Non-local effects in intermediate granular avalanching flows*

In this work we showed that photoelastic analysis allows the quantification of rheologies in an intermediate chute flow. We characterize stresses and velocities in a flow layer with regions below and above the yield ratio mu_s. We compare our experimental results with a nonlocal rheology. Preliminary results show that the timescale over which the force chains decorrelate is strongly associated with the inverse of the fluidity, a viscosity-like quantity. This provides a physical interpretation of its particle-scale origins.