scholarly journals Stream recession curves and storage variability in small watersheds

2011 ◽  
Vol 8 (1) ◽  
pp. 1827-1860 ◽  
Author(s):  
N. Y. Krakauer ◽  
M. Temimi
Keyword(s):  
Land Surface ◽  
Gravity Data ◽  
Regional Scale ◽  
Water Storage ◽  
High Flow ◽  
Water Infiltration ◽  
Low Flow ◽  
Stepwise Multiple Regression ◽  
Flow Rates ◽  
Small Watersheds

Abstract. The pattern of streamflow recession after rain events offers clues about the relationship between watershed runoff (observable as river discharge) and water storage (not directly observable) and can help in water resource assessment and prediction. However, it has not been systematically analyzed across flow rates or related to independent assessments of terrestrial water storage. We characterized the streamflow recession pattern in 61 relatively undisturbed small watersheds (1–100 km2) across the coterminous United States with multiyear records of hourly streamflow from automated gauges. We used the North American Regional Reanalysis (NARR) to help identify periods where precipitation, snowmelt, and evaporation were small compared to streamflow. The order of magnitude of the recession timescale increases from 1 day at high flow rates (~1 mm/h) to 10 days at low flow rates (~0.01 mm/h), leveling off at low flow rates. There is significant variability in the recession timescale at a given flow rate between basins, correlated with climate and geomorphic variables such as the ratio of mean streamflow to precipitation and soil water infiltration capacity. Stepwise multiple regression was used to construct a six-variable predictive model that explained some 80% of the variance in recession timescale at high flow rates and 30–50% at low flow rates. Seasonal and interannual variability in storage shows similar time evolution to but is up to a factor of 10 smaller than regional-scale water storage variability estimated from GRACE satellite gravity data and from land surface modeling forced by observed meteorology. The discrepancy may point to a "disconnection" between the conceptual pool that supplies streamflow during dry periods and other dynamic pools such as soil moisture and deep groundwater.

scholarly journals Stream recession curves and storage variability in small watersheds

2011 ◽  
Vol 15 (7) ◽  
pp. 2377-2389 ◽  
Author(s):  
N. Y. Krakauer ◽  
M. Temimi
Keyword(s):  
Land Surface ◽  
Regional Scale ◽  
Water Storage ◽  
High Flow ◽  
Water Infiltration ◽  
Low Flow ◽  
Stepwise Multiple Regression ◽  
Flow Rates ◽  
Small Watersheds ◽  
And Storage

Abstract. The pattern of streamflow recession after rain events offers clues about the relationship between watershed runoff (observable as river discharge) and water storage (not directly observable) and can help in water resource assessment and prediction. However, there have been few systematic assessments of how streamflow recession varies across flow rates and how it relates to independent assessments of terrestrial water storage. We characterized the streamflow recession pattern in 61 relatively undisturbed small watersheds (1–100 km2) across the coterminous United States with multiyear records of hourly streamflow from automated gauges. We used the North American Regional Reanalysis to help identify periods where precipitation, snowmelt, and evaporation were small compared to streamflow. The order of magnitude of the recession timescale increases from 1 day at high flow rates (~1 mm h−1) to 10 days at low flow rates (~0.01 mm h−1), leveling off at low flow rates. There is significant variability in the recession timescale at a given flow rate between basins, which correlates with climate and geomorphic variables such as the ratio of mean streamflow to precipitation and soil water infiltration capacity. Stepwise multiple regression was used to construct a six-variable predictive model that explained some 80 % of the variance in recession timescale at high flow rates and 30–50 % at low flow rates. Seasonal and interannual variability in inferred storage shows similar time evolution to regional-scale water storage variability estimated from GRACE satellite gravity data and from land surface modeling forced by observed meteorology, but is up to a factor of 10 smaller. Study of this discrepancy in the inferred storage amplitude may provide clues to the range of validity of the recession curve approach to relating runoff and storage.

Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump

2019 ◽  
Vol 36 (4) ◽  
pp. 401-410 ◽  
Author(s):  
Xiao-Qi Jia ◽  
Bao-Ling Cui ◽  
Zu-Chao Zhu ◽  
Yu-Liang Zhang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
High Flow ◽  
Low Flow ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Pressure Distributions ◽  
Blade Passing Frequency

Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.

