GEOMETRICAL ANALYSIS OF AVALANCHES IN A 2D DRUM

We present an experimental and numerical analysis of intermittent flow at the surface of a 5-dimensional granular medium. Two types of devices are used: a 2-dimensional drum and a long rectangular box. Two types of grains are used (disks and pentagons), and comparison is made between the different cases. The experimental data are compared with the results obtained from molecular dynamics simulations, using roughly the same number of particles. Dynamical conditions of stability are determined from the angle of repose theta(r) and the angle of maximum stability theta(m). Intermittent flow at the ''surface'' appears to be of two types, as in 5-dimension: small avalanches whose time fluctuations are characterised by a power spectrum obeying a power law, and large events with well-defined average size and duration time.