Granular coarsening: phase space and evolution analogies.

Various aspects of axial banding of size-varying bidisperse granular mixtures in cylindrical tumblers have been documented repeatedly over a decade or so, but the dependence of surface band formation on the relative concentration of particles and rotation rate has not been thoroughly examined. Coarsening patterns analogous to nucleation and spinodal decomposition occur as the relative concentration of small and large particles and the rotation rate of the tumbler are varied. A phase diagram with a portion analogous to a miscibility gap can be constructed from the space-time plots. A dynamic scaling approach similar to that for reacting lamellae can be applied to the coarsening patterns as a result of large bands growing at the expense of neighboring smaller bands.