Discharge flow of granular particles through an orifice on a horizontal hopper: Effect of the hopper angle

We experimentally investigate the effect of the hopper angle on the flow rate of grains discharged from a two-dimensional horizontal hopper on a conveyor belt. The flow rate grows with the hopper angle, and finally reaches a plateau. The curve feature appears to be similar for different orifice widths and conveyor belt-driven velocities. On the basis of an empirical law of flow rate for a flat-bottom hopper, we propose a modified equation to describe the relation between the flow rate and hopper angle, which is in a good agreement with the experimental results.