Mixing in a Mono-Disperse Granular Bed Subject to Vertical Oscillations

Abstract

Intentional and unintentional vibrational mixing of granular materials occurs in many.industrial operations. To study the degree of mixing resulting from vibrations, two-dimensional discrete element computer simulations of a mono-disperse granular material subject to vertical, sinusoidal oscillations are performed. The degree of mixing is quantified using a mixing index and diffusion coefficient. The simulation results indicate that mixing increases with decreasing frequency for a fixed acceleration amplitude and increasing amplitude for a fixed frequency. When plotted against oscillation velocity amplitude, the mixing index and diffusion coefficient data follow S-shaped curves. The simulations show that greater mixing occurs between the upper and lower halves of the bed than between the left and right halves. The simulations also indicate that the presence of kink convection cells results in enhanced mixing throughout the bed.