Collapse and Growth of Cavity in a Granular Material due to Viscous Flow

Abstract

Studies on the flow past a cavity region in an otherwise homogeneous granular material are made. In the case of a circular cylindrical cavity placed laterally to a uniform flow at infinity, the volume flux into this region increases as much as 2 times, whereas the velocity at the center of the void amounts to 3 times of those without that hole. The interaction of two cavities is also examined, which reveals the presence of a configuration with maximum flow rate. Due to the enhancement of fluid flow into cavity regions, the latter boundaries are destroyed even below the critical velocity, which further reinforces the flow around those cavities. This slowly progressing micro-scale interaction is repeated and develops into larger scale inhomogeneity of granular material, which is considered to be one of the fundamental processes leading to macroscopic long range catastrophic phenomena like network formation and landslides.