Outflow rate and wall stress for two-dimensional hoppers

We investigate how the discharge process in a two-dimensional hopper depends on various material and geometrical parameters. We use a molecular-dynamics-type simulation technique which allows for the rotation of the particles and use suitable parameters to describe acrylic glass. The outflow rate does not depend on the restitution coefficient and the transition from funnel-flow to mass-flow behavior is clearly observable when the hopper angle increases. The full discharge process of 10 000 particles is studied and the height dependence of the wall forces at the end is compared to that of a fluid.