Vertical Side Wall Convection in Deep Beds of Granular Material Subjected to Vertical, Sinusoidal Oscillations

Abstract

When a deep bed of granular material is subjected to vertical, sinusoidal oscillations, a number of interesting phenomena appear including heaps, convection cells, surface waves, and arches. This paper examines the convection cell phenomena associated with vertical side walls using two-dimensional discrete element simulations. Measurements from the simulations indicate that when the container aspect ratio, defined as the depth of the granular bed, H, divided by the width of the container, W, is large, convection cells interact and the boundary layer width of the downward flow of particles against the walls varies linearly with the container width. However, when the container aspect ratio [is] small and the convection cells do not interact, the boundary layer width remains at a nearly constant value of ten particle diameters. Other simulation measurements show that the vertical location of the convection cell center remains close to the free surface regardless of container aspect ratio. Additional measurements show that the particle flow rate per oscillation cycle in the boundary layer increases with increasing vibration amplitude and velocity. Lastly, the asymmetric drag mechanism proposed as the cause of the side wall convection cells is briefly examined.