Effects of convection and friction on size segregation in vibrated granular beds

In this study we investigate the size segregation of two-dimensional grains in vibrated granular beds using the particle dynamics method and analyze the influence of convection and friction between particles on the segregation. We found that the rate of segregation increases when the coefficient of friction increases and it becomes quite high with the appearance of the convective rolls. We studied the effect of the aspect ratio of the vibrated box on the roll size. It was found that during segregation with convection the large grains concentrate in the center of the rolls and not on the surface as in the case without convection. These phenomena are clearly demonstrated in a numerical experiment whereby the large grain located initially at the lower part of the vibrated box filled with 2400 small particles rises at the center of the box, oscillates around the center of the roll, and after some time the grain stabilizes at the center of the roll.