LANGEVIN DYNAMICS, SCALE-INVARIANCE, AND GRANULAR FLOWS

We propose a dynamic model for granular flows. Starting from the equation of motion for a grain together with the equation of continuity, we derive a Langevin equation describing the time evolution of the granular system. We show how the model displays scale invariance and reduces to several existing models in appropriate limits. In particular, we also point out the possibility of different behaviors in granular systems according to their sizes.