Granular Dam Break: The role of Particle Shape.

We performed Discrete Element Method (DEM) simulations and experiments in a rectangular setup to investigate the influence of particle shape on the collapse of a granular pile. We observed that particle shape does not have a strong influence on the final run-out distance and all particle shapes followed the same power-laws as were proposed in previous studies. We found out that the maximum frontal velocity initially increases linearly with increasing aspect ratio, but then starts to bend towards a constant value. We suggest that the behavior observed maximum frontal velocity is associated with the Rayleigh-Janssen effect where the side walls shield the pressure exerted by the mass added on the top of the pile through wall friction. We observed that the time evolution of energy takes place in three stages. In the initial stage, the total initial potential energy stored in the pile partly converts into vertical kinetic energy, which, in the second stage, partly converts in horizontal kinetic energy until, in the last stage, basal friction dissipates the kinetic energy of the particles and halt the collapse. We also observed that the efficiency of the conversion of vertical kinetic energy into horizontal kinetic energy tends to decrease with increasing aspect ratio.