An approach to distribute the marker points on non-spherical particle/boundary surface within the IBM-LBM framework

Abstract

IBM-LBM-DEM (immersed boundary method – lattice Boltzmann method – discrete element method) is a powerful tool to solve the particle-fluid interaction problems, and the super-ellipsoids can model particles of various shapes in DEM. To lay the foundation of IBM-LBM-DEM for particles with arbitrary shapes, the super-ellipsoid model is introduced to describe non-spherical particles. For the successful simulation of particle-fluid systems by IBM-LBM-DEM based on super-ellipsoids, adopting an appropriate method to distribute the discrete marker points on the surface of a super-ellipsoid within the IBM and DEM frameworks is indispensable. In light of this, a strip approach originally proposed for sphere is extended to super-ellipsoid to discretize the particle surface. For the surface discretization of arbitrary solid shapes, the multi-super-ellipsoid model is further proposed in this paper that a particle is composed of two or more super-ellipsoids. The IBM-LBM simulations of the flow over a stationary particle with different shapes, including spherical, cuboidal, ellipsoidal, cylindrical and spherocylindrical particles, are subsequently carried out to validate the capability of the proposed approaches. The fairly good agreement between the current simulation results and the relevant literature results demonstrates its feasibility in discretizing the particle surface. The comparisons between different shape-approximation accuracies for cuboidal and cylindrical particles modeled by super-ellipsoids further reveal that adopting the relatively low shape-approximation accuracy is also acceptable.