Relaxation of perturbed axial segregation bands: Dependence on perturbation intensity and rotation rate

Abstract

Granular mixtures inside rotating horizontal cylinders tend to axially segregate. Previously, the axial bands were observed to relax to their original position when perturbed from one end of the cylinder. Here, we report our initial findings on the dependence of relaxation time on the intensity (force) of the perturbation. Particularly, we axially segregated a mixture of fine and very fine sand grains inside a horizontal cylinder rotating at various rates ranging from 45 to 75 rotations per minute (rpm). Then we perturbed the mixture for a few second from one end of the cylinder using a balloon, which is connected to a ball pressed by a lever. The force applied by the perturbation was varied from 7 to 11 N. The free surface of the mixture was monitored before, during and after perturbation using a video camera. We measured and analyzed the relaxation times τ using the space-time diagrams. Initial finding is inconclusive on the dependence of relaxation on perturbation intensity while it suggest that is faster at higher rotational rates.