The spreading of a granular mass: role of grain properties and initial conditions

We present 2D numerical simulations of the collapse and spreading of granular columns for which the final geometry of the deposit and the runout distance are studied. Both the effects of the initial geometry and the effects of the details of the interactions between the grains are investigated. The scaling of the runout distance shows both a linear and a power-law dependence on the aspect ratio of the initial column, in agreement with previous findings (Balmforth and Kerswell in J. Fluid Mech. 538, 399-428, 2004; Lajeunesse et al. in Phys. Fluids 17, 103302, 2005; Lube et al. in Phys. Rev. E 72, 041301, 2005; Staron and Hinch in J. Fluid Mech. 545, 1-27, 2005), and independently of the value of the inter-grain friction. The latter controls the prefactor of the scaling, the effective frictional properties of the flow, and its internal structure. The non-trivial mass distribution induced by the initial geom- etry of the column strongly influences the dissipation process, and is believed to control the power-law dependence of the runout distance on the column aspect ratio.