Coupled LBM-DEM simulations using the partially saturated method: Theoretical and computational aspects

In this work, we investigate several theoretical and computational aspects of coupled lattice Boltzmann-discrete element simulations where the partially saturated method is used to resolve fluid-particle interactions. It is demonstrated that in some cases the non-physical velocities induced in the particle interior may lead to numerical instabilities. Therefore, a split version of the partially saturated method is proposed to resolve this issue. For cases with multiple particles intersecting a single computational cell, an improved formulation of the weight parameter is introduced to correctly describe the scenario that a computational cell is fully occupied by particles. The effect of the timesteps of the discrete element and lattice Boltzmann method on the accuracy of the coupled simulations is explored in detail.