scholarly journals Mixing enhancement mechanisms in aquifers affected by hydropeaking: Insights from flow‐through laboratory experiments

2021 ◽  
Author(s):  
F. Ziliotto ◽  
M. Basilio Hazas ◽  
M. Rolle ◽  
G. Chiogna
Keyword(s):  
Laboratory Experiments ◽  
Mixing Enhancement ◽  
Flow Through

Mixing Enhancement of Two Gases in a Microchannel Using DSMC

2013 ◽  
Vol 307 ◽  
pp. 166-169 ◽  
Author(s):  
Masoud Darbandi ◽  
Elyas Lakzian
Keyword(s):  
Gas Flow ◽  
Flow Analysis ◽  
Direct Simulation Monte Carlo ◽  
Equilibrium Composition ◽  
Mass Composition ◽  
Mixing Enhancement ◽  
Mixing Process ◽  
Result Section ◽  
Flow Through ◽  
Simulation Monte Carlo

Microgas flow analysis may not be performed accurately using the classical CFD methods because of encountering high Knudsen number regimes. Alternatively, the gas flow through micro-geometries can be investigated reliably using the direct simulation Monte Carlo (DSMC) method. Our concern in this paper is to use DSMC to study the mixing of two gases in a microchannel. The mixing process is assumed to be complete when the mass composition of each species deviates by no more than ±1% from its equilibrium composition. To enhance the mixing process, we focus on the effects of inlet-outlet pressure difference and the pressure ratios of the incoming CO and N2 streams on the mixing enhancement. The outcome of this study is suitably discussed in the result section.

scholarly journals The Influence of Grain Size Distribution on the Hydraulic Gradient for Initiating Backward Erosion

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2644 ◽  
Author(s):  
Willem-Jan Dirkx ◽  
Rens Beek ◽  
Marc Bierkens
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Laboratory Experiments ◽  
Hydraulic Gradient ◽  
Concentrated Flow ◽  
Pipe Formation ◽  
Novel Method ◽  
Flow Through ◽  
The Stability

Backward erosion by piping is one of the processes that threaten the stability of river embankments in the Netherlands. During high river stages, groundwater flow velocities underneath the embankment increase as a result of the steepened hydraulic gradient. If a single outflow point exists or forms, the concentrated flow can entrain soil particles, leading to the formation of a subsurface pipe. The processes controlling this phenomenon are still relatively unknown due to their limited occurrence and because piping is a subsurface phenomenon. To study the initiation of piping, we performed laboratory experiments in which we induced water flow through a porous medium with a vertically orientated outflow point. In these experiments, we explicitly considered grain size variations, thus adding to the existing database of experiments. Our experiments showed that the vertical velocity needed for the initiation of particle transport can be described well by Stokes’ law using the median grain size. We combine this with a novel method to relate bulk hydraulic conductivity to the grain size distribution. This shows that knowledge of the grain size distribution and the location of the outflow point are sufficient to estimate the hydraulic gradient needed to initiate pipe formation in the experiment box.

scholarly journals Mean zonal flows generated by librations of a rotating spherical cavity

2010 ◽  
Vol 650 ◽  
pp. 505-512 ◽  
Author(s):  
F. H. BUSSE
Keyword(s):  
Rotation Rate ◽  
Spherical Cavity ◽  
Laboratory Experiments ◽  
Liquid Core ◽  
Zonal Flow ◽  
Zonal Flows ◽  
Ekman Layers ◽  
Nonlinear Advection ◽  
Planets And Satellites ◽  
Flow Through

Longitudinal librations represent oscillations about the axis of a rotating axisymmetric fluid-filled cavity. An analytical theory is developed for the case of a spherical cavity in the limit when the libration frequency is small in comparison with the rotation rate, but large in comparison with the inverse of the spin-up time. It is shown that longitudinal librations create a steady zonal flow through the nonlinear advection in the Ekman layers. The theory can be applied to laboratory experiments as well as to solid planets and satellites with a liquid core.

scholarly journals Modelling of Flow Parameters through Subsurface Drainage Modules for Application in BIOECODS

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1823 ◽  
Author(s):  
Abdurrasheed Sa’id Abdurrasheed ◽  
Khamaruzaman Wan Yusof ◽  
Ebrahim Hamid Hussein Alqadami ◽  
Husna Takaijudin ◽  
Aminuddin Ab. Ghani ◽  
...  
Keyword(s):  
Flow Resistance ◽  
Laboratory Experiments ◽  
Drainage System ◽  
Roughness Coefficient ◽  
Complex Nature ◽  
Urban Drainage ◽  
River Engineering ◽  
Flow Conditions ◽  
Flow Parameters ◽  
Flow Through

The flow resistance of the existing modules in the bio-ecological drainage system (BIOECODS) is high and may lead to flood instead of its mitigation. As part of efforts to enhance the performance of the system, the river engineering and urban drainage research center (REDAC) module was developed. This study modelled the hydrodynamics of flow through this module using FLOW-3D and laboratory experiments for two cases of free flow without module (FFWM) and flow with a module (FWM) to understand and visualize the effects of the module. With less than 5% error between the numerical and experimental results, REDAC module altered the flow pattern and created resistance by increasing the Manning’s roughness coefficient at the upstream, depth-averaged flow velocity (43.50 cm/s to about 46.50 cm/s) at the downstream and decreasing water depth (7.75–6.50 cm). These variations can be attributed to the complex nature of the module pattern with further increase across the porous openings. Therefore, the technique used herein can be applied to characterize the behavior of fluids in larger arrangments of modules and under different flow conditions without the need for expensive laboratory experiments.

