Fluctuations and power-law scaling in granular flow simulations*

Accurate and general constitutive models of granular material flow would aid experimental flow characterization measurements, but yet remain elusive. Further development of these models requires understanding higher-order flow properties and fluctuations in steady granular flow. We perform particle-based stress-controlled discrete element modeling simulations of frictionless particles. The average values and fluctuations of steady flow properties, such as shear stress, pressure, strain rate and normal stress differences are presented. The number of particles is varied from 3x10² to 10⁵ and the pressure up to 6 orders of magnitude. We find that the critical shear stress ratio measured from arrest and taken from fits to the  disagree for small system sizes. Sufficiently large system sizes allow us to identify a non-monotonic dependence in the second normal difference with strain rate. We show how fluctuations of flow properties, such as normal stresses differences, scale and normalize with system size, pressure and strain rate.