An Efficient Multigrid-FEM Method for the Simulation of Liquid-Solid Two Phase Flows

An efficient multigrid-FEM method for the detailed simulation of solid-liquid two phase flows with large number of moving particles is presented. An explicit fictitious boundary method based on a FEM background grid which covers the whole computational domain and can be chosen independently from the particles of arbitrary shape, size and number is used to deal with the interactions between the fluid and the particles. Since the presented method treats the fluid part, the calculation of forces and the movement of the particles in a subsequent manner, it is potentially powerful to efficiently simulate real particulate flows with huge number of particles. The presented method is first validated using a series of simple test cases, and then as an illustration, simulations of three big particles plunging into 2000 small particles, and of sedimentation of 10,000 particles in a cavity are presented.