scholarly journals Pore-Scale Simulations of Particles Migration and Deposition in Porous Media Using LBM-DEM Coupling Method

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 465
Author(s):  
Yanjie Zhou ◽  
Liping Chen ◽  
Yanfeng Gong ◽  
Shilin Wang
Keyword(s):  
Porous Media ◽  
Critical Velocity ◽  
Flow Rate ◽  
Shear Force ◽  
Particle Deposition ◽  
Moving Boundary ◽  
Low Flow ◽  
Rate Condition ◽  
Groundwater Source ◽  
Low Flow Rate

This paper studies the migration and deposition of suspended particles in porous media. This problem results from the fact that during the operation of a groundwater source heat pump, the recharging process will contribute to the impairment of soil permeability. A coupling lattice Boltzmann method, discrete element method and immersed moving boundary method were used to investigate the migration of particles in porous media. The DKT (Drifting, Kissing, Tumbling) phenomena were employed to validate our program. The coupled effects of concentration, flow rate and pH on the clogging mechanism of the porous media were analyzed. Results show that, due to the repulsive barrier between the particles and porous media, there is a critical velocity. At a low flow rate, the deposition ratio increases with the increase in velocity. Beyond the critical velocity, the deposition ratio decreases when the velocity increases due to higher shear force. Permeability impairment increases with the increase in concentration, especially in the low flow rate condition. Changes in pH mainly affect the repulsive barrier. For a low flow rate, the decrease in repulsive barrier greatly promotes the deposition of particles. Under the condition of favorable deposition, the increase in flow rate reduces the deposition phenomenon. Under the condition of unfavorable deposition, the lower flow rate condition has a lower deposition ratio. The process of particle deposition and the dynamic motion after deposition were observed such as particles gliding over the surface. Accumulated particles in the downstream form bridges and hinder fluid flow. At a high flow rate, strong shear force is more capable of destroying bridges and recovering permeability. Adsorbed particles glide on the surface of the grain and deposit in the downstream. This paper aims to help understanding of the micro-events of particle deposition and the clogging process.

Abstract 295: Importance of the Rate of Platelet Activation by Thrombin for Regulating the Size of Thrombi Formed Under Low Blood Flow Velocity Conditions

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Shinichi Goto ◽  
Kengo Ayabe ◽  
Youth Kawamura ◽  
Noriko Tamura ◽  
Shinya Goto
Keyword(s):  
Blood Flow ◽  
Flow Velocity ◽  
Platelet Activation ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
Low Flow ◽  
Coagulation Cascade ◽  
Computer Simulation Model ◽  
Rate Condition ◽  
Low Flow Rate

Background: Platelets, coagulation cascade including thrombin and fibrin, and fibrinolysis by plasmin along with blood flow are known to play regulatory roles in thrombogenesis. However, quantitative and interactive contribution of these factors are not fully understood. Method: We developed a computer simulation model of thrombi at sites of vessel injury by implementing quantitative parameters of blood flow, platelet, coagulation cascade and fibrinolysis. In this model, we defined thrombi as the area where the amount of activated platelet become 80% or more of the global platelet count of 3.0х10 5 /mm 3 upon vessel damage We have measured the 3-dimensional size of thrombi as defined in various conditions with various parameters of flow velocity, rate of platelet activation by thrombin, rate of thrombin production on the surface of activated platelets, rate of fibrinolysis and rate of plasmin production. Results: Rate of platelet activation by thrombin had the largest influence on the size of thrombi under low flow rate condition of 0.5 (cm/sec) (Fig1 A). When blood flow rate increased to 2.0 (cm/sec), the absolute importance of this parameter decreased (Fig1 B). Conclusion: Our results show that the rate of platelet activation by thrombin, which are signaled with PAR-1 receptor in human, has a marked effect on the size of thrombi in low flow rate condition suggesting the benefit of blocking this receptor in low blood flow condition such as venous thrombosis.

Data Processing in Moving Boundary Problems of One-Dimensional Non-Darcy Flow in Semi-Infinite Porous Media

2014 ◽  
Vol 977 ◽  
pp. 515-519
Author(s):  
Rong Rong Jin ◽  
Jia Hang Wang
Keyword(s):  
Porous Media ◽  
Mathematical Models ◽  
Flow Rate ◽  
Analytical Solutions ◽  
Moving Boundary ◽  
Constant Flow ◽  
Production Time ◽  
Rate Condition ◽  
Exact Analytical Solutions ◽  
Constant Flow Rate

The paper establishes dimensionless mathematical models of the fluid flow in semi-infinite porous media with constant flow rate. Exact analytical solutions of these dimensionless mathematical models are derived by new definitions of dimensionless variables and Laplace transformation. Comparison curves of dimensionless moving boundary under different values of dimensionless Threshold Pressure Gradient (TPG) are plotted from newly proposed exact analytical solutions. An example is used to demonstrate pressure distribution in different positions with different TPG. It is shown that for the constant flow rate condition, the moving boundary extends to infinite in porous media with increasing production time. Steeper pressure curve is observed in larger TPG, which also exhibits greater pressure drop gradient and shorter pressure propagation distance at the same production time.

