG >5 mmHg). Baseline characteristics and 12-month patency rates between the groups were analyzed. Results: The angiography results placed 63 patients in the successful group and 31 patients in the acceptable group. The patency rate at 12 month was not statistically different (P = 0.167). When the patients were reclassified by the postintervention pullback PG, the patency rate at 12 months was significant (P = 0.048). Further analysis in groups redivided by different combinations of RS and PG criteria identified significant differences in the group with both RS {<=}30 % and PG {<=}5 mmHg compared with those with either RS >30 % (P = 0.047) or PG >5 mmHg (P = 0.027). In addition, there was a significant difference between those with both RS {<=}30 % and PG {<=}5 mmHg compared with those with both RS >30 % and PG >5 mmHg (P = 0.027). Conclusion: Postintervention PG can better predict long-term outcomes after angioplasty for CVS in nonstented dialysis patients than angiography.

  18. The fluid mechanics of a high aspect ratio slot with an impressed pressure gradient and secondary injection

    Sobanik, John Bertram


    A high aspect ratio slot flow (which emulates the gas leakage path in a gas turbine engine outer turbine air seal) is studied by use of a high aspect ratio slot using water as the working fluid. The cross section of the geometry is similar to a 'T', the slot being the vertical stroke and the main flow being the cross bar. A pressure gradient in the axial direction is created by blocking the main flow at a discreet location with an orifice plate (or blade tip simulator), located above the slot. Seven individually metered secondary flow injectors are located periodically along the bottom of the wall of the slot. Two slot widths, 1/8 and 1/4 inch, were investigated for length to width aspect ratios of 384 and 192 and height to width aspect ratios 33.2 and 16.6 respectively. Orifice plate pressure drops sufficient to give Reynolds numbers based upon half width of the slot, without secondary injection turned on, of 2350 and 4700 in the 1/8 inch slot and 4700 and 9400 in the 1/4 inch slot were run. Various secondary injection scenarios were added to the flow, the cases most studied being the no-injection and the all injectors flowing equal mass rates. Total injection rates for all seven injectors of 3.78 and 7.56 slot volumes per second were run. Laser velocimetry data and flow visualization pictures using fluorescein dye in the secondary flow are compared with computational results form the TEACH 3-D computer code. Major features and trends of the flow are captured by the computational model. Recommendations for further improvement of the numerical accuracy involves modification of the TEACH 3-D code to allow the 'slip condition' on all confining boundaries of the flow, or using a code which permits the 'slip condition' on all boundaries as a built-in option.

  19. A study of the three-dimensional spectral energy distribution in a zero pressure gradient turbulent boundary layer

    LeHew, J.; McKeon, B.J. [California Institute of Technology, Graduate Aerospace Laboratories, Pasadena, CA (United States); Guala, M. [California Institute of Technology, Graduate Aerospace Laboratories, Pasadena, CA (United States); University of Minnesota, Department of Civil Engineering, Minneapolis, MN (United States)


    Time-resolved particle image velocimetry (PIV) measurements performed in wall parallel planes at three wall normal locations, y{sup +} = 34, 108, and 278, in a zero pressure gradient turbulent boundary layer at Re{sub {tau}}=470 are used to illuminate the distribution of streamwise velocity fluctuations in a three-dimensional energy spectrum (2D in space and 1D in time) over streamwise, spanwise, and temporal wavelengths. Two high-speed cameras placed side by side in the streamwise direction give a 10{delta}x 5{delta} streamwise by spanwise field of view with a vector spacing of {delta}x{sup +}={delta}z{sup +}{approx} 37 and a time step of {delta}t{sup +}=0.5. Although 3D wavenumber-frequency spectra have been calculated in acoustics studies, to the authors' knowledge this is the first time they has been calculated and presented for a turbulent boundary layer. The calculation and normalization of this spectrum, its relation to 2D and 1D spectra, and the effects of the PIV algorithm on its shape are carefully analyzed and outlined. (orig.)

  20. Experimental Evidence of Near-Wall Reverse Flow Events in a Zero Pressure Gradient Turbulent Boundary Layer

    Willert, Christian E


    This study reports on experimentally observed near-wall reverse flow events in a fully developed flat plate boundary layer at zero pressure gradient with Reynolds numbers between $Re_\\tau = 1000$ and $Re_\\tau = 2700$. The reverse flow events are captured using high magnification particle image velocimetry sequences with record lengths varying from 50,000 to 126,000 samples. Time resolved particle image sequences allow singular reverse flow events to be followed over several time steps whereas long records of nearly statistically independent samples provide a variety of single snapshots at a higher spatial resolution. The probability of occurrence lies in the range of 0.01% to 0.1% which matches predictions made with direct numerical simulations (DNS). The self-similar size of the reverse flow bubble is about 30-50 wall units in length and 5 wall units in height which also agrees well to DNS data provided by Lenaers et al. (ETC13, Journal of Physics: Conference Series 318 (2011) 022013).

  1. Gastroesophageal pressure gradients in gastroesophageal reflux disease: relations with hiatal hernia, body mass index, and esophageal acid exposure.

    de Vries, Durk R; van Herwaarden, Margot A; Smout, André J P M; Samsom, Melvin


    The roles of intragastric pressure (IGP), intraesophageal pressure (IEP), gastroesophageal pressure gradient (GEPG), and body mass index (BMI) in the pathophysiology of gastroesophageal reflux disease (GERD) and hiatal hernia (HH) are only partly understood. In total, 149 GERD patients underwent stationary esophageal manometry, 24-h pH-metry, and endoscopy. One hundred three patients had HH. Linear regression analysis showed that each kilogram per square meter of BMI caused a 0.047-kPa increase in inspiratory IGP (95% confidence interval [CI] 0.026-0.067) and a 0.031-kPa increase in inspiratory GEPG (95% CI 0.007-0.055). Each kilogram per square meter of BMI caused expiratory IGP to increase with 0.043 kPa (95% CI 0.025-0.060) and expiratory IEP with 0.052 kPa (95% CI 0.027-0.077). Each added year of age caused inspiratory IEP to decrease by 0.008 kPa (95% CI -0.015-0.001) and inspiratory GEPG to increase by 0.008 kPa (95% CI 0.000-0.015). In binary logistic regression analysis, HH was predicted by inspiratory and expiratory IGP (odds ratio [OR] 2.93 and 2.62, respectively), inspiratory and expiratory GEPG (OR 3.19 and 2.68, respectively), and BMI (OR 1.72/5 kg/m(2)). In linear regression analysis, HH caused an average 5.09% increase in supine acid exposure (95% CI 0.96-9.22) and an average 3.46% increase in total acid exposure (95% CI 0.82-6.09). Each added year of age caused an average 0.10% increase in upright acid exposure and a 0.09% increase in total acid exposure (95% CI 0.00-0.20 and 0.00-0.18). BMI predicts IGP, inspiratory GEPG, and expiratory IEP. Age predicts inspiratory IEP and GEPG. Presence of HH is predicted by IGP, GEPG, and BMI. GEPG is not associated with acid exposure.

  2. Cavitation in Hydraulic Machinery

    Kjeldsen, M.


    The main purpose of this doctoral thesis on cavitation in hydraulic machinery is to change focus towards the coupling of non-stationary flow phenomena and cavitation. It is argued that, in addition to turbulence, superimposed sound pressure fluctuations can have a major impact on cavitation and lead to particularly severe erosion. For the design of hydraulic devices this finding may indicate how to further limit the cavitation problems. Chapter 1 reviews cavitation in general in the context of hydraulic machinery, emphasizing the initial cavitation event and the role of the water quality. Chapter 2 discusses the existence of pressure fluctuations for situations common in such machinery. Chapter 3 on cavitation dynamics presents an algorithm for calculating the nucleation of a cavity cluster. Chapter 4 describes the equipment used in this work. 53 refs., 55 figs.,10 tabs.

  3. Thermal-Hydraulic Integral Effect Test with ATLAS for an Intermediate Break Loss of Coolant Accident at a Pressurizer Surge Line

    Kang, Kyoung Ho; Seok Cho; Park, Hyun Sik; Choi, Nam Hyun; Park, Yu Sun; Kim, Jong Rok; Bae, Byoung Uhn; Kim, Yeon Sik; Kim, Kyung Doo; Choi, Ki Yong; Song, Chul Hwa [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)


    The main objectives of this test were not only to provide physical insight into the system response of the APR1400 during the pressurizer surge line break accident but also to produce an integral effect test data to validate the SPACE code. In order to simulate a double-ended guillotine break of a pressurizer surge line in the APR1400, the IB-SUR-01R test was performed with ATLAS. The major thermal-hydraulic phenomena such as the system pressures, the collapsed water levels, and the break flow rate were presented and discussed. Despite the core was uncovered, no excursion in the cladding temperature was observed. The pressurizer surge line break can be classified as a hot leg break from a break location point of view. Compared with a cold leg break, coolability in the core may be better in case of a hot leg break due to the enhanced flow in the core region. This integral effect test data will be used to evaluate the prediction capability of existing safety analysis codes of the MARS and the RELAP5 as well as the SPACE code. Furthermore, this data can be utilized to identify any code deficiency for an IBLOCA simulation, especially for DVI-adapted plants. Redefinition of break size for design basis accident (DBA) based on risk information is being extensively investigated due to the potential for safety benefits and unnecessary burden reduction from current LBLOCA (large break loss of coolant accident)-based ECC (Emergency Core Cooling) Acceptance Criteria. As a transition break size (TBS), the rupture of medium-size pipe is considered to be more important than ever in risk-informed regulation (RIR)-relevant safety analysis. As plants age, are up-rated, and continue to seek improved operating efficiencies, the small break and intermediate break LOCA (IBLOCA) can become a concern. In particular, IBLOCA with DVI (Direct Vessel Injection) features will be addressed to support redefinition of a design-basis LOCA. With an aim of expanding code validation to address small

  4. Hydraulic hoist-press

    Babayev, Z.B.; Abashev, Z.V.


    The efficiency expert of the Angrenskiy production-technological administration of the production association Sredazugol A. V. Bubnov has suggested a hydraulic hoist-press for repairing road equipment which is a device consisting of lifting mechanism, press and test stand for verifying the high pressure hoses and pumps.

  5. Accurate prediction of retention in hydrophilic interaction chromatography (HILIC) by back calculation of high pressure liquid chromatography (HPLC) gradient profiles.

    Wang, Nu; Boswell, Paul G


    Gradient retention times are difficult to project from the underlying retention factor (k) vs. solvent composition (φ) relationships. A major reason for this difficulty is that gradients produced by HPLC pumps are imperfect - gradient delay, gradient dispersion, and solvent mis-proportioning are all difficult to account for in calculations. However, we recently showed that a gradient "back-calculation" methodology can measure these imperfections and take them into account. In RPLC, when the back-calculation methodology was used, error in projected gradient retention times is as low as could be expected based on repeatability in the k vs. φ relationships. HILIC, however, presents a new challenge: the selectivity of HILIC columns drift strongly over time. Retention is repeatable in short time, but selectivity frequently drifts over the course of weeks. In this study, we set out to understand if the issue of selectivity drift can be avoid by doing our experiments quickly, and if there any other factors that make it difficult to predict gradient retention times from isocratic k vs. φ relationships when gradient imperfections are taken into account with the back-calculation methodology. While in past reports, the accuracy of retention projections was >5%, the back-calculation methodology brought our error down to ∼1%. This result was 6-43 times more accurate than projections made using ideal gradients and 3-5 times more accurate than the same retention projections made using offset gradients (i.e., gradients that only took gradient delay into account). Still, the error remained higher in our HILIC projections than in RPLC. Based on the shape of the back-calculated gradients, we suspect the higher error is a result of prominent gradient distortion caused by strong, preferential water uptake from the mobile phase into the stationary phase during the gradient - a factor our model did not properly take into account. It appears that, at least with the stationary phase

  6. Trace metal concentrations in forest and lawn soils of Paris region (France) along a gradient of urban pressure

    Ludovic, Foti


    concentrations and subsequent risks in soils of Paris and Paris region (Île-de-France). Our study aims at filling this knowledge gap, focusing on contamination and pollution by TMs in lawns and forests that constitute the main types of vegetation in urban areas of Paris region. Considering the rational described above, the aims of the present study were (i) to examine the concentration of eight selected TMs (As, Cd, Cr, Cu, Fe, Ni, Pb, Zn) in soils of two land-uses (public lawns and woods) along an urban pressure gradient in Paris region, (ii) to distinguish origins and sources of contamination or pollution, (iii) to evaluate the individual and overall TM contamination degree as well as the individual and overall TM pollution degree, (iiii) to use soil characteristics to better understand soil origins and histories along the urban pressure gradient and the relationship between these characteristics and TM concentrations. Ultimately, this study provides a baseline TM assessment for the long-term monitoring of the evolution of TM soil contents in urban area of the Paris region.

  7. Evidence for impact induced pressure gradients on the Allende CV3 parent body: Consequences for fluid and volatile transport

    Tait, Alastair W.; Fisher, Kent R.; Srinivasan, Poorna; Simon, Justin I.


    Carbonaceous chondrites, such as those associated with the Vigarano (CV) parent body, exhibit a diverse range of oxidative/reduced alteration mineralogy (McSween, 1977). Although fluids are often cited as the medium by which this occurs (Rubin, 2012), a mechanism to explain how this fluid migrates, and why some meteorite subtypes from the same planetary body are more oxidized than others remains elusive. In our study we examined a slab of the well-known Allende (CV3OxA) meteorite. Using several petrological techniques (e.g., Fry's and Flinn) and Computerized Tomography (CT) we discover it exhibits a strong penetrative planar fabric, resulting from strain partitioning among its major components: Calcium-Aluminum-rich Inclusions (CAIs) (64.5%CT) > matrix (21.5%Fry) > chondrules (17.6%CT). In addition to the planar fabric, we found a strong lineation defined by the alignment of the maximum elongation of flattened particles interpreted to have developed by an impact event. The existence of a lineation could either be non-coaxial deformation, or the result of a mechanically heterogeneous target material. In the later case it could have formed due to discontinuous patches of sub-surface ice and/or fabrics developed through prior impact compaction (MacPherson and Krot, 2014), which would have encouraged preferential flow within the target material immediately following the impact, compacting pore spaces. We suggest that structurally controlled movement of alteration fluids in the asteroid parent body along pressure gradients contributed to the formation of secondary minerals, which may have ultimately lead to the different oxidized subtypes.

  8. A high-pressure thermal gradient block for investigating microbial activity in multiple deep-sea samples

    Kallmeyer, J.; Ferdelman, TG; Jansen, KH


    of the sample vessels, a back-pressure system with a constant leak rate was installed. Pressure is applied through high-pressure liquid chromatography (HPLC) pumps that run in constant pressure mode with variable flow rate, thereby regulating any pressure fluctuations. The device allows incubations along a wide...

  9. 适用于动静压试验的综合液压源的设计%A Multifunctional Pump Station Designed for Dynamic and Static Pressure Hydraulic Tests



    分析了液压元件动静压试验的测试需求,据此进行了液压泵站的设计。液压泵站液压能由电动泵和手动泵提供,满足不同性质的液压实验需求。实践证明,对于实验类型较多,特别是静压实验较多的场合,综合液压源与常规液压源相比,具有明显优势。%Based on the dynamic and static pressure test requirement of hydraulic components, the pump station is designed. The hydraulic power of the pump station is provided by its motor pump and hand pump in accordance with different hydraulic tests. It is proved in practice that the pump station is more adequate than normal hydraulic power source to tests which need the hydraulic pressure to be hold for a long time, such as a leak test.

  10. Experimental study on thermal-hydraulic behaviors of a pressure balanced coolant injection system for a passive safety light water reactor JPSR

    Satoh, Takashi; Watanabe, Hironori; Araya, Fumimasa; Nakajima, Katsutoshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Iwamura, Takamichi; Murao, Yoshio


    A conceptual design study of a passive safety light water reactor JPSR has been performed at Japan Atomic Energy Research Institute JAERI. A pressure balanced coolant injection experiment has been carried out, with an objective to understand thermal-hydraulic characteristics of a passive coolant injection system which has been considered to be adopted to JPSR. This report summarizes experimental results and data recorded in experiment run performed in FY. 1993 and 1994. Preliminary experiments previously performed are also briefly described. As the results of the experiment, it was found that an initiation of coolant injection was delayed with increase in a subcooling in the pressure balance line. By inserting a separation device which divides the inside of core make-up tank (CMT) into several small compartments, a diffusion of a high temperature region formed just under the water surface was restrained and then a steam condensation was suppressed. A time interval from an uncovery of the pressure balance line to the initiation of the coolant injection was not related by a linear function with a discharge flow rate simulating a loss-of-coolant accident (LOCA) condition. The coolant was injected intermittently by actuation of a trial fabricated passive valve actuated by pressure difference for the present experiment. It was also found that the trial passive valve had difficulties in setting an actuation set point and vibrations noises and some fraction of the coolant was remained in CMT without effective use. A modification was proposed for resolving these problems by introducing an anti-closing mechanism. (author)

  11. Basic hydraulics

    Smith, P D


    BASIC Hydraulics aims to help students both to become proficient in the BASIC programming language by actually using the language in an important field of engineering and to use computing as a means of mastering the subject of hydraulics. The book begins with a summary of the technique of computing in BASIC together with comments and listing of the main commands and statements. Subsequent chapters introduce the fundamental concepts and appropriate governing equations. Topics covered include principles of fluid mechanics; flow in pipes, pipe networks and open channels; hydraulic machinery;

  12. The influence of a transmembrane pH gradient on protonation probabilities of bacteriorhodopsin: the structural basis of the back-pressure effect.

    Calimet, Nicolas; Ullmann, G Matthias


    Bacteriorhodopsin pumps protons across a membrane using the energy of light. The proton pumping is inhibited when the transmembrane proton gradient that the protein generates becomes larger than four pH units. This phenomenon is known as the back-pressure effect. Here, we investigate the structural basis of this effect by predicting the influence of a transmembrane pH gradient on the titration behavior of bacteriorhodopsin. For this purpose we introduce a method that accounts for a pH gradient in protonation probability calculations. The method considers that in a transmembrane protein, which is exposed to two different aqueous phases, each titratable residue is accessible for protons from one side of the membrane depending on its hydrogen-bond pattern. This method is applied to several ground-state structures of bacteriorhodopsin, which residues already present complicated titration behaviors in the absence of a proton gradient. Our calculations show that a pH gradient across the membrane influences in a non-trivial manner the protonation probabilities of six titratable residues which are known to participate in the proton transfer: D85, D96, D115, E194, E204, and the Schiff base. The residues connected to one side of the membrane are influenced by the pH on the other side because of their long-range electrostatic interactions within the protein. In particular, D115 senses the pH at the cytoplasmic side of the membrane and transmits this information to D85 and the Schiff base. We propose that the strong electrostatic interactions found between D85, D115, and the Schiff base as well as the interplay of their respective protonation states under the influence of a transmembrane pH gradient are responsible for the back-pressure effect on bacteriorhodopsin.

  13. Flame AAS/flame AES for trace determination in fresh and used lubricating oils with sample introduction by hydraulic high-pressure nebulization.

    Berndt, H; Schaldach, G; Kägler, S H


    In hydraulic high-pressure nebulization (HHPN) an aerosol is produced by means of an HPLC-pump and a special nebulization nozzle, applying a pressure of about 200 bar. This spray technique has been employed for sample introduction of mineral oil samples in flame atomic absorption/flame emission spectrometry. The determination of the trace elements Al, Cr, Cu, Fe, K, Na, Ni, Pb, Si and V has been investigated. Viscosity hardly acts upon the sensitivity of the determination, thereby avoiding a time consuming dilution of oil samples. By means of two interconnecting sampling valves a calibration method based on the standard addition technique can be performed which is both simple and easy to carry out. In samples of used oils, results for Cu and Pb equalled those of XRF-analysis. Regarding Fe traces, data obtained from AAS and XRF measurement correlate. In comparison with sample uptake by pneumatic nebulization, which is restricted to diluted oil samples, detection limits decrease by a factor of 2 to 4, indicating the dilution required in pneumatic nebulization.

  14. TRAC-PF1/MOD1: an advanced best-estimate computer program for pressurized water reactor thermal-hydraulic analysis

    Liles, D.R.; Mahaffy, J.H.


    The Los Alamos National Laboratory is developing the Transient Reactor Analysis Code (TRAC) to provide advanced best-estimate predictions of postulated accidents in light-water reactors. The TRAC-PF1/MOD1 program provides this capability for pressurized water reactors and for many thermal-hydraulic test facilities. The code features either a one- or a three-dimensional treatment of the pressure vessel and its associated internals, a two-fluid nonequilibrium hydrodynamics model with a noncondensable gas field and solute tracking, flow-regime-dependent constitutive equation treatment, optional reflood tracking capability for bottom-flood and falling-film quench fronts, and consistent treatment of entire accident sequences including the generation of consistent initial conditions. The stability-enhancing two-step (SETS) numerical algorithm is used in the one-dimensional hydrodynamics and permits this portion of the fluid dynamics to violate the material Courant condition. This technique permits large time steps and, hence, reduced running time for slow transients.

  15. Power Law or Logarithmic Law?—A data Analysis for Zero Pressure Gradient Turbulent Boundary Layers with Low Reδs



    The paper presents an analysis of two-dimensional zero pressure gradient(ZPG) turbulent boundary layers(TBL) with regard to the application of power laws,only TBL with low Reynolds number 300pressure gradient(APG) TBL.To brdge the gap between the wall and the power law region an approach for the turbulent viscosity is suggested.

  16. Application of double faced pressure hydraulic molding press in the production of automobile interiors%双面对压成形液压机在汽车生产中的应用



    The status of traditional hydraulic molding press in the production of automobile interiors has been introduced. The advantages and development trend of double faced pressure hydraulic molding press in the production of same domain have been put forward.%介绍了普通成形液压机在汽车内饰件生产中的应用现状.在此基础上介绍了双面对压成形液压机在该领域中的优势及其发展趋势.

  17. 浅谈复合式高低压缸液力端在四缸试压泵中的应用%On Application of Compound High and Low Pressure Cylinder Hydraulic Side in the Four Cylinder Hydraulic Test Pump



    复合式高低压缸液力端,是将泵体上两平行的复合缸分别与一根大小直径的阶梯柱塞配合,形成大流量低压缸和小流量高压缸,解决了现有四缸往复式试压泵存在的问题。%Compound high and low pressure cylinder hydraulic side means to match the two parallel composite cylinder on the pump body, respectively with ladder plunger with big diameter on one side and small diameter on the other side, forming large flow low pressure cylinder and small flow high pressure cylinder, which has solved the existing problems of four cylinder reciprocating hydraulic test pump.

  18. Hydraulic Structures

    Department of Homeland Security — This table is required whenever hydraulic structures are shown in the flood profile. It is also required if levees are shown on the FIRM, channels containing the...

