中文摘要：

在离散元（DEM）和计算流体动力学（CFD）程序基础上,运用流-固相互作用力方程建立三维CFD-DEM细观耦合数值模拟模型。CFD-DEM的控制方程包括流体-颗粒相互作用力方程、CFD的流体和DEM的颗粒运动方程。其中,考虑到土颗粒的形状效应,引入颗粒滚动阻力机制,介绍了适用性较强的滚动阻力模型。在开源耦合程序CFDEM的框架下,定制CFD开源程序Open FOAM与DEM开源程序LIGGGHTS之间的双向耦合,实现基于颗粒细观的流-固耦合计算。通过砂堆和砂土渗流的模拟分别验证了所嵌入的滚动阻力模型的有效性及耦合模型的可行性。模拟结果表明,圆柱土体中向上渗流流速与水力梯度关系与经典的Ergun理论解接近;耦合模型中所引入的颗粒间滚动阻力模型能够很好地反映颗粒形状对砂堆形成休止角和土体堆积孔隙率的影响。

英文摘要：

A numerical model for analyzing microscopic fluid flow in granular media is developed using a coupled discrete element method （DEM） and computational fluid dynamic （CFD） approach to investigate fluid-particle interaction. The CFD-DEM coupling algorithm was implemented using open source code LIGGGHTS and OpenFOAM, within the f~amework of open source code CFDEM. A rigorous rolling resistance model was incorporated into the DEM code to approximately represent the effect of particle shape. Two benchmark examples, i.e., sand pile formation and upward seepage flow in sand, were presented to demonstrate the effectiveness of rolling resistance model and validate the CFD-DEM coupling model, respectively. The results show that the prediction of the relationship between seepage flow velocity and hydraulic gradient is consistent with classical Ergun theory. The incorporated rolling resistance model shows capability of representing the particle shape effect on the sand pile repose angle and packing porosity of sand columns.