LAUSR

The local flow rule and the cooperativity length are the crucial ingredients of non-local rheology of granular matter. Once they are known as functions of the stress ratio, one can predict steady-state flow in arbitrarily complex geometries. We show how these functions can most easily be extracted from simulated velocity profiles for three-dimensional simple shear. The critical behaviour at the yield threshold and its rounding by finite size effects are discussed. The simple shear is simulated with smooth frictional walls, which provide the spatial inhomogeneity necessary to determine the cooperativity length. They also allow for slip, so that the particle velocity at the wall adjusts itself according to the stress ratio and is sensitive to the bulk yield.