  19. Flow field and pressure loss analysis of junction and its structure optimization of aircraft hydraulic pipe system

    Li Xin; Wang Shaoping


    The flow field in junction is complicated due to the ripple property of oil flow velocity and different frequencies of two pumps in aircraft.In this study,the flow fields of T-junction and Y-junction were analyzed using shear stress transport (SST) model in ANSYS/CFX software.The simulation results identified the variation rule of velocity peak in T-junction with different frequencies and phase-differences,meanwhile,the eddy and velocity shock existed in the corner of the T-junction,and the limit working state was obtained.Although the eddy disappeared in Y-junction,the velocity shock and pressure loss were still too big.To address these faults,an arc-junction was designed.Based on the flow fields of arc-junction,the eddy in the junction corner disappeared and the maximum of velocity peak declined compared to T-and Y-junction.Additionally,8 series of arcjunction with different radiuses were tested to get the variation rule of velocity peak.Through the computation of the pressure loss of three junctions,the arc-junction had a lowest loss value,and its pressure loss reached the minimum value when the curvature radius is 35.42 mm,meanwhile,the velocity shock has decreased in a low phase.

  20. An experimental study on single phase convection heat transfer and pressure drop in two brazed plate heat exchangers with different chevron shapes and hydraulic diameters

    Kim, Man Bae; Park, Chang Yong [Seoul National University of Science and Technology, Seoul (Korea, Republic of)


    An experimental study on heat transfer and pressure drop characteristics was performed at single phase flow in two Brazed plate heat exchangers (BPHEs) with different geometries. The corrugation density of one of the BPHE (Type II) was two times as high as that of the other BPHE (Type I). The hydraulic diameter of the type II BPHE was 2.13 mm, which was 38 % smaller than that of the type I BPHE. Also, the cross section shape of the flow channels for the type II BPHE was different from that for conventional BPHEs due to the unusual corrugation patterns and brazing points. The experimental conditions for temperatures were varied from 4.6 °C to 49.1 °C, and for mass flow rates were changed from 0.07 kg/s to 1.24 kg/s. The measured results showed that pressure drop in the type II BPHE was about 110 % higher than that in the type I BPHE. Nu of the type II was higher than that of the type I BPHE and the enhancement became larger with the increase of Re at the ranges above 800. New correlations for fF and Nu were proposed by this study and their prediction accuracy could be improved by considering the surface enlargement factor in the correlations. The performance evaluation of the two BPHEs was performed by (j/f{sub F}1{sup /3}) which represented the ratio of heat transfer and pressure drop performance. Also, a new parameter, the capacity compactness of PHE, was proposed and it presented the PHE capacity per unit volume and unit log mean temperature difference. The comparison showed that the two BPHEs had similar values of the (j/f{sub F}1{sup /3}), whereas they had significantly different values of the capacity compactness. The capacity compactness of the type II BPHE was 1.5 times higher than that for the type I BPHE.

  1. 液压冲击器氮气室预充压力对冲击性能的影响研究%Influence of Precharge Pressure of Nitrogen Chamber on Hydraulic Impactor's Performance

    梁翠平; 杨国平; 王亮; 丁冲冲


    Based on analyzing the working principle and characteristics of hydraulic impactor, the nonlinear mathematical model of a hydraulic impactor system was established. By using MATLAB/ Simulink, the simulation of two processes including the accelerated return stroke and travel stroke of the hydraulic impactor were researched, and the influence of precharge pressure of nitrogen chamber on the percussion performance was analyzed. The results show that: if the precharge pressure of nitrogen chamber is too Large , it will result in hydraulic fluid can not move the piston to return, and hydraulic impactor can not start up; if the pressure is too small, it will induce difficulty to raise the impacting pressure, and the impacting energy will be small.%在分析液压冲击器工作原理及特点的基础上,建立液压冲击器系统的非线性数学模型.运用MATLAB/Simulink 分别对液压冲击器的回程加速过程和冲程过程进行仿真研究,分析氮气室预充压力对冲击器冲击性能的影响程度.结果表明:氮气室预充压力过大,会导致液压油不能推动活塞进行回程,液压冲击器起动不了;压力过小,则很容易使冲击压力升不上去,冲击能小.

  2. Analysis on Infiltration Capacity in Asphalt Pavement Subjected to Dynamic Hydraulic Pressure%动水压力作用下沥青路面渗水量影响分析

    高俊启; 盛余祥; 张世铎; 于凤强; 蒋泽民


    It is important of infiltration capacity for the drainage design in asphalt pavement.In order to calculate infiltration capacity in asphalt pavement subjected to dynamic hydraulic pressure,the dynamic hydraulic pressures in asphalt pavement at some running speeds are measured,and the relationship of the hydraulic pressure and car speed is built.Furthermore,a falling head permeameter method is used to measure the permeability coefficients of asphalt mixture exposed to hydraulic pressures whose peak values are from 40 to 350 kPa,and the correlation between permeability and hydraulic pressure is obtained.In addition,a dynamic permeability test system is presented to measure the dynamic permeability of asphalt mixture subjected to vehicle impulsive pressures,and the calculation formula for calculating infiltration capacity in asphalt pavement subjected to dynamic hydraulic pressure is established.The results show that the infiltration capacity is proportionate to the permeability coefficient and effective tire ground area respectively,and is inversely proportional to the thickness of asphalt pavement.The infiltration capacity decreases with the increment of car's speed.%沥青路面渗水量对于沥青路面内部排水设计非常重要.为计算动水压力作用下沥青路面渗水量,实地测试了不同车速下沥青路面表面的动态水压力数值,建立了动态水压力与车速的关系.根据变水头试验方法,测试了沥青混合料芯样在40~350 kPa水压力下的渗透系数,建立了沥青混合料渗透系数与水压力的关系.为研究路面在交通荷载作用下的动态渗透性能,设计了动态渗透试验测量系统.建立了动水压力作用下沥青路面渗水量的计算模型.结果表明:沥青路面渗水量与路面渗透系数、轮胎有效接地面积成正比,与路面厚度成反比;随车速增加,动水压力作用下沥青路面渗水量减小.

  3. Trend of hydraulic units

    Deshimaru, Jun' ichi


    The gear, vane and piston pumps occupy a more then 90% share in the hydraulic pumps. Comparatively large pumps are mainly variable delivery piston pumps. The piston pumps are comparatively high in output density (output per unit weight), indicating the hydraulic pump in performance, and tend to become higher and higher in it. Though they are mainly 210 to 350kgf/cm/sup 2/ in rated pressure, some of them come to surpass 400kgf/cm/sup 3/ in it. While the progress in computation also requires the high speed operation, high accuracy and other severe conditions for the hydraulic units, which accordingly and increasingly intensify the requirement for hydraulic oil in abrasion resistibility, oxidation stability and response characteristics. While cavitation comes to easily occur, which considerably and disadvantageously influences hydraulic oil in life through degradation, noise level and respondingness. From now on, the development of high performance oil and study of mechanical structure are important. 19 references, 9 figures, 2 tables.

  4. Experimental investigation of the dielectric properties of soil under hydraulic loading

    Bittner, Tilman; Bore, Thierry; Wagner, Norman; Karlovšek, Jurij; Scheuermann, Alexander


    An experimental set-up was developed in order to determine the coupled hydraulic, dielectric and mechanical properties of granular media under hydraulic loading. The set-up consisted of a modified column for permeability tests involving a flow meter and pressure transducers along the sample to quantify the hydraulic gradient. A newly developed open-ended coaxial probe allowed the measurement of the frequency dependent dielectric permittivity of the material under test. The shear strength of the sample within the column was measured using a conventional vane shear device. In this paper, the overall set-up is introduced with focus on the open-ended coaxial probe. The design and calibration of the probe are introduced in detail. A numerical study showed that the sensitive cylindrical volume of the probe was approximately 150 mm in diameter with a depth of 65 mm. An investigation with glass beads showed that the set-up allowed the parameterization of the hydraulic, mechanic and dielectric parameters of granular materials under the influence of vertical flow. A satisfactorily good correlation between porosity and the real part of the dielectric permittivity was detected. The critical hydraulic gradient defining the transition of a fixed bed of particles to fluidization was characterized by a sharp peak in the evolution of the hydraulic conductivity and could easily be determined from the measurements. The shear strength of the material under test reduces linearly with increasing hydraulic gradient. Future investigations will be carried out to provide the required parameterizations for experimental and numerical investigations of the internal erosion of granular media.

  5. Comparison of Laboratory and Field Methods for Determining the Quasi-Saturated Hydraulic Conductivity of Soils

    Faybishenko, Boris


    Laboratory and field ponded infiltration tests in quasi-saturated soils (containing entrapped air) exhibit the same three-stage temporal variability for the flow rate and hydraulic conductivity. However, the values for the hydraulic conductivity may differ by as much as two orders of magnitude due to differences in the geometry and physics of flow when different laboratory and field methods are applied. The purpose of this paper is to investigate this variability using a comparison of results of ponded infiltration tests conducted under laboratory conditions using confined cores, with results of field tests conducted using partially isolated cores and double-ring infiltrometers. Under laboratory conditions in confined cores, during the firs stage, the water flux decreases over time because entrapped air plugs the largest pores in the soils; during the second stage, the quasi-saturated hydraulic conductivity increases by one to two orders of magnitude, essentially reaching the saturated hydraulic conductivity, when entrapped air is discharged from the soils; during the third stage, the hydraulic conductivity decreases to minimum values due to sealing of the soil surface and the effect of biofilms sealing the pores within the wetted zone. Under field conditions, the second stage is only partially developed, and when the surface sealing process begins, the hydraulic pressure drops below the air entry value, thereby causing atmospheric air to enter the soils. As a result, the soils become unsaturated with a low hydraulic conductivity, and the infiltration rate consequently decreases. Contrary to the laboratory experiments in confined cores, the saturated hydraulic conductivity cannot be reached under field conditions. In computations of infiltration one has to take into account the variations in the quasi-saturated and unsaturated hydraulic conductivities, moisture and entrapped air content, and the hydraulic gradient in the quasi-saturated or unsaturated soils.

  6. A revised and unified pressure-clamp/relaxation theory for studying plant cell water relations with pressure probes: in-situ determination of cell volume for calculation of volumetric elastic modulus and hydraulic conductivity.

    Knipfer, T; Fei, J; Gambetta, G A; Shackel, K A; Matthews, M A


    The cell-pressure-probe is a unique tool to study plant water relations in-situ. Inaccuracy in the estimation of cell volume (νo) is the major source of error in the calculation of both cell volumetric elastic modulus (ε) and cell hydraulic conductivity (Lp). Estimates of νo and Lp can be obtained with the pressure-clamp (PC) and pressure-relaxation (PR) methods. In theory, both methods should result in comparable νo and Lp estimates, but this has not been the case. In this study, the existing νo-theories for PC and PR methods were reviewed and clarified. A revised νo-theory was developed that is equally valid for the PC and PR methods. The revised theory was used to determine νo for two extreme scenarios of solute mixing between the experimental cell and sap in the pressure probe microcapillary. Using a fully automated cell-pressure-probe (ACPP) on leaf epidermal cells of Tradescantia virginiana, the validity of the revised theory was tested with experimental data. Calculated νo values from both methods were in the range of optically determined νo (=1.1-5.0nL) for T. virginiana. However, the PC method produced a systematically lower (21%) calculated νo compared to the PR method. Effects of solute mixing could only explain a potential error in calculated νo of cell turgor) of 19%, which is a fundamental parameter in calculating νo. It followed from the revised theory that the ratio of ΔV/ΔP was inversely related to the solute reflection coefficient. This highlighted that treating the experimental cell as an ideal osmometer in both methods is potentially not correct. Effects of non-ideal osmotic behavior by transmembrane solute movement may be minimized in the PR as compared to the PC method.

  7. Vibrations of hydraulic pump and their solution

    Dobšáková Lenka; Nováková Naděžda; Habán Vladimír; Hudec Martin; Jandourek Pavel


    The vibrations of hydraulic pump and connected pipeline system are very problematic and often hardly soluble. The high pressure pulsations of hydraulic pump with the double suction inlet are investigated. For that reason the static pressure and accelerations are measured. The numerical simulations are carried out in order to correlate computed data with experimental ones and assess the main source of vibrations. Consequently the design optimization of the inner hydraulic part of pump is done ...

  8. A calculation method of water distribution network hydraulic based on preconditioned conjugate gradient method%一种基于预处理共轭梯度法的给水管网水力计算方法



    提出了一种新的给水管网水力计算方法.该方法对给水管网系统的节点流量连续性方程进行重新构造,用改进的Cholesky分解方法对重新构造的矩阵进行三角分解,然后使用预处理共轭梯度法求解.经用供水管网模型进行验证并与EPANET软件的计算结果进行比较,结果表明:该算法共迭代5次,用时0.102 s,与EPANET混合节点-环方法的求解精度和速度非常接近,且弥补了EPA-NET软件的应用缺陷,可用于求解大型城市的给水管网系统.%A calculation method of water distribution network hydraulic was proposed.The nodes flow conti-nuity equation of water distribution system was reconstructed,the reconstructed matrix was decomposed tri-angularly by a modified Cholesky decomposition method,and thus it was suitable for the use of precondi-tioned conjugate gradient method.It was tested by the model of water distribution network(WDN)hydrau-lic.Compared with calculation result of EPANET software,the proposed algorithm does total iteration five times in 0.1 02 s,which closed to the result of mixed node-ring method used in EPANET software in the as-pect of accuracy and speed.The proposed algorithm overcame the defects of EPANET software,which could be used to solve large-scale urban water supply network system.

  9. The Injector Solenoid Valve Hydraulic Study of High Pressure Common-Rail%高压共轨喷油器电磁阀液力特性研究

    王国莹; 袁永先; 徐春龙; 吴小军


    高压共轨系统喷油器电磁阀是高压共轨系统的关键技术,为进一步了解其液力特性,本研究基于Hydsim软件平台,针对2进油量孔的大流量电磁阀喷油器结构建立仿真模型,通过试验校验了模型的准确性,并通过模拟仿真方法,分析了控制量孔的结构对大流量喷油器液力特性的影响.%Solenoid valve is the key technology of diesel engine high pressure common rail system. For knowing about the basic hydraulic concept, a common-rail injector simulation model has been developed with Hydsim software, which has 2 inlet orifices. The model shows good agreement with the measurements. The study shows the influence of the orifice structure to the injector.

  10. Experiments on Performance Sensitivity of SMART PRHRS using the High Temperature/High Pressure Thermal-Hydraulic Test Facility (VISTA)

    Park, Hyun Sik; Choi, Ki Yong; Cho, Seok; Lee, Sung Jae; Choi, Nam Hyun; Min, Kyong Ho; Song, Chul Hwa; Park, Chun Kyong; Chung, Moon Ki


    The VISTA (Experimental Verification by Integral Simulation of Transients and Accidents) is an experimental facility to verify the performance and safety issues of the SMART-P (Pilot plant of the System-integrated Modular Advanced Reactor). The basic design of the SMART-P has been completed by KAERI. The present report describes the experimental results on the overall performance sensitivity of SMART PRHRS. During the reference test a stable flow occurs in a natural circulation loop which is composed of a steam generator secondary side, a secondary system, and a PRHRS, and it is ascertained by a repetition test. When the bypass valves of PRHRS are operated earlier than the isolation valves of secondary system, the primary system is effectively cooled but the inventory of PRHRS compensation tank is drained earlier. When the bypass valves of PRHRS are operated later than the isolation valves of secondary system, the primary system is not cooled. As the initial level of compensation tank is lowered to 16% of the full level, the steady natural circulation stops around 500 seconds. When the initial pressure of PRHRS is at 0.1 MPa, the natural circulation is not performed properly. When they are 2.5 and 3.5 MPa, it shows better performance than the reference test. Also when the isolation valve connecting the compensation tank is operated simultaneously with the PRHRS isolation valves, the primary system is more efficiently cooled but the inventory of PRHRS compensation tank is drained earlier.

  11. Hydraulic conductivity of GCLs in MSW landfills

    LI Guo-cheng; YANG Wu-chao; DAN Tang-hui


    The state of the art of the study on the hydraulic conductivity of GCLs is presented in terms of the in-fluence of the effective stress, chemical interactions, freeze - thaw cycles and temperature gradients. The chan-ges of void ratio caused by changes of effective stress have a direct linear effect on the hydraulic conductivity, regardless of the cation concentration or the thickness of the adsorbed layer. The hydraulic conductivity is relat-ed to the relative abundance of monovalent and divalent cation(RMD), and RMD has a great effect on the hy-draulic conductivity in weak solution. The long-term susceptibility of GCLs to increased hydraulic conductivity as a response to repeated freeze-thaw cycling is minimal, which has been proved after 150 freeze-thaw cycles. The potential of desiccation cracking increases with the increasing temperature gradient and is related to the ini-tial subsoil water content, the applied overburden stress, etc.

  12. Design of Hydraulic Gauge Head of Differential Pressure Type and Parameter Optimization of the Gauge Head%差压式液压测头的设计及参数优化

    母德强; 崔博; 范以撒; 陈懿


    The design and working principle of a hydraulic gauge head is intruced in this paper, which is based on the differential pressure-measuring principle with liquid as working media. With the help of CFX, the differential pres-sure system characteristics curves are plotted and the influence level of the structure parameters on working perfor-mance of the hydraulic gauge head is also analyzed. Bsides, the parameters of the gauge head are optimized.%提出一种以液体为工作介质,基于差压法的液压测头的设计和工作原理。利用CFX软件绘制了Δp-s工作曲线图,分析了各参数对液压测头工作性能的影响,对液压测头的几个重要参数进行了优化。

  13. Thermal Hydraulic Performance of Tight Lattice Bundle

    Yamamoto, Yasushi; Akiba, Miyuki; Morooka, Shinichi; Shirakawa, Kenetsu; Abe, Nobuaki

    Recently, the reduced moderation spectrum BWR has been studied. The fast neutron spectrum is obtained through triangular tight lattice fuel. However, there are few thermal hydraulic test data and thermal hydraulic correlation applicable to critical power prediction in such a tight lattice bundle. This study aims to enhance the database of the thermal hydraulic performance of the tight lattice bundle whose rod gap is about 1mm. Therefore, thermal hydraulic performance measurement tests of tight lattice bundles for the critical power, the pressure drop and the counter current flow limiting were performed. Moreover, the correlations to evaluate the thermal-hydraulic performance of the tight lattice bundle were developed.

  14. Design of hydraulic output Stirling engine

    Toscano, W. M.; Harvey, A. C.; Lee, K.


    A hydraulic output system for the RE-1000 free piston stirling engine (FPSE) was designed. The hydraulic output system can be readily integrated with the existing hot section of RE-1000 FPSE. The system has two simply supported diaphragms which separate the engine gas from the hydraulic fluid, a dynamic balance mechanism, and a novel, null center band hydraulic pump. The diaphragms are designed to endure more than 10 billion cycles, and to withstand the differential pressure load as high as 14 MPa. The projected thermodynamic performance of the hydraulic output version of RE-1000 FPSE is 1.87 kW at 29/7 percent brake efficiency.

  15. Hardness-gradient reversion in FeMnSiCr shape memory alloy modules produced by high-speed high pressure torsion

    Bujoreanu Leandru-Gheorghe


    Full Text Available High pressure torsion (HPT processing technology, consisting in the obtainment of (ultrafine bulk metallic structure during 2–3 complete rotations of the superior anvil at low speed (~10-1 rpm under high applied pressure (~ GPa applied on the lower anvil, has been modified as to allow the application of elevated number of rotation numbers (~102 rpm. By high-speed high pressure torsion (HS-HPT, coned-disk spring shape modules were processed from an as cast Fe-28Mn-6Si-5Cr (mass % shape memory alloy (SMA. Scanning electron microscopy (SEM and X-ray diffraction (XRD studies revealed that the modules became nanostructured as an effect of HS-HPT processing. After processing, a hardness gradient was obtained along the truncated cone generator, increasing from inner to outer areas, due to different deformation degrees in these zones. After complete flattening, the measurements revealed that the hardness gradient maintained its value but reversed its variation sense.

  16. The Optimal Design of Articulated Point Location Articulated Mechanical Change Diretion Hydraulic Pressure Vat%铰接式机械转向液压缸铰接点位置的优化设计



    According to the most left and right side for front m achine frame, this paper introduces the optimal design of articulated point loca tion of change direction hydraulic pressure vat.%以前车架在最左和最右转向位置为计算点,对转向液压缸铰接点位置进行了优化设计。

  17. 基于AMESet的压力油箱供油系统建模与仿真研究%Research on Modeling and Simulation of Hydraulic Oil Supply System with Pressurized Tank Based on AMESet

    吕庆军; 杨庆俊; 朱冬


    Pressurized tank was used for hydraulic system in armoured vehicle to provide instantaneous high flow for hydraulic brake and to supply hydraulic oil to other branches such as lubricating systems.By mathematically modeling the pneumatic gear pump, hybrid relief valve for both air and oil,and pressurized tank,a complete simulation model for this hydraulic system with pressurized tank as its core element was established based on AMESet,which was easily embedded in the system established by AMESim for simu-lation.The simulation model shows that the model is correct to represent characteristics of the pneumatic pump,hybrid relief valve and the tank,and thus can be used for the optimization design of the pressurized tank.%装甲车辆的供油系统采用压力油箱以提供制动时所需的瞬时大流量液流,同时保证润滑等其他油路的用油。基于AMESet构建了以压力油箱为核心的供油系统仿真模型,对压力油箱中气动齿轮泵、气液混合溢流阀和油箱等子模型进行了数学建模,可以方便地嵌入到AMESim构建的总系统中进行仿真。该仿真模型能够正确仿真压力油箱中气泵、气液混合溢流阀等特性,为压力油箱的优化设计提供了依据。

  18. 玻璃酸钠注射加液压扩张治疗肩关节周围炎%Hydraulic pressure distersion and sodium hyluronate injection treatment for scapulohumeral periarthritis

    刘勇; 吴权; 瞿懿; 寿奎水; 殷渠东


    Objective To investigate the efficacy of hydraulic pressure distersion and sodium hyluronate injection on scapulohumeral periarthritis. Methods 48 cases of scapulohumeral periarthritis were given hydraulic pressure distension with sodium hyaluronate and lidocaine injection,as well as properly exercises. Results 7 cases were lost, and the other patients were followed up for more than 5 months after surgery. The effective rate was 90 % , and the excellent rate was 89 % . Conclusion Hydraulic pressure distension is a reliable and highly effective treatment for scapulohumeral periarthritis in the slight or moderate patients.%目的 探讨玻璃酸钠注射加液压扩张疗法对肩周炎的疗效.方法 对64例肩周炎进行关节囊内液压扩张治疗,局麻加玻璃酸钠注射,适当辅助锻炼.结果 64例患者中,7例未能完成1个疗程治疗,其余术后5个月以上随访,有效率为90%,优良率为89 %.结论 液压扩张疗法是治疗肩周炎的有效方法,尤其对轻中型患者疗效明显.

