scholarly journals Numerical study on particle transport and deposition in rough fractures

2020 ◽  
Vol 75 ◽  
pp. 23 ◽  
Author(s):  
Xiaoyu Wang ◽  
Jun Yao ◽  
Liang Gong ◽  
Hai Sun ◽  
Yongfei Yang ◽  
...  
Keyword(s):  
Particle Deposition ◽  
Numerical Study ◽  
Density Ratio ◽  
Sediment Distribution ◽  
Particulate Materials ◽  
Transport Distance ◽  
Clear Insight ◽  
Flow Through ◽  
The Mean ◽  
Development Engineering

The transport and deposition of particulate materials through fractures is widely involved in environmental engineering and resource development engineering. A 3D Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) coupling method was used to investigate the particle and fluid flow. The Gauss Model was applied to construct the rough surfaces. First, the numerical results were compared with the previous results and reasonable agreements were obtained. Second, the results indicated a novel flow pattern of particles in rough fractures. Then, a comprehensive particle sedimentary analysis indicated that the deposition distance of particles was inversely proportional to the particle size and density ratio. In addition, the particle deposition rates were increased by the mean roughness and there was an uneven sediment distribution impacted by roughness. Reasons for this uneven sediment distribution were analyzed in detail. Moreover, the bridge plugs of particles considering the closure of fractures were simulated as well. A part of particulate materials would be filtered at the inlet due to size effect and the transport distance of entered particles decreased significantly when the particle was large. A critical particle radius (R < 0.27 mm) that can flow through closure fracture in this work was found. This work can provide a clear insight into the migration and deposition characteristics of particles in the rough fractures underground.

Numerical Study on the Effect of Bend Angle on Turbulent Flow through Oscillating Bend

2009 ◽  
Vol 4 (1) ◽  
Author(s):  
Elham Ameri ◽  
M Nasr Esfahany
Keyword(s):  
Numerical Study ◽  
Bend Angle ◽  
Curvature Radius ◽  
Primary Flow ◽  
Mean Velocity ◽  
Contour Map ◽  
Curved Pipes ◽  
Flow Through ◽  
The Mean ◽  
Turbulent Air Flow

The effect of the bend angle on the unsteady developing turbulent air flow through oscillating circular-sectioned curved pipes with the various angles of 180°, 135° and 90° was investigated numerically. The bends had a diameter of 106 mm and a curvature radius ratio of 6.0 with long, straight upstream and downstream sections. Results of the mean velocity and static pressure were obtained at a Reynolds number of 31200 and at various longitudinal stations. The velocity of the primary flow was illustrated in the form of contour map and vector diagram. From the inlet plane of the three oscillating bends to the angle of 45°, the velocity fields in 180°, 90° and 135° bends are similar. The high velocity regions, however, occur near the upper and lower parts in 90° and 180° bends, respectively.

Study of the Influence of the Add оf Micropores on Filtering Characteristics of High Porous Structures

2020 ◽  
Vol 24 (9) ◽  
pp. 39-43
Author(s):  
O.V. Soloveva ◽  
S.A. Solovev ◽  
R.R. Yafizov
Keyword(s):  
Quality Factor ◽  
Particle Deposition ◽  
Gas Flow ◽  
Numerical Study ◽  
Total Porosity ◽  
Deposition Efficiency ◽  
Open Cell Foam ◽  
Flow Through ◽  
Highly Porous ◽  
Highly Porous Material

In this work we carried out a numerical study of the gas flow through an open cell foam material with solid-state partitions and partitions containing micropores. The effect of a geometry change by adding micropores on the pressure drop, particle deposition efficiency, and filter quality factor is estimated. The results showed that the addition of micropores positively affects the filtering and hydrodynamic properties of the highly porous material for the same macroporosity of the medium, and for the case of total porosity of the medium, the material with micropores allows one to obtain an increased value of the deposition efficiency and filter quality factor for small particles.

