ABSTRACT
A particular feature of granular flows is called “inverse grading”: during the gravity-driven flow of a mixture of different sized grains, the larger particles concentrate in the upper flow layers, while the smaller ones are more likely to be found in the vicinity of the bottom. To model this effect, an event-driven hard-sphere model is used: different sized spheres interact by binary, instantaneous collisions, which are parametrisized by coefficients of longitudinal and tangential restitution and the tangential friction coefficient. Parametrical dependencies of global flow behaviour and onset of inverse grading are investigated. In a distinct parameter range, inverse grading is visible after a period of flow. Experimental results of restitution behaviour of snow are tentatively interpreted in the frame of the presented model.
