### Rheology of confined granular flows: scale invariance, glass transition and friction weakening

Valance, A; Richard, P; Louge, M *(Rennes 1)*

Friday 09 January 2009, 12:10-12:35

Seminar Room 1, Newton Institute

#### Abstract

We study fully developed, steady granular flows confined between parallel flat frictional sidewalls using numerical simulations and experiments. Above a critical rate, sidewall friction on the flow stabilises the underlying heap at an inclination larger than the angle of repose. The shear rate is constant and independent of inclination over much of the flowing layer. In the direction normal to the free surface, the solid volume fraction increases on a characteristic scale equal to half the flowing layer depth. Beneath a crictical depth at which internal friction is invariant, grains exhibit creeping and intermittent cage motion similar to that in glasses, causing gradual weakening of friction at the walls.

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