A coupled Particle-In-Cell (PIC)-Discrete Element Method (DEM) solver for fluid–solid mixture flow simulations

Abstract In this paper, a coupled Particle-In-Cell (PIC)-Discrete Element Method (DEM) model is developed for numerical simulations of complex fluid–solid mixture flows. The fluid–solid interaction part is solved using the hybrid Eulerian–Lagrangian PIC model, and the solid–solid interaction part is simulated using the Lagrangian DEM model. The PIC model gives the coupled PIC-DEM model both Eulerian efficiency and Lagrangian flexibility, compared to purely Lagrangian methods such as Smoothed Particle Hydrodynamics (SPH). The time step difference between the PIC model and the DEM model is handled using the idea of subcycles. In addition, a straightforward method is proposed for mitigating the issue of unphysical gaps between solids during collision due to the use of the Cartesian cut cell method for fluid–solid interaction. The PIC-DEM model is validated by physical experiments of the collapse of solid cylinder layers with and without water. Following that, the capability of the numerical model is further demonstrated through a more complex problem of solid dumping through fall pipes. The results show great potential of the PIC-DEM model being a useful tool for simulating complex fluid–solid mixture flows.