Relevant bibliographies by topics / Flow gradients

Academic literature on the topic 'Flow gradients'

Author: Grafiati
Published: 7 July 2024

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Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Journal articles on the topic "Flow gradients":

1

B N, Shobha, Govind R. Kadambi, S. R. Shankapal, and Yuri Vershinim. "Effect of variation in colour gradient information for optic flow computations." International Journal of Engineering & Technology 3, no. 4 (September 17, 2014): 445. http://dx.doi.org/10.14419/ijet.v3i4.2722.

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Optic flow algorithms provide mapping of 3D velocities on 2D image space. Optic flow is computed on the pair of images which are in sequence and is normally gray scale images. Optic flow computation using Horn and Schunck assumes that brightness consistency is maintained. Colour optic flow has the advantage that optic flow vectors are obtained even when there is a variation of brightness in the input images. The use of colour bands for optic flow is investigated by considering gradients of colour bands and component gradients. Results of applying these two types of gradients to three colour models are presented and analyzed. Decision logic is proposed to select the best colour model for colour optic flow computation based on gradient analysis. Keywords: Activity Measure. Colour Bands, Component Gradients, Decision Logic, Optic Flow Computation.
2

Xu, Wenrui, and James M. Stone. "Bondi–Hoyle–Lyttleton accretion in supergiant X-ray binaries: stability and disc formation." Monthly Notices of the Royal Astronomical Society 488, no. 4 (July 25, 2019): 5162–84. http://dx.doi.org/10.1093/mnras/stz2002.

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Abstract We use 2D (axisymmetric) and 3D hydrodynamic simulations to study Bondi–Hoyle–Lyttleton accretion with and without transverse upstream gradients. We mainly focus on the regime of high (upstream) Mach number, weak upstream gradients, and small accretor size, which is relevant to neutron star accretion in wind-fed supergiant X-ray binaries (SgXBs). We present a systematic exploration of the flow in this regime. When there are no upstream gradients, the flow is always stable regardless of accretor size or Mach number. For finite upstream gradients, there are three main types of behaviour: stable flow (small upstream gradient), turbulent unstable flow without a disc (intermediate upstream gradient), and turbulent flow with a disc-like structure (relatively large upstream gradient). When the accretion flow is turbulent, the accretion rate decreases non-convergently as the accretor size decreases. The flow is more prone to instability and the disc is less likely to form than previously expected; the parameters of most observed SgXBs place them in the regime of a turbulent, disc-less accretion flow. Among the SgXBs with relatively well-determined parameters, we find OAO 1657−415 to be the only one that is likely to host a persistent disc (or disc-like structure); this finding is consistent with observations.
3

Alicia, Toh G. G., Chun Yang, Zhiping Wang, and Nam-Trung Nguyen. "Combinational concentration gradient confinement through stagnation flow." Lab on a Chip 16, no. 2 (2016): 368–76. http://dx.doi.org/10.1039/c5lc01137j.

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Herbelin, Armando, and Jaromir Ruzicka. "Pulse Modulation - A Novel Approach to Gradient-Based Flow Injection Techniques." Collection of Czechoslovak Chemical Communications 66, no. 8 (2001): 1219–37. http://dx.doi.org/10.1135/cccc20011219.

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Development of a novel system for generation of gradients in flow injection analysis by pulse modulation is described. These user-selectable gradients are created by computer-controlled mixing of two solutions with a total volume as low as 75 μl and can be delivered under incremental or continuous flow conditions. Applications such as automated, single-standard instrument calibration are expected to benefit from high-precision linear gradients (r2 = 0.99989, n = 55). Gradient methods in biochemisty and immunology such as kinetic measurement of biomolecular interactions will benefit from the small volume of these gradients, especially for analytes with limited availability.
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Wright, Stephen P., Alexander R. Opotowsky, Tayler A. Buchan, Sam Esfandiari, John T. Granton, Jack M. Goodman, and Susanna Mak. "Flow-related right ventricular to pulmonary arterial pressure gradients during exercise." Cardiovascular Research 115, no. 1 (June 6, 2018): 222–29. http://dx.doi.org/10.1093/cvr/cvy138.

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Abstract Aims The assumption of equivalence between right ventricular (RV) and pulmonary arterial systolic pressure is fundamental to several assessments of RV or pulmonary vascular haemodynamic function. Our aims were to (i) determine whether systolic pressure gradients develop across the RV outflow tract in healthy adults during exercise, (ii) examine the potential correlates of such gradients, and (iii) consider the effect of such gradients on calculated indices of RV function. Methods and results Healthy untrained and endurance-trained adult volunteers were studied using right-heart catheterization at rest and during submaximal cycle ergometry. RV and pulmonary artery (PA) pressures were simultaneously transduced, and the cardiac output was determined by thermodilution. Systolic pressures, peak and mean gradients, and indices of chamber, vascular, and valve function were analysed offline. Summary data are reported as mean ± standard deviation or median (interquartile range). No significant RV outflow tract gradients were observed at rest [mean gradient = 4 (3–5) mmHg], and the calculated effective orifice area was 3.6 ± 1.0 cm2. The increase in right ventricular systolic pressure during exercise was greater than the PA systolic pressure. Accordingly, mean gradients were developed during light exercise [8 (7–9) mmHg] and increased during moderate exercise [12 (9–14) mmHg, P < 0.001]. The magnitude of the mean gradient was linearly related to the cardiac output (r2 = 0.70, P < 0.001). Conclusions In healthy adults without pulmonic stenosis, systolic pressure gradients develop during exercise, and the magnitude is related to the blood flow rate.
6

Dai, Bo, Yan Long, Jiandong Wu, Shaoqi Huang, Yuan Zhao, Lulu Zheng, Chunxian Tao, et al. "Generation of flow and droplets with an ultra-long-range linear concentration gradient." Lab on a Chip 21, no. 22 (2021): 4390–400. http://dx.doi.org/10.1039/d1lc00749a.

