Discrete Element Simulation of Gas–Solid and Gas–Liquid–Solid Flows

Multiphase flow (i.e., gas–solid flow and gas–liquid–solid flow) extensively exists in industries, yet the strong coupling between different phases poses challenges in the discrete element method (DEM)-based model establishment. This work developed a fully coupled framework by combining computational fluid dynamics (CFD) with DEM, with the further extension to incorporate volume-of-fluid (VOF) to study multiphase flow systems. A smoothing method is implemented to allow the grid size to be close to or smaller than the diameter of the particles, benefiting the subsequent interphase and interfacial interactions calculation. Iso-Advector, an advanced VOF-based surface-capturing method, is further introduced to describe interface evolution and interfacial interactions effectively. The integrated model is verified in three benchmark cases, i.e., a quasi-two-dimensional spouted bed, a fully three-dimensional spout-fluid bed, and a dam-break flow. The numerical results agree well with experimental measurements, confirming the model's reliability in simulating multiphase flow systems.