Sensitivity of granular surface flows to preparation

The transient surface granular flow occurring when a cylindrical pile of granular media supported by a disc crumbles to form a cone is investigated. The experiments show that this flow depends strongly on the way the granular material was prepared. We found a clear dependence on the density of the packing, leading from a deep bulk flow for low densities to an erosive surface flow for high ones. But the flow is also sensitive to possible asymmetries of the internal structure of the material.