Rapid granular flows as mesoscopic systems

The dissipative nature of the particle interactions is responsible for an inherent lack of scale separation in granular systems which is not related to the typical grain/container size ratios. It is demonstrated that rapid granular flows are typically supersonic, shear rates in these systems are nearly always "large," the mean free times are comparable with the macroscopic time scale(s), and the mean free paths can be of macroscopic dimensions, the latter indicating nonlocality. Additional physical and computational implications are discussed.