  19. Electrohydrodynamics within electrical double layer in a pressure-driven flow in presence of finite temperature gradients

    Ghonge, Tanmay; Chakraborty, Jeevanjyoti; Chakraborty, Suman


    A wide spectrum of electrokinetic studies is modelled as isothermal ones to expedite analysis even when such conditions may be extremely difficult to realize in practice. As a clear and novel departure from this trend, we address the case of flow-induced electrohydrodynamics, commonly referred to as streaming potential, in a situation where finite temperature gradients do indeed exit. By way of analysing a model problem of flow through a narrow parallel plate channel, we show that the temperature gradients have a significant effect on the streaming potential, and, consequently, on the flow itself. We incorporate thermoelectic effects in our model by a full-fledged coupling among the electric potential, the ionic species distribution, the fluid velocity and the local fluid temperature fields without resorting to ad hoc simplifications. We expect this expository study to contribute towards more sophisticated future inquiries into practical micro-/nano-fluidic applications coupling thermal field focusing with el...

  20. Study on the effects of gradient mechanical pressures on the proliferation, apoptosis, chondrogenesis and hypertrophy of mandibular condylar chondrocytes in vitro.

    Li, Hui; Huang, Linjian; Xie, Qianyang; Cai, Xieyi; Yang, Chi; Wang, Shaoyi; Zhang, Min


    To investigate the effects of gradient mechanical pressure on chondrocyte proliferation, apoptosis, and the expression of markers of chondrogenesis and chondrocyte hypertrophy. Mandibular condylar chondrocytes from 5 rabbits were cultured in vitro, and pressed with static pressures of 50kPa, 100kPa, 150kPa and 200kPa for 3h, respectively. The chondrocytes cultured without pressure (0kPa) were used as control. Cell proliferation, apoptosis, and the expression of aggrecan (AGG), collagen II (COL2), collagen X (COL10), alkaline phosphatase (ALP) were investigated. Ultrastructures of the pressurized chondrocytes under transmission electron microscopy (TEM) were observed. Chondrocyte proliferation increased at 100kPa and decreased at 200kPa. Chondrocyte apoptosis increased with peak pressure at 200kPa in a dose-dependent manner. Chondrocyte necrosis increased at 200kPa. The expression of AGG increased at 200kPa. The expression of COL2 decreased at 50kPa and increased at 150kPa. The expression of COL10 and ALP increased at 150kPa. Ultrastructure of the pressurized chondrocytes under TEM showed: at 100kPa, cells were enlarged with less cellular microvillus and a bigger nucleus; at 200kPa, cells shrank with the sign of apoptosis, and apoptosis cells were found. The mechanical loading of 150kPa is the moderate pressure for chondrocyte: cell proliferation and apoptosis is balanced, necrosis is reduced, and chondrogenesis and chondrocyte hypertrophy are promoted. When the pressure is lower, chondrogenesis and chondrocyte hypertrophy are inhibited. At 200kPa, degeneration of cartilage is implied. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. PLC control system of 1600-ton hydraulic pressure machine for abrasive products%1600吨磨料制品液压机的PLC控制



    针对继电器控制的大型砂轮成型设备,1600吨液压机电气线路复杂和故障率高的状况,采用三菱FX2N系列的可编程逻辑控制器对原有的继电器控制系统进行改造,以软继电器的逻辑运算取代传统继电器的硬线连接;运用PLC的顺序控制设计法,并按照工艺流程,以输出元件的变化设计控制功能图和梯形图,简化了线路;采用硬件软件双重联锁提高了控制系统的可靠性.%In order to remedy the complex electrical circuits and high failure rate with the large wheel molding equipment of 1600 tons hydraulic pressure machines, which were controlled by relay, MITSUBISHI FX2N programmable logical controller was adopted to replace the original relay control system. The traditional relay's hard-wired connections were replaced by logical operation of soft relay. What's more, PLC sequential control method was adopted and circuits were simplified by changing design control function diagram and ladder chart of the output components according to the technological process. The reliability of the control system was improved with double chain of hardware and software.

  2. Influence of a pressure gradient distal to implanted bare-metal stent on in-stent restenosis after percutaneous coronary intervention

    Jensen, Lisette Okkels; Thayssen, Per; Thuesen, Leif


    BACKGROUND: Fractional flow reserve predicts cardiac events after coronary stent implantation. The aim of the present study was to assess the 9-month angiographic in-stent restenosis rate in the setting of optimal stenting and a persisting gradient distal to the stent as assessed by a pressure wire...... performed in the target vessel: (1) P(d)/P(a) as distal to the artery as possible (fractional flow reserve per definition); (2) P(d)/P(a) just distal to the stent; (3) P(d)/P(a) just proximal to the stent; and (4) P(d)/P(a) at the ostium. Residual abnormal P(d)/P(a) was defined as a pressure drop between P......(d)/P(a) measured at points 1 and 2. Fractional flow reserve distal to the artery after stenting was significantly lower (0.88+/-0.21 versus 0.97+/-0.05; P

  3. Experimental and Analysis for Self-excited Pressure Oscillations and Noise of Hydraulic Jet Pipe Servo-valve%液压射流管伺服阀自激振荡和噪声实验与分析



    在液压流场中,液压伺服阀的高频噪声主要来自于自身的震荡。采用压电式动态压力传感器和扩音器对液压射流管伺服阀的自激振荡和噪声进行检测。试验中,将伺服阀的进口压力控制在11~21 MPa。为了将实验数据精准化,利用FFT和小波分析法对压力震荡信号和噪声信号进行处理。根据分析结果找出自激振荡和噪声产生的原因,并为降低液压伺服阀的自激振荡和噪声提供了方法。%In the hydraulic flow field, the high frequency noise of the hydraulic servo-valve is mainly derived from its own shock. Using the piezoelectric dynamic pressure sensor and amplifier, hydraulic jet pipe servo-valve self-excited vibration and noise were de-tected.In the test, the inlet pressure of the servo-valve was controlled in 11~21 MPa.In order to make the experimental data accurate, FFT and wavelet analysis method were used to deal with the pressure oscillation signal and noise signal.According to the analysis re-sults, the causes of the self-excited oscillation and noise were found out.It provides method for reducing vibration and noise of hydrau-lic servo-valve.

  4. Effects of Drought, Pest Pressure and Light Availability on Seedling Establishment and Growth: Their Role for Distribution of Tree Species across a Tropical Rainfall Gradient.

    Gaviria, Julian; Engelbrecht, Bettina M J


    Tree species distributions associated with rainfall are among the most prominent patterns in tropical forests. Understanding the mechanisms shaping these patterns is important to project impacts of global climate change on tree distributions and diversity in the tropics. Beside direct effects of water availability, additional factors co-varying with rainfall have been hypothesized to play an important role, including pest pressure and light availability. While low water availability is expected to exclude drought-intolerant wet forest species from drier forests (physiological tolerance hypothesis), high pest pressure or low light availability are hypothesized to exclude dry forest species from wetter forests (pest pressure gradient and light availability hypothesis, respectively). To test these hypotheses at the seed-to-seedling transition, the potentially most critical stage for species discrimination, we conducted a reciprocal transplant experiment combined with a pest exclosure treatment at a wet and a dry forest site in Panama with seeds of 26 species with contrasting origin. Establishment success after one year did not reflect species distribution patterns. However, in the wet forest, wet origin species had a home advantage over dry forest species through higher growth rates. At the same time, drought limited survival of wet origin species in the dry forest, supporting the physiological tolerance hypothesis. Together these processes sort species over longer time frames, and exclude species outside their respective home range. Although we found pronounced effects of pests and some effects of light availability on the seedlings, they did not corroborate the pest pressure nor light availability hypotheses at the seed-to-seedling transition. Our results underline that changes in water availability due to climate change will have direct consequences on tree regeneration and distributions along tropical rainfall gradients, while indirect effects of light and pests

  5. Effects of Drought, Pest Pressure and Light Availability on Seedling Establishment and Growth: Their Role for Distribution of Tree Species across a Tropical Rainfall Gradient.

    Julian Gaviria

    Full Text Available Tree species distributions associated with rainfall are among the most prominent patterns in tropical forests. Understanding the mechanisms shaping these patterns is important to project impacts of global climate change on tree distributions and diversity in the tropics. Beside direct effects of water availability, additional factors co-varying with rainfall have been hypothesized to play an important role, including pest pressure and light availability. While low water availability is expected to exclude drought-intolerant wet forest species from drier forests (physiological tolerance hypothesis, high pest pressure or low light availability are hypothesized to exclude dry forest species from wetter forests (pest pressure gradient and light availability hypothesis, respectively. To test these hypotheses at the seed-to-seedling transition, the potentially most critical stage for species discrimination, we conducted a reciprocal transplant experiment combined with a pest exclosure treatment at a wet and a dry forest site in Panama with seeds of 26 species with contrasting origin. Establishment success after one year did not reflect species distribution patterns. However, in the wet forest, wet origin species had a home advantage over dry forest species through higher growth rates. At the same time, drought limited survival of wet origin species in the dry forest, supporting the physiological tolerance hypothesis. Together these processes sort species over longer time frames, and exclude species outside their respective home range. Although we found pronounced effects of pests and some effects of light availability on the seedlings, they did not corroborate the pest pressure nor light availability hypotheses at the seed-to-seedling transition. Our results underline that changes in water availability due to climate change will have direct consequences on tree regeneration and distributions along tropical rainfall gradients, while indirect effects of

  6. A Computational Model of Hydraulic Volume Displacement Drive

    V. N. Pil'gunov


    Full Text Available The paper offers a computational model of industrial-purpose hydraulic drive with two hydraulic volume adjustable working chamber machines (pump and motor. Adjustable pump equipped with the pressure control unit can be run together with several adjustable hydraulic motors on the principle of three-phase hydraulic socket-outlet with high-pressure lines, drain, and drainage system. The paper considers the pressure-controlled hydrostatic transmission with hydraulic motor as an output link. It shows a possibility to create a saving hydraulic drive using a functional tie between the adjusting parameters of the pump and hydraulic motor through the pressure difference, torque, and angular rate of the hydraulic motor shaft rotation. The programmable logic controller can implement such tie. The Coulomb and viscous frictions are taken into consideration when developing a computational model of the hydraulic volume displacement drive. Discharge balance considers external and internal leakages in equivalent clearances of hydraulic machines, as well as compression loss volume caused by hydraulic fluid compressibility and deformation of pipe walls. To correct dynamic properties of hydraulic drive, the paper offers that in discharge balance are included the additional regulated external leakages in the open circuit of hydraulic drive and regulated internal leakages in the closed-loop circuit. Generalized differential equations having functional multipliers and multilinked nature have been obtained to describe the operation of hydraulic positioning and speed drive with two hydraulic volume adjustable working chamber machines. It is shown that a proposed computational model of hydraulic drive can be taken into consideration in development of LS («Load-Sensing» drives, in which the pumping pressure is tuned to the value required for the most loaded slave motor to overcome the load. Results attained can be used both in designing the industrial-purpose heavy

  7. Hydraulic wind energy conversion system


    The purpose of this research was to design, build and test a hydraulic wind energy system. This design used a three bladed turbine, which drove a hydraulic pump. The energy is transmitted from the pump through a long hose and into a hydraulic motor, where the energy is used. This wind system was built and tested during the winter of 1980-1981. The power train included a five meter, three bladed wind turbine, a 9.8:1 ratio gearbox, a 1.44 cubic inch displacement pump with a small supercharge gear pump attached. The hydraulic fluid was pumped through a 70', 3/4'' I-D-high pressure flexhose, then through a volume control valve and into a 1.44 cubic inch displacement motor. The fluid was returned through a 70', 1'' I-D-flexhose.

  8. What Sets Temperature Gradients in Galaxy Clusters? Implications for non-thermal pressure support and mass-observable scaling relations

    McCourt, Michael; Parrish, Ian J


    We present a spherically symmetric model for the origin and evolution of the temperature profiles in the hot plasma filling galaxy groups and clusters. We find that the gas in clusters is generically not isothermal, and that the temperature declines with radius at large distances from the cluster center (outside the core- and scale radii). This temperature profile is determined by the accretion history of the halo, and is not quantitatively well-described by a polytropic model. We explain quantitatively how the large-scale temperature gradient persists in spite of thermal conduction and convection. These results are a consequence of the cosmological assembly of clusters and cannot be reproduced with non-cosmological simulations of isolated halos. We show that the variation in halo assembly histories produces a ~10% scatter in temperature at fixed mass. On top of this scatter, conduction decreases the temperature of the gas near the scale radius in massive clusters, which may bias hydrostatic mass estimates in...

  9. “三软”煤层水力冲孔卸压增透技术研究%Study on pressure releasing and permeability improving technology with hydraulic flushing in “three soft”coal seam

    何志龙; 孙谦; 宋大钊; 高勤琼


    针对糯东煤矿“三软”高瓦斯低透气性煤层易流变、难抽采的问题,提出了底板巷道穿层水力冲孔卸压增透技术,并在糯东煤矿11702掘进工作面进行了现场试验。结果表明:冲孔后比冲孔前抽采瓦斯浓度上升3.4倍,瓦斯抽采流量增加4.4倍,炮掘工作面回风流中的瓦斯(体积分数)由冲孔前0.8%的超限预警状态变成冲孔后的0.4%的安全范围,水力冲孔技术应用效果显著,在糯东煤矿取得了良好的卸压增透效果。%To solve the problem of easy rheology and hard drainage in"three soft"coal seam with high gas concentration and low permeability in Nuodong coal mine,the pressure releasing and permeability improving technology with hydraulic flushing in floor gateway was proposed,and corresponding field test at the No.11702 heading face of Nuodong coal mine was carried out.The re-sults show that the drained gas concentration after hydraulic flushing is 3.4 times as that without hydraulic flushing and the gas flow rate is increased by 4.4 times;and the gas concentration at the blasting working face changes from 0.8% (overrun warning state,before hydraulic flushing)to 0.4% (safety state,after hydraulic flushing).The application of hydraulic flushing technolo-gy is more effective and remarkable in releasing pressure and improving permeability in Nuodong coal mine.

  10. Numerical simulation of water hammer in low pressurized pipe: comparison of SimHydraulics and Lax-Wendroff method with experiment

    Himr D.


    Full Text Available Article describes simulation of unsteady flow during water hammer with two programs, which use different numerical approaches to solve ordinary one dimensional differential equations describing the dynamics of hydraulic elements and pipes. First one is Matlab-Simulink-SimHydraulics, which is a commercial software developed to solve the dynamics of general hydraulic systems. It defines them with block elements. The other software is called HYDRA and it is based on the Lax-Wendrff numerical method, which serves as a tool to solve the momentum and continuity equations. This program was developed in Matlab by Brno University of Technology. Experimental measurements were performed on a simple test rig, which consists of an elastic pipe with strong damping connecting two reservoirs. Water hammer is induced with fast closing the valve. Physical properties of liquid and pipe elasticity parameters were considered in both simulations, which are in very good agreement and differences in comparison with experimental data are minimal.

  11. Numerical simulation of water hammer in low pressurized pipe: comparison of SimHydraulics and Lax-Wendroff method with experiment

    Himr, D.


    Article describes simulation of unsteady flow during water hammer with two programs, which use different numerical approaches to solve ordinary one dimensional differential equations describing the dynamics of hydraulic elements and pipes. First one is Matlab-Simulink-SimHydraulics, which is a commercial software developed to solve the dynamics of general hydraulic systems. It defines them with block elements. The other software is called HYDRA and it is based on the Lax-Wendrff numerical method, which serves as a tool to solve the momentum and continuity equations. This program was developed in Matlab by Brno University of Technology. Experimental measurements were performed on a simple test rig, which consists of an elastic pipe with strong damping connecting two reservoirs. Water hammer is induced with fast closing the valve. Physical properties of liquid and pipe elasticity parameters were considered in both simulations, which are in very good agreement and differences in comparison with experimental data are minimal.

  12. Development of two-phase pipeline hydraulic analysis model based on Beggs-Brill correlation

    Waluyo, Joko; Hermawan, Achilleus; Indarto


    The hydraulic analysis is an important stage in a reliable pipeline design. In the implementation, fluid distribution from a source to the sinks often occurs on parallel pipeline networks. The solution to the problem is complicated because of the iterative technique requirement. Regarding its solution effectiveness, there is a need for analysis related to the model and the solution method. This study aims to investigate pipeline hydraulic analysis on distributing of two-phase fluids flow. The model uses Beggs-Brill correlation to converse mass flow rates into pressure drops. In the solution technique, the Newton-Raphson iterative method is utilized. The iterative technique is solved using a computer program. The study is carried out using a certain pipeline network. The model is validated by comparing between Beggs-Brill towards Mukherjee-Brill correlation. The result reveals that the computer program enables solving of iterative calculation on the parallel pipeline hydraulic analysis. Convergence iteration is achieved by 50 iterations. The main results of the model are mass flow rate and pressure drop. The mass flow rate is obtained in the deviation up to 2.06%, between Beggs-Brill and Mukherjee-Brill correlation. On the other hand, the pressure gradient deviation is achieved on a higher deviation due to the different approach of the two correlations. The model can be further developed in the hydraulic pipeline analysis for two-phase flow.

  13. 新型压差式吸附式制冷机的设计%Design of the pressure gradient adsorption refrigerator

    张艳飞; 余晓明


    In this paper, the pressure gradient adsorption refrigerator system was introduced, this system based on the solar energy as the energy source used the osmotic pressure which could take the water from evaporator to the condenser. Water was absorbed by the absorption plate firstly, and then arrived the last circle by the osmotic pressure, and then extruded out from absorption material to condenser intermittently so as to take water out from the evaporator to produce refrigerating effect. The continuous adsorption refrigeration could be achieved by virtue of changing open direction of four - way directional control valve in the solar refrigeration system.%设计了一种以太阳能为驱动力,利用渗透压将水分从蒸发器端传输到冷凝器端的压差式吸附制冷机.水分先在蒸发器端被吸附板吸收,再通过渗透压自动运输到最后环节段,并被膨胀物质间歇式地挤压出吸水材料,进入冷凝器,从而保证水分不断从蒸发器抽出,产生制冷效果.通过改变太阳能制冷系统的四通换向阀的开启方向,实现吸附式制冷系统的连续制冷.

  14. Thermal hydraulic evaluation for an experimental facility to investigate pressurized thermal shock (PTS) in CDTN/CNEN; Avaliacao termo-hidraulica da montagem experimental de choque termico pressurizado do CDTN/CNEN

    Palmieri, Elcio T.; Navarro, Moyses A.; Aronne, Ivam D.; Terra, Jose L. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, MG (Brazil)


    The goal of the work presented in this paper is to provide necessary thermal hydraulics information to the design of an experimental installation to investigate the Pressurized Thermal Shock (PTS) to be implemented at Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN). The envisaged installation has a test section that represents, in a small scale, a pressure vessel of a nuclear reactor. This test section will be heated and then exposed to a PTS in order to evaluate the appearance and development of cracks. To verify the behavior of the temperatures of the pressure vessel after a sudden flood through the annulus, calculations were made using the RELAP5/MOD 3.2.2 gamma code. Different outer radiuses were studied for the annular region. The results showed that the smaller annulus spacing (20 mm) anticipates the wetting of the surface and produces a higher cooling of the external surface, which stays completely wet for a longer time. (author)

  15. Undular Hydraulic Jump

    Oscar Castro-Orgaz


    Full Text Available The transition from subcritical to supercritical flow when the inflow Froude number Fo is close to unity appears in the form of steady state waves called undular hydraulic jump. The characterization of the undular hydraulic jump is complex due to the existence of a non-hydrostatic pressure distribution that invalidates the gradually-varied flow theory, and supercritical shock waves. The objective of this work is to present a mathematical model for the undular hydraulic jump obtained from an approximate integration of the Reynolds equations for turbulent flow assuming that the Reynolds number R is high. Simple analytical solutions are presented to reveal the physics of the theory, and a numerical model is used to integrate the complete equations. The limit of application of the theory is discussed using a wave breaking condition for the inception of a surface roller. The validity of the mathematical predictions is critically assessed using physical data, thereby revealing aspects on which more research is needed

  16. Investigation of the effects of time periodic pressure and engpotential gradients on viscoelastic fluid flow in circular narrow confinements

    Nguyen, Trieu; van der Meer, Devaraj; van den Berg, Albert


    -Boltzmann equation, together with the incompressible Cauchy momentum equation under no-slip boundary conditions for viscoelastic fluid in the case of a combination of time periodic pressure-driven and electro-osmotic flow. The resulting solutions allow us to predict the electrical current and solution flow rate....... As expected from the assumption of linear viscoelasticity, the results satisfy the Onsager reciprocal relation, which is important since it enables an analogy between fluidic networks in this flow configuration and electric circuits. The results especially are of interest for micro-and nanofluidic energy...

  17. Comments on Evanescent Pressure Gradient Response in the Upper Ocean to Subinertial Wind Stress Forcing of Finite Wavelength


    IIl/r’ (b). The dashed curve is the solution presented by response in the upper ocean to subinertial wind stress forcing Codes WM and the solid curve...especially as c hand side of Eq. (3). approaches the inertial frequency f,. h nd s re is 0 With pressure terms included, the expression for The wind ... stress is mixed layer velocities are [Eq. (3.1) in WM], in the 7 = [0, r’ Re(e""’ C)] (6) usual fluid mechanical notation. and following WM. we are

  18. Hydraulic mining method

    Huffman, Lester H.; Knoke, Gerald S.


    A method of hydraulically mining an underground pitched mineral vein comprising drilling a vertical borehole through the earth's lithosphere into the vein and drilling a slant borehole along the footwall of the vein to intersect the vertical borehole. Material is removed from the mineral vein by directing a high pressure water jet thereagainst. The resulting slurry of mineral fragments and water flows along the slant borehole into the lower end of the vertical borehole from where it is pumped upwardly through the vertical borehole to the surface.

  19. Hydraulic fracturing in cells and tissues: fracking meets cell biology.

    Arroyo, Marino; Trepat, Xavier


    The animal body is largely made of water. A small fraction of body water is freely flowing in blood and lymph, but most of it is trapped in hydrogels such as the extracellular matrix (ECM), the cytoskeleton, and chromatin. Besides providing a medium for biological molecules to diffuse, water trapped in hydrogels plays a fundamental mechanical role. This role is well captured by the theory of poroelasticity, which explains how any deformation applied to a hydrogel causes pressure gradients and water flows, much like compressing a sponge squeezes water out of it. Here we review recent evidence that poroelastic pressures and flows can fracture essential biological barriers such as the nuclear envelope, the cellular cortex, and epithelial layers. This type of fracture is known in engineering literature as hydraulic fracturing or 'fracking'.

