(587e) Effect of Surface Asperities on Particle-Phase Stress in Granular Flows

In most industrial processes involving granular flows, even generally rounded particles are typically not perfect spheres and have irregularities on the surface. In order to describe the flow behavior of these types of particles, the effect of particle surface asperities must be understood. In this study, the effect of surface asperities in dilute and dense-phase granular flows is investigated using discrete element method (DEM) simulations of a 3D system of particles in simple shear flow applying Lees-Edwards periodic boundary conditions. The particles are described by a main sphere with surface asperities depicted as hemispherical protrusions. The effect of surface asperities is assessed by progressively varying the asperity height, the concentration of asperities, and the arrangement of asperities on the surface. It is found that at low solid volume fractions, the shear stress increases linearly with the inverse squared of the particle normalized effective projected area. For larger solids concentrations, once the asperities reach a critical height, they can have a profound, order-of-magnitude effect on ease of particle flow. For each particle simulated, interlocking conditions, such as distances between asperities that yield more interlocks, are determined over a range of solid concentrations. The shear and normal stresses increase with asperity abundance, showing a dependence between stress and the number of surface asperities.