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A concentration gradient generator is demonstrated to generate ultra-long linear gradients, periodic gradients and droplets with various concentrations and produce drugs with different concentrations for drug screening applications.
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Chittur K, Subramaniam, Aishwarya Chandran, Ashwini Khandelwal, and Sivakumar A. "Energy Conversion using electrolytic concentration gradients." MRS Proceedings 1774 (2015): 51–62. http://dx.doi.org/10.1557/opl.2015.758.

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ABSTRACTSalinity gradient is an enormous source of clean energy. A process for potential generation from an ionic concentration gradient produced in single and multicell assembly is presented. The ionic gradient is created using a fuel cell type cell with a micro-porous ion exchange membrane, both anionic (AEM) and cationic (CEM). Various salinity gradients, Salt : Fresh, from 100 : 0 to 16000 : 0 was established using NaCl solution, in the electrode chambers. A potential of 20 mV/cm to 25 mV/cm can be realized at ambient temperatures and pressures for a bipolar AEM/CEM cell. The performance was optimized for various static and dynamic flow rates of the saline and fresh water. The cell performance can further be optimized for Membrane Electrode System (MES) morphology. A multicell unit was assembled and the results presented for various conditions like concentration gradients, flow rates and pressure. The thermodynamic and electrical efficiency needs to be evaluated for various gradients and flow rates. The relation with number of valance electrons/ ion and the potential generated changes for various dynamic condition of salinity. The higher the salinity gradient the larger is the potential generated. This is limited by the membrane characteristics. There exists a monotonic relation between the number of valence electron/ion/unit time and the potential generated up to about 16000 concentration. The membrane characteristics have been studied for optimal ion crossover for various gradients and flow. The graph between ln (gradient) versus Voltage provides insights into this process. This presents a very cost effective and clean process of energy conversion.
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Williams, Ian, Sangyoon Lee, Azzurra Apriceno, Richard P. Sear, and Giuseppe Battaglia. "Diffusioosmotic and convective flows induced by a nonelectrolyte concentration gradient." Proceedings of the National Academy of Sciences 117, no. 41 (September 28, 2020): 25263–71. http://dx.doi.org/10.1073/pnas.2009072117.

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Glucose is an important energy source in our bodies, and its consumption results in gradients over length scales ranging from the subcellular to entire organs. Concentration gradients can drive material transport through both diffusioosmosis and convection. Convection arises because concentration gradients are mass density gradients. Diffusioosmosis is fluid flow induced by the interaction between a solute and a solid surface. A concentration gradient parallel to a surface creates an osmotic pressure gradient near the surface, resulting in flow. Diffusioosmosis is well understood for electrolyte solutes, but is more poorly characterized for nonelectrolytes such as glucose. We measure fluid flow in glucose gradients formed in a millimeter-long thin channel and find that increasing the gradient causes a crossover from diffusioosmosis-dominated to convection-dominated flow. We cannot explain this with established theories of these phenomena which predict that both scale linearly. In our system, the convection speed is linear in the gradient, but the diffusioosmotic speed has a much weaker concentration dependence and is large even for dilute solutions. We develop existing models and show that a strong surface–solute interaction, a heterogeneous surface, and accounting for a concentration-dependent solution viscosity can explain our data. This demonstrates how sensitive nonelectrolyte diffusioosmosis is to surface and solution properties and to surface–solute interactions. A comprehensive understanding of this sensitivity is required to understand transport in biological systems on length scales from micrometers to millimeters where surfaces are invariably complex and heterogeneous.
9

Dixon, D. A., J. Graham, and M. N. Gray. "Hydraulic conductivity of clays in confined tests under low hydraulic gradients." Canadian Geotechnical Journal 36, no. 5 (November 23, 1999): 815–25. http://dx.doi.org/10.1139/t99-057.

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Clay barriers normally function at hydraulic gradients much lower than are commonly used in laboratory tests for hydraulic conductivity. This paper describes low-gradient tests on compacted illite, Na-bentonite, and sand-bentonite specimens at a range of dry densities. The tests examined the effects of deionized or saline pore fluid, the initial degree of saturation at the time of compaction, and back-pressuring to achieve saturation during permeation. No "critical" or "threshold" gradients were observed. In low-density materials, "transitional" gradients defined two separate regions of Darcian flow. Low flow rates and low hydraulic conductivities were associated with hydraulic gradients below the transitional gradient. Higher conductivities were associated with gradients above the transitional gradient. Hydraulic conductivities decreased with increasing initial density. They appeared independent of initial degree of saturation or back-pressuring. Tests on Na-rich bentonite showed that deionized and saline permeants produced similar hydraulic conductivities. Measured hydraulic conductivities were in reasonable agreement with values computed using the Poiseuille and Kozeny-Carman equations. Key words: hydraulic conductivity, gradient, Darcian, illite, bentonite.
10

Cardin, Velia, and Andrew T. Smith. "Sensitivity of human visual cortical area V6 to stereoscopic depth gradients associated with self-motion." Journal of Neurophysiology 106, no. 3 (September 2011): 1240–49. http://dx.doi.org/10.1152/jn.01120.2010.

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The principal visual cue to self-motion (egomotion) is optic flow, which is specified in terms of local 2D velocities in the retinal image without reference to depth cues. However, in general, points near the center of expansion of natural flow fields are distant, whereas those in the periphery are closer, creating gradients of horizontal binocular disparity. To assess whether the brain combines disparity gradients with optic flow when encoding egomotion, stereoscopic gradients were applied to expanding dot patterns presented to observers during functional MRI scanning. The gradients were radially symmetrical, disparity changing as a function of eccentricity. The depth cues were either consistent with egomotion (peripheral dots perceived as near and central dots perceived as far) or inconsistent (the reverse gradient, central dots near, peripheral dots far). The BOLD activity generated by these stimuli was compared in a range of predefined visual regions in 13 participants with good stereoacuity. Visual area V6, in the parieto-occipital sulcus, showed a unique pattern of results, responding well to all optic flow patterns but much more strongly when they were paired with consistent rather than inconsistent or zero-disparity gradients. Of the other areas examined, a region of the precuneus and parietoinsular vestibular cortex also differentiate between consistent and inconsistent gradients, but with weak or suppressive responses. V3A, V7, MT, and ventral intraparietal area responded more strongly in the presence of a depth gradient but were indifferent to its depth-flow congruence. The results suggest that depth and flow cues are integrated in V6 to improve estimation of egomotion.
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Journal articles Dissertations / Theses Books

Dissertations / Theses on the topic "Flow gradients":

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Herbelin, Armando L. "Dispersion and gradients in flow injection /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/11548.

