| Granular material convects in response to vertical vibrations of sufficient peak acceleration. Particles circulate in stable rolls whose number and sense of rotation depend upon the boundary conditions. The relationship between boundaries and flow is a key element to understanding granular convection and to the broader goal of evaluating the fluid properties of granular materials. I describe here three boundary conditions that can be manipulated to alter the direction of convective flow: varying the angle of the side walls, permitting collision with the container lid, and allowing internal shear bands to form. The relative importance of each in determining the overall flow pattern depends sensitively on wall friction. |
