### Axisymmetric granular collapse: a transient 3D flow test of visco-plasticity

**Lacaze, L; Kerswell, RR ***(Ins of Fluid Mechanics of Toulouse)*

Tuesday 06 January 2009, 10:05-10:30

Seminar Room 1, Newton Institute

#### Abstract

A viscoplastic continuum theory has recently been proposed to model dense, cohesion-less granular flows (Jop et al. Nature, 441, 727, 2006). We confront this theory for the first time with a transient, 3-dimensional flow situation - the simple collapse of a cylinder of granular matter onto a horizontal plane - by extracting stress and strain rate tensors directly from soft particle simulations. These simulations faithfully reproduce the different flow regimes and capture the observed scalling laws for the final deposit. Remarkably, the theoretical hypothesis that there is a simple stress-strain rate tensorial relationship does seem to hold over the whole flow during the evolution even close to the rough boundary provided the flow is dense enough. These encouraging results suggest viscoplastic theory is more generally applicable to transient, multi-directional, dense flow and open the way for quantitative predictions in real applications.