Analysis of radial segregation of granular mixtures in a rotating drum

This paper considers the segregation of a granular mixture in a rotating dr um. Extending a recent kinematic model for grain transport on sandpile surf aces to the case of rotating drums, an analysis is presented for radial seg regation in the rolling regime, where a thin layer is avalanching down whil e the rest of the material follows rigid body rotation.We argue that segreg ation is driven not just LS differences in the angle of repose of the speci es, as has been assumed in earlier investigations, but also by differences in the size and surface properties of the grains. The cases of grains diffe ring only in size (slightly or widely) and only in surface properties are c onsidered, and the predictions are in qualitative agreement with observatio ns. The model yields results inconsistent with the assumptions for more gen eral cases, and we speculate on how this may be corrected.