(310c) Influence of Particle Size In a Bladed Mixer Using the Discrete Element Method (DEM)

Present computational hardware limits the number of particles that can be realistically simulated using DEM to O(10⁶) or less, whereas typical granular systems may contain more than O(10⁹) particles.  Most DEM simulations of granular mixers model particles that are several orders of magnitude larger than the particle size expected in real systems.  The goal of this work is to characterize the influence of particle size on flow and mixing in a mechanically agitated granular system.  A periodic section of a horizontal cylindrical mixer with a pair of impeller blades is modeled using the discrete element method (DEM).  The ratios of mixer diameter to particle diameter investigated range from 12.5 to 75.  Comparisons of flow, microstructure, and mixing are presented using measurements of flow fields, velocity distributions, coordination number, and granular diffusion coefficients.  Results suggest that particle level measurements such as coordination number and mixing rates are a strong function of particle size, but the macroscopic flow velocities are not affected significantly when using larger particles.  The choice of particle size in DEM simulations should be decided based on the measurements that are of interest, along with the available computational resources.