In spite of many attempts to model dense granular flow, there is still nogeneral theory capable of describing different types of flows, such asgravity-driven drainage in silos and wall-driven shear flows in Couette cells.Here, we summarize our recent proposal of the Stochastic Flow Rule (SFR), whichis able to describe these cases in good agreement with experiments, and wefocus on testing the theory in more detail against brute-force simulations withthe discrete-element method (DEM). The SFR is a general rate-independentconstitutive law for plastic flow, based on diffusing spots of fluidization. Inthe case of quasi-2D granular materials, we assume limit-state stresses fromMohr-Coulomb plasticity and postulate that spots undergo biased random walksalong slip-lines, driven by local stress imbalances. We compare analyticalpredictions of the SFR against DEM simulations for silos and Couette cells,carrying out several parametric studies in the latter case, and find goodagreement.
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