Influence of grain bidispersity on dense granular flow in a two-dimensional hopper

Abstract

This work uses the discrete-element method to investigate bidisperse dense granular flow with large and small grains in a two-dimensional hopper. A half-circular dynamical force arch forms above the outlet, and the robustness of Beverloo's law is verified to describe the relationship between flow rate and outlet size. The bidisperse flow peaks when monodisperse flow of small grains is supplemented with a small fraction of large grains. The dense flow rate relates closely to the local flow characteristics of a key area. However, the interior packing structures (i.e., an ordered arrangement for monodisperse flow and a disordered arrangement for bidisperse flow) dominate the flow-pattern transition from mass flow to funnel flow. The earlier occurrence of the transition increases the grain velocity and therefore the flow rate. This discovery of interior flow rheology provides a plausible basis for constructing a general constitutive framework for dense granular flow.