(381a) Effect of Surface Asperities on Particle-Phase Stress in Granular Flows

In most industrial processes involving granular flows, such as pharmaceutical manufacturing and food processing, particles described as rounded tend not to be perfect spheres, having 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 particle surface asperities in dilute and dense-phase granular flows is investigated using discrete element method (DEM) simulations of a 3D system of particles with surface asperities 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 as well as asperity abundance. Asperity height is measured as the distance from the surface of the main sphere to the top of the asperity. The asperities are distributed uniformly across the surface of the sphere. It is found that at low solid volume fractions, the asperities do not have a significant effect on the stress of the system. For larger solids concentrations, the asperities only have a significant effect on stress and flowability after they reach a critical height. For each particle simulated, the type and distribution of contacts 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.