Abstract In this study, a coupling rule based on Lattice Boltzmann Method (LBM), Immersed Boundary Method (IBM), and Discrete Element Method (DEM) was developed to simulate settling of particles in Newtonian liquid. The direct forcing IB-LBM, which was enhanced by the split-forcing technique, was utilized to account for fluid/solid interactions. Dynamic behavior of particles during collisions was evaluated by DEM, in which contact forces were computed based on overlap distances and relative velocity between two particles. The lubrication force was also included in equation of motions that allowed the coupled IB-LB-DEM to accurately account for the fluid film before collision. The hybrid model was verified by examining the freely falling of single and tandem circular particles in a vertical box. The particle-particle collision was included in the model and particular attention was given to the examination of the effects of collision parameters including restitution and friction coefficients on the particle sedimentation behavior. The transverse and longitudinal positions and velocities of two falling particles are compared for a wide range of physical parameters. Finally, free falling of 28 particles for two different friction coefficients were simulated to show capability of the new model for analyzing particulate flows.

中文翻译：

---

混合浸入边界对自由下落粒子的直接数值模拟 – 格子玻尔兹曼 – 离散元方法

摘要 本研究开发了一种基于格子玻尔兹曼法（LBM）、浸入边界法（IBM）和离散元法（DEM）的耦合规则来模拟牛顿液体中的颗粒沉降。通过分裂强迫技术增强的直接强迫 IB-LBM 被用来解释流体/固体相互作用。碰撞过程中粒子的动态行为由 DEM 评估，其中基于两个粒子之间的重叠距离和相对速度计算接触力。润滑力也包含在运动方程中，使耦合的 IB-LB-DEM 能够准确地解释碰撞前的流体膜。通过检查垂直盒子中单个和串联圆形颗粒的自由下落来验证混合模型。模型中包括颗粒-颗粒碰撞，并特别注意检查碰撞参数（包括恢复和摩擦系数）对颗粒沉降行为的影响。比较两个下落粒子的横向和纵向位置和速度，以获得广泛的物理参数。最后，模拟了两种不同摩擦系数下 28 个颗粒的自由落体，以展示新模型分析颗粒流的能力。