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Woods, George Stephen. "Studies in vertical multiphase flow." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247344.

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Ganti, Raman S. "Microscopic forces and flows due to temperature gradients." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274324.

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Nano-scale fluid flow is unlike transport on the macro-scale. Pressure gradients typically dominate effects on a large scale while thermal gradients contribute negligibly to the motion of fluid. The situation entirely reverses on the nano-scale. At a microscopic level, flows induced by thermal gradients are caused by forces that act on atoms or molecules near an interface. These thermo-osmotic forces cannot, at present, be derived analytically or measured experimentally. Clearly, it would be useful to calculate these forces via molecular simulations, but direct approaches fail because in the steady-state, the average force per particle vanishes, as the thermo-osmotic force is balanced by a gradient in shear stress. In our journey to indirectly calculate the osmotic force, we met another unknown in the field of molecular theory at interfaces: the microscopic pressure tensor. The latter is an open problem since the microscopic pressure near an interface is not uniquely defined. Using local thermodynamics theories, we relate the thermo-osmotic force to the gradient of the microscopic pressure tensor. Yet, because the pressure is not uniquely defined, we arrive at multiple answers for the thermo-osmotic force, where at most one can be correct. To resolve the latter puzzle, we develop a direct, non-equilibrium simulation protocol to measure the thermo-osmotic force, whereby a thermal gradient is imposed and the osmotic force is measured by eliminating the shear force. Surprisingly, we find that the osmotic force cannot be derived from the gradient of well-known microscopic pressure expressions. We, therefore, derive a thermodynamic expression that gets close. In this work, we report the first, direct calculation of the thermo-osmotic force while simultaneously showing that standard microscopic pressure expressions fail to predict pressure gradients.
4

Adigio, Emmanuel M. "Modelling gas flow pressure gradients in Gelcast ceramic foam diesel particulate filters." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/33933.

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Internal combustion engines are significant contributors to air pollution. To meet the future legislative particu1ate matter (PM) emissions targets for diesel engines there is a need for aftertreatment of the exhaust gases. Previous investigations have shown that diesel particulate filters (DPFs) are a potential exhaust aftertreatment technology for the reduction of PM emissions. DPF systems generally contain two elements; one or more filters (i.e. porous media) and a means of regenerating (i.e. cleaning) the filter(s). The filter must be regenerated intermittently or continuously to prevent imposing high exhaust back pressures on the engine. This thesis presents the study of fluid flow through Gelcast ceramic foams that are a potential candidate filter material for use in DPF systems.
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Hacker, Wayne. "An asymptotic theory for distributed receptivity of flow fields with pressure gradients." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/280035.

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A systematic asymptotic analysis is used to devise a model for distributed boundary-layer receptivity for flow fields with pressure gradients. The model predicts the generation of a Tollmien-Schlichting (TS) wave due to the interaction of a time-harmonic free-stream disturbance with distributed wall waviness and the subsequent evolution of this TS wave under the influence of wall waviness. The model is restricted to two dimensions and the Reynolds number is assumed to be large. Unlike previous models, the present model allows a nonzero pressure gradient in the base flow, and accounts for nonparallel-flow effects. A Green's-function approach was employed. The interaction between the free-stream disturbance and a point source at the wall was first examined in a local region near the point source. Only the component corresponding to the largest-growing instability wave was determined. The downstream evolution of this wave was then investigated over a region that extended for many TS wavelengths. For this reason it was necessary to account for the nonparallel-flow effects. By solving for the dispersion relation in this downstream region, the evolution of the eigenmode was determined. A match between the local-region and the downstream solution led to a uniform approximation for the TS wave emerging from the point source. Summing over a region of point-source solutions and approximating the resulting integral using the method of steepest descents yielded the instability wave for the wavy wall. The principal results of the present work included a solution to the dispersion relation for a general base flow with a nonzero pressure gradient beyond leading order. A region of maximal growth for TS waves that were generated from point sources located in a region of width O (Re-3/16) surrounding the lower branch neutral stability point (LBNSP) was identified. Here Re is the global Reynolds number. For adverse pressure gradients, it was also determined that, when the wall waviness and the TS wave are in exact resonance, the wave produced from distributed receptivity is significantly smaller than the wave generated by a point source at the LBNSP. For the case of a strong favorable pressure gradient the reverse is true. Finally, an investigation of the effect of pressure gradient on detuning was carried out. It showed that complete detuning occurs when the relative difference between the wavenumber of the TS wave at the LBNSP and the wavenumber of the sinusoidal wall is O (Re-3/16). It also revealed that the response to detuning varies with pressure gradient. For situations with a strong favorable pressure gradient, growth rates are highly sensitive to an exact match between the wavenumbers of the wall and the TS wave. On the other hand, as the pressure gradient grows less favorable, sensitivity to detuning decreases.
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Benton, Joshua Robert. "Temporal Dynamics of Groundwater Flow Direction in a Glaciated, Headwater Catchment." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/104222.

