Influence of an inserted bar on the flow regimes in the hopper*

Abstract

We investigated the influence of an inserted bar on the hopper flow experimentally. Three geometrical parameters, size of upper outlet D 1, size of lower outlet D 0, and the height of bar H, are variables here. With varying H we found three regimes: one transition from clogging to a surface flow and another transition from a surface flow to a dense flow. For the dense flow, the flow rate follows Beverloo’s law and there is a saturation of inclination of free surface θ. We plotted the velocity field and there is a uniform linear relation between the particle velocity and depth from the free surface. We also found that the required value of D 1 to guarantee the connectivity of flow is little smaller than D 0. For the transition from a surface flow to a dense flow, there is a jump of flow rate and the minimum θ for flowing is two degrees larger than the repose angle.