Influence of Particle Size On Mixing In a Simple Bladed System

The single-bladed mixing experiments of Bridgwater et al. (1968/69) are modeled using the discrete element method (DEM). The DEM simulations are performed over a wider range of parameters than those studied by Bridgwater et al., and the measurements of the particle movement are much more precise. The goal of the studies is to determine how particle size influences their mean and diffusive displacement in a simple mixing system.

The principle results of Bridgwater et al. are confirmed: mean particle displacement is independent of particle size, but the standard deviation is dependent on size. Variations in Froude number have little effect on particle displacement, especially after the critical value of Fr = 1.0; however, variations in the bed depth-to-blade height ratio are strongly correlated with the mean and standard deviation of particle displacement. These results indicate that it may be possible to use large-particle DEM simulations to predict the macroscopic flow of smaller particles in some systems.