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Shallow groundwater flow in the critical zone of steep headwater mountain catchments is often assumed to mimic surface topography. However, groundwater flow is influenced by other variables, such as the elevation of the water table and subsurface hydraulic conductivity, which can result in temporal variations in both magnitude and direction of flow. In this study, I investigated the temporal variability of groundwater flow in the soil zone (solum) within the critical zone of a headwater catchment at the Hubbard Brook Experimental Forest in North Woodstock, NH. Groundwater levels were continuously monitored throughout several seasons (March 2019 to Jan 2020) in a network of wells comprising three hillslope transects within the upper hillslopes of the catchment. Five clusters of three wells per cluster were screened from 0.18 – 1.1 m depth at the base of the solum. Water levels were also monitored in five deeper wells, screened from 2.4 - 6.9 m depth within glacial sediments of the C horizon. I conducted 47 slug tests across the well network to determine hydraulic properties of the aquifer materials surrounding each well. In addition, our team conducted a large-scale auger investigation mapping soil horizon depths and thicknesses. Results show that the magnitude of hydraulic gradients and subsurface hydrologic fluxes varied at each site with respect to changing water-table elevation, having a maximum range of 0.12 m/m and 9.19 x 10-6 m/s, respectively. The direction of groundwater flow had an arithmetic mean deviating from surface topography by 2-10 degrees, and a total range that deviated from surface topography by as much as 51 degrees. During lower water table regimes, groundwater flow direction deviated from the ground surface, but under higher water table regimes, in response to recharge events, flow direction mimicked surface topography. Within most of the well clusters, there is an observable connection between the slope direction of the top of the C horizon and the direction of groundwater flow during lower water table regimes. Slug test results show the interquartile range of saturated hydraulic conductivity (K¬sat¬) within the C horizon (1.5×10-7 to 9.8×10-7 m/s) is two orders of magnitude lower than the interquartile range of K¬sat¬ values within the solum (2.9×10-5 to 5.2×10-5 m/s). Thus, the C horizon is on average a confining unit relative to the solum that may constrict groundwater flow below the solum. Additionally, results from the larger scale auger investigation suggest that deviations in subsurface topography of the C horizon may be generalizable at the larger hillslope scale. Overall, these results indicate that 1) shallow groundwater flow direction and magnitude within this headwater catchment are dynamic and can deviate from surface topography, and 2) the subsurface topography of the C horizon can influence groundwater flow direction. These results imply that temporal dynamics of groundwater flow direction and magnitude should be considered when characterizing subsurface flow in critical zone studies. Additionally, knowledge of subsurface topography of confining units may provide constraints on the temporal variability of groundwater flow direction.
M.S.
Streams that originate at higher elevations (defined as headwater streams) are important drinking water sources and deliver water and nutrients to maintain freshwater ecosystems. Groundwater is a major source of water to these streams, but little is known about how groundwater flows in these areas. Scientists delineate watersheds (areas of land that drain water to the same point) using surface topography. This approach works well for surface water, but not as well for groundwater, as groundwater may not flow in the same direction as surface water. Thus, assuming that the ground-watershed is the same as the surface watershed can lead to errors in hydrologic studies. To obtain more accurate information about groundwater flow in headwater areas, I continuously measured groundwater levels in forest soils at the Hubbard Brook Experimental Forest in North Woodstock, NH. My main objective was to determine if there is variability in the direction and amount of groundwater flow. I also measured the characteristics of the soils to identify the thicknesses of soil units and the permeability of those units. I used these data to evaluate the relationship between groundwater flow direction, surface topography, and the permeability of soil units. Overall, I found that groundwater flow direction can differ significantly from surface topography, and groundwater flow direction was influenced by the groundwater levels. When groundwater levels were high (closer to the land surface), groundwater flow was generally in the same direction as surface topography. However, when groundwater levels were lower, flow direction typically followed the slope of the lowest permeability soil unit. These results suggest that scientists should not assume that groundwater flow follows the land surface topography and should directly measure groundwater levels to determine flow direction. In addition, results from this study show that characterizing soil permeability can help scientists make more accurate measurements of groundwater flow.
7

Kuřátko, Jiří. "Počítání lidí ve videu." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2016. http://www.nusl.cz/ntk/nusl-255470.

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This master's thesis prepared the programme which is able to follow the trajectories of the movement of people and based on this to create various statistics. In practice it is an effective marketing tool which can be used for instance for customer flow analyses, optimal evaluation of opening hours, visitor traffic analyses and for a lot of other benefits. Histograms of oriented gradients, SVM classificator and optical flow monitoring were used to solve this problem. The method of multiple hypothesis tracking was selected for the association data. The system's quality was evaluated from the video footage of the street with the large concentration of pedestrians and from the school's camera system, where the movement in the corridor was monitored and the number of people counted.
8

Memory, Curtis Lynn. "Numerical Simulation of Vortex Generating Jets in Zero and Adverse Pressure Gradients." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2098.pdf.

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Gibson, Jeffrey Reed. "Direct Numerical Simulation of Transonic Wake Flow in the Presence of an Adverse Pressure Gradient and Streamline Curvature." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2795.

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Wakes are present in many engineering flows. These flows include internal flows such as mixing chambers and turbomachinery as well as external flows like flow over high-lift or multi-element airfoils. Many times these wakes are exposed to flow conditions such as adverse pressure gradients and streamline curvature that alter the mean flow and turbulent structure of the wake. The ability to understand how pressure gradients and streamline curvature affects the structure of the wake is essential to predicting how the wake will affect the performance of the application in which it is found. The effects of pressure gradients and curvature of low-speed wakes has been extensively documented. As the transonic flow regime is becoming of more interest as gas speeds in turbomachinery increase this work fills a void in the body of wake knowledge pertaining to curved wakes in high speed flows. An under-resolved direct numerical simulation of transonic wake flow being shed by a cambered airfoil in the presence of adverse pressure gradients and streamline curvature is therefore presented here. It was observed that the turbulence characteristics arising from the cambered airfoil that generates the wake dominate the evolution of the wake for different distances downstream depending on the component of the Reynolds stresses that is being considered. These characteristics dissipated the most quickly in the shear stresses and endured the longest in the tangential normal stresses. Previous work in low-speed wakes has indicated that curvature creates new production terms that translate into asymmetry in the profiles of the wake. Curvature was observed to have limited influence on the evolution of the streamwise normal stresses and an extensive impact on the tangential normal stresses. The transport of the Reynolds shear stresses indicate that the asymmetry in this stress is caused indeed by curvature but through turbulent diffusion and not production. The k-ε turbulence model overpredicted the effect of curvature on the turbulence stresses in the wake. This led to accelerated wake decay and spread compared to the UDNS data.
10

Khabbaz, Saberi Hamid. "Hydraulic characteristics and performance of stormwater pollutant trap respect to weir's height, flow gradients, pipe diameters and pollutant capture." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2143.

