Flow profile of granular avalanches with imposed vertical vibration

Abstract

We report experimental results on the effect of imposed vertical vibration on the flow of pentagonal grains in a two-dimensional rotation drum. While dimensionless acceleration $$\varGamma $$ can be tuned either by increasing vibration frequency or amplitude, the former leads to stabilization an increase in the angle of repose while the latter leads to destabilization and a decrease in the critical angle for failure. Increased vibration amplitude leads to continuous avalanching and a more uniform flow profile, with a flowing layer composed of increasingly long-lived, shallower avalanches before a continuous flow regime is reached. The slope and grain-scale roughness of the surface decrease and interface curvature increases as vibration amplitude is increased and collective motion allows relaxation of the surface. While qualitative flow characteristics are similar both with and without vibration, vibration allows the system to evolve continuously in a nearly steady-state profile.