Effects of dilation and contraction on immersed granular column collapse

Abstract

Hydro-granular flow is a widespread problem characterized by the complicate fluid-particle interactions. The aim of this study is to investigate the crucial role of initial packing density in the immersed granular column collapse using the coupled lattice Boltzmann method and discrete element method. A dense case and a loose case are compared in terms of the collapsing dynamics, runout distance and induced excess pore fluid pressure. It is found that the dense case shows a dilative behavior associated with slow collapse and short runout distance with the excess pore fluid pressure being negative. While the loose case shows a contractive behavior associated with fast collapse and long runout distance with the excess pore fluid pressure being positive. These observations reveal that the macroscopic behaviors of particles collapsing in fluid heavily depends on the microscopic rheology, which is controlled by the dilation and contraction of the granular assembly.