Leach Behavior of SRL TDS-131 Defense Waste Glass in Water at High&Low Flow Rates

1983 ◽  
Vol 26 ◽  
Author(s):  
Aaron Barkatt ◽  
William Sousanpour ◽  
Alisa Barkatt ◽  
Morad A. Boroomand ◽  
Pedro B. Macedo
Keyword(s):  
Contact Time ◽  
Protective Layer ◽  
High Flow ◽  
Low Flow ◽  
Matrix Elements ◽  
Flow Rates ◽  
Low Concentrations ◽  
Controlling Mechanism ◽  
The Matrix ◽  
Leach Behavior

ABSTRACTLeach tests carried out on SRL TDS-131 Defense Waste Class indicate that at high flow rates the controlling mechanism is simple corrosion. The matrix elements (Si, Al) are leached out at rates similar to those of the leaching of the alkalis and of boron, and the leaching process is nearly linear with time. At slow flow rates (below 1 m/yr) leaching becomes controlled by the build-up of a protective layer. Al and most of the Si remain in the leached surface layer. The leach rates decrease in the course of the test before leveling off at constant values which are almost inversely proportional to the contact time, indicating that leachate concentrations have become solubility-limited. The low concentrations observed at this stage indicate the formation of alteration products.

scholarly journals An In Vitro Evaluation of the Red Cell Damage and Hemocompatibility of Different Central Venous Catheters

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Alojz Ihan ◽  
Stefan Grosek ◽  
David Stubljar
Keyword(s):  
Blood Cell ◽  
Flow Rate ◽  
Blood Cells ◽  
Cell Damage ◽  
Central Venous Catheters ◽  
High Flow ◽  
High Flow Rate ◽  
Low Flow ◽  
Central Venous ◽  
Flow Rates

Background. The aim of our study was to evaluate the damaging impact of characteristics of the central venous catheters (CVCs) on red blood cells. Methods. CVCs from three different manufacturers were analyzed, including the presence of coating, tunnel geometry, length, lumen diameter, and number of lumens with two respective flow rates (33 mL/min and 500 mL/min). Blood cell damage was defined by analyzing microparticle (MP) and hematologic analysis. MPs were isolated by ultracentrifugation of erythrocyte concentrate and analyzed on a flow cytometer. Results. Characteristics of catheters were not associated with blood cell damage at a low flow rate but showed an effect with a high flow rate. CVCs with a polyhexanide methacrylate coating have caused statistically less blood cell damage than noncoated CVCs. The length of lumens, diameter, and geometry of the tunnel showed no differences in blood cell damage. Meanwhile, the number of lumens was predicted to have a greater effect on the erythrocyte damage, which was revealed with the formation of MPs and hematological parameters. CVCs with five lumens caused significantly less damage to the blood cells than CVCs with a single lumen. Moreover, a high flow rate of 500 mL/min caused less damage to the blood cells than a low rate of 33 mL/min. Conclusion. Properties of CVCs are an important factor for quality patient care, especially when transfusing blood with high flow rates, as we want to provide a patient with high-quality blood with as few damaged cells as possible.

Rheological Effects of Blood in a Nonplanar Distal End-to-Side Anastomosis

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Qian-Qian Wang ◽  
Bao-Hong Ping ◽  
Qing-Bo Xu ◽  
Wen Wang
Keyword(s):  
Flow Rate ◽  
Stokes Equations ◽  
Bypass Graft ◽  
High Flow ◽  
Secondary Flows ◽  
Newtonian Fluids ◽  
Low Flow ◽  
Flow Rates ◽  
Flow Recirculation ◽  
Low Flow Rate

This study investigates rheological effects of blood on steady flows in a nonplanar distal end-to-side anastomosis. The shear-thinning behavior of blood is depicted by a Carreau–Yasuda model and a modified power-law model. To explore effects of nonplanarity in vessel geometry, a curved bypass graft is considered that connects to the host artery with a 90deg out-of-plane curvature. Navier–Stokes equations are solved using a finite volume method. Velocity and wall shear stress (WSS) are compared between Newtonian and non-Newtonian fluids at different flow rates. At low flow rate, difference in axial velocity profiles between Newtonian and non-Newtonian fluids is significant and secondary flows are weaker for non-Newtonian fluids. At high flow rate, non-Newtonian fluids have bigger peak WSS and WSS gradient. The size of the flow recirculation zone near the toe is smaller for non-Newtonian fluids and the difference is significant at low flow rate. The nonplanar bypass graft introduces helical flow in the host vessel. Results from the study reveal that near the bed, heel, and toe of the anastomotic junction where intimal hyperplasia occurs preferentially, WSS gradients are all very big. At high flow rates, WSS gradients are elevated by the non-Newtonian effect of blood but they are reduced at low flow rates. At these locations, blood rheology not only affects the WSS and its gradient but also secondary flow patterns and the size of flow recirculation near the toe. This study reemphasizes that the rheological property of blood is a key factor in studying hemodynamic effects on vascular diseases.

