非均匀分布颗粒群中的曳力分布

Drag force distribution of heterogeneous particle clusters

本文采用格子Boltzmann方法(LBM)在图形处理器(GPU)上计算了由静止圆柱阵列组成的团聚物周期单元内的不可压缩流体流动,流固交界面处采用直接反弹以实现无滑移边界,每个圆柱上的曳力通过统计动量交换直接求得。根据LBM求得的流体速度,对于团聚物中的单圆柱按能量最小多尺度(EMMS)模型计算平均曳力系数,并考察了将聚团近似为均匀悬浮的临界条件。对颗粒雷诺数Re_p在0～10之间的80种固相份额的模拟结果表明,密相空隙率可以表征这种临界条件。当固相份额恒定时,该临界空隙率随着Re_p的增加而降低;当Re_p恒定时,该临界空隙率随着固相份额的增加而降低。

The incompressible fluid flowing through a cluster formed by arrays of cylinders in a periodic domain with was simulated by performing lattice Boltzmarm method （LBM） on graphics processing units （GPUs）. The bounce-back scheme was adopted on the fluid-solid interfaces, which insures the no-slip boundary condition. The drag force on each cylinder was calculated by the momentum exchange method directly. Based on the flow field thus obtained, the average drag coefficient of each cylinder inside particle cluster is calculated by the Energy-Minimization Multi-Scale （EMMS） model, and the critical condition for treating the cluster as homogenous suspension approximately is investigated. Eighty average solid fractions were studied for particle Reynolds number Rep ranging from 0 to 10, indicating that the critical condition can be characterized by the voidage of dense phase. The critical condition is subject not only to Rep but also to average solid fraction： it decreases with the increase of Rep at constant average solid fraction or increases with average solid fraction at constant Rep.