ROTATIONALLY INDUCED SEGREGATION OF GRANULAR-MATERIALS

We have studied segregation in binary mixtures of different granular m edia 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 a nd induce segregation in otherwise nonsegregating mixtures of glass be ads. The segregation results from an instability analogous to spinodal decomposition, and we present a model which describes this instabilit y.