Laboratory Experiments on Solute Transport in Non-Homogeneous Porous Media

1986 ◽  
Vol 17 (4-5) ◽  
pp. 305-314 ◽  
Author(s):  
Anders Refsgaard
Keyword(s):  
Porous Media ◽  
Hydraulic Conductivity ◽  
Solute Transport ◽  
Laboratory Experiments ◽  
Heterogeneous Porous Media ◽  
Heterogeneous Porous Medium ◽  
Dispersion Parameters ◽  
Homogeneous Porous Media ◽  
Flow Through ◽  
Good Agreement

Solute transport in groundwater is a process which has become of major importance during the last decades due to increasing contamination of ground water. This process usually occurs in a medium heterogeneous with respect to hydraulic conductivity and porosity, properties that affect the dispersion of the solutes. The present paper describes an experimental investigation of the solute transport process in heterogeneous porous media, especially the connection between the statistical properties of their hydraulic conductivity distributions and the dispersion parameters governing the spreading of the solutes. The experimental results are compared to theoretical solutions derived for the same case of a solute pulse in an average uniform flow through a heterogeneous porous medium. Generally there is good agreement between the theory and the experiments. In field applications this means that the dispersion parameters can be more readily determined from the soil properties. Furthermore, the deviations between dispersivities determined in laboratory columns and dispersitivies found under field conditions can be explained quantitatively by the differencies in the length scales and in the variances of the hydraulic conductivity distributions.

Multi-layer hydraulic exchange flows

2000 ◽  
Vol 416 ◽  
pp. 269-296 ◽  
Author(s):  
G. F. LANE-SERFF ◽  
D. A. SMEED ◽  
C. R. POSTLETHWAITE
Keyword(s):  
Internal Wave ◽  
Laboratory Experiments ◽  
Rectangular Cross Section ◽  
Wave Mode ◽  
Uniform Density ◽  
Exchange Flow ◽  
Hydraulic Control ◽  
Narrow Channels ◽  
Reservoir Conditions ◽  
Flow Through

Flows between ocean basins are often controlled by narrow channels and shallow sills. A multi-layer hydraulic control theory is developed for exchange flow through such constrictions. The theory is based on the inviscid shallow-water equations and extends the functional approach introduced by Gill (1977) and developed by Dalziel (1991). The flows considered are those in rectangular–cross-section channels connecting two large reservoirs, with a single constriction (sill and/or narrows). The exchange flow depends on the stratification in the two reservoirs, represented as a finite number of immiscible layers of (different) uniform density. For most cases the flow is ‘controlled’ at the constriction and often at other points along the channel (virtual controls) too. As with one- and two-layer hydraulics, controls are locations at which the flow passes from one solution branch to another, and at which (at least) one internal wave mode is stationary. The theory is applied to three-layer flows, which have two internal wave modes, predicting interface heights and layer fluxes from the given reservoir conditions. The theoretical results for three-layer flows are compared to a comprehensive set of laboratory experiments and found to give good agreement. The laboratory experiments also show other features of the flow, such as the formation of waves on the interfaces. The implications of the results for oceanographic flows and ocean modelling are discussed.

On buoyancy-driven natural ventilation of a room with a heated floor

2001 ◽  
Vol 441 ◽  
pp. 293-314 ◽  
Author(s):  
CHARLOTTE GLADSTONE ◽  
ANDREW W. WOODS
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Laboratory Experiments ◽  
Natural Ventilation ◽  
Quantitative Model ◽  
Small Scale ◽  
Heated Floor ◽  
Flow Through ◽  
Lower Temperature ◽  
Advective Heat Transfer

The natural ventilation of a room, both with a heated floor and connected to a cold exterior through two openings, is investigated by combining quantitative models with analogue laboratory experiments. The heated floor generates an areal source of buoyancy while the openings allow displacement ventilation to operate. When combined, these produce a steady state in which the air in the room is well-mixed, and the heat provided by the floor equals the heat lost by displacement. We develop a quantitative model describing this process, in which the advective heat transfer through the openings is balanced with the heat flux supplied at the floor. This model is successfully tested with observations from small-scale analogue laboratory experiments. We compare our results with the steady-state flow associated with a point source of buoyancy: for a given applied heat flux, an areal source produces heated air of lower temperature but a greater volume flux of air circulates through the room. We generalize the model to account for the effects of (i) a cooled roof as well as a heated floor, and (ii) an external wind or temperature gradient. In the former case, the direction of the flow through the openings depends on the temperature of the exterior air relative to an averaged roof and floor temperature. In the latter case, the flow is either buoyancy dominated or wind dominated depending on the strength of the pressure associated with the wind. Furthermore, there is an intermediate multiple-solution regime in which either flow regime may develop.

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