Collapse of sand columns submerged in water: the role of the aspect ratio and the grain size.

Granular flows occur in numerous natural phenomena and industrial applications. However, they often exhibit counter-intuitive behavior and many of their features are still not well understood. In this talk, we report on results from laboratory-scale simulations of an archetypal type of such flows, namely, the collapse of sand columns, submerged in water, under their own weight. Our simulations are based on a two-pressure, two-velocity flow model for granular suspensions. This model incorporates a non-linear representation of the granular rheology and an evolution equation for the volume fraction of the granular phase. The algorithm used to solve the governing equations is based on a predictor-corrector time-integration scheme and incorporates a generalized projection method for the dynamic pressures of the two phases. First, we briefly describe the mathematical model. We then present results from our parametric studies with respect to the aspect ratio and the grain size. More specifically, we elaborate on the effect of these parameters on the time evolution of the column collapse as well as on the shape and dimensions of the remnant pile. The emerging flow patterns and the amount of sand transported away from the column are also discussed herein.