Axisymmetric Granular Collapse: a Transient 3D flow Test of Viscoplasticity

The collapse of a stationary cylinder of granular material onto a horizontal plan is a deceptively simple experiment rich in flow behaviour. Using 3-dimensional soft particle simulations, we reproduce the observed scaling laws for the maximum final runout and height of the deposit as a function of the initial aspect ratio. The flow simulations of this unsteady, largely axisymmetric flow are then used to confront a recently-introduced visco-plastic continuum theory (Jop, Forterre \& Pouliquen, {\em Nature}, {\bf 441},727,2006) which has seen some success modelling steady, unidirectional flows.