Convection cells and segregation in a vibrated granular bed

Abstract

Granular materials may be circulated in a container with two symmetric convection cells under external vertical vibration conditions. Effects of the container geometry on the convection strength and segregation process are studied experimentally. First, the wall tilted outward angles are changed to observe the direction of the convection roll and convection strength. The strength of the normal convection rolls decreases by increasing the wall angles of the container from 0° (vertical walls). The convection rolls become reversed when the wall tilted outward angles are greater than a transition angle. The wall roughness and vibration velocity amplitude are also changed to investigate their influences on the convection cell strength. The segregation of a larger disk induced by the convection cells of smaller disks shows that the normal convection rolls induce the upward motion of the larger disk, and the reverse convection rolls result in the downward motion of the larger disk. The separation velocity increases linearly with the convection flow rate.