(225f) Effect of Surface Roughness and Particle Size on Wall Friction

Friction between particulate materials and the process, storage and transfer equipment wall surface is of critical importance for design and operation of solids processing systems. A typical example would be hoppers. The wall friction angle between the particulate material and the hopperâ??s material of construction is measured and used along with the particle-particle friction to calculate the required outlet diameter of a hopper for unobstructed flow (i.e. without forming solid bridge). The type of the material, the surface finish (i.e. the degree of roughness), and the coating used inside the equipment may vary greatly and affect the wall friction. Despite the vast amount of experimental data collected for various surfaces and particulate materials over the last couple of decades, the effect of surface roughness on wall friction is unpredictable and depends on the particulate material. In this study, we investigate the effect of wall roughness systematically for model materials such as glass spheres and polymer particles. The effect of particle size will be also presented.