Numerical Analysis of the Effects of Bed Particle Physical Properties on the Cooperative Behavior of Disks Falling in the Bed

We focused on the cooperative behavior of disks falling in a particle bed, which five-disk shows upward and downward convex configurations repeatedly during the disk falling. We used DEM simulation to investigate the effects of the bed particle physical properties (density, diameter, and frictional coefficient) on the falling behavior. Here, we also used 10 different initial packing structures of the bed to investigate the effects of the packing structures on the falling behavior. As a result, when particle mass increased owing to changing density and diameter, the occurrence of the cooperative behavior depended on the packing structure. This leads to decreasing occurrence probability of the cooperative behavior. On the other hand, the occurrence probability is independent of particle frictional coefficient. This is because particle mass is a significant parameter, and the mass would affect contact force distributions of disks and the bed particle flow direction during the disks falling.