Critical Velocity for the Collapse of a Cavity Region in a Granular Material and Its Size Dependence

Abstract

An experiment on the collapse of a two-dimensional macroscopic cavity region in a granular material due to a viscous flow was performed. The cavity was destroyed above a certain magnitude of fluid velocity depending on the hardness of the granular assembly and was filled with the fluidized granular material. For a given granular material, the rate of cavity filling was measured under various flow magnitudes, and the critical velocity U c , above which the collapse of cavity occurs, was determined. The dependence of U c on the cavity size D was obtained.