A NEW KINETIC-MODEL FOR RAPID GRANULAR FLOW

The fluid motion of an assemblage of cohesionless granules is governed by the balance laws of mass, momentum and energy and is special becau se due to the variability of the mean free path of the particles the d ensity is not preserved and the particle fluctuation energy (= granula r temperature) is determined together with the mean fields. Constituti ve equations are postulated for the dispersive pressure, viscosity, '' thermal diffusivity'' and energy annihilation rate in terms of the mea n free path length, the time of encounter between two collisions and g eometric and dynamic quantities via dimensional arguments. The model d efines the time of encounter to consist of the free flying time betwee n collisions plus the contact duration. The inclusion of the latter br ings in the elasticity of the particles and introduces a relaxation me chanism that explains the typical behaviour of shear and fluidized lay ers better than has been done by previous models.