D12 Flow Fields of Semi-Open Axial Fan at Low Flow Rate Condition

2008 ◽  
Vol 2008 (0) ◽  
pp. 151-152
Author(s):  
Sho KUMAMOTO ◽  
Norimasa SHIOMI ◽  
Yoichi KINOUE ◽  
Kenji KANEKO ◽  
Toshiaki SETOGUCHI
Keyword(s):  
Flow Rate ◽  
Flow Fields ◽  
Low Flow ◽  
Axial Fan ◽  
Rate Condition ◽  
Low Flow Rate

scholarly journals Backflow effects on mass flow gain factor in a centrifugal pump

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042199886
Author(s):  
Wenzhe Kang ◽  
Lingjiu Zhou ◽  
Dianhai Liu ◽  
Zhengwei Wang
Keyword(s):  
Centrifugal Pump ◽  
Mass Flow ◽  
Flow Rate ◽  
Low Frequency ◽  
Gain Factor ◽  
Low Flow ◽  
Cavity Volume ◽  
Cavitating Flows ◽  
Inlet Tube ◽  
Low Flow Rate

Previous researches has shown that inlet backflow may occur in a centrifugal pump when running at low-flow-rate conditions and have nonnegligible effects on cavitation behaviors (e.g. mass flow gain factor) and cavitation stability (e.g. cavitation surge). To analyze the influences of backflow in impeller inlet, comparative studies of cavitating flows are carried out for two typical centrifugal pumps. A series of computational fluid dynamics (CFD) simulations were carried out for the cavitating flows in two pumps, based on the RANS (Reynolds-Averaged Naiver-Stokes) solver with the turbulence model of k- ω shear stress transport and homogeneous multiphase model. The cavity volume in Pump A (with less reversed flow in impeller inlet) decreases with the decreasing of flow rate, while the cavity volume in Pump B (with obvious inlet backflow) reach the minimum values at δ = 0.1285 and then increase as the flow rate decreases. For Pump A, the mass flow gain factors are negative and the absolute values increase with the decrease of cavitation number for all calculation conditions. For Pump B, the mass flow gain factors are negative for most conditions but positive for some conditions with low flow rate coefficients and low cavitation numbers, reaching the minimum value at condition of σ = 0.151 for most cases. The development of backflow in impeller inlet is found to be the essential reason for the great differences. For Pump B, the strong shearing between backflow and main flow lead to the cavitation in inlet tube. The cavity volume in the impeller decreases while that in the inlet tube increases with the decreasing of flow rate, which make the total cavity volume reaches the minimum value at δ = 0.1285 and then the mass flow gain factor become positive. Through the transient calculations for cavitating flows in two pumps, low-frequency fluctuations of pressure and flow rate are found in Pump B at some off-designed conditions (e.g. δ = 0.107, σ = 0.195). The relations among inlet pressure, inlet flow rate, cavity volume, and backflow are analyzed in detail to understand the periodic evolution of low-frequency fluctuations. Backflow is found to be the main reason which cause the positive value of mass flow gain factor at low-flow-rate conditions. Through the transient simulations of cavitating flow, backflow is considered as an important aspect closely related to the hydraulic stability of cavitating pumping system.

A Meanline Model for Impeller Flow Recirculation

2008 ◽  
Author(s):  
Xuwen Qiu ◽  
David Japikse ◽  
Mark Anderson
Keyword(s):  
Flow Rate ◽  
Recirculation Zone ◽  
Reverse Flow ◽  
Low Flow ◽  
Suction Surface ◽  
Blade Loading ◽  
Flow Recirculation ◽  
Impeller Outlet ◽  
Active Flow ◽  
Low Flow Rate

Flow recirculation at the impeller inlet and outlet is an important feature that affects impeller performance, especially the power consumption at a very low flow rate. Although the mechanisms for this flow phenomenon have been studied, a practical model is needed for meanline modeling of impeller off-design performance. In this paper, a meanline recirculation model is proposed. At the inlet, the recirculation zone acts as area blockage to relieve the large incidence of the active flow at a low flow rate. The size of the blockage is estimated through a critical area ratio of an artificial “inlet diffuser” from the inlet to throat. The intensity of the reverse flow can then be calculated by assuming a linear velocity profile of meridional velocity in the recirculation zone. At the impeller outlet, a recirculation zone near the suction surface is established to balance the velocity difference on the pressure and suction sides of the blade. The size and the intensity of the outlet recirculation zone is assumed related to blade loading, which can be evaluated based on flow turning and Coriolis force. A few validation cases are presented showing a good comparison between test data and prediction by the model.

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