壁面对简单立方排布颗粒所受曳力的影响及建模

Effect of a Wall on the Drag Force on Simple Cubic Arrays of Particles and Modeling

壁面会显著影响其附近颗粒和流体的动力学行为,然而传统微尺度曳力模型往往基于全周期气固系统模拟结果构建,未考虑壁面对颗粒所受曳力的影响。为了探究壁面效应对气固相间曳力的影响,本工作采用具有二阶精度的浸没边界-格子玻尔兹曼方法对全周期边界条件和含壁面边界条件下气体流经简单立方排布颗粒的气固系统进行了直接数值模拟,结果发现基于全周期边界条件构建的曳力模型低估了近壁面处简单立方排布颗粒所受曳力,在所计算的参数范围内最高低估可达28%。进一步研究发现,壁面对于近壁处颗粒所受曳力的增大效应随固含率和雷诺数的增大而增大,并且随着固含率的增大,雷诺数的影响逐渐减弱。基于以上发现,提出了中低雷诺数条件下考虑壁面影响的简单立方排布颗粒所受曳力的模型。该模型可直接应用于含壁面边界条件气固系统的欧拉-欧拉和欧拉-拉格朗日细网格模拟中,有望进一步提高壁面附近细网格模拟的准确程度。

Traditional microscale drag correlations are often constructed based on the simulation results of the full-period boundary gas-solid systems without considering the influence of the wall on the drag force on the particles.In order to investigate the effect of a wall on the drag force between gas-solid phases,this work employs the Immersed Boundary-Lattice Boltzmann Method with second-order accuracy to simulate flow past simple cubic arrays of particles with and without wall boundary conditions.It is found that the drag model based on full-period boundary conditions underestimates the drag force on the simple cubic arrays of particles near the wall by up to 28%in the simulated parameter scope.It is further found that the effect of a wall on the drag force of particles near the wall increases with the increase of solid volume fraction and the Reynolds number,and the effect of the Reynolds number gradually decreases with the increase of solid volume fraction.Based on the above findings,a model of the drag force on a simple cubic arrays of particles at low and moderate Reynolds numbers is proposed,taking into account the effect of the wall.The model can be directly applied to Eulerian-Eulerian and Eulerian-Lagrangian fine-grid simulations of gas-solid systems with wall boundary conditions,which is expected to further improve the accuracy of fine-grid simulations near the wall.