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The main focus of urban stormwater runoff disposal has traditionally been to provide structurally-sound drainage systems to carry runoff from many different surfaces without considering water quality at outfall. This has contributed to the decline of water quality in rivers and lakes and other receiving bodies. According to Lord (1987), "stormwater management is primarily concerned with limiting future flood damages and environmental impacts due to development, where as flood control aims at reducing the extent of flooding that occurs under current conditions". Recent developments in stormwater pollutant trap (SPTs), which are generally end-of-the-line devices designed to capture and store gross pollutants, for subsequent removal and disposal.During the last few decades, use of SPTs as a source of collecting and removing pollutants from stormwater (which carries many different types of chemicals and nonchemical pollutants that contaminates our rivers, lakes and other receiving bodies) has increased considerably. Wide-ranging efforts and attempts have been made in both academic and industrial research to improve the quality of stormwater by improving the use of gross pollutant traps (GPTs – known as hydrodynamic separators) by utilising and improving available experimental and modelling techniques. The use of vortex phenomena has always been a challenging problem and available data is rare and complicated in the literature. This research focuses on detailed investigation by experimental means. The generated vortex in this experiment is created in a cylindrical chamber above the level of a cylindrical screening basket. In addition, the research analyses the processes involved in this separation technique.One scale model of a Versa Trap (Type A) was experimentally analysed to investigate and establish the relationship between headloss and flow rate and hydraulic characteristics of a weir in a diversion weir pit. The Versa trap Type A storm pollutant traps are usually used as off-line traps in city and urban areas to capture and store debris – especially those which are captured from surfaces such as rooftops, paved streets, highways, parking lots, lawns, and paved and gravelled roads (Allison et al., 1998). The Versa Trap Type A utilises an upstream diversion weir pit to divert the design treatment flow (DTF) into the treatment chamber. Treated flow returns to the diversion pit downstream of the weir, where it re-enters the drainage system. Peak flow in excess of the DTF bypasses the SPT over the weir into the pipeline downstream.It has been demonstrated that the aggregate of all flows of three months average recurrence interval (ARI) and less represented the majority (up to 97.5%) of the total flow generated by a stormwater drainage catchment (Works, 2006). There is some conjecture as to the veracity of the ‘first flush’ theory, which holds that most of the pollutants in the catchments are transported during the first flush of the storm event (Lee et al., 2007). However, it is generally accepted that SPTs should be sized so as to treat only a portion of the peak flow, with excess flows bypassing the trap. The three month ARI peak flow is commonly taken as appropriate for establishing the minimum DTF required of the SPT.The measurement of headloss across a scale model of a VT Type A storm pollutant trap at a range of flow rates through the SPT, provide data from which a mathematical relationship between flow rate and the headloss cab be established for the device.The resultant relationship then can be used in another part of the experiment to establish the hydraulic characteristics of a weir across a cylindrical chamber, as used for the upstream diversion weir pit in conjunction with the Type A VT range of SPTs. By varying the weir height in a scale model of a diversion weir pit and measuring the flow rates associated with headlosses determined from the previously established relationship, the relationship between weir height and diverted flow can be established. This allows the designer to specify the weir height required to divert the flow rate associated with a specific peak flow or treatment flow of SPT design.Two main characteristics which determine the performance of a gross pollutant trap are trapping efficiency and required maintenance. The trapping efficiency is defined as the portion of the total mass of gross pollutant transported by stormwater that is retained by the trap. A low trapping efficiency means that gross pollutants pass through the trap and reach downstream waters. A poorly-maintained trap will be inefficient at trapping pollutants and is also a potential source of pollutants as trapped materials break down.The experiment parts of this project were tested at Curtin University of Technology’s Hydraulic Laboratory. To replicate typical in-situ conditions, the VT Type A was tested for 0, 22, 33, 44, 55, 66 and 77% simulated blocked screen conditions for trapping efficiency. Data analysis has demonstrated that the headloss increases in proportion to flow rates and screen blockage condition. The results were scaled up to provide data on the full range of unit sizes. This research describes the testing and scaling methodologies in detail, with graphical representation of headloss and other hydraulic parameters at various conditions. The study’s findings have capabilities to optimise any other types of stormwater treatment systems. These types of traps’ are used in commercial and residential environment.This experiment is in continuation of the experiment which was conducted by Muhammad Ismail on industrial gross pollutant traps using double basket to trap the debris for industrial application.Also another good reference for pollutant build up and wash off modelling of impervious surfaces in Perth area, is done by Saadat Ashraf in his PhD thesis. For more information refer to references.
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Books on the topic "Flow gradients":

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E, Zorumski W., Rawls John W, and Langley Research Center, eds. Experimental feasibility of investigating acoustic waves in Couette flow with entropy and pressure gradients. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1990.

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Otto, S. R. The effect of crossflow on Görtler vortices. Hampton, VA: Institute for Computer Applications in Science and Engineering, NASA Langley Research Center, 1994.

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United States. National Aeronautics and Space Administration. Scientific and Technical Information Branch., ed. A root-mean-square pressure fluctuations model for internal flow applications. [Washington, DC]: National Aeronautics and Space Administration, Scientific and Technical Information Branch, 1985.

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P, Leonard B., and United States. National Aeronautics and Space Administration., eds. A modified mixing length turbulence model for zero and adverse pressure gradients. [Washington, DC]: National Aeronautics and Space Administration, 1994.