scholarly journals Turbulent and viscous sediment transport – a numerical study

2014 ◽  
Vol 37 ◽  
pp. 73-80 ◽  
Author(s):  
O. Durán ◽  
B. Andreotti ◽  
P. Claudin
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Numerical Study ◽  
Fluid Velocity ◽  
Density Ratio ◽  
Shear Velocity ◽  
Transport Layer ◽  
Two Phase ◽  
Unit Surface ◽  
The Mean

Abstract. Sediment transport is studied as a function of the grain to fluid density ratio using two phase numerical simulations based on a discrete element method (DEM) for particles coupled to a continuum Reynolds averaged description of hydrodynamics. At a density ratio close to unity (typically under water), sediment transport occurs in a thin layer at the surface of the static bed, and is called bed load. Steady, or "saturated" transport is reached when the fluid borne shear stress at the interface between the mobile grains and the static grains is reduced to its threshold value. The number of grains transported per unit surface therefore scales as the excess shear stress. However, the fluid velocity in the transport layer remains almost undisturbed so that the mean grain velocity scales with the shear velocity u*. At large density ratio (typically in air), the vertical velocities are large enough to make the transport layer wide and dilute. Sediment transport is then called saltation. In this case, particles are able to eject others when they collide with the granular bed. The number of grains transported per unit surface is selected by the balance between erosion and deposition and saturation is reached when one grain is statistically replaced by exactly one grain after a collision, which has the consequence that the mean grain velocity remains independent of u*. The influence of the density ratio is systematically studied to reveal the transition between these two transport regimes. Finally, for the subaqueous case, the grain Reynolds number is lowered to investigate the change from turbulent and viscous transport.

Stochastic homogenization and macroscopic modelling of composites and flow through porous media

2002 ◽  
pp. 337-378 ◽  
Author(s):  
Jozef Telega ◽  
Wlodzimierz Bielski
Keyword(s):  
Porous Medium ◽  
Random Distribution ◽  
Flow Through Porous Media ◽  
Macroscopic Models ◽  
Linear Elastic ◽  
Multi Scale ◽  
Convergence Method ◽  
Flow Through ◽  
The Mean ◽  
Random Porous Medium

The aim of this contribution is mainly twofold. First, the stochastic two-scale convergence in the mean developed by Bourgeat et al. [13] is used to derive the macroscopic models of: (i) diffusion in random porous medium, (ii) nonstationary flow of Stokesian fluid through random linear elastic porous medium. Second, the multi-scale convergence method developed by Allaire and Briane [7] for the case of several microperiodic scales is extended to random distribution of heterogeneities characterized by separated scales (stochastic reiterated homogenization). .

Study of pumping effect in flow-through electrolysers

1983 ◽  
Vol 48 (8) ◽  
pp. 2232-2248 ◽  
Author(s):  
Ivo Roušar ◽  
Michal Provazník ◽  
Pavel Stuhl
Keyword(s):  
Natural Convection ◽  
Balance Equation ◽  
Volume Fraction ◽  
Industrial Applications ◽  
Pumping Effect ◽  
Flow Through ◽  
The Mean ◽  
The Difference

In electrolysers with recirculation, where a gas is evolved, the pumping of electrolyte from a lower to a higher level can be effected by natural convection due to the difference between the densities of the inlet electrolyte and the gaseous emulsion at the outlet. An accurate balance equation for calculation of the rate of flow of the pumped liquid is derived. An equation for the calculation of the mean volume fraction of bubbles in the space between the electrodes is proposed and verified experimentally on a pilot electrolyser. Two examples of industrial applications are presented.

scholarly journals A Numerical Study of the Effect of Particle Size on Particle Deposition on Turbine Vanes and Blades

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110178
Author(s):  
Zhengang Liu ◽  
Weinan Diao ◽  
Zhenxia Liu ◽  
Fei Zhang
Keyword(s):  
Particle Size ◽  
Particle Deposition ◽  
Numerical Study ◽  
Stokes Number ◽  
Capture Efficiency ◽  
Particle Capture ◽  
Factors Affecting ◽  
Pressure Surface ◽  
Deposition Area ◽  
Turbine Vanes