  20. 底板巷水力冲孔卸压增透技术的研究与应用%Study and Application on Pressure Releasing and Permeability Improved Technology with Hydraulic Flushing in Floor Gateway

    徐东方; 黄渊跃; 罗治顺; 杨献东


    In order to investigate the effect of the pressure releasing and permeability improved technology with hydraulic flushing in floor gateway to improve the seam permeability and to improve the gas drainage rate, a trial was conducted on the pressure releasing and permeability improved technology with hydraulic flushing in No. 1259(3) floor gateway of Puxijing.The results showed that the radius of the pressure releasing and permeability improvement with the hydraulic flushing borehole could reach 4~5 m and would be 1.6~2.0 times higher than the influence radius of the gas drainage with a conventional borehole. Within half month after the hydraulic flushing measures conducted, the average gas drainage concentration of the borehole was 2.77 times higher than the conventional borehole,the average gas flow value was 3.43 times higher than the conventional borehole,the effect of the pressure releasing and permeability improvement was relatively remarkable , the seam permeability was improved and the outburst danger was reduced.%为了考察底板巷水力冲孔卸压增透技术对增加煤层透气性,提高瓦斯抽采效果,在浦溪井1259(3)底板巷实施水力冲孔卸压增透技术试验.结果表明:水力冲孔卸压增透半径达到4~5m,为普通钻孔抽采影响半径的1.6~2.0倍;采取水力冲孔措施的半个月内,钻孔的平均瓦斯抽采浓度是普通钻孔的2.77倍,平均瓦斯流量是普通钻孔的3.43倍,卸压增透效果比较明显,提高了煤层透气性,降低了突出危险性.

  1. Demonstration of a Piston Plug feed System for Feeding Coal/Biomass Mixtures across a Pressure Gradient for Application to a Commercial CBTL System

    Santosh Gangwal


    Producing liquid transportation fuels and power via coal and biomass to liquids (CBTL) and integrated gasification combined cycle (IGCC) processes can significantly improve the nation's energy security. The Energy Independence and Security Act of 2007 mandates increasing renewable fuels nearly 10-fold to >2.3 million barrels per day by 2022. Coal is abundantly available and coal to liquids (CTL) plants can be deployed today, but they will not become sustainable without large scale CO{sub 2} capture and storage. Co-processing of coal and biomass in CBTL processes in a 60 to 40 ratio is an attractive option that has the potential to produce 4 million barrels of transportation fuels per day by 2020 at the same level of CO{sub 2} emission as petroleum. In this work, Southern Research Institute (Southern) has made an attempt to address one of the major barriers to the development of large scale CBTL processes - cost effective/reliable dry-feeding of coal-biomass mixtures into a high pressure vessel representative of commercial entrained-flow gasifiers. Present method for dry coal feeding involves the use of pressurized lock-hopper arrangements that are not only very expensive with large space requirements but also have not been proven for reliably feeding coal-biomass mixtures without the potential problems of segregation and bridging. The project involved the development of a pilot-scale 250 lb/h high pressure dry coal-biomass mixture feeder provided by TKEnergi and proven for feeding biomass at a scale up to 6 ton/day. The aim of this project is to demonstrate cost effective feeding of coal-biomass mixtures (50:50 to 70:30) made from a variety of coals (bituminous, lignite) and biomass (wood, corn stover, switch grass). The feeder uses a hydraulic piston-based approach to produce a series of plugs of the mixture that act as a seal against high back-pressure of the gasification vessel in to which the mixture is being fed. The plugs are then fed one by one via a

  2. Pressure gradient of a two-region solid-liquid flow in horizontal wells; Gradiente de presion de un flujo bifasico solido-liquido de dos regiones en pozos horizontales

    Salazar Mendoza, R.; Garcia Gutierrez, A. [Centro Nacional de Investigacion y Desarrollo Tecnologico (CENIDET), Cuernavaca, Morelos (Mexico); Espinosa Paredes, G. [Universidad Autonoma Metropolitana-Iztapalapa, Mexico, D.F. (Mexico)


    A theoretical analysis is presented for the problem of cutting transport in a two-region, slurry-flow system in horizontal pipes, with a stationary bed of drill cuttings as a porous medium (w-region) below a two-phase dispersed flow (n-region). Volume averaging was applied to derive a rigorous mathematical model where each variable is precisely defined. The model includes volume-averaged transport equations for both the two-phase dispersed flow and the porous-medium regions, and terms from a macroscopic forces balance. The solution of the two-region model allowed evaluation of the behavior of the pressure gradient as a function of velocity, total volume fraction of cuttings, and the relationship between the height of the stationary bed and pipe diameter. It is based on a backward, finite-difference explicit scheme. The simulated physical system is a pipe diameter. It is based on a backward, finite-difference explicit scheme. The simulated physical system is a pipe of 4.135 m in horizontal length and 0.0508 m in diameter. A one dimensional, mesh-centered grid is used, consisting of 10 nodes. The numerical results were compared with experimental data on slurry flows and a good agreement was found. [Spanish] Se presenta un analisis teorico del problema de transporte de recortes de perforacion en pozos horizontales. Se estudia el flujo bifasico solido-liquido en dos regiones donde la region inferior es un lecho estacionario de recortes, considerado como medio poroso, mientras que la region superior es un flujo bifasico disperso solido-liquido. Se aplica el metodo de promediado en volumen para derivar de manera matematicamente rigurosa el modelo de dos regiones. El modelo incluye las ecuaciones de transporte promediadas en volumen para cada region y terminos que resultan de un balance de fuerzas macroscopico. La solucion del modelo permite evaluar el comportamiento del gradiente de presion como funcion de la velocidad, la fraccion de volumen de recortes total y la

  3. Measurement and evaluation of static characteristics of rotary hydraulic motor

    Hružík Lumír


    Full Text Available The paper describes experimental equipment for measurement of static characteristics of rotary hydraulic motor. It is possible to measure flow, pressure, temperature, speed and torque by means of this equipment. It deals with measurement of static characteristics of a gear rotary hydraulic motor. Mineral oil is used as hydraulic liquid in this case. Flow, torque and speed characteristics are evaluated from measured parameters. Measured mechanical-hydraulic, flow and total efficiencies of the rotary hydraulic motor are adduced in the paper. It is possible to diagnose technical conditions of the hydraulic motor (eventually to recommend its exchange from the experimental measurements.

  4. Improper use of the starting pressure gradient of linear flow in the plane radial flow equation%线性流的启动压力梯度不能用于平面径向流方程



    Bear first presented a physical concept and discriminant of the starting pressure gradient in 1972 when he studied the applied lower limit of the Darcy law. And then Professor Ge Jiali introduced the starting pressure gradient to China in 1982. The so-called starting pressure gradient refers to a pressure gradient that makes a fluid in fluid-saturated cores begin to flow. It should be pointed out that the pressure gradient of linear flow is directly proportional to the flow rate, while the starting pressure gradient is a constant. The pressure gradient of plane radial flow is directly proportional to the flow rate but inversely to the radial radius. Moreover, the starting pressure7 gradient at a position of different radial radius is variable. It is controversial for the correctness to have directly applied the Bear's starting pressure gradient and discriminant of linear flow to the plane radial flow equation by some researchers. Theoretically, the paper analyzed both the pressure gradient and starting pressure gradient of linear flow and plane radial flow and proposed the conception of starting flow rate. At the same time, a more applicable method to evaluate the starting drawdown pressure and starting bottomhole flowing pressure of low permeability tight reservoirs was proposed.%启动压力梯度的物理概念及判别式是Bear于1972年在利用岩心测试资料研究达西定律的应用下限时提出来的,葛家理教授首次介绍到我国.所谓启动压力梯度,是指流体在饱和的岩心开始发生流动时的压力梯度.应当指出,线性流的压力梯度与流量成正比,启动压力梯度为常数;平面径向流的压力梯度与流量成正比,与径向半径成反比,而且,不同径向半径位置的启动压力梯度是不同的.有关学者将线性流启动的压力梯度及判别式直接用于平面径向流方程的正确性值得质疑.笔者对线性流和平面径向流的压力梯度和启动压力梯度问题进行了

  5. Hydraulic Actuators with Autonomous Hydraulic Supply for the Mainline Aircrafts

    I. S. Shumilov


    Full Text Available Applied in the aircraft control systems, hydraulic servo actuators with autonomous hydraulic supply, so-called, hydraulic actuators of integrated configuration, i.e. combination of a source of hydraulic power and its load in the single unit, are aimed at increasing control system reliability both owing to elimination of the pipelines connecting the actuator to the hydraulic supply source, and owing to avoidance of influence of other loads failure on the actuator operability. Their purpose is also to raise control system survivability by eliminating the long pipeline communications and their replacing for the electro-conductive power supply system, thus reducing the vulnerability of systems. The main reason for a delayed application of the hydraulic actuators in the cutting-edge aircrafts was that such aircrafts require hydraulic actuators of considerably higher power with considerable heat releases, which caused an unacceptable overheat of the hydraulic actuators. Positive and negative sides of the hydraulic actuators, their alternative options of increased reliability and survivability, local hydraulic systems as an advanced alternative to independent hydraulic actuators are considered.Now to use hydraulic actuators in mainline aircrafts is inexpedient since there are the unfairly large number of the problems reducing, first and last, safety of flights, with no essential weight and operational advantages. Still works to create competitive hydraulic actuators ought to be continued.Application of local hydraulic systems (LHS will allow us to reduce length of pressure head and drain pipelines and mass of pipelines, as well as to raise their general fail-safety and survivability. Application of the LHS principle will allow us to use a majority of steering drive advantages. It is necessary to allocate especially the following:- ease of meeting requirements for the non-local spread of the engine weight;- essentially reducing length and weight of

  6. Pressure shifts and abundance gradients in the atmosphere of the DAZ white dwarf GALEX J193156.8+011745

    Vennes, S; Nemeth, P


    We present a detailed model atmosphere analysis of high-dispersion and high signal-to-noise ratio spectra of the heavily polluted DAZ white dwarf GALEX J1931+0117. The spectra obtained with the VLT-Kueyen/UV-Visual Echelle Spectrograph show several well-resolved Si II spectral lines enabling a study of pressure effects on line profiles. We observed large Stark shifts in silicon lines in agreement with theoretical predictions and laboratory measurements. Taking into account Stark shifts in the calculation of synthetic spectra we reduced the scatter in individual line radial velocity measurements from ~ 3 to < 1 km/s. We present revised abundances of O, Mg, Si, Ca, and Fe based on a critical review of line broadening parameters and oscillator strengths. The new measurements are generally in agreement with our previous analysis with the exception of magnesium with a revised abundance a factor of two lower than previously estimated. The magnesium, silicon and iron abundances exceed solar abundances, but the ox...

  7. 反转压水反应堆热工水力特性初步研究%The Preliminary Research of Thermal-Hydraulic Behavior of an Inverted Pressurized Water Reactor

    刘杰; 于涛; 谢金森; 曾正魁; 秦勉


    In this paper, CFD analysis is carried out to study the single fuel element and the coolant channel flow field of the Inverted Pressurized Water Reactor (IPWR) using commercial CFD code FLUENT,which analyses and compares the thermal-hydraulic char- acteristics of different grid size. The calculation results show that the dimensions of the IPWR fuel cell has greater influence on the temperature and heat transfer characteristics of coolant, and the study provides preliminary reference and basis for the next design of the IPWR fuel cell,fuel assembly, reactor core and the thermal-hydraulic analysis.%采用CFD软件FLUENT对反转压水反应堆(IPWR:Inverted PressurizedWaterReactor)单个燃料元件及冷却剂通道流场进行了数值模拟计算,分析比较了不同栅格尺寸情况下的热工水力特性.计算结果表明,栅格尺寸对IPWR燃料元件温度及冷却剂流动传热特性有较大影响,为今后IPWR燃料栅元、组件、堆芯设计和热工水力分析提供了初步参考和依据.

  8. 组合式增压液压缸在立车横梁卸荷中的应用%The Application of Combined Pressurized Hydraulic Cylinder Using in Vertical Lathe Beams Unloading



    应用组合式增压液压缸对重型双柱立车横梁进行卸荷,使刀架50%的重量作用在横梁卸荷梁上,以减小横梁导轨的比压及变形,从而保证机床几何精度检验G5项规定要求。%A combined pressurized hydraulic cylinder is used to unload heavy-duty double column vertical lathe beams. In that way, 50%weight will act on unloading beams, in order to reduce the beam rails the pressure and de-formation. All these can guarantee geometric tests matching for machines G5 entry requirements.

  9. Hydraulic responses of whole vines and individual roots of kiwifruit (Actinidia chinensis) following root severance.

    Black, Marykate Z; Patterson, Kevin J; Minchin, Peter E H; Gould, Kevin S; Clearwater, Michael J


    Whole vine (K(plant)) and individual root (K(root)) hydraulic conductances were measured in kiwifruit (Actinidia chinensis Planch. var. chinensis 'Hort16A') vines to observe hydraulic responses following partial root system excision. Heat dissipation and compensation heat pulse techniques were used to measure sap flow in trunks and individual roots, respectively. Sap flux and measurements of xylem pressure potential (Ψ) were used to calculate K(plant) and K(root) in vines with zero and ∼80% of roots severed. Whole vine transpiration (E), Ψ and K(plant) were significantly reduced within 24 h of root pruning, and did not recover within 6 weeks. Sap flux in intact roots increased within 24 h of root pruning, driven by an increase in the pressure gradient between the soil and canopy and without any change in root hydraulic conductance. Photosynthesis (A) and stomatal conductance (g(s)) were reduced, without significant effects on leaf internal CO(2) concentration (c(i)). Shoot growth rates were maintained; fruit growth and dry matter content were increased following pruning. The woody roots of kiwifruit did not demonstrate a rapid dynamic response to root system damage as has been observed previously in monocot seedlings. Increased sap flux in intact roots with no change in K(root) and only a moderate decline in shoot A suggests that under normal growing conditions root hydraulic conductance greatly exceeds requirements for adequate shoot hydration.

  10. Hydraulic Presses,


    and storage tanks of liquids and gases under the low and high pressure (bottom, frontal walls, shell, etc.), part of housings and skin/ sheathing of...and workers under the severe conditions, frequently manufacture from alloy chrome -nickel and chrome -molybdenum steel; the hardness of the working

  11. 液力透平非定常压力脉动的数值计算与分析%Simulation and analysis of unsteady pressure fluctuation in hydraulic turbine

    杨孙圣; 孔繁余; 张新鹏; 黄志攀; 成军


    液力透平内部流场的非定常压力脉动是影响机组运行稳定性的关键因素之一,为了研究液力透平内部压力脉动,采用流场分析软件CFX对液力透平内部流场进行了三维非定常数值模拟,通过设置监测点,得到了不同位置处的压力脉动结果,并对压力脉动进行了频域分析.结果表明,液力透平内部压力沿着流道逐渐减弱;蜗壳环形部分入口位置和割舍处压力脉动较小,割舍前端和蜗壳中部位置处压力脉动较大,压力脉动主频为转频的2倍;叶轮内部的压力脉动在液力透平各过流部件的脉动中最为强烈,最大压力脉动发生在叶轮中间位置,压力脉动主频为叶频的2倍;尾水管内的压力脉动沿着尾水管流道逐渐减弱,压力脉动主频与蜗壳内部的压力脉动主频相同,为转频的2倍.%Pressure pulsation of internal flow field within pump as turbine is one of the major factors affecting the stability of turbine unit. To research the unsteady pressure field in pump as turbine, computational fluid dynamics software CFX was adopted in the unsteady flow field analysis. Pressure pulsation results at various monitoring points were acquired and frequency analyses were performed based on these results. Results show that the pressure value decreases along the flow channel of hydraulic turbine. The pressure pulsations at volute cut water and the inlet of volute spiral development part are small. The main frequency of pressure pulsation in volute is two times of the impeller rotational frequency. The most intensive pressure pulsation of hydraulic part in hydraulic turbine is impeller and the most intensive location happens at the middle of impeller passage. The main frequency of impeller pressure pulsation is two times of the blade passing frequency. The pressure pulsation in outlet pipe gradually decreases along the pipe, and its main frequency of pressure pulsation is two times of the impeller rotational

  12. Transitional Boundary Layers Under the Influence of High Free Stream Turbulence, Intensive Wall Cooling and High Pressure Gradients in Hot Gas Circulation. Ph.D. Thesis - Technische Hochschule, Karlsruhe, 1985

    Rued, Klaus


    The requirements for fundamental experimental studies of the influence of free stream turbulence, pressure gradients and wall cooling are discussed. Under turbine-like free stream conditions, comprehensive tests of transitional boundary layers with laminar, reversing and turbulent flow increments were performed to decouple the effects of the parameters and to determine the effects during mutual interaction.

  13. 流体属性可变的水压轴向柱塞泵压力流量模型%Pressure and flow characteristic modeling of water hydraulic axial piston pump based on variable fluid properties

    翟江; 周华


    Considering cavitation due to the high saturation vapor pressure of water and main fluid properties variation-with pressure, a mathematical model of the dynamic pressure and flow characteristics of a water hydraulic axial piston pump was built. The model was programmed in a MATLAB/Simulink platform and a prototype of water hydraulic pump was simulated as an example. The pressure,flow and cavitation characteristics of the prototype were analyzed based on simulation results. The investigation shows that the average discharge flow of the pump will decrease, obvious cavitation will occur in the cylinder chambers that are in suction process,flow and pressure ripple will be severe when the inlet pressure is low. As the inlet pressure increases, the cavitation in the cylinder chambers will reduce and only occur in transition regions between discharge and suction. The internal leakage of the pump is mainly due to the gap flow of the slipper/swash plate combination and the cylinder block/valve plate combination, and the effects of the piston/cylinder-block can be ignored.%考虑了由于水的高饱和蒸汽压引起的空化及水的主要流体属性随压力变化的特性,建立了水压轴向柱塞泵的压力流量特性模型.以研制的水压轴向柱塞泵样机为例在MATLAB/Simulink环境下编程仿真,分析了泵的压力、流量和空化等特性.研究结果表明:泵入口压力较低时会引起排水流量的下降,在吸水区的缸体柱塞腔内出现明显的空化,泵出口的流量脉动和压力脉动大幅增加;提高泵的入口压力能够减小缸体柱塞腔内的空化程度,此时空化主要发生在由排水向吸水变换的瞬间;泵的内泄漏主要以滑靴副和配流副的泄露为主,柱塞副的泄露可以忽略.

  14. Buoyancy-Driven Heat Transfer During Application of a Thermal Gradient for the Study of Vapor Deposition at Low Pressure Using and Ideal Gas

    Frazier, D. O.; Hung, R. J.; Paley, M. S.; Penn, B. G.; Long, Y. T.


    A mathematical model has been developed to determine heat transfer during vapor deposition of source materials under a variety of orientations relative to gravitational accelerations. The model demonstrates that convection can occur at total pressures as low as 10-2 mm Hg. Through numerical computation, using physical material parameters of air, a series of time steps demonstrates the development of flow and temperature profiles during the course of vapor deposition. These computations show that in unit gravity vapor deposition occurs by transport through a fairly complicated circulating flow pattern when applying heat to the bottom of the vessel with parallel orientation with respect to the gravity vector. The model material parameters for air predict the effect of kinematic viscosity to be of the same order as thermal diffusivity, which is the case for Prandtl number approx. 1 fluids. Qualitative agreement between experiment and the model indicates that 6-(2-methyl-4-nitroanilino)-2,4-hexadiyn-l-ol (DAMNA) at these pressures indeed approximates an ideal gas at the experiment temperatures, and may validate the use of air physical constants. It is apparent that complicated nonuniform temperature distribution in the vapor could dramatically affect the homogeneity, orientation, and quality of deposited films. The experimental test i's a qualitative comparison of film thickness using ultraviolet-visible spectroscopy on films generated in appropriately oriented vapor deposition cells. In the case where heating of the reaction vessel occurs from the top, deposition of vapor does not normally occur by convection due to a stable stratified medium. When vapor deposition occurs in vessels heated at the bottom, but oriented relative to the gravity vector between these two extremes, horizontal thermal gradients induce a complex flow pattern. In the plane parallel to the tilt axis, the flow pattern is symmetrical and opposite in direction from that where the vessel is

  15. Pressure Control Characteristics of Main Transmission System of Hydraulic Transmission Wind Energy Conversion System%液压型风力发电机组主传动系统压力控制特性研究

    艾超; 叶壮壮; 孔祥东; 廖利辉


    Fixed displacement pump-variable displacement motor is the main drive system of hy-draulic type wind turbine,the system is controlled by a variable displacement mechanism after grid-connected.To study the pressure control characteristics,a mathematical model was built and the trans-fer function describing the pressure to the position of the motor swash plate was derived.Compared with the identified model obtained from data identification in MATLAB system,the built model was verified,which laid theoretical and test foundation for further maximum power point tracking(MPPT) based on pressure control in hydraulic type wind turbine.%液压型风力发电机组主传动系统为定量泵变量马达闭式系统,风机并网后依靠变量马达变排量机构对系统进行控制。研究了系统压力控制特性,建立了并网后主传动系统数学模型,得出了系统压力对马达斜盘摆角的传递函数。利用 MATLAB 辨识工具箱,根据实验数据,对系统压力控制模型进行数据辨识,并与理论模型进行对比,验证了理论模型的准确性,为液压型风力发电机组通过压力控制实现最佳功率追踪控制奠定理论与实验基础。

  16. Experimental Study For Pizometric Head Distribution Under Hydraulic Structures

    Dr. Najm Obaid Salim Alghazali


    Full Text Available Abstract In this research the experimental method by using Hydraulic modeling used to determination the flow net in order to analyses seepage flow through single- layer soil foundation underneath hydraulic structure. as well as steady the consequence of the cut-off inclination angle on exit gradient factor of safety uplift pressure and quantity of seepage by using seepage tank were designed in the laboratory with proper dimensions with two cutoffs . The physical model seepage tank was designed in two downstream cutoff angles which are 90 and 120 and upstream cutoff angles 90 45 120. After steady state flow the flow line is constructed by dye injection in the soil from the upstream side in front view of the seepage tank and the equipotentials line can be constructed by pizometer fixed to measure the total head. From the result It is concluded that using downstream cut-off inclined towards the downstream side with amp1256 equal 120 that given value of redaction 25 is beneficial in increasing the safety factor against the piping phenomenon. using upstream cut-off inclined towards the downstream side with amp1256 equal 45 that given value of redaction 52 is beneficial in decreasing uplift pressure and quantity of seepage.

  17. Portal hypertension in patients with cirrhosis: indirect assessment of hepatic venous pressure gradient by measuring azygos flow with 2D-cine phase-contrast magnetic resonance imaging.

    Gouya, Hervé; Grabar, Sophie; Vignaux, Olivier; Saade, Anastasia; Pol, Stanislas; Legmann, Paul; Sogni, Philippe


    To measure azygos, portal and aortic flow by two-dimensional cine phase-contrast magnetic resonance imaging (2D-cine PC MRI), and to compare the MRI values to hepatic venous pressure gradient (HVPG) measurements, in patients with cirrhosis. Sixty-nine patients with cirrhosis were prospectively included. All patients underwent HVPG measurements, upper gastrointestinal endoscopy and 2D-cine PC MRI measurements of azygos, portal and aortic blood flow. Univariate and multivariate regression analyses were used to evaluate the correlation between the blood flow and HVPG. The performance of 2D-cine PC MRI to diagnose severe portal hypertension (HVPG ≥ 16 mmHg) was determined by receiver operating characteristic curve (ROC) analysis, and area under the curves (AUC) were compared. Azygos and aortic flow values were associated with HVPG in univariate linear regression model. Azygos flow (p cine PC MRI is a promising technique to evaluate significant portal hypertension in patients with cirrhosis. • Noninvasive HVPG assessment can be performed with MRI azygos flow. • Azygos MRI flow is an easy-to-measure marker to detect significant portal hypertension. • MRI flow is more specific that varice grade to detect portal hypertension.