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Conley, J. M. A modified mixing length turbulence model for zero and adverse pressure gradients. [Washington, DC]: National Aeronautics and Space Administration, 1994.

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Johnston, Craig M. Documentation and application of a method to compute maximum slope and aspect of hydraulic gradients. Pembroke, N.H: U.S. Dept. of the Interior, U.S. Geological Survey, 1998.

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Johnston, Craig M. Documentation and application of a method to compute maximum slope and aspect of hydraulic gradients. Pembroke, N.H: U.S. Dept. of the Interior, U.S. Geological Survey, 1998.

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Johnston, Craig M. Documentation and application of a method to compute maximum slope and aspect of hydraulic gradients. Pembroke, N.H: U.S. Dept. of the Interior, U.S. Geological Survey, 1998.

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E, Kelly R., and United States. National Aeronautics and Space Administration., eds. Effect of density gradients in confined supersonic shear layers. [Washington, DC: National Aeronautics and Space Administration, 1994.

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Li, C. Mixing enhancement due to pressure and density gradients generated by expansion waves in supersonic flows. Washington, D. C: American Institute of Aeronautics and Astronautics, 1991.

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Book chapters on the topic "Flow gradients":

1

Machtejevas, Egidijus. "Additional Tools for Method Development: Flow and Temperature Gradients." In Gradient HPLC for Practitioners, 215–21. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2019. http://dx.doi.org/10.1002/9783527812745.ch9.

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Kit, E., A. Tsinober, and T. Dracos. "Velocity Gradients in a Turbulent Jet Flow." In Advances in Turbulence IV, 185–90. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1689-3_31.

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Lemonis, G., T. Dracos, and A. Tsinober. "Velocity Gradients Depending Quantities in Turbulent Grid Flow." In Fluid Mechanics and Its Applications, 308–13. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0457-9_55.

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Michael, Joel, William Cliff, Jenny McFarland, Harold Modell, and Ann Wright. "The “Unpacked” Core Concept of Flow Down Gradients." In The Core Concepts of Physiology, 55–61. New York, NY: Springer New York, 2017. http://dx.doi.org/10.1007/978-1-4939-6909-8_6.

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Ma, Sizhuo, Brandon M. Smith, and Mohit Gupta. "3D Scene Flow from 4D Light Field Gradients." In Computer Vision – ECCV 2018, 681–98. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-01237-3_41.

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Medhi, Biswajit, Abhishek Khatta, G. M. Hegde, K. P. J. Reddy, D. Roy, and R. M. Vasu. "Improved Flow Visualization for Fast Recovery of Flow Gradients in Shadow-Casting Technique." In 30th International Symposium on Shock Waves 2, 1473–76. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-44866-4_119.

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Moeller, Mark J., Teresa S. Miller, and Richard G. DeJong. "Effect of Developing Pressure Gradients on TBL Wall Pressure Spectrums." In Flinovia - Flow Induced Noise and Vibration Issues and Aspects, 47–65. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-09713-8_3.

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Wei, Liang, and Andrew Pollard. "Direct Numerical Simulation of a Turbulent Flow with Pressure Gradients." In Springer Proceedings in Physics, 131–34. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-02225-8_31.

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Callaghan, P. T. "NMR in polymers using magnetic field gradients: imaging, diffusion and flow." In NMR Spectroscopy of Polymers, 308–42. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-2150-7_9.

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Rashwan, Hatem A., Mahmoud A. Mohamed, Miguel Angel García, Bärbel Mertsching, and Domenec Puig. "Illumination Robust Optical Flow Model Based on Histogram of Oriented Gradients." In Lecture Notes in Computer Science, 354–63. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-40602-7_38.

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Conference papers on the topic "Flow gradients":

1

Smith, Barton L. "Oscillating Flow in Adverse Pressure Gradients." In INNOVATIONS IN NONLINEAR ACOUSTICS: ISNA17 - 17th International Symposium on Nonlinear Acoustics including the International Sonic Boom Forum. AIP, 2006. http://dx.doi.org/10.1063/1.2210383.

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Smith, Barton L., Kristen V. Mortensen, and Spencer Wendel. "Oscillating Flow in Adverse Pressure Gradients." In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77458.

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Separating oscillating flow in an internal adverse pressure gradient geometry is studied experimentally. Phase-locked PIV measurements and simultaneous pressure measurements reveal that during the accelerating portion of the cycle, the flow remains attached in spite of a very large adverse pressure gradient. During the decelerating portion of the cycle, the flow is more prone to separation. The duration and extent of the separation depend strongly on the oscillation displacement amplitude relative to the cross-stream dimension. In some cases, the flow separates but reattaches as the separated shear layer is accelerated temporally. The time-varying pressure measurements are used to determine the resultant minor losses for the flow in each direction. These are found to be an increasing function of displacement amplitude and independent of the Reynolds number.
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MĄDRY, ALEKSANDER. "GRADIENTS AND FLOWS: CONTINUOUS OPTIMIZATION APPROACHES TO THE MAXIMUM FLOW PROBLEM." In International Congress of Mathematicians 2018. WORLD SCIENTIFIC, 2019. http://dx.doi.org/10.1142/9789813272880_0185.

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Helgason, Eysteinn, and Siniša Krajnović. "A Comparison of Adjoint-Based Optimizations for Industrial Pipe Flow." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21542.

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This paper presents results from adjoint-based optimization processes applied to an inlet pipe of an exhaust gas recirculation cooler in a diesel engine. The boundary conditions applied resemble those of a truck at cruising speed. Three implementations are considered for the gradient calculations with the objective of minimizing the total pressure drop through the pipe. In the first implementation the gradients are evaluated with respect to the motion of the center of the cell using a newly presented implementation based on the ALE formulation of the Navier-Stokes equations. The results are compared to the surface sensitivities, where the gradient of the cost function is evaluated with respect to the normal motion of the surface of the pipe. In the last approach a topological optimization is performed where the gradients are evaluated with respect to a momentum loss in each cell. This gives information that is used when blocking the cells.
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Temeng, K. O., and R. N. Horne. "The Effect of High-Pressure Gradients on Gas Flow." In SPE Annual Technical Conference and Exhibition. Society of Petroleum Engineers, 1988. http://dx.doi.org/10.2118/18269-ms.

