Dense granular rheology from fluctuations

A unifying framework to describe dense flows of dry, deformable grains is proposed. Perturbative analysis of a granular temperature equation describing flows with contact stresses, supported by the recovery of the nonlocal granular fluidity equation, is used to derive an expression for a recently postulated critical exponent. Direct numerical simulation justifies models for the unclosed terms that provide a material-dependent estimate. Non-universality of the velocity and strain rate distributions, arising from competition between production and diffusion, rationalizes model shortcomings.