  18. Design of a laboratory hydraulic device for testing of hydraulic pumps

    Pavel Máchal


    Full Text Available The present contribution deals with solves problem of research of testing device to monitor of hydrostatic pumps durability about dynamic loading under laboratory conditions. When carrying out the design of testing device are based on load characteristics of tractor hydraulic circuit, the individual characteristics of hydraulic components and performed calculations. Load characteristics on the tractors CASE IH Magnum 310, JOHN DEERE 8100, ZETOR FORTERRA 114 41 and Fendt 926 Vario were measured. Design of a hydraulic laboratory device is based on the need for testing new types of hydraulic pumps or various types of hydraulic fluids. When creating of hydraulic device we focused on testing hydraulic pumps used in agricultural and forestry tractors. Proportional pressure control valve is an active member of the hydraulic device, which provides change of a continuous control signal into relative pressure of operating fluid. The advantage of a designed hydraulic system is possibility of simulation of dynamic operating loading, which is obtained by measurement under real conditions, and thereby creates laboratory conditions as close to real conditions as possible. The laboratory device is constructed at the Department of Transport and Handling, Faculty of Engineering, Slovak University of Agriculture in Nitra.

  19. Modeling and Simulation of Hydraulic Engine Mounts

    DUAN Shanzhong; Marshall McNea


    Hydraulic engine mounts are widely used in automotive powertrains for vibration isolation.A lumped mechanical parameter model is a traditional approach to model and simulate such mounts.This paper presents a dynamical model of a passive hydraulic engine mount with a double-chamber,an inertia track,a decoupler,and a plunger.The model is developed based on analogy between electrical systems and mechanical-hydraulic systems.The model is established to capture both low and high frequency dynatmic behaviors of the hydraulic mount.The model will be further used to find the approximate pulse responses of the mounts in terms of the force transmission and top chamber pressure.The close form solution from the simplifiod linear model may provide some insight into the highly nonlinear behavior of the mounts.Based on the model,computer simulation has been carried out to study dynamic performance of the hydraulic mount.

  20. Mechatronic Hydraulic Drive with Regulator, Based on Artificial Neural Network

    Burennikov, Y.; Kozlov, L.; Pyliavets, V.; Piontkevych, O.


    Mechatronic hydraulic drives, based on variable pump, proportional hydraulics and controllers find wide application in technological machines and testing equipment. Mechatronic hydraulic drives provide necessary parameters of actuating elements motion with the possibility of their correction in case of external loads change. This enables to improve the quality of working operations, increase the capacity of machines. The scheme of mechatronic hydraulic drive, based on the pump, hydraulic cylinder, proportional valve with electrohydraulic control and programmable controller is suggested. Algorithm for the control of mechatronic hydraulic drive to provide necessary pressure change law in hydraulic cylinder is developed. For the realization of control algorithm in the controller artificial neural networks are used. Mathematical model of mechatronic hydraulic drive, enabling to create the training base for adjustment of artificial neural networks of the regulator is developed.

  1. Analysis on Performance and Fault Relation for Automatic Pressure Keeping Weight Type Hydraulic Control Butterfly Valve%自动保压重锤式液控蝶阀性能与故障关系分析

    陈培兴; 狄翠霞


    自动保压重锤式液控蝶阀采用二阶段关闭,与普通阀门有所不同.简单介绍蝶阀可能出现的主要故障及其原因,通过具体实例说明如何根据二阶段液控蝶阀的最主要性能指标即开阀时间、快关时间、慢关时间的变化及相互之间的关系排除故障.%Because two-stage closing is adopted in automatic pressure keeping weight type hydraulic control butterfly valve, it is different from common valves. The main faults and causes of the butterfly valve were introduced. Through an example, it was shown that how to remove faults according to the main performance indexes changes of the hydraulic controlled butterfly valve and their mutual relations.

  2. Status and Trends of Thermal-Hydraulic System Codes for Nuclear Power Plants With Pressurized Water Reactors%压水堆核电站热工水力系统程序的研发现状与趋势

    刘志弢; 秦本科; 解衡; 王炳华


    比较分析了目前世界上典型的压水堆核电站热工水力系统程序的研发历程、发展现状、应用范围,着重指出了最佳估算、程序耦合、程序评估在热工水力系统程序研发中的重要作用,阐述了各国热工水力系统程序研发模式对我国自主创新的借鉴意义.%Research and development of thermal-hydraulic system codes for nuclear power plants with pressurized water reactors were analyzed on their history, status and application ranges. The important roles of best-estimate methodology, codes coupling and codes qualification were pointed out. The development models of thermal-hydraulic system codes around the world provide references to China's self-innovation.

  3. Hydraulic fracture during epithelial stretching

    Casares, Laura; Vincent, Romaric; Zalvidea, Dobryna; Campillo, Noelia; Navajas, Daniel; Arroyo, Marino; Trepat, Xavier


    The origin of fracture in epithelial cell sheets subject to stretch is commonly attributed to excess tension in the cells’ cytoskeleton, in the plasma membrane, or in cell-cell contacts. Here, we demonstrate that for a variety of synthetic and physiological hydrogel substrates the formation of epithelial cracks is caused by tissue stretching independently of epithelial tension. We show that the origin of the cracks is hydraulic; they result from a transient pressure build-up in the substrate during stretch and compression manoeuvres. After pressure equilibration, cracks heal readily through actomyosin-dependent mechanisms. The observed phenomenology is captured by the theory of poroelasticity, which predicts the size and healing dynamics of epithelial cracks as a function of the stiffness, geometry and composition of the hydrogel substrate. Our findings demonstrate that epithelial integrity is determined in a tension-independent manner by the coupling between tissue stretching and matrix hydraulics.

  4. Detection of cavitation vortex in hydraulic turbines using acoustic techniques

    Candel, I.; Bunea, F.; Dunca, G.; Bucur, D. M.; Ioana, C.; Reeb, B.; Ciocan, G. D.


    Cavitation phenomena are known for their destructive capacity in hydraulic machineries and are caused by the pressure decrease followed by an implosion when the cavitation bubbles find an adverse pressure gradient. A helical vortex appears in the turbine diffuser cone at partial flow rate operation and can be cavitating in its core. Cavity volumes and vortex frequencies vary with the under-pressure level. If the vortex frequency comes close to one of the eigen frequencies of the turbine, a resonance phenomenon may occur, the unsteady fluctuations can be amplified and lead to important turbine and hydraulic circuit damage. Conventional cavitation vortex detection techniques are based on passive devices (pressure sensors or accelerometers). Limited sensor bandwidths and low frequency response limit the vortex detection and characterization information provided by the passive techniques. In order to go beyond these techniques and develop a new active one that will remove these drawbacks, previous work in the field has shown that techniques based on acoustic signals using adapted signal content to a particular hydraulic situation, can be more robust and accurate. The cavitation vortex effects in the water flow profile downstream hydraulic turbines runner are responsible for signal content modifications. Basic signal techniques use narrow band signals traveling inside the flow from an emitting transducer to a receiving one (active sensors). Emissions of wide band signals in the flow during the apparition and development of the vortex embeds changes in the received signals. Signal processing methods are used to estimate the cavitation apparition and evolution. Tests done in a reduced scale facility showed that due to the increasing flow rate, the signal -- vortex interaction is seen as modifications on the received signal's high order statistics and bandwidth. Wide band acoustic transducers have a higher dynamic range over mechanical elements; the system's reaction time

  5. Evaluation of TASS/SMR with steady state analysis of high temperature/high pressure thermal-hydraulic test facility (VISTA)

    Jang, Dong Ju; Choi, Yong Won; Park, Chang Hwan; Lee, Un Chul [Seoul National University, Seoul (Korea, Republic of); Hwang, Young Dong; Lee, Kyu Hyung; Kim, Hee Chul [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)


    The TASS/SMR code is the revised version of the TASS code, which is the result of code development effort of KAERI since 1997, for safety analysis of NPP coolant system. Lately, it is scheduled to evaluate thermal-hydraulic phenomena during several transient periods of SMART-P with TASS/SMR. To establish the pertinence of the calculative results of TASS/SMR, there should be a process of validation and verification of TASS/SMR. The objective of this study is validating the numerical capability and reliability of TASS/SMR with steady state analysis of VISTA (Experimental Verification by Integral Simulation of Transient and Accidents) that was designed to simulate SMART-P.

  6. Hydraulic Calculation and Purging Coefficient Determination for High Pressure Steam Network%高压蒸汽管网的水力学计算及吹扫参数确定

    袁良正; 贾金洁


    Exampled with a large scale of coal-to-natural gas plant, hydraulic and purging parameters for high pressure and superheated steam pipe network were studied in this article. By using chemical process simulation software ASPEN HYSIS, the model of steam pipeline net was established and then it was calculated, with which the method based on quantitative analysis for calculating steam purging parameters was found.%以某大型煤制天然气项目为例,对高压过热蒸汽管网的水力学及吹扫参数进行研究。采用化工流程模拟软件ASPEN HYSYS对蒸汽管网进行建模计算,找到了一种定量分析计算蒸汽吹扫参数的方法。


    Federal Emergency Management Agency, Department of Homeland Security — Hydraulic data include spatial datasets and data tables necessary for documenting the hydraulic analysis for estimating flood stages for a flood insurance study. It...

  8. Hydraulic Hybrid Vehicles

    EPA and the United Parcel Service (UPS) have developed a hydraulic hybrid delivery vehicle to explore and demonstrate the environmental benefits of the hydraulic hybrid for urban pick-up and delivery fleets.

  9. Hydraulics and pneumatics a technician's and engineer's guide

    Parr, Andrew


    Hydraulics and Pneumatics: A Technician's and Engineer's Guide provides an introduction to the components and operation of a hydraulic or pneumatic system. This book discusses the main advantages and disadvantages of pneumatic or hydraulic systems.Organized into eight chapters, this book begins with an overview of industrial prime movers. This text then examines the three different types of positive displacement pump used in hydraulic systems, namely, gear pumps, vane pumps, and piston pumps. Other chapters consider the pressure in a hydraulic system, which can be quickly and easily controlled

  10. Revisiting the quest for a universal log-law and the role of pressure gradient in "canonical" wall-bounded turbulent flows

    Monkewitz, Peter A.


    The trinity of so-called "canonical" wall-bounded turbulent flows, comprising the zero pressure gradient turbulent boundary layer, abbreviated ZPG TBL, turbulent pipe flow, and channel/duct flows has continued to receive intense attention as new and more reliable experimental data have become available. Nevertheless, the debate on whether the logarithmic part of the mean velocity profile, in particular the Kármán constant κ , is identical for these three canonical flows or flow-dependent is still ongoing. In this paper, the asymptotic matching requirement of equal κ in the logarithmic overlap layer, which links the inner and outer flow regions, and in the expression for the centerline/free-stream velocity is reiterated and shown to preclude a universal logarithmic overlap layer in the three canonical flows. However, the majority of pipe and channel flow studies at friction Reynolds numbers Reτ below ≈104 extract from near-wall profiles the same κ of 0.38-0.39 as in the ZPG TBL. This apparent contradiction is resolved by a careful reanalysis of high-quality mean velocity profiles in the Princeton "Superpipe" and other pipes, channels, and ducts, which shows that the mean velocity in a near-wall region extending to around 700 "+" units in channels and ducts and 500 "+" units in pipes is the same as in the ZPG TBL. In other words, all the "canonical" flow profiles contain the lower end of the ZPG TBL log-region, which starts at a wall distance of 150 -200 "+" units with a universal κ of κZPG≈0.384 . This interior log-region is followed by a second logarithmic region with a flow specific κ >κZPG , which increases monotonically with pressure gradient. This second, exterior log-layer is the actual overlap layer matching up to the outer expansion, which implies equality of the exterior κ and κCL obtained from the evolution of the respective centerline velocity with Reynolds number. The location of the switch-over point implies furthermore that this second

  11. Blood pressure gradients and cardiovascular risk factors in urban and rural populations in Abia State South Eastern Nigeria using the WHO STEPwise approach.

    Ikechi Gareth Okpechi

    Full Text Available BACKGROUND: Developing countries of sub-Saharan Africa (SSA face a double burden of non-communicable diseases (NCDs and communicable diseases. As high blood pressure (BP is a common global cardiovascular (CV disorder associated with high morbidity and mortality, the relationship between gradients of BP and other CV risk factors was assessed in Abia State, Nigeria. METHODS: Using the WHO STEPwise approach to surveillance of chronic disease risk factors, we conducted a population-based cross-sectional survey in Abia state, Nigeria from August 2011 to March 2012. Data collected at various steps included: demographic and behavioral risk factors (Step 1; BP and anthropometric measurements (Step 2, and fasting blood cholesterol and glucose (Step 3. RESULTS: Of the 2983 subjects with complete data for analysis, 52.1% were females and 53.2% were rural dwellers. Overall, the distribution of selected CV disease risk factors was diabetes (3.6%, hypertension (31.4%, cigarette smoking (13.3%, use of smokeless tobacco (4.8%, physical inactivity (64.2% and being overweight or obese (33.7%. Presence of hypertension, excessive intake of alcohol, smoking (cigarette and smokeless tobacco and physical inactivity occurred more frequently in males than in females (p<0.05; while low income, lack of any formal education and use of smokeless tobacco were seen more frequently in rural dwellers than in those living in urban areas (p<0.05. The frequency of selected CV risk factors increased as BP was graded from optimal, normal to hypertension; and high BP correlated with age, gender, smokeless tobacco, overweight or obesity, annual income and level of education. CONCLUSION: Given the high prevalence of hypertension in this part of Nigeria, there is an urgent need to focus on the reduction of preventable CV risk factors we have observed to be associated with hypertension, in order to effectively reduce the burden of NCDs in Africa.

  12. 一体式电液复合制动系统轮缸压力的精细调节%Wheel cylinder pressure fine regulation for integrated electro-hydraulic brake system

    刘杨; 孙泽昌; 邹小琼; 王猛


    Wheel cylinder pressure fine regulation was studied for electro‐hydraulic brake system with an integrated master cylinder .Pressure regulation process and system structural characteristics were analyzed .The impact of brake disc gap on pressure regulation was studied ,pressure control dividing point of non‐linear and linear region was determined ,using the ladder method and interpolation table method to estimate cylinder pressure ,also the impact of w heel cylinder piston hysteresis characteris‐tics on linear region was considered ,and then the segmented‐ladder‐lookup fine regulation strategy was developed .Hardware in the loop simulation bench was built using xPC target to verify the pres‐sure regulation performance by sine target pressure test and comparisons of single increase‐decrease interpolation table strategy and the proposed one .Test results show that the wheel cylinder pressure could keep up with the target curve ,and the proposed system structure and pressure regulation meth‐od could meet the pressure control requirements .%针对基于一体式主缸的电液复合制动系统,进行了轮缸压力的精细调节研究,分析了一体式复合制动系统轮缸压力调节过程及其结构特点。探讨了制动间隙对盘式制动器轮缸压力调节的影响,确定了轮缸压力控制的非线性区及线性区,采用阶梯估算和基本插值数表的方法对轮缸压力进行估计,并考虑了线性区轮缸活塞运动迟滞特性对插值数表的影响,综合上述因素制定了分段阶梯查表的轮缸压力精细调节策略。采用xPC target搭建了硬件在环仿真台架,进行了正弦曲线跟随和与单一增/减压数表法的对比试验。试验结果表明:轮缸压力能够实时跟随目标曲线变化,所提出的结构及控制方法能够满足轮缸压力精细调节的控制需求。

  13. An evaluation of calculation procedures affecting the constituent factors of equivalent circulating density for drilling hydraulics

    Bailey, William J.


    This Dr. ing. thesis covers a study of drilling hydraulics offshore. The purpose of drilling hydraulics is to provide information about downhole pressure, suitable surface pump rates, the quality of hole cleaning and optimum tripping speeds during drilling operations. Main fields covered are drilling hydraulics, fluid characterisation, pressure losses, and equivalent circulating density. 197 refs., 23 figs., 22 tabs.

  14. Final report on key comparison EURAMET.M.P-K13 in the range 50 MPa to 500 MPa of hydraulic gauge pressure

    Kocas, I.; Sabuga, W.; Bergoglio, M.; Eltaweel, A.; Korasie, C.; Farar, P.; Setina, J.; Waller, B.; Durgut, Y.


    The regional key comparison EURAMET.M.P-K13 for pressure measurements in liquid media from 50 MPa to 500 MPa was piloted by the TÜBİTAK UME Pressure Group Laboratories, Turkey. The transfer standard was a DH-Budenberg pressure balance with a free deformation piston-cylinder unit of 2 mm2 nominal effective area. Six laboratories from the EURAMET region, namely PTB, INRIM, SMU, IMT, NPL and UME, and two laboratories from the AFRIMETS region, NIS and NMISA participated in this comparison. Participant laboratories and countries are given in the bottom of the page. PTB participated in this comparison to provide a link to corresponding 500 MPa CCM key comparison CCM.P-K13. The results of all participants excepting NMISA and NPL were found to be consistent with the reference value of the actual comparison and of CCM.P-K13 within their claimed uncertainties (k = 2), at all pressures. Compared in pairs all laboratories with exception of NPL and NMISA demonstrate their agreement with each other within the expanded uncertainties (k = 2) at all pressures. The results are therefore considered to be satisfactory. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database The final report has been peer-reviewed and approved for publication by CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).


    Xu Bing; Ma Jien; Lin Jianjie


    The computational flow rate feedback and control method, which can be used in proportional valve controlled hydraulic elevators, is discussed and analyzed. In a hydraulic elevator with this method, microprocessor receives pressure information from the pressure transducers and computes the flow rate through the proportional valve based on pressure-flow conversion real time algorithm. This hydraulic elevator is of lower cost and energy consumption than the conventional closed loop control hydraulic elevator whose flow rate is measured by a flow meter. Experiments are carried out on a test rig which could simulate the load of hydraulic elevator. According to the experiment results, the means to modify the pressure-flow conversion algorithm are pointed out.

  16. Hydraulic test for evaluation of hydrophone VSP

    Yabuuchi, Satoshi; Koide, Kaoru [Power Reactor and Nuclear Fuel Development Corp., Toki, Gifu (Japan). Tono Geoscience Center


    This hydraulic test was carried out at the test site of Tono Geoscience Center, Mizunami-shi, Gifu Pref. in order to evaluate the reliability of the hydraulic conductivity estimated from hydrophone VSP experiment. From March to April 1997, we carried out measurements of pore-water pressure at five depths and permeability tests at seven depths down to G.L.-300m, within a borehole drilled in granitic rock. We compared the results of hydraulic test with hydrophone VSP experiment on condition that a single open fracture existed, and we obtained two notable results. First, for the granitic rock at which a single open fracture was found by BTV and also detected by hydrophone VSP experiment, the hydraulic conductivity was 1.54 x 10{sup -7} cm/sec, while for the same granitic rock at which another single open fracture was found by BTV but not detected by hydrophone VSP experiment, the hydraulic conductivity was less than 6 x 10{sup -10} cm/sec. Second, we converted the hydraulic conductivity of 1.54 x 10{sup -7} cm/sec which was obtained in a hydraulic test section of length 2.5 m into an equivalent value for a single open fracture of width 1 mm. The converted value (3.8 x 10{sup -4} cm/sec) was similar to the hydraulic conductivity estimated from hydrophone VSP experiment. In conclusion, the hydraulic test result shows that hydrophone VSP is useful to estimate an approximate hydraulic conductivity of a single open fracture. (author)

  17. Gradient networks

    Toroczkai, Zoltán; Kozma, Balázs; Bassler, Kevin E.; Hengartner, N. W.; Korniss, G.


    Gradient networks are defined (Toroczkai and Bassler 2004 Nature 428 716) as directed graphs formed by local gradients of a scalar field distributed on the nodes of a substrate network G. We present the derivation for some of the general properties of gradient graphs and give an exact expression for the in-degree distribution R(l) of the gradient network when the substrate is a binomial (Erd{\\;\\kern -0.10em \\raise -0.35ex \\{{^{^{\\prime\\prime}}}}\\kern -0.57em \\o} s-Rényi) random graph, G_{N,p} , and the scalars are independent identically distributed (i.i.d.) random variables. We show that in the limit N \\to \\infty, p \\to 0, z = pN = \\mbox{const} \\gg 1, R(l)\\propto l^{-1} for l Bassler (2004 Nature 428 716).

  18. Hydraulic characteristics of converse curvature section and aerator in high-head and large discharge spillway tunnel


    The hydraulic characteristics and cavitation erosion near the converse curvature section in the high-head and large discharge spillway tunnel have been important issues of concern to the hydropower project.In this paper,the evolutions of hydraulic elements such as pressure,flow velocity,wall shear stress, the converse curvature section are analyzed and the impacts of bottom aerator on hydraulic characteristics are discussed,with the commercial software FLUENT6.3 as a platform and combining the k-model and VOF method.The flow pattern in the converse curvature section of spillway tunnel is given by the three-dimensional numerical simulation.It indicates that the pressure changes rapidly with great pressure gradient from the beginning to the end of the curve.It also shows that the shear stress on side wall just downstream the end of the converse curvature curve is still increasing;the aeration cavity formed downstream the bottom aerator may cause the side wall pressure decreased to worsen the cavitation characteristics near the side wall.By means of the physical model experiment,the three-dimensional aerator composed of side wall baffling aerator and bottom aerator is studied,the baffling aerator suitable for the water flow conditions with water depth of 6.0 to 8.0 m and flow velocity of 35 to 50 m/s is proposed.

  19. Pressure shock analyses in a power plant cooling system and a hydraulic stowing system in a potassium mine; Druckstossanalysen am Beispiel eines Kraftwerkskuehlsystems und einer Spuelversatzanlage im Kalibergbau

    Lange, H. [Babcock Borsig Power Service GmbH, Oberhausen (Germany)


    Pressure shocks in pipeline systems are caused by acceleration or delaying of fluid flow. They depend on the acceleration or delay rate, the medium density, and the local sound velocity with which the pressure waves propagate. Pressure shocks cause dynamic external loads which may cause damage to pipes, connections or supports and should therefore precalculated already in the planning stage in order to prevent damage. The contribution shows how precalculation of the flow data in a complex, meshed pipeline system will help to optimize the sytem and to maintain its integrity in case of pressure shocks. [German] Druckstoesse in Leitungssystemen werden erzeugt, wenn ein Fluid beschleunigt oder abgebremst (verzoegert wird). Die Groesse dieser Druckstoesse haengt von der Verzoegerung (Beschleunigung) deren Mediumsdichte sowie von der oertlichen Schallgeschwindigkeit ab mit der sich diese Druckwellen fortpflanzen. Druckstoesse bewirken nicht nur eine kurzzeitige Druckaenderung im System, sondern erzeugen dynamische aeussere Lasten, die erhebliche Groessen annehmen und fuer diverse Schaeden an Leitungen, Anschluessen oder Unterstuetzungen verantwortlich sein koennen. Daher ist die Berechnung im voraus wuenschenswert und notwendig, um schon in der Planung entsprechende konstruktive Massnahmen einfliessen zu lassen, damit keine Ueberbeanspruchung des Systems eintreten kann. In den vorliegenden Analysen wird gezeigt, dass fuer ein komplexes, vermaschtes Rohrleitungssystem mit Rueckschlagklappen und Pumpen bei Pumpenausfall durch Vorausberechnungen der Stroemungsdaten, wie Massenstroeme, Stroemungsgeschwindigkeiten, Druecke usw., fuer verschiedene Lastfaelle eine Systemoptimierung durchgefuehrt werden kann. Ausserdem wird gezeigt, dass durch geeignete Massnahmen bei einer Spuelversatzanlage der Druckstoss so abgemindert werden kann, dass die Integritaet des Systems gewaehrleistet wird. (orig.)

