Continuous avalanche mixing of granular solids in a rotating drum

¹ Department of Mathematical Sciences, University of Delaware, Newark, DE 19716, USA
² Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA

Received: 20 November 1995
Accepted: 9 May 1996

Abstract

We consider the avalanche mixing of a monodisperse collection of granular solids in a slowly rotating drum. This process has been studied for the case where the drum rotates slowly enough that each avalanche ceases completely before a new one begins (Metcalfe G., Shinbrot T., McCarthy J.J. and Ottino J.M., Nature, 374 (1995) 39). We developa mathematical model for the mixing both in this discrete avalanche case and in the more useful case where the drum is rotated quickly enough to induce a continuous avalanche in the material but slowly enough to avoid significant inertial effects. When applied to the discrete case, our model yields results which are consistent with those obtained experimentally by Metcalfe et al.