Rapid Granular Avalanches

Granular avalanches are one of the fundamental grain transport mechanisms in our natural environment and in many industrial grain-processing flows. In recent years significant progress has been made in describing the flow of granular avalanches over complex rigid topography. Often the fluid-like granular avalanches flow over a region of solid-like grains at which there may be erosion or deposition. These phase-transition flows are very poorly understood, yet are of crucial importance in industrial rotating tumblers in which powders and grains are mixed. This paper reviews recent work on granular avalanche flows and presents a generalization of the Savage–Hutter theory that includes both surface and basal erosion and deposition. Elementary similarity and shock wave solutions are reviewed and a simple mass-coupling to a rigid body of grains is used to investigate the steady mixing of grains of equal size in a rotating tumbler of circular cross-section.