  20. Response of Compacted Bentonites to Thermal and Thermo-Hydraulic Loadings at High Temperatures

    Snehasis Tripathy


    Full Text Available The final disposal of high-level nuclear waste in many countries is preferred to be in deep geological repositories. Compacted bentonites are proposed for use as the buffer surrounding the waste canisters which may be subjected to both thermal and hydraulic loadings. A significant increase in the temperature is anticipated within the buffer, particularly during the early phase of the repository lifetime. In this study, several non-isothermal and non-isothermal hydraulic tests were carried on compacted MX80 bentonite. Compacted bentonite specimens (water content = 15.2%, dry density = 1.65 Mg/m3 were subjected to a temperature of either 85 or 150 °C at one end, whereas the temperature at the opposite end was maintained at 25 °C. During the non-isothermal hydraulic tests, water was supplied from the opposite end of the heat source. The temperature and relative humidity were monitored along predetermined depths of the specimens. The profiles of water content, dry density, and degree of saturation were established after termination of the tests. The test results showed that thermal gradients caused redistribution of the water content, whereas thermo-hydraulic gradients caused both redistribution and an increase in the water content within compacted bentonites, both leading to development of axial stress of various magnitudes. The applied water injection pressures (5 and 600 kPa and temperature gradients appeared to have very minimal impact on the magnitude of axial stress developed. The thickness of thermal insulation layer surrounding the testing devices was found to influence the temperature and relative humidity profiles thereby impacting the redistribution of water content within compacted bentonites. Under the influence of both the applied thermal and thermo-hydraulic gradients, the dry density of the bentonite specimens increased near the heat source, whereas it decreased at the opposite end. The test results emphasized the influence of

  1. Model based monitoring of wellbore hydraulics for abnormal event detection

    Todorov, Dimitar; Fruhwirth, Rudolf K. [Thonhauser Data Engineering GmbH, Leoben (Austria); Thonhauser, Gerhard [Montanuniversitaet Leoben (Austria)


    With the increasing demand for energy in the last decades, the petroleum industry was forced to push the limits to levels that have never been reached before. Exploring very deep waters, drilling under varying conditions of extreme pressure and temperature and dealing with issues, which involve a new level of understanding, are challenges, which need to be overcome in order to safely and successfully accomplish the planned goals. Operating under such circumstances obligates the driller to be extremely precise in his actions. Even with the driller's extensive experience and training, the possible reaction time is in some cases extremely short. This article discusses the reasons for automatic trouble event recognition systems in the drilling process and how these affect the drilling operations and optimization processes. In this respect a concept of a real time hydraulic monitor will be developed helping the driller to visualize calculations in a plot, showing the pump limitations, the limitations due to the formation fracture gradient and the hole cleaning requirements. Additionally, taking into account the complete wellbore hydraulics and introducing various well behavior models and different algorithms, the system is capable of operating as a real-time indicator for undesired downhole events. (orig.)

  2. Hydraulic Conductivity Anisotropy of Heterogeneous Unsaturated Soils

    Sun, Dongmin; Zhu, Jianting


    The effects of saturation degree (or capillary pressure) on hydraulic conductivity anisotropy in unsaturated soils have not been fully understood. This study developed an approach based on a conceptualization of combining the neural network based pedo-transfer function (PTF) results with the thin layer concept to explore the capillary pressure-dependent anisotropy in relation to soil texture and soil bulk density. The main objective is to examine how anisotropy characteristics are related to the relationships between hydraulic parameters and the basic soil attributes such as texture and bulk density. The hydraulic parameters are correlated with the texture and bulk density based on the pedo-transfer function (PTF) results. It is demonstrated that non-monotonic behavior of the unsaturated soil anisotropy in relation to the capillary pressure is only observed when the saturated hydraulic conductivity and the shape parameter are both related to the mean particle diameter. When only one hydraulic parameter is related to the grain diameter or when both are not related to the same attribute simultaneously, the unsaturated soil anisotropy increases monotonically with the increasing capillary pressure head. Therefore, it is suggested that this behavior is mainly due to the coupled dependence of the layer saturated hydraulic conductivities and the shape factors on the texture and bulk density. The correlation between the soil grain diameter and bulk density decreases the anisotropy effects of the unsaturated layered soils. The study illustrates that the inter-relationships of soil texture, bulk density, and hydraulic properties may cause vastly different characteristics of anisotropic unsaturated soils.

  3. Integrated hydraulic cooler and return rail in camless cylinder head

    Marriott, Craig D [Clawson, MI; Neal, Timothy L [Ortonville, MI; Swain, Jeff L [Flushing, MI; Raimao, Miguel A [Colorado Springs, CO


    An engine assembly may include a cylinder head defining an engine coolant reservoir, a pressurized fluid supply, a valve actuation assembly, and a hydraulic fluid reservoir. The valve actuation assembly may be in fluid communication with the pressurized fluid supply and may include a valve member displaceable by a force applied by the pressurized fluid supply. The hydraulic fluid reservoir may be in fluid communication with the valve actuation assembly and in a heat exchange relation to the engine coolant reservoir.

  4. Analysis of clinical value of hydraulic pressure method in diagnosis of fallobian tube patency%输卵管通液测压诊断输卵管通畅性的临床价值分析

    王本立; 郝天然; 张学鸿; 徐自全


    Objective To evaluate the clinical value of hydraulic pressure method in diagnosis of fallobian tube patency. Methods Summarize and analyze the hydrotubation diagnosis and hysterosal-pingography (HSG) data of 158 patients with infertility diseases. Use SJ - 1 fallobian tube hydraulic pressure diagnostic and therapeutic instrument to cany out hydrotubation and HSG diagnosis and compare the results of each diagnosis. The results of hydrotubation include patency, incomplete patency and tubal nowhere. The results of HSG diagnosis include normal, incomplete jam and jam. Then analyze the accuracy of the two methods in diagnosis of tubal patency and tubal diseases and conduct x2 examination. Results Using the hydrotubation method, among the 158 cases, we have found 100 cases of patency, 36 cases of incomplete patency and 22 cases of tubal nowhere. Using the HSG method, we have found 66 cases of normal, 7 cases of incomplete jam and 8 cases of jam in regard of light tubal diseases. In regard of serious tubal diseases and using the HSG method, we have found 39 cases of normal, 12 cases of incomplete jam and 18 cases of jam.x2 examination showed that the two methods differ significantly in diagnosis. Conclustions The hydraulic pressure method may cause many errors in diagnosis, for it is unable to distinguish the part, nature and degree of diseases. Thus it doesnt have much clinical vaulue and is not suitable in diagnosis.%目的 评价输卵管通液测压诊断输卵管通畅性的临床价值.方法 总结分析158例不孕症患者通液诊断和子宫输卵管造影( hysterosalpingography,HSG)资料,应用SJ -1宫腔输卵管注液测压诊疗仪分别进行通液诊断、HSG诊断,对比分析每例通液诊断结果与相应HSG诊断结果,通液诊断结果分通畅、不全通畅、不通,HSG相应诊断正常、不全阻塞、阻塞,分别评价两种检查方法诊断输卵管通畅性及输卵管病变的准确性,进行X2检验.结果 158例通液诊断通畅100

  5. Self-potential observations during hydraulic fracturing

    Moore, Jeffrey R.; Glaser, Steven D.


    The self-potential (SP) response during hydraulic fracturing of intact Sierra granite was investigated in the laboratory. Excellent correlation of pressure drop and SP suggests that the SP response is created primarily by electrokinetic coupling. For low pressures, the variation of SP with pressure drop is linear, indicating a constant coupling coefficient (Cc) of -200 mV/MPa. However for pressure drops >2 MPa, the magnitude of the Cc increases by 80% in an exponential trend. This increasing Cc is related to increasing permeability at high pore pressures caused by dilatancy of micro-cracks, and is explained by a decrease in the hydraulic tortuosity. Resistivity measurements reveal a decrease of 2% prior to hydraulic fracturing and a decrease of {approx}35% after fracturing. An asymmetric spatial SP response created by injectate diffusion into dilatant zones is observed prior to hydraulic fracturing, and in most cases this SP variation revealed the impending crack geometry seconds before failure. At rupture, injectate rushes into the new fracture area where the zeta potential is different than in the rock porosity, and an anomalous SP spike is observed. After fracturing, the spatial SP distribution reveals the direction of fracture propagation. Finally, during tensile cracking in a point load device with no water flow, a SP spike is observed that is caused by contact electrification. However, the time constant of this event is much less than that for transients observed during hydraulic fracturing, suggesting that SP created solely from material fracture does not contribute to the SP response during hydraulic fracturing.

  6. Experimental study on the effects of big particles physical characteristics on the hydraulic transport inside a horizontal pipe

    Salah Zouaoui; Hassane Djebouri; Kamal Mohammedi; Sofiane Khelladi; Aomar Ait Aider


    This paper presents an experimental study of the physical characteristic effects of large particles on hydraulic transport in a horizontal pipe. The particles are spherical and are large with respect to the diameter of the pipe (8%, 10%, 16%and 25%). Experiments were done to test the important parameters in solid transport (pressure, velocity, etc.). As a result, the relationship between the pressure gradient forces and the mixture velocity was sub-stantially different from the pure liquid flow. However, in a single-phase flow a monotonous behavior of the pres-sure drop curve is observed, and the curve of the solid particle flow attains its minimum at the critical velocity. The regimes are characterized with differential pressure measurements and visualizations.

  7. Pulsating hydraulic fracturing technology in low permeability coal seams

    Wang Wenchao; Li Xianzhong; Lin Baiquan; Zhai Cheng


    Based on the difficult situation of gas drainage in a single coal bed of high gas content and low perme-ability, we investigate the technology of pulsating hydraulic pressure relief, the process of crank plunger movement and the mechanism of pulsating pressure formation using theoretical research, mathematical modeling and field testing. We analyze the effect of pulsating pressure on the formation and growth of fractures in coal by using the pulsating hydraulic theory in hydraulics. The research results show that the amplitude of fluctuating pressure tends to increase in the case where the exit is blocked, caused by pulsating pressure reflection and frictional resistance superposition, and it contributes to the growth of fractures in coal. The crack initiation pressure of pulsating hydraulic fracturing is 8 MPa, which is half than that of normal hydraulic fracturing;the pulsating hydraulic fracturing influence radius reaches 8 m. The total amount of gas extraction is increased by 3.6 times, and reaches 50 L/min at the highest point. The extraction flow increases greatly, and is 4 times larger than that of drilling without fracturing and 1.2 times larger than that of normal hydraulic fracturing. The technology provides a technical measure for gas drainage of high gas content and low permeability in the single coal bed.

  8. Simulation and experiment on static characteristic of water hydraulic proportional pressure relief valve%纯水比例溢流阀静态特性的仿真与试验

    张增猛; 周华; 高院安; 陈英龙


    A three-stage water hydraulic proportional pressure relief valve, with ball seat valve as the throttle control pilot stage, was investigated on the static characteristic. An AMESim model was built based on structure and mathematic analysis. The friction at spool, proportional electromagnetic actuator and steady flow force, which cause the valve hysteresis, were analyzed through simulation. The experiment results were also analyzed and compared to simulation results. The investigation shows that the large hysteresis mainly comes from flow force, hysteresis of electromagnetic actuator, and friction. Due to the static and coulomb friction and the structure of lever, the range of the input signal responding to pressure increasing section is narrower than pressure decreasing. The width of hysteresis is larger at low pressure than high pressure. For the reason of nonlinearity and large hysteresis of the valve, closed-loop control will be unstable and large oscillation may be induced. It should be improved through structure optimization or control compensation.%以带球阀比例节流先导级的三级座式纯水比例溢流阀为对象,在结构分析和数学建模的基础上,建立了阀的AMESim模型,仿真分析了稳态液动力、比例电磁铁、阀芯摩擦力等对阀静态特性的影响,并与试验对比. 结果表明:阀芯摩擦力及力放大杠杆结构降低了阀的静态性能,阀的滞环大,且随控制信号增大的可控线性段窄,阀在低压段的滞环大于高压工况. 阀的大滞环和严重的非线性降低了闭环系统稳定性,应通过改进结构和控制补偿等措施改善静态特性.

  9. Maintaining Optimum Pump Performance with Specially- Formulated Hydraulic Fluids


    This paper describes a battery of tests, and related results, that were performed under normal and severe conditions designed to demonstrate that hydraulic fluids formulated with Lubrizol' s high quality anti - wear hydraulic fluid technology can stand up to today's increasing demands for longer life and provide excellent performance under higher operating temperatures and pressures.

  10. Hydraulic Redistribution: A Modeling Perspective

    Daly, E.; Verma, P.; Loheide, S. P., III


    Roots play a key role in the soil water balance. They extract and transport water for transpiration, which usually represents the most important soil water loss in vegetated areas, and can redistribute soil water, thereby increasing transpiration rates and enhancing root nutrient uptake. We present here a two-dimensional model capable of describing two key aspects of root water uptake: root water compensation and hydraulic redistribution. Root water compensation is the ability of root systems to respond to the reduction of water uptake from areas of the soil with low soil water potential by increasing the water uptake from the roots in soil parts with higher water potential. Hydraulic redistribution is a passive transfer of water through the root system from areas of the soil with greater water potential to areas with lower water potential. Both mechanisms are driven by gradients of water potential in the soil and the roots. The inclusion of root water compensation and hydraulic redistribution in models can be achieved by describing root water uptake as a function of the difference in water potential between soil and root xylem. We use a model comprising the Richards equation for the water flow in variably saturated soils and the Darcy's equation for the water flow in the xylem. The two equations are coupled via a sink term, which is assumed to be proportional to the difference between soil and xylem water potentials. The model is applied in two case studies to describe vertical and horizontal hydraulic redistribution and the interaction between vegetation with different root depths. In the case of horizontal redistribution, the model is used to reproduce the fluxes of water across the root system of a tree subjected to uneven irrigation. This example can be extended to situations when only part of the root system has access to water, such as vegetation near creeks, trees at the edge of forests, and street trees in urban areas. The second case is inspired by recent

  11. Parametric study on effect of break size during LOCA on thermal hydraulic conditions in an indian pressurized heavy water reactor (220 MWe)

    Rao, G.S.; Gupta, S.K.; Raj, V.V. [Bhabha Atomic Research Centre, Mumbai (India)


    Loss Of Coolant Accident (LOCA) in a Pressurized Heavy Water Reactor (PHWR) leads to coolant expulsion in a primary heat transport system resulting in depressurization and possible core voiding. This results in deterioration of cooling conditions in reactor channels and increase in power before reactor shutdown, leading to higher fuel temperatures. Coolant expulsion rates during LOCA are dictated by critical flow conditions governed by initial plant conditions prior to the accident, break geometry, location of break, etc. In addition the PHWRs have positive void-coefficient of reactivity for coolant resulting in reactor power rise in earlier part of LOCA, when the stored heat of the fuel has yet not been removed. If, in addition, heat transfer to the coolant drops sharply very high fuel surface temperatures are expected. The paper describes analyses carried out for three different break sizes. (author)

  12. Simulation Analysis of PID Optimization of Hydraulic Pressure System Based on Genetic Algorithm%基于遗传算法的液压压上系统的PID优化仿真分析



    In order to improve the dynamic characteristics of cold rol ing temper mil hydraulic pres-sure system,a new PID parameter control method-genetic algorithm was proposed.By using MATLAB/SIMULINK software to solve the optimization model.the PID control parameter self-tun-ing was achieved.The optimized PID parameters and Z-N tuning PID control effects were com-pared and the results showed that:the genetic algorithm PID control is much better than that of the Z-N tuning PID control.Furthermore,the feasibility and practicality of the genetic algorithm were verified as wel .%为了进一步提高冷轧平整机液压压上系统的动态特性,提出了新的PID 参数设计方法:遗传算法。利用Matlab/SIMULINK软件求解优化模型,实现了PID控制参数自整定。对优化得到的PID参数和Z-N整定PID控制效果进行比较,结果表明:遗传算法PID控制优于Z-N整定PID控制,验证了遗传算法的可行性和实用性。

  13. Study on Vickers 20VQ5 High-Pressure Pump Bench Evaluation Method for the Oxidation Durability of Hydraulic Oils%液压油氧化耐久性Vickers 20VQ5高压泵台架评定方法研究

    黄胜军; 王泽恩


    To study the oxidation durability of hydraulic oils,the Vickers 20VQ5 high pressure vane pump test-bed system and hydraulic oil oxidation durability evaluation method were designed to do air entrainment test under high temperature and high pressure.The situation of oil viscosity,acid value increase and sludge formation was investigated.Reference oil experiment showed that the bench system keeps smooth operation,and can be used to distinguish different hydraulic oil oxidation durability and sludge formation trend,and can meet the testing and evaluation requirements of the development of long-lived hydraulic oil new products.%为考察液压油的氧化耐久性能,设计建立了Vickers 20VQ5高压叶片泵台架系统及液压油氧化耐久性评定方法,在高温、高压下进行空气夹带试验。考察油品黏度变化、酸值增加和油泥生成情况。参比油实验表明,台架运行平稳,能较好地区分不同液压油品氧化耐久性能和油泥生成趋势,满足长寿命液压油新产品开发的试验评定需求。

  14. Research on the closure law of hydraulic control slow closing butterfly valve in pressure flow water diversion system%压力流输水系统中缓闭式液控蝶阀关闭规律研究

    刘奕朗; 高学平; 蒋琳琳


    Water diversion system of long - distance and high - lift pressure flow will produce serious damage once pump - stopping water hammer takes place. It is a simple and effective water hammer protection measure to set one hydraulic control slow closing butterfly valve at the outlet of pump with appropriate closure way. The thesis, combining practical engineering, solve the water hammer basic equations by the method of characteristics, compare the results of different valve closure way, including the envelope line of piezometric head, pressure change at outlet of pump station and rotate speed change, then proposes the appropriate way of valve closure. The results can provide a reference for the setting of pump - stopping water hammer protective measures.%对于长距离、高扬程压力流输水系统,一旦发生停泵水锤,将对输水系统产生严重危害.在泵出口设置缓闭式液控蝶阀并以适当的方式关阀是一种简单有效的水锤防护措施.本文结合实际工程,通过特征线法求解水锤基本方程,比较不同关阀方式下管路沿程压力变化、泵站出口断面压力变化及水泵转速变化,提出合适的关阀方式.研究成果可为停泵水锤防护措施的设置提供参考.

  15. Hydraulic Monitoring of Low-Permeability Argillite at the Meuse/Haute Marne Underground Research Laboratory

    Delay, Jacques; Cruchaudet, Martin

    ANDRA (Agence Nationale pour la Gestion de Déchets Radioactifs) has developed an electromagnetic permanent gauge (EPG) for long term monitoring of pore pressures in low permeability Callovo-Oxfordian argillites. The EPG is a pressure gauge that is permanently cemented into a borehole with no wire or tubing connections. The EPG transmits its data electromagnetically through the rock. Improvements in batteries have extended the life of the EPG to six years or more. Data from EPG installations in two holes near ANDRAs underground laboratory provide information on hydraulic conductivity and head. The heads in the argillites of the laboratory site are higher than heads in the two encasing carbonate units. These anomalous overpressures provide evidence for the very low permeability of the rock. Possible mechanisms for the overpressure include osmotic flows due to chemical potential gradients or delayed responses to the evolution of the regional groundwater hydrodynamics.

  16. Thermal-hydraulic analysis techniques for axisymmetric pebble bed nuclear reactor cores. [PEBBLE code

    Stroh, K.R.


    The pebble bed reactor's cylindrical core volume contains a random bed of small, spherical fuel-moderator elements. These graphite spheres, containing a central region of dispersed coated-particle fissile and fertile material, are cooled by high pressure helium flowing through the connected interstitial voids. A mathematical model and numerical solution technique have been developed which allow calculation of macroscopic values of thermal-hydraulic variables in an axisymmetric pebble bed nuclear reactor core. The computer program PEBBLE is based on a mathematical model which treats the bed macroscopically as a generating, conducting porous medium. The steady-state model uses a nonlinear Forchheimer-type relation between the coolant pressure gradient and mass flux, with newly derived coefficients for the linear and quadratic resistance terms. The remaining equations in the model make use of mass continuity, and thermal energy balances for the solid and fluid phases.



    Newton's general similarity criterion was applied to the distorted model. The results for the similarities of gravity force, drag force and pressure force are identical with those derived from relevant differential equations of fluid flow. And the selected limits of the distorted ratio were studied and the simulation of roughness coefficient of distorted model was conducted by means of hydraulic test.

  18. Handbook of hydraulic fluid technology

    Totten, George E


    ""The Handbook of Hydraulic Fluid Technology"" serves as the foremost resource for designing hydraulic systems and for selecting hydraulic fluids used in engineering applications. Featuring new illustrations, data tables, as well as practical examples, this second edition is updated with essential information on the latest hydraulic fluids and testing methods. The detailed text facilitates unparalleled understanding of the total hydraulic system, including important hardware, fluid properties, and hydraulic lubricants. Written by worldwide experts, the book also offers a rigorous overview of h

  19. Dynamic Analysis & Characterization of Conventional Hydraulic Power Supply Units

    Schmidt, Lasse; Liedhegener, Michael; Bech, Michael Møller


    Hydraulic power units operated as constant supply pres-sure systems remain to be widely used in the industry, to supply valve controlled hydraulic drives etc., where the hydraulic power units are constituted by variable pumps with mechanical outlet pressure control, driven by induction motors...... and drives will reduce the flow-to-pressure gain of the supply system, and hence increase the time constant of the sup-ply pressure dynamics. A consequence of this may be large vari-ations in the supply pressure, hence large variations in the pump shaft torque, and thereby the induction motor load torque......, with possible excitation of the induction motor dynamics as a result. In such cases, the coupled dynamics of the pressure controlled pump and induction motor may influence the supply pressure sig-nificantly, possibly affecting the dynamics of the supplied drives, especially in cases where pilot operated valves...

  20. Trends in Design of Water Hydraulics

    Conrad, Finn


    The paper presents and discusses a R&D-view on trends in development and best practise in design of both low-pressure and high-pressure tap water hydraulic components and systems for motion control as well as open-ended solutions various industrial applications. The focus is on the advantages using...... ordinary tap water and the range of application areas are illustrated with examples, in particular within the food processing industry, humidification operations, water mist systems for fire fighting, high water pressure cleaners, water moisturising systems for wood processing, lumber drying process...... operate with pure water from the tap without additives of any kind. Hence water hydraulics takes the benefit of pure water as fluid being environmentally friendly, easy to clean sanitary design, non-toxic, non-flammable, inexpensive, readily available and easily disposable. The low-pressure tap water...