Particle deposition could decrease the aerodynamic performance and cooling efficiency of turbine vanes and blades. The particle motion in the flow and its temperature are two important factors affecting its deposition. The size of the particle influences both its motion and temperature. In this study, the motion of particles with the sizes from 1 to 20 μm in the first stage of a turbine are firstly numerically simulated with the steady method, then the particle deposition on the vanes and blades are numerically simulated with the unsteady method based on the critical viscosity model. It is discovered that the particle deposition on vanes mainly formed near the leading and trailing edge on the pressure surface, and the deposition area expands slowly to the whole pressure surface with the particle size increasing. For the particle deposition on blades, the deposition area moves from the entire pressure surface toward the tip with the particle size increasing due to the effect of rotation. For vanes, the particle capture efficiency increases with the particle size increasing since Stokes number and temperature of the particle both increase with its size. For blades, the particle capture efficiency increases firstly and then decreases with the particle size increasing.

scholarly journals Numerical Study of Blood Flow Through Artificial Heart Valves

2021 ◽  
Vol 1094 (1) ◽  
pp. 012120
Author(s):  
Hussein Togun ◽  
Ali Abdul Hussain ◽  
Saja Ahmed ◽  
Iman Abdul hussain ◽  
Huda Shaker
Keyword(s):  
Blood Flow ◽  
Artificial Heart ◽  
Heart Valves ◽  
Numerical Study ◽  
Artificial Heart Valves ◽  
Flow Through

scholarly journals Generation of Reverse Meniscus Flow by Applying An Electromagnetic Brake

2021 ◽  
Author(s):  
Alexander Vakhrushev ◽  
Abdellah Kharicha ◽  
Ebrahim Karimi-Sibaki ◽  
Menghuai Wu ◽  
Andreas Ludwig ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Lorentz Force ◽  
Applied Magnetic Field ◽  
Numerical Study ◽  
Flow Direction ◽  
Experimental Studies ◽  
Submerged Entry Nozzle ◽  
Mean Flow ◽  
Slab Caster ◽  
The Mean

AbstractA numerical study is presented that deals with the flow in the mold of a continuous slab caster under the influence of a DC magnetic field (electromagnetic brakes (EMBrs)). The arrangement and geometry investigated here is based on a series of previous experimental studies carried out at the mini-LIMMCAST facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The magnetic field models a ruler-type EMBr and is installed in the region of the ports of the submerged entry nozzle (SEN). The current article considers magnet field strengths up to 441 mT, corresponding to a Hartmann number of about 600, and takes the electrical conductivity of the solidified shell into account. The numerical model of the turbulent flow under the applied magnetic field is implemented using the open-source CFD package OpenFOAM®. Our numerical results reveal that a growing magnitude of the applied magnetic field may cause a reversal of the flow direction at the meniscus surface, which is related the formation of a “multiroll” flow pattern in the mold. This phenomenon can be explained as a classical magnetohydrodynamics (MHD) effect: (1) the closure of the induced electric current results not primarily in a braking Lorentz force inside the jet but in an acceleration in regions of previously weak velocities, which initiates the formation of an opposite vortex (OV) close to the mean jet; (2) this vortex develops in size at the expense of the main vortex until it reaches the meniscus surface, where it becomes clearly visible. We also show that an acceleration of the meniscus flow must be expected when the applied magnetic field is smaller than a critical value. This acceleration is due to the transfer of kinetic energy from smaller turbulent structures into the mean flow. A further increase in the EMBr intensity leads to the expected damping of the mean flow and, consequently, to a reduction in the size of the upper roll. These investigations show that the Lorentz force cannot be reduced to a simple damping effect; depending on the field strength, its action is found to be topologically complex.

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