Mixing in vibrated granular beds with the effect of electrostatic force

In this study, the DEM (Discrete Elementary Method) is used to simulate the behavior of granular mixing in vibrated beds. First, the velocity fields are simulated by the DEM model to examine the convective currents in a three-dimensional vibrated granular bed. Then, in order to characterize the effect of electrostatic force on the granular flow, the electrostatic number Es is defined as the ratio of the electrostatic force to the particle weight. Also, to quantify the quality of mixing, the mixing degree M is used by the well-known Lacey index. The top-bottom and the side-side initial loading patterns of two groups of glass bead with different colors are employed to investigate the influence of the convective currents on the granular mixing. To simplify the electrostatic effect, these two groups of glass beads are given opposite charges and the charged strength is assumed to be constant. The simulation results demonstrate that the granular temperatures increase linearly with the increasing Es number. Meanwhile, the mixing rate constants, calculated from the time evolutions of mixing degree, increase with the increasing Es number in power law relations. The role of granular temperature in the granular mixing is also discussed in this paper.