Filling height dependence of dense granular flow in a hopper: Transition from fluid‐like flow to Beverloo flow

Gravity‐driven dense granular flow in a hopper is investigated using a fixed‐grain‐number discrete element method. Two flow regimes are identified: a fluid‐like flow at low grain numbers, with a flow rate governed by filling height, and a Beverloo flow at high grain numbers, where the flow rate becomes independent of filling height. The transition grain number increases with outlet size. In the Beverloo regime, a dynamic force arch forms above the outlet, accompanied by a dynamic Janssen effect at the sidewalls, which causes contact forces along the central axis to saturate. These findings provide a micromechanical explanation for the constant flow rate and advance the understanding of granular flow transitions.