MICROSCOPIC MODEL FOR GRANULAR STRATIFICATION AND SEGREGATION

We study segregation and stratification of mixtures of grains differin g in size, shape and material properties poured into two-dimensional s ilos using a microscopic lattice model for surface flows of grains. Th e model incorporates the dissipation of energy in collisions between r olling and static grains and an energy barrier describing the geometri cal asperities of the grains. We study the phase diagram of the differ ent morphologies predicted by the model as a function of the two param eters. We find regions of segregation and stratification, in agreement with experimental finding, as well as a region of total mixing.