Experimental analysis and modelling of particle-wall collisions

A detailed experimental analysis of the particle-wall collision process in a particle-laden horizontal channel flow was performed using particle track ing velocimetry. The particles used in this study were glass beads with a d iameter of 100 and 500 mu m and quartz particles with a size of about 100 m u m. Moreover, the effect of wall material on the collision process was ana lysed. Special attention was paid to the influence of wall roughness and th erefore, untreated stainless steel, polished stainless steel, Plexiglas, an d rubber gum were used. It was found that wall roughness considerably alter s the rebound behaviour of the particles and causes in average a re-dispers ion of the particles, i.e. gravitational settling is reduced. A similar eff ect was observed for the non-spherical quartz particles and a polished stai nless steel wall. The experimental data were used to improve and validate a wall collision model to be used in the frame of the Lagrangian approach. I n this model the wall roughness is simulated by assuming that the impact an gle is composed of the trajectory angle with respect to the plane wall and a stochastic component caused by wall roughness. A modified normal distribu tion function was assumed for the roughness angle distribution. All the par ameters for the wall collision model, such as restitution coefficient and f riction coefficient as functions of the impact angle were obtained from the experiments. The simulations showed a very good agreement with the measure ments for the particle rebound properties. (C) 1999 Elsevier Science Ltd. A ll rights reserved.