Robust coupled fluid‐particle simulation scheme in Stokes‐flow regime: Toward the geodynamic simulation including granular media

Abstract

AbstractWe present a simulation scheme for solving high‐viscosity fluid and particle dynamics in a coupled computational fluid dynamics and discrete element method (CFD‐DEM) framework. This simulation scheme is intended to be used for geodynamical magmatic studies such as crystal settling at the melting roof of a magma chamber. The high‐viscosity fluid is treated by the Stokes‐flow approximation, where the fluid interacts with particles via the drag force in a cell‐averaged manner. The particles are tracked with contact forces by DEM. To efficiently solve such Stokes‐DEM coupled equations, we propose two key techniques. One is formulation of particle motion without the inertial term, allowing a larger time step at higher viscosities. The other is a semi‐implicit treatment of the cell‐averaged particle velocity in the fluid equation to stabilize the calculation. We simulate the settling particles in strongly viscous fluids in three dimensions and compare the results with the experimental and theoretical results. Our solution strategy is found to be robust and successfully captures the collective behavior of the particles. The simulation method presented here will be useful in various fields interested in long‐term dynamics of high‐viscosity granular media.