Superstable granular heap in thin channel.
Abstract: The purpose of this work is to present experimental studies on granular flow in a thin channel. We report the existence of an unexpected regime in which flow occurs atop a static granular heap whose angle is considerably higher than those usually exhibited by granular heaps. We show, by means of numerical simulation and theoretical analysis that this regime can be explained by the side-walls friction. This points out that the relevant parameter to characterize whether the channel is narrow or not is not the W/d where W is the distance between walls and d the grains diameter but W/h where h is the height of the flow.