On granular surface flow equations

Abstract. Conservation equations are written for surface flows (either fluid or granular). The particularity of granular surface flows is then pointed out, namely that the depth of the flowing layer is not a priori xed, leading to open equations. It is shown how some hypothesis on the flowing layer allows to close the system of equations. A possible hypothesis, similar to that made for a fluid layer, but inspired from granular flow experiments, is presented. The force acting on the flowing layer is discussed. Averaging over the flowing depth, as in shallow water theory, then allows to transform these conservation laws into equations for the evolution of the prole of a granular pile. Apart from their interest for building models, these conservation laws can be used to measure experimentally the eective forces acting on a flowing layer. PACS. 83.70.Fn Granular solids { 46.10.+z Mechanics of discrete systems