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ONITSUKA, K., and I. NEZU. "SIMILARITY LAW IN OPEN-CHANNEL FLOWS WITH FAVORABLE-PRESSURE GRADIENTS." In Proceedings of the 8th International Symposium on Flow Modeling and Turbulence Measurements. WORLD SCIENTIFIC, 2002. http://dx.doi.org/10.1142/9789812777591_0003.

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Ahmed, Moinuddin, and Roger E. Khayat. "Flow of a Thin Viscoelastic Jet." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30505.

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The influence of elasticity and inertia for steady flow of a thin viscoelastic fluid jet is examined theoretically. The fluid is assumed to emerge from a vertical channel and driven by a pressure gradient and/or gravity. The boundary-layer equations are generalized for a viscoelastic thin film obeying the Oldroyd-b constitutive model. Special emphasis is placed on the initial stages of jet development. The formulation and simulation are carried out for two-dimensional jet flow in order to better understand the intricate wave and flow structures for a viscoelastic jet. In contrast to the commonly used depth-averaging solution method, the strong nonlinearities are preserved in the present formulation as the viscoelastic boundary-layer equations are solved by expanding the flow field in terms of orthonormal shape functions. It is found that for a steady viscoelastic jet, a reduction in inertia or a rise in elasticity leads to the emergence of surface waviness and excessive normal stress, which leads to the formation of sharp gradients in the velocity and shear stress. These gradients can be sufficiently substantial to cause a discontinuity or shock in the flow. During transition, the surface profiles adhere earlier to the shape of the final steady state instead of a traveling wave, the transition between the two states takes the form of a standing wave, which grows essentially in amplitude only.
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Phillips, Michael, Steve Deutsch, Arnie Fontaine, and Savas Yavuzkurt. "Experimental and Fundamental Analysis of Flow in Corners: Favorable and Adverse Pressure Gradients." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-61019.

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Three dimensional instantaneous velocity data were taken in a turbulent corner flow with smooth walls under zero, a favorable, and an adverse pressure gradient. The favorable pressure gradient was −26.5 Pa/m (K = 0.15E−6) and the adverse gradient was 34.9 Pa/m (K = −0.20E−6). This paper will concentrate on effects of the favorable and adverse pressure gradients. Zero pressure gradient results were published in an earlier manuscript [1]. Experiments were carried out in air with a free stream inlet velocity of 13 m/s and an axial Reynolds number of about one million. The data were collected using a three-component LDV system that was configured in a nearly orthogonal setup. Measurements were made down to a y+ of approximately 5, and should provide a valuable data set in developing models and predictive codes. Data were collected at two axial locations, 0.93 and 1.26 m measured from the virtual origin. The boundary layer thickness was 20.90 mm and 24.91 mm respectively at these locations for the zero gradient case. The favorable gradient had thicknesses of 19.35 mm and 22.53 mm respectively, whereas the thicknesses of adverse pressure gradient were 28.89 mm and 36.81 mm. At each position, instantaneous velocity profiles were measured at 6.35, 12.7, 20.6, 41.2, 82.3, 121.9, 164.5, 184.8, and 205.1 mm from the corner. The centerline profiles agree well with classical flat plate data. Three mean velocity and six Reynolds stress components have been calculated. The instantaneous velocity field data set is sufficient to compute higher order correlations. The data will be very valuable for development of computer codes and models for corner flows of all kinds and for heat transfer studies in the internal cooling channels of gas turbine blades and turbine end wall flow. An analysis of the data is presented and will provide a detailed database for this complex three dimensional flow fields.
9

Awad, M. M., and Y. S. Muzychka. "Two-Phase Flow Modeling in Microchannels and Minichannels." In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62134.

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In the present paper, three different methods for two-phase flow modeling in microchannels and minichannels are presented. They are effective property models for homogeneous two-phase flows, an asymptotic modeling approach for separated two-phase flow, and bounds on two-phase frictional pressure gradient. In the first method, new definitions for two-phase viscosity are proposed using a one dimensional transport analogy between thermal conductivity of porous media and viscosity in two-phase flow. These new definitions can be used to compute the two-phase frictional pressure gradient using the homogeneous modeling approach. In the second method, a simple semi-theoretical method for calculating two-phase frictional pressure gradient using asymptotic analysis is presented. Two-phase frictional pressure gradient is expressed in terms of the asymptotic single-phase frictional pressure gradients for liquid and gas flowing alone. In the final method, simple rules are developed for obtaining rational bounds for two-phase frictional pressure gradient in minichannels and microchannels. In all cases, the proposed modeling approaches are validated using the published experimental data.
10

Hatman, Anca, and Ting Wang. "Separated-Flow Transition: Part 2 — Experimental Results." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-462.

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The present paper focuses on presenting the results of the experimental investigation of the transition process in separated boundary layers on a flat plate at zero incidence, with imposed adverse pressure gradients. The combined effects of Reynolds number and adverse pressure gradient strength on the transition mechanism, bubble geometry, and bubble bursting process are studied. The flow structures and the unsteady aspects associated with separated-flow transition are analyzed for three representative experimental cases. Surface pressure results and detailed boundary layer measurements using hot-wire anemometry are presented as mean and rms velocity profiles, and Reynolds shear stress distribution. Turbulent intermittency and spectral analysis results are briefly introduced.

Reports on the topic "Flow gradients":

1

Montalvo-Bartolomei, Axel, Bryant Robbins, Erica Medley, and Benjamin Breland. Backward erosion testing : Magnolia Levee. Engineer Research and Development Center (U.S.), September 2021. http://dx.doi.org/10.21079/11681/42140.

