Rotationally Induced Segregation of Granular Materials

Abstract

We have studied segregation in binary mixtures of different granular media subjected to rotation in horizontal tubes. Mixtures separate into bands of different relative concentrations arranged along the axis of the tubes. Axial modulations of the tube radius lock bands in space and induce segregation in otherwise nonsegregating mixtures of glass beads. The segregation results from an instability analogous to spinodal decomposition, and we present a model which describes this instability.