Axial segregation of granular mixtures as the rotational stabilization of the radial core

Abstract

We use the concept of rotational stability to explain the axial segregation of granular mixture inside a rotating horizontal container. We consider the core of radially segregated granular mixture as a dissipative rotating rigid body. The geometric constraints imposed by the container and the minimization of the rotational kinetic energy favor the deformation of the radial core from prolate to oblate configurations, which has larger moment of inertia. Axial segregation is the regime when the oblates pierce the sheath made of the larger grains. The thickness of the oblate is limited by the axial diffusion. This model naturally and parsimoniously accounts for several salient features of axial segregation, such as the location of first formation, scaling with container diameter, inversion, coarsening and transient oscillation of the axial bands.