Granular flow down a rough inclined plane: Transition between thin and thick piles

The rheology of granular particles in an inclined plane geometry is studied using three dimensional molecular dynamics simulations. The flow–no-flow boundary is determined for piles of varying heights over a range of inclination angles θ. Three angles determine the phase diagram: θr, the angle of repose, is the angle at which a flowing system comes to rest; θm, the maximum angle of stability, is the inclination required to induce flow in a static system; and θmax is the maximum angle for which stable, steady state flow is observed. In the stable flow region θr<θ<θmax, three flow regimes can be distinguished that depend on how close θ is to θr: (i) θ≫θr: Bagnold rheology, characterized by a mean particle velocity vx in the direction of flow that scales as vx∝h3/2, for a pile of height h, (ii) θ≳θr: The slow flow regime, characterized by a linear velocity profile with depth, and (iii) θ≈θr: Avalanche flow characterized by a slow underlying creep motion combined with occasional free surface events and large ...