Control of Self-Excited Flow Oscillations in Vaneless Diffuser of Centrifugal Compression Systems

1982 ◽  
Author(s):  
A. N. Abdelhamid
Keyword(s):  
Flow Field ◽  
Performance Improvement ◽  
High Flow ◽  
Low Flow ◽  
Flow Oscillation ◽  
Vaneless Diffuser ◽  
Flow Area ◽  
Flow Measurements ◽  
Flow Rates ◽  
Flow Oscillations

Experiments were conducted to evaluate the effectiveness of axisymmetric diffuser exit throttle in delaying the occurrence of self-excited flow oscillation in vaneless diffusers. Sharp edge rings were installed at diffuser exit in order to change the exit flow area. Tests were carried out with the rings attached to one or both of the diffuser walls. Steady and unsteady flow measurements were used to determine the flow field in the diffuser at the onset of the flow oscillations. Results showed that the occurrence of flow oscillation was continuously delayed as the diffuser exit flow area was reduced for all these configurations and impeller speeds. Comparison between the performance of the compression system with and without diffuser exit blockage indicated that although large losses occur at high flow rates, the use of diffuser exit rings resulted in overall diffuser performance improvement at low flow rates. Retractable diffuser exit rings would therefore be ideal for centrifugal compression systems with vaneless diffuser.

scholarly journals Variations of Surface and Subsurface Water Storage in the Lower Mekong Basin (Vietnam and Cambodia) from Multisatellite Observations

Water ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 75 ◽  
Author(s):  
Binh Pham-Duc ◽  
Fabrice Papa ◽  
Catherine Prigent ◽  
Filipe Aires ◽  
Sylvain Biancamaria ◽  
...  
Keyword(s):  
Surface Water ◽  
Land Surface ◽  
Regional Scale ◽  
Water Storage ◽  
High Water ◽  
Subsurface Water ◽  
Annual Variations ◽  
Mekong Basin ◽  
Lower Mekong Basin ◽  
Monthly Variations

In this study, we estimate monthly variations of surface-water storage (SWS) and subsurface water storage (SSWS, including groundwater and soil moisture) within the Lower Mekong Basin located in Vietnam and Cambodia during the 2003–2009 period. The approach is based on the combination of multisatellite observations using surface-water extent from MODIS atmospherically corrected land-surface imagery, and water-level variations from 45 virtual stations (VS) derived from ENVISAT altimetry measurements. Surface-water extent ranges from ∼6500 to ∼40,000 km 2 during low and high water stages, respectively. Across the study area, seasonal variations of water stages range from 8 m in the upstream parts to 1 m in the downstream regions. Annual variation of SWS is ∼40 km 3 for the 2003–2009 period that contributes to 40–45% of total water-storage (TWS) variations derived from Gravity Recovery And Climate Experiment (GRACE) data. By removing the variations of SWS from GRACE-derived TWS, we can isolate the monthly variations of SSWS, and estimate its mean annual variations of ∼50 km 3 (55–60% of the TWS). This study highlights the ability to combine multisatellite observations to monitor land-water storage and the variations of its different components at regional scale. The results of this study represent important information to improve the overall quality of regional hydrological models and to assess the impacts of human activities on the hydrological cycles.

