Stresses in Smooth Flows of Dense Granular Media

Abstract

The form of the stress tensor is investigated in smooth, dense granular flows which are generated in split-bottom shear geometries. We find that, within a fluctuation fluidized spatial region, the form of the stress tensor is directly dictated by the flow field: The stress and strain-rate tensors are co-linear. The effective friction, defined as the ratio between shear and normal stresses acting on a shearing plane, is found not to be constant but to vary throughout the flowing zone. This variation can not be explained by inertial effects, but appears to be set by the local geometry of the flow field. This is in agreement with a recent prediction, but in contrast with most models for slow grain flows, and points to there being a subtle mechanism that selects the flow profiles.

5 pages, 4 figures

References in corpus (2)

• Dynamics of Random Packings in Granular Flow
• Shear Zones in granular materials: Optimization in a self-organized random potential

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• Evolution of shear zones in granular materials
• Shear Is Not Always Simple: Rate-Dependent Effects of Flow Type on Granular Rheology
• Wide shear zones and the spot model: Implications from the split-bottom geometry