Long-time limit of rotational segregation of granular media

Abstract

We performed simulations of a model for the segregation of a powder mixture in a horizontal half-filled tube under slow rotation. Fluctuations of the particles' flux play an essential role in our model. We found that an initially homogeneous mixture decomposes on a fast time scale into a sequence of domains of the pure components; this stage is followed by a long coarsening period, with decreasing number of domains. The coarsening rate increases strongly with the level of the fluctuations. After this stage, at very long times, the system approaches an equilibrium state, in which the number of bands fluctuates about its mean value. The obtained results are compared with recent experiments, and a good agreement is found.