Estimating Large-Scale Precipitation Minus Evapotranspiration from GRACE Satellite Gravity Measurements

2006 ◽  
Vol 7 (2) ◽  
pp. 252-270 ◽  
Author(s):  
Sean Swenson ◽  
John Wahr
Keyword(s):  
Land Surface ◽  
Seasonal Cycle ◽  
Large Scale ◽  
Gravity Data ◽  
Water Storage ◽  
Department Of Energy ◽  
Surface Model ◽  
Satellite Gravity ◽  
Discharge Data ◽  
Temporal Sampling

Abstract Currently, observations of key components of the earth's large-scale water and energy budgets are sparse or even nonexistent. One key component, precipitation minus evapotranspiration (P − ET), remains largely unmeasured due to the absence of observations of ET. Precipitation minus evapotranspiration describes the flux of water between the atmosphere and the earth's surface, and therefore provides important information regarding the interaction of the atmosphere with the land surface. In this paper, large-scale changes in continental water storage derived from satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) project are combined with river discharge data to obtain estimates of areally averaged P − ET. After constructing an equation describing the large-scale terrestrial water balance reflecting the temporal sampling of GRACE water storage estimates, GRACE-derived P − ET estimates are compared to those obtained from a reanalysis dataset [NCEP/Department of Energy (DOE) reanalysis-2] and a land surface model driven with observation-based forcing [Global Land Data Assimilation System (GLDAS)/Noah] for two large U.S. river basins. GRACE-derived P − ET compares quite favorably with the reanalysis-2 output, while P − ET from the Noah model shows significant differences. Because the uncertainties in the GRACE results can be computed rigorously, this comparison may be considered as a validation of the models. In addition to showing how GRACE P − ET estimates may be used to validate model output, the accuracy of GRACE estimates of both the seasonal cycle and the monthly averaged rate of P − ET is examined. Finally, the potential for estimating seasonal evapotranspiration is demonstrated by combining GRACE seasonal P − ET estimates with independent estimates of the seasonal cycle of precipitation.

Speed Matching of the Second Rotor in a Counter-Rotating Fan Under Off-Design Conditions

2017 ◽  
Author(s):  
Zijian Ai ◽  
Guoliang Qin ◽  
Xuefei Chen ◽  
Jingxiang Lin ◽  
Wenqiang He
Keyword(s):  
Numerical Simulation ◽  
Theoretical Analysis ◽  
High Efficiency ◽  
Pressure Rise ◽  
High Flow ◽  
Low Flow ◽  
Flow Rates ◽  
Fan Performance ◽  
Power Characteristics ◽  
Equal Power

A method for speed matching of the second rotor (R2) with equal power for two rotors was proposed to improve the performance of the counter-rotating fan under off-design conditions. In this method, the speed of R2 is adjusted until the power of R2 is equal to the power of the first rotor (R1). The fan performance during constant speed operation and during R2 speed matching operation is presented and discussed using theoretical analysis, numerical simulation, and experimental research. The results show that R2 speed matching improves the power and efficiency characteristics of R2. Thus, the pressure rise and power characteristics of the fan were improved. The load of R2 under low flow rates condition was decreased, and the pressure rise and efficiency of R2 under high flow rates condition were increased. The blocking condition margin increased from 37.2% to 48.0%, and the high-efficiency working range of the fan increased from 33.2% to 37.9%.

scholarly journals Impact of the Microstructure of Polymer Drag Reducer on Slick-Water Fracturing

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Zhi-yu Liu ◽  
Fu-jian Zhou ◽  
Hong-yan Qu ◽  
Zhao Yang ◽  
Yu-shi Zou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Drag Reduction ◽  
Network Structure ◽  
High Flow ◽  
Low Flow ◽  
Distributed Network ◽  
Reduction Mechanism ◽  
Flow Rates ◽  
Transmission Electron

Many studies have focused on the drag reduction performance of slick-water, but the microdrag reduction mechanism remains unclear since the microstructure of the drag reducer and its effect on this mechanism have not been well studied. In this study, the microstructure of the drag reducer in slick-water was effectively characterized by transmission electron microscopy. The viscoelasticity and drag reduction performance of the drag reducer with different microstructures were then investigated. Further, the effects of the microstructure of the drag reducer on the viscoelasticity and drag reduction performance of slick-water were analyzed. The results demonstrated that the viscoelasticity of slick-water is governed by the microstructure of the drag reducer, which exhibits a network structure. In addition, the drag reduction performance is related to the viscoelasticity. At low flow rates, the drag reduction performance is dominantly influenced by viscosity, whereas, at high flow rates, it is governed mainly by elasticity. Furthermore, the drag reducer with a uniformly distributed network structure exhibits the most stable drag reduction performance. This drag reducer was used in a field test and the obtained results were consistent with those of a laboratory experiment.

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