PARTICLE DYNAMICS CALCULATIONS OF WALL STRESSES AND SLIP VELOCITIES -FOR COUETTE-FLOW OF SMOOTH INELASTIC SPHERES

The objective of this work is to characterize the effects of boundary geometry on the flow of dry granular materials composed of smooth, ine lastic spheres between parallel, bumpy walls in the absence of gravity . Particle dynamic simulations are done in which wall stresses and sli p velocities are computed over a wide range of parameters, including s hear gap height, geometry of the wall particles, wall to free particle diameter ratio, and normal restitution coefficient. Calculated wall s tresses and slip velocities are found to be highly sensitive to bounda ry roughness, which is characterized in terms of the mean spacing valu e for the wall particles. Most noticeable is a pronounced stress drop for dense flows with an associated large slip velocity in a system hav ing a narrow shear gap height.