SMOOTHING OF SANDPILE SURFACES AFTER INTERMITTENT AND CONTINUOUS AVALANCHES - 3 MODELS IN SEARCH OF AN EXPERIMENT

We present and analyze in this paper three models of coupled continuum equations all united by a common theme: the intuitive notion that san dpile surfaces are left smoother by the propagation of avalanches acro ss them. Two of these concern smoothing at the ''bare'' interface, app ropriate to intermittent avalanche flow, while one of them models smoo thing at the effective surface defined by a cloud of flowing grains ac ross the ''bare'' interface, which is appropriate to the regime where avalanches flow continuously across the sandpile.