基于有限体积法的三维CFD-DEM耦合方法

本文基于有限单元法对流体控制方程进行离散,并与离散单元法进行三维流固耦合计算。首先,针对多孔介质土体选取合适的控制方程,包括流体运动方程、颗粒运动方程及流固相互作用方程。然后将编译的计算流体力学程序引入离散单元法中进行耦合计算。最后,针对单颗粒沉降进行了数值模拟,结果表明:颗粒在刚开始下落时,速度增加较快,然后增加速率逐渐变缓并趋于稳定;随着颗粒的不断下降,其所受拖拽力随着时间先迅速增加,然后逐渐与浮重力一致;颗粒下降速度稳定后,水压(扣除静水压力)在颗粒附近呈蝶翼状分布,且颗粒上方为负压,下方为正压;颗粒下方水流向两侧外流,而上方水流向颗粒上方汇聚。以上研究结果表明此次编译的计算流体力学程序能够很好地和离散单元法进行耦合,并可用于研究多孔介质流固耦合问题。

Three dimensional CFD - DEM coupling method based on finite volume method

In this paper, the fluid governing equations were discretized based on the Finite Volume Method (FVM), and then the three-dimensional fluid-solid coupling calculation was performed with the Discrete Element Method (DEM). First, the appropriate control equations were selected for the porous media, including the motion equation for fluid, the motion equation for particle and the fluid-solid interaction equation. Then the compiled program of Computational Fluid Dynamics (CFD) was introduced into the DEM for coupling computation. Finally, the numerical simulation of the single particle sedimentation was performed. The results showed that: when the particle began to fall, the speed increased rapidly, then the increasing rate gradually slowed down and the speed gradually became stable; as the particle descended, the drag force increased rapidly and gradually coincidd with the floating gravity; after the particle speed was stable, the water pressure (deducting the hydrostatic pressure)was a butterfly-shaped distribution near the particle, and the negative pressure rised above the particle and the positive pressure appears below it; the water below the particle flowed downward to both sides while the water above the particle converged toward the upper portion of the particle. The results showed that the compiled CFD programs coupled well with the DEM, and can be used to study the fluid-solid coupling problems of porous media.