  1. Numerical Investigation into the Effect of Natural Fracture Density on Hydraulic Fracture Network Propagation

    Zhaohui Chong


    Full Text Available Hydraulic fracturing is an important method to enhance permeability in oil and gas exploitation projects and weaken hard roofs of coal seams to reduce dynamic disasters, for example, rock burst. It is necessary to fully understand the mechanism of the initiation, propagation, and coalescence of hydraulic fracture network (HFN caused by fluid flow in rock formations. In this study, a coupled hydro-mechanical model was built based on synthetic rock mass (SRM method to investigate the effects of natural fracture (NF density on HFN propagation. Firstly, the geometrical structures of NF obtained from borehole images at the field scale were applied to the model. Secondly, the micro-parameters of the proposed model were validated against the interaction between NF and hydraulic fracture (HF in physical experiments. Finally, a series of numerical simulations were performed to study the mechanism of HFN propagation. In addition, confining pressure ratio (CPR and injection rate were also taken into consideration. The results suggested that the increase of NF density drives the growth of stimulated reservoir volume (SRV, concentration area of injection pressure (CAIP, and the number of cracks caused by NF. The number of tensile cracks caused by rock matrix decrease gradually with the increase of NF density, and the number of shear cracks caused by rock matrix are almost immune to the change of NF density. The propagation orientation of HFN and the breakdown pressure in rock formations are mainly controlled by CPR. Different injection rates would result in a relatively big difference in the gradient of injection pressure, but this difference would be gradually narrowed with the increase of NF density. Natural fracture density is the key factor that influences the percentages of different crack types in HFN, regardless of the value of CPR and injection rate. The proposed model may help predict HFN propagation and optimize fracturing treatment designs in

  2. Hydraulic Simulation and Safety Assessment of Secondary Water Supply System with Anti-Negative Pressure Facility%无负压供水模式下管网水力模拟与安全评价分析

    王欢欢; 刘书明; 姜帅; 孟凡琳; 白璐


    近些年,无负压供水设备作为新型供水模式,在城市二次供水管网中广泛使用.本研究针对无负压供水对整个管网的影响并不明确的现状,分析了无负压供水模式对管网供水安全的影响,利用管网水力学模型,提出了一种无负压供水状态下的管网水力学模拟方法,应用该方法建立了一种用以确定管网可承受安装无负压供水设备的最大节点数的方法,将此方法应用于两个算例管网,其结果表明算例管网中分别有67%、89%的节点不适合安装无负压供水设备.该方法简单实用,推荐在管网设计与规划中使用,以提高管网供水安全性.%In the last few decades, anti-negative pressure facility ( ANPF) has been emerged as a revolutionary approach for sloving the pollution in the Second Water Supply System (SWSS) in China. This study analyzed implications of the safety in SWSS with ANPF, utilizing the water distribution network hydraulic model. A method of hydraulic simulation and security assessment was presented which was able to reflect the number and location of nodes that can be installed in ANPF. Benchmark results through two instance networks showed that 67% and 89% of nodes in each network did not fit the ANPFs for installation. The simple and pratical algorithm was recommended in the water distribution network design and planing in order to increase the security of SWSS.

  3. The Potential Impacts of Hydraulic Fracturing on Agriculture

    Beng Ong


    Hydraulic fracturing (or “fracking”) is a method of extracting oil and natural gas trapped in deep rock layers underground by pumping water, sand, and other chemicals/additives at high pressures into a well drilled vertically...

  4. Analysis of Innovative Design of Energy Efficient Hydraulic Actuators

    M Osman Abdalla


    Full Text Available Hydraulic cylinder actuators are used extensively in industrial, construction and agricultural works. The small sized outlet ports of the cylinders resist the flow of discharged oil; and as a result the piston motion is slowed down. This causes a lot of heat generation and energy loss within the actuators. The study investigates and analyzes the possibilities of reducing the hydraulic resistance and increasing efficiency of the hydraulic actuator. Conventional hydraulic cylinders are simulated in FLUENT. Results show that the small outlet ports are the sources of energy loss in hydraulic cylinders. A new hydraulic system was proposed as a solution to relieve the hydraulic resistance in the actuators. The proposed system is a four ports hydraulic cylinder fitted with a novel flow control valve. The proposed four ports cylinder was simulated and parameters such as ports sizes, loads and pressures are varied during the simulation. The hydraulic resisting forces, piston speed and mass flow rates are computed. Results show that the hydraulic resistance is significantly reduced in the proposed four ports actuators; and the proposed cylinders run faster than the conventional cylinders and a considerable amount of energyis saved as well.

  5. Modeling and parameter estimation for hydraulic system of excavator's arm

    HE Qing-hua; HAO Peng; ZHANG Da-qing


    A retrofitted electro-bydraulic proportional system for hydraulic excavator was introduced firstly. According to the principle and characteristic of load independent flow distribution(LUDV)system, taking boom hydraulic system as an example and ignoring the leakage of hydraulic cylinder and the mass of oil in it,a force equilibrium equation and a continuous equation of hydraulic cylinder were set up.Based On the flow equation of electro-hydraulic proportional valve, the pressure passing through the valve and the difference of pressure were tested and analyzed.The results show that the difference of pressure does not change with load, and it approximates to 2.0 MPa. And then, assume the flow across the valve is directly proportional to spool displacement andis not influenced by load, a simplified model of electro-hydraulic system was put forward. At the same time, by analyzing the structure and load-bearing of boom instrument, and combining moment equivalent equation of manipulator with rotating law, the estimation methods and equations for such parameters as equivalent mass and bearing force of hydraulic cylinder were set up. Finally, the step response of flow of boom cylinder was tested when the electro-hydraulic proportional valve was controlled by the stepcurrent. Based on the experiment curve, the flow gain coefficient of valve is identified as 2.825×10-4m3/(s·A)and the model is verified.

  6. Design of a Resistively Heated Thermal Hydraulic Simulator for Nuclear Rocket Reactor Cores

    Litchford, Ron J.; Foote, John P.; Ramachandran, Narayanan; Wang, Ten-See; Anghaie, Samim


    A preliminary design study is presented for a non-nuclear test facility which uses ohmic heating to replicate the thermal hydraulic characteristics of solid core nuclear reactor fuel element passages. The basis for this testing capability is a recently commissioned nuclear thermal rocket environments simulator, which uses a high-power, multi-gas, wall-stabilized constricted arc-heater to produce high-temperature pressurized hydrogen flows representative of reactor core environments, excepting radiation effects. Initially, the baseline test fixture for this non-nuclear environments simulator was configured for long duration hot hydrogen exposure of small cylindrical material specimens as a low cost means of evaluating material compatibility. It became evident, however, that additional functionality enhancements were needed to permit a critical examination of thermal hydraulic effects in fuel element passages. Thus, a design configuration was conceived whereby a short tubular material specimen, representing a fuel element passage segment, is surrounded by a backside resistive tungsten heater element and mounted within a self-contained module that inserts directly into the baseline test fixture assembly. With this configuration, it becomes possible to create an inward directed radial thermal gradient within the tubular material specimen such that the wall-to-gas heat flux characteristics of a typical fuel element passage are effectively simulated. The results of a preliminary engineering study for this innovative concept are fully summarized, including high-fidelity multi-physics thermal hydraulic simulations and detailed design features.


    LAI Xi-de


    With the development of large-capacity hydro turbines, the hydraulic instability of bydro turbines has become one of the most important problems that affect the stable operation of the hydro-electric units. The hydraulic vibration and unstable operation of Francis hydro turbines are primarily caused by the unsteady pressure pulsations inside draft tubes.The forced rotating vortex core at the runner exit and the channel vortices inside Francis turbine runners are origins of the unsteady pressure pulsations when operating at partial load. This paper briefly analyzes the hydraulic instability of operation caused by the vortex core and channel vortices at partial load, then, presents a way to estimate the hydraulic stability by calculation of the flow behavior at the runner exit.The validity of estimation is examined by comparison with experimental data. This will be helpful to evaluate the alternative design and predict the hydraulic stability for both the prototype and model hydro turbines.

  8. Investigation of Valve Plate in Water Hydraulic Axial Piston Motor

    聂松林; 李壮云; 等


    This paper has introduced the developments of water hydraulic axial piston equipments.According to the effects of physicochemical properties of water on water hydraulic components,a novel valve plate for water hydraulic axial motor has been put forward,whose moment exerted by the fluid field between valve plate and bearing plate is balanced entirely.The material screening experiment of valve plate is done on the test rig.Through numerical simulation the effects of some geometry parameters on the performance of water hydraulic motor have been studied.The silencing grooves on the valve plate in water hydraulic motor can reduce the pressure shock and the occurrence of cavitation effectively.It is evident that the appropriate structure should change the wear status between matching paris and reduces the wear and specific pressure of the matching pairs.The specimen with the new type valve plate is used in a tool system.

  9. Parameter Designing for Heave Compensation Hydraulic System Installed in Deepwater

    Zhao Teng


    Full Text Available The function diagram of active heave compensation hydraulic system has been given, besides, the mathematics model for the principal hydraulic components of the compensation system has been built, and the input-output relation between components has been made clear. Aimed at compensating work capacity for the system, design and research on parameters as the bearing pressure, the initial state and the maximum flow of hydraulic cylinder, accumulator and other principal components have been made separately, and standardized design has been accomplished in accordance with relevant standards. Furthermore, calculus and verification for the capacity of the hydraulic system in different working stages have been made in order to calculate the pressure lose of the system and provide objective data for the hardware system design of the hydraulic components of the heave compensation system.

  10. Helical coil thermal hydraulic model

    Caramello, M.; Bertani, C.; De Salve, M.; Panella, B.


    A model has been developed in Matlab environment for the thermal hydraulic analysis of helical coil and shell steam generators. The model considers the internal flow inside one helix and its associated control volume of water on the external side, both characterized by their inlet thermodynamic conditions and the characteristic geometry data. The model evaluates the behaviour of the thermal-hydraulic parameters of the two fluids, such as temperature, pressure, heat transfer coefficients, flow quality, void fraction and heat flux. The evaluation of the heat transfer coefficients as well as the pressure drops has been performed by means of the most validated literature correlations. The model has been applied to one of the steam generators of the IRIS modular reactor and a comparison has been performed with the RELAP5/Mod.3.3 code applied to an inclined straight pipe that has the same length and the same elevation change between inlet and outlet of the real helix. The predictions of the developed model and RELAP5/Mod.3.3 code are in fairly good agreement before the dryout region, while the dryout front inside the helical pipes is predicted at a lower distance from inlet by the model.

  11. Non-stationary flow of hydraulic oil in long pipe

    Hružík Lumír


    Full Text Available The paper deals with experimental evaluation and numerical simulation of non-stationary flow of hydraulic oil in a long hydraulic line. Non-stationary flow is caused by a quick closing of valves at the beginning and the end of the pipe. Time dependence of pressure is measured by means of pressure sensors at the beginning and the end of the pipe. A mathematical model of a given circuit is created using Matlab SimHydraulics software. The long line is simulated by means of segmented pipe. The simulation is verified by experiment.

  12. Regional maps of subsurface geopressure gradients of the onshore and offshore Gulf of Mexico basin

    Burke, Lauri A.; Kinney, Scott A.; Dubiel, Russell F.; Pitman, Janet K.


    The U.S. Geological Survey created a comprehensive geopressure-gradient model of the regional pressure system spanning the onshore and offshore Gulf of Mexico basin, USA. This model was used to generate ten maps that included (1) five contour maps characterizing the depth to the surface defined by the first occurrence of isopressure gradients ranging from 0.60 psi/ft to 1.00 psi/ft, in 0.10-psi/ft increments; and (2) five supporting maps illustrating the spatial density of the data used to construct the contour maps. These contour maps of isopressure-gradients at various increments enable the identification and quantification of the occurrence, magnitude, location, and depth of the subsurface pressure system, which allows for the broad characterization of regions exhibiting overpressured, underpressured, and normally pressured strata. Identification of overpressured regions is critical for exploration and evaluation of potential undiscovered hydrocarbon accumulations based on petroleum-generation pressure signatures and pressure-retention properties of reservoir seals. Characterization of normally pressured regions is essential for field development decisions such as determining the dominant production drive mechanisms, evaluating well placement and drainage patterns, and deciding on well stimulation methods such as hydraulic fracturing. Identification of underpressured regions is essential for evaluating the feasibility of geological sequestration and long-term containment of fluids such as supercritical carbon dioxide for alternative disposal methods of greenhouse gases. This study is the first, quantitative investigation of the regional pressure systems of one of the most important petroleum provinces in the United States. Although this methodology was developed for pressure studies in the Gulf of Mexico basin, it is applicable to any basin worldwide.

  13. Thermal Hydraulic Stability in a Coaxial Thermosyphon

    YANG Jianhui; LU Wenqiang; LI Qing; LI Qiang; ZHOU Yuan


    The heat transfer and thermal hydraulic stability in a two-phase thermosyphon with coaxial riser and down-comer has been experimentally investigated and theoretically analyzed to facilitate its application in cold neutron source. The flow in a coaxial thermosyphon was studied experimentally for a variety of heating rates, transfer tube lengths, charge capacities, and area ratios. A numerical analysis of the hydraulic balance between the driving pressure head and the resistance loss has also been performed. The results show that the presented coaxial thermosyphon has dynamic performance advantages relative to natural circulation in a boiling water reactor.

  14. Ahorro energético en tándem de molinos de caña de azúcar mediante regulación de presiones hidráulicas//Energy saving in tandem of sugar cane mills by means regulation of hydraulic pressures

    Jorge Michel Corrales‐Suárez


    Full Text Available Entre las áreas de mayor consumo de energía en un central azucarero se encuentra el tándem de molinos. Una de las variables que influye sobre este consumo es la presión hidráulica aplicada a la maza superior. La investigación tuvo como objetivo determinar las posibilidades de reducir este consumo regulandoapropiadamente las presiones hidráulicas sin disminuir la eficiencia del proceso de extracción, se llevó a cabo en un tándem de seis molinos donde solo se varió las presiones en los molinos intermedios según un diseño estadístico factorial completo 24. Las variables independientes fueron: las presiones hidráulicasen los molinos intermedios; las dependientes: la demanda de potencia, el % pol y % humedad. Se concluyó que en las condiciones del experimento, el empleo de presiones hidráulicas de trabajo menores en 3,45 MPa en los molinos intermedios, no afectó el proceso de extracción de la sacarosa, pero disminuyó en un 8,12% la demanda de potencia.Palabras claves: presión hidráulica, molino de caña de azúcar, ahorro de energía, tándem.______________________________________________________________________________AbstractAmong the areas of more energy consumption in a sugar power station is the tandem of mills. One of the variables that influences on this consumption is the hydraulic pressure applied to the superior mass. The investigation had as objective to determine the possibilities to reduce this consumption regulating the hydraulic pressures appropriately without diminishing the efficiency of the extraction process, it was carried out in a tandem of six mills where alone it was varied the pressures in the intermediate mills according to a complete factorial statistical design 24. The independent variables were: the hydraulic pressures in the intermediate mills; the dependents: the demand of power, the %pol and %humidity. You concluded thatunder the conditions of the experiment, the employment of hydraulic pressures

  15. On the Hydraulics of Flowing Horizontal Wells

    Bian, A.; Zhan, H.


    A flowing horizontal well is a special type of horizontal well that does not have pumping/injecting facility. The discharge rate of a flowing horizontal well is controlled by the hydraulic gradient between the aquifer and the well and it generally varies with time if the hydraulic head of the aquifer is transient. This type of well has been used in landslide control, mining dewatering, water table control, underground water transportation through a horizontal tunnel, agricultural water drainage, and other applications. Flowing horizontal wells have quite different hydrodynamic characteristics from horizontal wells with fixed pumping or injecting rates because their discharge rates are functions of the aquifer hydraulic heads (Zhan et al, 2001; Zhan and Zlotnik, 2002). Hydraulics of flowing horizontal wells have rarely been studied although the hydraulics of flowing vertical wells have been extensively investigated before. The purpose of this paper is to obtain analytical solutions of groundwater flow to a flowing horizontal-well in a confined aquifer, in a water table aquifer without precipitation, and in a water table aquifer with precipitation. The functions of the flowing horizontal well discharge rates versus time will be obtained under above mentioned different aquifer conditions. The relationships of the aquifer hydraulic heads versus the discharge rates of the well will be investigated. The rate of water table decline due to the dewatering of the well will also be computed, and this solution is particularly useful for landslide control and mining dewatering. The theoretical solutions will be compared with results of experiments that will be conducted in the hydrological laboratory at Texas A&M University. Reference: Zhan, H., Wang, L.V., and Park, E, On the horizontal well pumping tests in the anisotropic confined aquifers, J. hydrol., 252, 37-50, 2001. Zhan, H., and Zlotnik, V. A., Groundwater flow to a horizontal or slanted well in an unconfined aquifer

  16. FEMA DFIRM Hydraulic Structures

    Minnesota Department of Natural Resources — This layer and accompanying attribute table is required whenever hydraulic structures are shown in the flood profile. It is also required if levees are shown on the...

  17. Water Hydraulic Systems

    Conrad, Finn


    The paper presents research results using IT-Tools for CAD and dynamic modelling, simulation, analysis, and design of water hydraulic actuators for motion control of machines, lifts, cranes and robots. Matlab/Simulink and CATIA are used as IT-Tools. The contributions include results from on......-going research projects on fluid power and mechatronics based on tap water hydraulic servovalves and linear servo actuators and rotary vane actuators for motion control and power transmission. Development and design a novel water hydraulic rotary vane actuator for robot manipulators. Proposed mathematical...... modelling, control and simulation of a water hydraulic rotary vane actuator applied to power and control a two-links manipulator and evaluate performance. The results include engineering design and test of the proposed simulation models compared with IHA Tampere University’s presentation of research...

  18. Root water extraction and limiting soil hydraulic conditions estimated by numerical simulation

    Jong van Lier, de Q.; Metselaar, K.; Dam, van J.C.


    Root density, soil hydraulic functions, and hydraulic head gradients play an important role in the determination of transpiration-rate-limiting soil water contents. We developed an implicit numerical root water extraction model to solve the Richards equation for the modeling of radial root water

  19. Simulation of a Hydraulic Pump Control Valve

    Molen, G. Vander; Akers, A.


    This paper describes the mode of operation of a control valve assembly that is used with a hydraulic pump. The operating system of the valve is modelled in a simplified form, and an analogy for hydraulic resonance of the pressure sensing system is presented. For the control valve investigated, air entrainment, length and diameter of the resonator neck, and valve mass produced the greatest shift in resonant frequency. Experimental work was conducted on the hydraulic system so that the resonance levels and frequencies could be measured and the accuracy of the theory verified. The results obtained make it possible to evaluate what changes to any of the variables considered would be most effective in driving the second harmonic frequency above the operating range.

  20. Growth model for large branched three-dimensional hydraulic crack system in gas or oil shale.

    Chau, Viet T; Bažant, Zdeněk P; Su, Yewang


    Recent analysis of gas outflow histories at wellheads shows that the hydraulic crack spacing must be of the order of 0.1 m (rather than 1 m or 10 m). Consequently, the existing models, limited to one or several cracks, are unrealistic. The reality is 10(5)-10(6) almost vertical hydraulic cracks per fracking stage. Here, we study the growth of two intersecting near-orthogonal systems of parallel hydraulic cracks spaced at 0.1 m, preferably following pre-existing rock joints. One key idea is that, to model lateral cracks branching from a primary crack wall, crack pressurization, by viscous Poiseuille-type flow, of compressible (proppant-laden) frac water must be complemented with the pressurization of a sufficient volume of micropores and microcracks by Darcy-type water diffusion into the shale, to generate tension along existing crack walls, overcoming the strength limit of the cohesive-crack or crack-band model. A second key idea is that enforcing the equilibrium of stresses in cracks, pores and water, with the generation of tension in the solid phase, requires a new three-phase medium concept, which is transitional between Biot's two-phase medium and Terzaghi's effective stress and introduces the loading of the solid by pressure gradients of diffusing pore water. A computer program, combining finite elements for deformation and fracture with volume elements for water flow, is developed to validate the new model.This article is part of the themed issue 'Energy and the subsurface'.

  1. A low order adaptive control scheme for hydraulic servo systems

    Andersen, Torben Ole; Pedersen, Henrik Clemmensen; Bech, Michael Møller;


    This paper deals with high-performance position control of hydraulics servo systems in general. The hydraulic servo system used is a two link robotic manipulator actuated by two hydraulic servo cylinders. A non-linear model of the hydraulic system and a Newton-Euler based model of the mechanical...... system were constructed and linearized. Controllers are implemented and tested on the manipulator. Pressure feedback was found to greatly improve system stability margins. Passive gain feedforward shows improved tracking performance for small changes in load pressure. For large changes in load pressure......, active gain feedforward shows a slightly improved performance. Computed-Torque Control shows better performance, but requires a well described system for best performance. A novel Adaptive Inverse Dynamics Controller was tested and the performance was found to be similar to that of Computed...

  2. Estimation of Joule heating effect on temperature and pressure distribution in electrokinetic-driven microchannel flows.

    Chein, Reiyu; Yang, Yeong Chin; Lin, Yushan


    In this study we present simple analytical models that predict the temperature and pressure variations in electrokinetic-driven microchannel flow under the Joule heating effect. For temperature prediction, a simple model shows that the temperature is related to the Joule heating parameter, autothermal Joule heating parameter, external cooling parameter, Peclet number, and the channel length to channel hydraulic diameter ratio. The simple model overpredicted the thermally developed temperature compared with the full numerical simulation, but in good agreement with the experimental measurements. The factors that affect the external cooling parameters, such as the heat transfer coefficient, channel configuration, and channel material are also examined based on this simple model. Based on the mass conservation, a simple model is developed that predicts the pressure variations, including the temperature effect. An adverse pressure gradient is required to satisfy the mass conservation requirement. The temperature effect on the pressure gradient is via the temperature-dependent fluid viscosity and electroosmotic velocity.

  3. Effect of pressure on Fe3+/ΣFe ratio in a mafic magma and consequences for magma ocean redox gradients

    Zhang, H. L.; Hirschmann, M. M.; Cottrell, E.; Withers, A. C.