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Using a confined flume device, an experimental study investigated the critical horizontal gradient of soils obtained from a site identified as potentially vulnerable to backward erosion piping (BEP). Tests were conducted on glacial outwash material obtained from a sand and gravel quarry in the vicinity of Magnolia Levee in the community of Magnolia, OH. The two bulk samples collected from the quarry had similar grain-size distributions, grain roundness, and depositional environments as the foundation materials beneath the levee. Samples were prepared at various densities and subjected to gradual increases of flow in a wooden flume with an acrylic top until BEP was observed. The critical average horizontal gradient ranged from 0.21 to 0.30 for a bulk sample with a coefficient of uniformity of 1.6, while tests conducted on a bulk sample with a coefficient of uniformity of 2.5 yielded critical average horizontal gradients of 0.31 to 0.36. The critical average gradients measured during these tests compared favorably to values in the literature after applying adjustments according to Schmertmann’s method.
2

Dement, Franklin L. Effects of Pressure Gradients on Turbulent Boundary Layer Flow Over a Flat Plate with Riblets. Fort Belvoir, VA: Defense Technical Information Center, March 1999. http://dx.doi.org/10.21236/ada361555.

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Schlossnagle, Trevor H., Janae Wallace,, and Nathan Payne. Analysis of Septic-Tank Density for Four Communities in Iron County, Utah - Newcastle, Kanarraville, Summit, and Paragonah. Utah Geological Survey, December 2022. http://dx.doi.org/10.34191/ri-284.

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Iron County is a semi-rural area in southwestern Utah that is experiencing an increase in residential development. Although much of the development is on community sewer systems, many subdivisions use septic tank soil-absorption systems for wastewater disposal. Many of these septic-tank systems overlie the basin-fill deposits that compose the principal aquifer for the area. The purpose of our study is to provide tools for waterresource management and land-use planning. In this study we (1) characterize the water quality of four areas in Iron County (Newcastle, Kanarraville, Summit, and Paragonah) with emphasis on nutrients, and (2) provide a mass-balance analysis based on numbers of septic-tank systems, groundwater flow available for mixing, and baseline nitrate concentrations, and thereby recommend appropriate septic-system density requirements to limit water-quality degradation. We collected 57 groundwater samples and three surface water samples across the four study areas to establish baseline nitrate concentrations. The baseline nitrate concentrations for Newcastle, Kanarraville, Summit, and Paragonah are 1.51 mg/L, 1.42 mg/L, 2.2 mg/L, and 1.76 mg/L, respectively. We employed a mass-balance approach to determine septic-tank densities using existing septic systems and baseline nitrate concentrations for each region. Nitrogen in the form of nitrate is one of the principal indicators of pollution from septic tank soil-absorption systems. To provide recommended septic-system densities, we used a mass-balance approach in which the nitrogen mass from projected additional septic tanks is added to the current nitrogen mass and then diluted with groundwater flow available for mixing plus the water added by the septic-tank systems themselves. We used an allowable degradation of 1 mg/L with respect to nitrate. Groundwater flow volume available for mixing was calculated from existing hydrogeologic data. We used data from aquifer tests compiled from drinking water source protection documents to derive hydraulic conductivity from reported transmissivities. Potentiometric surface maps from existing publications and datasets were used to determine groundwater flow directions and hydraulic gradients. Our results using the mass balance approach indicate that the most appropriate recommended maximum septic-tank densities in Newcastle, Kanarraville, Summit, and Paragonah are 23 acres per system, 7 acres per system, 5 acres per system, and 11 acres per system, respectively. These recommendations are based on hydrogeologic parameters used to estimate groundwater flow volume. Public valley-wide sewer systems may be a better alternative to septic-tank systems where feasible.
4

Steinerberger, Stefan, and Aleh Tsyvinski. Tax Mechanisms and Gradient Flows. Cambridge, MA: National Bureau of Economic Research, May 2019. http://dx.doi.org/10.3386/w25821.

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Starr, T. L., and A. W. Smith. Modeling of forced flow/thermal gradient chemical vapor infiltration. Office of Scientific and Technical Information (OSTI), September 1992. http://dx.doi.org/10.2172/7038514.

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Starr, T. L., and A. W. Smith. Modeling of forced flow/thermal gradient chemical vapor infiltration. Office of Scientific and Technical Information (OSTI), September 1992. http://dx.doi.org/10.2172/10185554.

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Allison. L51510 Field Observations of Two-Phase Flow in the Matagorda Offshore Pipeline System. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), May 1986. http://dx.doi.org/10.55274/r0010071.

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Offshore gas production typically involves the simultaneous flow of oil and/or condensate. The oil may he entrained in the gas rising in the vertical well from the sea-bed or may flow under its own pressure gradient; condensate may result from the reduction of pressure from well conditions to pipeline transport pressure and from cooling sea temperatures. It would be unduly expensive to build a gas-liquid separation facility on a production platform, followed by two separate pipeline transport systems for the two phases. It is therefore desirable to examine pipeline systems that carry hydrocarbon liquid and gas together. Two-phase flow of oil and gas under steady-state operation of the Matagorda Offshore Pipeline System was observed by nuclear densitometry at two onshore sites. Oil flowed into the pipeline system at an average rate of 1.6 Bbl/ MMSCF over the two-month data acquisition period; gas flow was constant at about 200 MMSCF per day.
8

Starr, T. L., and A. W. Smith. Finite volume model for forced flow/thermal gradient chemical vapor infiltration. Office of Scientific and Technical Information (OSTI), March 1991. http://dx.doi.org/10.2172/10104941.

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Yochum, Steven E., Francesco Comiti, Ellen Wohl, Gabrielle C. L. David, and Luca Mao. Photographic guidance for selecting flow resistance coefficients in high-gradient channels. Ft. Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 2014. http://dx.doi.org/10.2737/rmrs-gtr-323.

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Starr, T. L., and A. W. Smith. Finite volume model for forced flow/thermal gradient chemical vapor infiltration. Office of Scientific and Technical Information (OSTI), March 1991. http://dx.doi.org/10.2172/6111003.

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