    Experiments establishing the effect of pressure on the Fe3+/ΣFe ratio of andesitic silicate melts buffered by coexisting Ru and RuO2 were performed from 100 kPa to 7 GPa and 1400–1750 °C. Fe3+/ΣFe ratios were determined by room temperature Mössbauer spectroscopy, but corrected for the effects of recoilless fraction. Fe3+/ΣFe ratios in quenched glasses decrease with increasing pressure consistent with previous results between 100 kPa and 3 GPa (O’Neill et al., 2006), but show only small pressure effects above 5 GPa. Ratios also decrease with increasing temperature. Mössbauer hyperfine parameters indicate mean coordination of Fe3+ ions of ~5 in glasses, with no dependence on the pressure from which the glasses were quenched, but show an increase with pressure in mean coordination of Fe2+ ions, from ~5 to ~6. XANES spectra on these glasses show variations in pre-edge intensities and centroid positions that are systematic with Fe3+/ΣFe, but are displaced from those established from otherwise identical andesitic glasses quenched at 100 kPa (Zhang et al., 2016). These systematics permit construction of a new XANES calibration curve relating pre-edge sub-peak intensities to Fe3+/ΣFe applicable to high pressure glasses. Consistent with interpretations of the Mössbauer hyperfine parameters, XANES pre-edge peak features in high pressure glasses are owing chiefly to the effects of pressure on the coordination of Fe2+ ions from ~5.5 to ~6, with negligible effects evident for Fe3+ ions. We use the new data to construct a thermodynamic model relating the effects of oxygen fugacity and pressure on Fe3+/ΣFe. We apply this model to calculate variations in oxygen fugacity in isochemical (constant Fe3+/ΣFe) columns of magma representative of magma oceans, in which fO2 is fixed at the base by equilibration with molten Fe. These calculations

  4. Effect of pressure on Fe3+/ΣFe ratio in a mafic magma and consequences for magma ocean redox gradients

    Zhang, H. L.; Hirschmann, M. M.; Cottrell, E.; Withers, A. C.


    Experiments establishing the effect of pressure on the Fe3+/ΣFe ratio of andesitic silicate melts buffered by coexisting Ru and RuO2 were performed from 100 kPa to 7 GPa and 1400-1750 °C. Fe3+/ΣFe ratios were determined by room temperature Mössbauer spectroscopy, but corrected for the effects of recoilless fraction. Fe3+/ΣFe ratios in quenched glasses decrease with increasing pressure consistent with previous results between 100 kPa and 3 GPa (O'Neill et al., 2006), but show only small pressure effects above 5 GPa. Ratios also decrease with increasing temperature. Mössbauer hyperfine parameters indicate mean coordination of Fe3+ ions of ∼5 in glasses, with no dependence on the pressure from which the glasses were quenched, but show an increase with pressure in mean coordination of Fe2+ ions, from ∼5 to ∼6. XANES spectra on these glasses show variations in pre-edge intensities and centroid positions that are systematic with Fe3+/ΣFe, but are displaced from those established from otherwise identical andesitic glasses quenched at 100 kPa (Zhang et al., 2016). These systematics permit construction of a new XANES calibration curve relating pre-edge sub-peak intensities to Fe3+/ΣFe applicable to high pressure glasses. Consistent with interpretations of the Mössbauer hyperfine parameters, XANES pre-edge peak features in high pressure glasses are owing chiefly to the effects of pressure on the coordination of Fe2+ ions from ∼5.5 to ∼6, with negligible effects evident for Fe3+ ions. We use the new data to construct a thermodynamic model relating the effects of oxygen fugacity and pressure on Fe3+/ΣFe. We apply this model to calculate variations in oxygen fugacity in isochemical (constant Fe3+/ΣFe) columns of magma representative of magma oceans, in which fO2 is fixed at the base by equilibration with molten Fe. These calculations indicate that oxygen fugacities at the surface of shallow magma oceans are more reduced than at depth. For magma oceans in

  5. Hydraulic resistance of biofilms

    Dreszer, C.


    Biofilms may interfere with membrane performance in at least three ways: (i) increase of the transmembrane pressure drop, (ii) increase of feed channel (feed-concentrate) pressure drop, and (iii) increase of transmembrane passage. Given the relevance of biofouling, it is surprising how few data exist about the hydraulic resistance of biofilms that may affect the transmembrane pressure drop and membrane passage. In this study, biofilms were generated in a lab scale cross flow microfiltration system at two fluxes (20 and 100Lm-2h-1) and constant cross flow (0.1ms-1). As a nutrient source, acetate was added (1.0mgL-1 acetate C) besides a control without nutrient supply. A microfiltration (MF) membrane was chosen because the MF membrane resistance is very low compared to the expected biofilm resistance and, thus, biofilm resistance can be determined accurately. Transmembrane pressure drop was monitored. As biofilm parameters, thickness, total cell number, TOC, and extracellular polymeric substances (EPS) were determined, it was demonstrated that no internal membrane fouling occurred and that the fouling layer actually consisted of a grown biofilm and was not a filter cake of accumulated bacterial cells. At 20Lm-2h-1 flux with a nutrient dosage of 1mgL-1 acetate C, the resistance after 4 days reached a value of 6×1012m-1. At 100Lm-2h-1 flux under the same conditions, the resistance was 5×1013m-1. No correlation of biofilm resistance to biofilm thickness was found; Biofilms with similar thickness could have different resistance depending on the applied flux. The cell number in biofilms was between 4×107 and 5×108 cellscm-2. At this number, bacterial cells make up less than a half percent of the overall biofilm volume and therefore did not hamper the water flow through the biofilm significantly. A flux of 100Lm-2h-1 with nutrient supply caused higher cell numbers, more biomass, and higher biofilm resistance than a flux of 20Lm-2h-1. However, the biofilm thickness

  6. Effect of Natural Fractures on Hydraulic Fracturing

    Ben, Y.; Wang, Y.; Shi, G.


    Hydraulic Fracturing has been used successfully in the oil and gas industry to enhance oil and gas production in the past few decades. Recent years have seen the great development of tight gas, coal bed methane and shale gas. Natural fractures are believed to play an important role in the hydraulic fracturing of such formations. Whether natural fractures can benefit the fracture propagation and enhance final production needs to be studied. Various methods have been used to study the effect of natural fractures on hydraulic fracturing. Discontinuous Deformation Analysis (DDA) is a numerical method which belongs to the family of discrete element methods. In this paper, DDA is coupled with a fluid pipe network model to simulate the pressure response in the formation during hydraulic fracturing. The focus is to study the effect of natural fractures on hydraulic fracturing. In particular, the effect of rock joint properties, joint orientations and rock properties on fracture initiation and propagation will be analyzed. The result shows that DDA is a promising tool to study such complex behavior of rocks. Finally, the advantages of disadvantages of our current model and future research directions will be discussed.

  7. Valor do gradiente de pressão retal e anal na evacuação em megacólon adquirido Rectal and anal pressure variation during defecation in patients with acquired megacolon

    Chia Bin Fang


    Full Text Available O megacólon resulta de lesão extensa dos plexos mioentéricos, a qual se traduz por incoordenação motora do cólon com inércia funcional e acalasia do esfíncter anal. Disso resulta duplo distúrbio, em que à dificuldade motora agrega-se o obstáculo para evacuar. Para que haja eliminação fecal é necessário que a pressão retal ultrapasse a anal, havendo um gradiente reto-anal. O objetivo do trabalho foi avaliar este gradiente em 29 pacientes portadores de megacólon, em que as pressões retais e anais foram medidas ao evacuar, comparadas com pessoas normais. Os resultados mostraram que havia pressão retal em centímetros de água aumentada em homens (72,2 ± 29,1 e mulheres (64,5 ± 20,1, superando as respectivas pressões anais de evacuação (66,4 ± 23,2 e 62,1 ± 28,7. As pressões de evacuação, por sua vez, eram muito maiores que as do grupo controle. Isto permitiu concluir haver uma reação adaptativa com maior esforço muscular para evacuar, a fim de superar o obstáculo da acalasia.Megacolon is the result of an extensive lesion of the mioenteric plexus, with lack of motor coordination and achalasia of the anal sphincter. The motility disorder caused by the muscle contraction problems added to a mechanical obstacle results cause constipation. The defecation rectal pressure increases and reaches its peak with the start of fecal flow, exceeding the anal pressure. The objective of this work was to assess the ratio of rectal / anal pressure on 29 megacolon sufferers, compared to normal subjects. Results have shown that defecation rectal pressure was higher than expected for both men (72,2 ± 29,1 cm water and women (64,5 ± 20,1 cm water exceeding the defecation anal pressure (66,4 ± 23,2 and 62,1 ± 28,7 cm water, for men and women, respectively. The defecation pressures were much higher than those of the control group, what led to the conclusion that as an adaptive reaction, muscular effort increases to make evacuation

  8. Exact analytical solutions for moving boundary problems of one-dimensional flow in semi-infinite porous media with consideration of threshold pressure gradient

    王晓冬; 朱光亚; 王磊


    By defining new dimensionless variables, nonlinear mathematical models for one-dimensional flow with unknown moving boundaries in semi-infinite porous media are modified to be solved analytically. The exact analytical solutions for both constant-rate and constant-pressure inner boundary constraint problems are obtained by applying the Green’s function. Two transcendental equations for moving boundary problems are obtained and solved using the Newton-Raphson iteration. The exact analytical solutions are then compared with the approximate solutions. The Pascal’s approximate formula in reference is fairly accurate for the moving boundary development under the constant-rate condition. But another Pascal’s approximate formula given in reference is not very robust for constant-pressure condition problems during the early production period, and could lead to false results at the maximum moving boundary distance. Our results also show that, in presence of larger TPG, more pressure drop is required to maintain a constant-rate production. Under the constant-pressure producing condition, the flow rate may decline dramatically due to a large TPG. What’s more, there exists a maximum distance for a given TPG, beyond which the porous media is not disturbed.

  9. Dynamic characteristics of hydraulic power steering system with accumulator in load-haul-dump vehicle

    杨忠炯; 何清华; 柳波


    Using hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle as a simulation example, the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle were simulated and discussed with SIMULINK software and hydraulic control theory. The results show that the dynamic characteristics of hydraulic power steering system are improved obviously by using bladder accumulator, the hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle generates vibration at the initial stage under the normal steering condition of pulse input, and its static response time is 0.25 s shorter than that without bladder accumulator. Under the normal steering working condition, the capacity of steering accumulator for absorbing pulse is directly proportional to the cross section area of connecting pipeline, and inversely proportional to the length of connecting pipeline. At the same time, the precharge pressure of nitrogen in steering accumulator should be 60%- 80% of the rated minimum working pressure of hydraulic power steering system. Under the abnormal steering working condition, the steering cylinder piston may obtain higher motion velocity, and the dynamic response velocity of hydraulic power steering system can be increased by reducing the pressure drop of hydraulic pipelines between the accumulator and steering cylinder and by increasing the rated pressure of hydraulic power steering system, but the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle have nothing to do with the precharge pressure of nitrogen in steering accumulator.

  10. Spatial variability in streambed hydraulic conductivity of contrasting stream morphologies

    Sebök, Éva; Calvache, Carlos Duque; Engesgaard, Peter Knudegaard;


    Streambed hydraulic conductivity is one of the main factors controlling variability in surface water-groundwater interactions, but only few studies aim at quantifying its spatial and temporal variability in different stream morphologies. Streambed horizontal hydraulic conductivities (Kh) were...... therefore determined from in-stream slug tests, vertical hydraulic conductivities (Kv) were calculated with in-stream permeameter tests and hydraulic heads were measured to obtain vertical head gradients at eight transects, each comprising five test locations, in a groundwater-dominated stream. Seasonal...... small-scale measurements were taken in December 2011 and August 2012, both in a straight stream channel with homogeneous elevation and downstream of a channel meander with heterogeneous elevation. All streambed attributes showed large spatial variability. Kh values were the highest at the depositional...

  11. Numerical Research on Flow Characteristics around a Hydraulic Turbine Runner at Small Opening of Cylindrical Valve

    Zhenwei Mo


    Full Text Available We use the continuity equation and the Reynolds averaged Navier-Stokes equations to study the flow-pattern characteristics around a turbine runner for the small-opening cylindrical valve of a hydraulic turbine. For closure, we adopt the renormalization-group k-ε two-equation turbulence model and use the computational fluid dynamics (CFD software FLUENT to numerically simulate the three-dimensional unsteady turbulent flow through the entire passage of the hydraulic turbine. The results show that a low-pressure zone develops around the runner blades when the cylindrical valve is closed in a small opening; cavitation occurs at the blades, and a vortex appears at the outlet of the runner. As the cylindrical valve is gradually closed, the flow velocity over the runner area increases, and the pressure gradient becomes more significant as the discharge decreases. In addition, the fluid flow velocity is relatively high between the lower end of the cylindrical valve and the base, so that a high-velocity jet is easily induced. The calculation and analysis provide a theoretical basis for improving the performance of cylindrical-valve operating systems.

  12. Elevator and hydraulics; Elevator to yuatsu

    Nakamura, I. [Hitachi, Ltd., Tokyo (Japan)


    A hydraulic type elevator is installed in relatively lower buildings as compared with a rope type elevator, but the ratio in the number of installation of the former elevator is increasing. This paper explains from its construction and features to especially various control systems for the riding comfort and safety. A direct push-up system with hydraulic jacks arranged beneath a car, and an indirect push-up system that has hydraulic jacks arranged on flank of a car and transmits the movement of a plunger via a rope are available. The latter system eliminates the need of large holes to embed hydraulic jacks. While the speed is controlled by controlling flow rates of high-pressure oil, the speed, position, acceleration and even time differential calculus of the acceleration must be controlled severely. The system uses two-step control for the through-speed and the landing speed. Different systems that have been realized may include compensation for temperatures in flow rate control valves, load pressures, and oil viscosity, from learning control to fuzzy control for psychological effects, or control of inverters in motors. 13 refs., 12 figs., 1 tab.

  13. Double-Twisted Conductive Smart Threads Comprising a Homogeneously and a Gradient-Coated Thread for Multidimensional Flexible Pressure-Sensing Devices

    Tai, Yanlong


    Fiber-based, flexible pressure-sensing systems have attracted attention recently due to their promising application as electronic skins. Here, a new kind of flexible pressure-sensing device based on a polydimethylsiloxane membrane instrumented with double-twisted smart threads (DTSTs) is reported. DTSTs are made of two conductive threads obtained by coating cotton threads with carbon nanotubes. One thread is coated with a homogeneous thickness of single-walled carbon nanotubes (SWCNTs) to detect the intensity of an applied load and the other is coated with a graded thickness of SWCNTs to identify the position of the load along the thread. The mechanism and capacity of DTSTs to accurately sense an applied load are systematically analyzed. Results demonstrate that the fabricated 1D, 2D, and 3D sensing devices can be used to predict both the intensity and the position of an applied load. The sensors feature high sensitivity (between ≈0.1% and 1.56% kPa) and tunable resolution, good cycling resilience (>104 cycles), and a short response time (minimum 2.5 Hz). The presented strategy is a viable alternative for the design of simple, low-cost pressure sensors.

  14. A New Way to Calculate the Critical Pressure Gradient of Sand Production%计算砂岩出砂临界压力梯度的新方法

    聂向荣; 杨胜来; 丁景辰; 李芳芳; 章星


    A capillary-tube model is proposed which could transform the porous medium solid liquid coupling problems to duct flow problems,and the dynamic mechanism of sand production is studied according to the fluid mechanics as well as skin effect considered.The critical pressure gradient formula is as a quantifying characterization for the sand production.Based on sensitivity analysis,the critical pressure gradient rises with its thickness increasing.With the sand particle radius increasing,the critical pressure gradient also rises.In order to validate the effectiveness of the formula,a physical simulation experiment is designed.The formulae has a good agreement with experimental,and the average error is only 16%.%将毛管束模型引入到出砂问题的研究中,同时考虑了表皮效应,建立了出砂毛管束物理模型,该模型能够将复杂的多孔介质固液耦合问题转化为宏观的管流流动问题,通过分析砂岩颗粒在毛管束中的受力和运动,建立了砂岩出砂数学模型,分析了出砂过程动态机理,推导了出砂临界压力梯度公式,该公式从理论上对出砂问题进行了定量表征.敏感性分析表明:随着表皮厚度的增大,临界压力梯度增大;随着砂粒半径的增大,临界压力梯度也随之增大.为了验证公式的有效性,设计了砂岩出砂物理模拟实验,结果表明平均误差为16%,和实验符合较好.

  15. Multilevel groundwater monitoring of hydraulic head and temperature in the eastern Snake River Plain aquifer, Idaho National Laboratory, Idaho, 2007-08

    Fisher, Jason C.; Twining, Brian V.


    During 2007 and 2008, the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, collected quarterly depth-discrete measurements of fluid pressure and temperature in six boreholes located in the eastern Snake River Plain aquifer of Idaho. Each borehole was instrumented with a multilevel monitoring system consisting of a series of valved measurement ports, packer bladders, casing segments, and couplers. Hydraulic heads (head) and water temperatures in boreholes were monitored at 86 hydraulically-isolated depth intervals located 448.0 to 1,377.6 feet below land surface. The calculation of head is most sensitive to fluid pressure and the altitude of the pressure transducer at each port coupling; it is least sensitive to barometric pressure and water temperature. An analysis of errors associated with the head calculation determined the accuracy of an individual head measurement at +/- 2.3 feet. Many of the sources of measurement error are diminished when considering the differences between two closely-spaced readings of head; therefore, a +/- 0.1 foot measurement accuracy was assumed for vertical head differences (and gradients) calculated between adjacent monitoring zones. Vertical head and temperature profiles were unique to each borehole, and were characteristic of the heterogeneity and anisotropy of the eastern Snake River Plain aquifer. The vertical hydraulic gradients in each borehole remained relatively constant over time with minimum Pearson correlation coefficients between head profiles ranging from 0.72 at borehole USGS 103 to 1.00 at boreholes USGS 133 and MIDDLE 2051. Major inflections in the head profiles almost always coincided with low permeability sediment layers. The presence of a sediment layer, however, was insufficient for identifying the location of a major head change in a borehole. The vertical hydraulic gradients were defined for the major inflections in the head profiles and were as much as 2.2 feet per foot. Head gradients

  16. Hydraulic conductivity of a firn aquifer system in southeast Greenland

    Miller, Olivia L.; Solomon, D. Kip; Miège, Clément; Koenig, Lora S.; Forster, Richard R.; Montgomery, Lynn N.; Schmerr, Nicholas; Ligtenberg, Stefan R. M.; Legchenko, Anatoly; Brucker, Ludovic


    Some regions of the Greenland ice sheet, where snow accumulation and melt rates are high, currently retain substantial volumes of liquid water within the firn pore space throughout the year. These firn aquifers, found between 10-30 m below the snow surface, may significantly affect sea level rise by storing or draining surface meltwater. The hydraulic gradient and the hydraulic conductivity control flow of meltwater through the firn. Here we describe the hydraulic conductivity of the firn aquifer estimated from slug tests and aquifer tests at six sites located upstream of Helheim Glacier in southeastern Greenland. We conducted slug tests using a novel instrument, a piezometer with a heated tip that melts itself into the ice sheet. Hydraulic conductivity ranges between 2.5x10-5 and 1.1x10-3 m/s. The geometric mean of hydraulic conductivity of the aquifer is 2.7x10-4 m/s with a geometric standard deviation of 1.4 from both depth specific slug tests (analyzed using the Hvorslev method) and aquifer tests during the recovery period. Hydraulic conductivity is relatively consistent between boreholes and only decreases slightly with depth. The hydraulic conductivity of the firn aquifer is crucial for determining flow rates and patterns within the aquifer, which inform hydrologic models of the aquifer, its relation to the broader glacial hydrologic system, and its effect on sea level rise.

  17. Hydraulic Conductivity of a Firn Aquifer in Southeast Greenland

    Olivia L. Miller


    Full Text Available Some regions of the Greenland ice sheet, where snow accumulation and melt rates are high, currently retain substantial volumes of liquid water within the firn pore space throughout the year. These firn aquifers, found between ~10 and 30 m below the snow surface, may significantly affect sea level rise by storing or draining surface meltwater. The hydraulic gradient and the hydraulic conductivity control flow of meltwater through the firn. Here we describe the hydraulic conductivity of the firn aquifer estimated from slug tests and aquifer tests at six sites located upstream of Helheim Glacier in southeastern Greenland. We conducted slug tests using a novel instrument, a piezometer with a heated tip that melts itself into the ice sheet. Hydraulic conductivity ranges between 2.5 × 10−5 and 1.1 × 10−3 m/s. The geometric mean of hydraulic conductivity of the aquifer is 2.7 × 10−4 m/s with a geometric standard deviation of 1.4 from both depth specific slug tests (analyzed using the Hvorslev method and aquifer tests during the recovery period. Hydraulic conductivity is relatively consistent between boreholes and only decreases slightly with depth. The hydraulic conductivity of the firn aquifer is crucial for determining flow rates and patterns within the aquifer, which inform hydrologic models of the aquifer, its relation to the broader glacial hydrologic system, and its effect on sea level rise.

  18. Microfluidic parallel circuit for measurement of hydraulic resistance.

    Choi, Sungyoung; Lee, Myung Gwon; Park, Je-Kyun


    We present a microfluidic parallel circuit that directly compares the test channel of an unknown hydraulic resistance with the reference channel with a known resistance, thereby measuring the unknown resistance without any measurement setup, such as standard pressure gauges. Many of microfluidic applications require the precise transport of fluid along a channel network with complex patterns. Therefore, it is important to accurately characterize and measure the hydraulic resistance of each channel segment, and determines whether the device principle works well. However, there is no fluidic device that includes features, such as the ability to diagnose microfluidic problems by measuring the hydraulic resistance of a microfluidic component in microscales. To address the above need, we demonstrate a simple strategy to measure an unknown hydraulic resistance, by characterizing the hydraulic resistance of microchannels with different widths and defining an equivalent linear channel of a microchannel with repeated patterns of a sudden contraction and expansion.

  19. Effect of cavitation bubble collapse on hydraulic oil temperature

    沈伟; 张健; 孙毅; 张迪嘉; 姜继海


    Cavitation bubble collapse has a great influence on the temperature of hydraulic oil. Herein, cone-type throttle valve experiments are carried out to study the thermodynamic processes of cavitation. First, the processes of growth and collapse are analysed, and the relationships between the hydraulic oil temperature and bubble growth and collapse are deduced. The effect of temperature is then considered on the hydraulic oil viscosity and saturated vapour pressure. Additionally, an improved form of the Rayleigh–Plesset equation is developed. The effect of cavitation on the hydraulic oil temperature is experimentally studied and the effects of cavitation bubble collapse in the hydraulic system are summarised. Using the cone-type throttle valve as an example, a method to suppress cavitation is proposed.


    Zuorong Chen; A.P. Bunger; Xi Zhang; Robert G. Jeffrey


    Hydraulic fracturing is a powerful technology used to stimulate fluid production from reservoirs. The fully 3-D numerical simulation of the hydraulic fracturing process is of great importance to the efficient application of this technology, but is also a great challenge because of the strong nonlinear coupling between the viscous flow of fluid and fracture propagation. By taking advantage of a cohesive zone method to simulate the fracture process, a finite element model based on the existing pore pressure cohesive finite elements has been established to investigate the propagation of a penny-shaped hydraulic fracture in an infinite elastic medium. The effect of cohesive material parameters and fluid viscosity on the hydraulic fracture behaviour has been investigated. Excellent agreement between the finite element results and analytical solutions for the limiting case where the fracture process is dominated by rock fracture toughness demonstrates the ability of the cohesive zone finite element model in simulating the hydraulic fracture growth for this case.