From a grain to avalanches: on the physics of granular surface flows

Granular surface flows have still to be fully modelled. Analysing the motion of a single grain can already help us to understand the physical origin of several characteristic angles (starting, stopping, jumping angles). Then looking at layers of grains allows the inference of the velocity profile inside the flowing layer, and the physical origin of the flow depth selection. Then these results can be plugged into a general model of mass and momentum conservation integrated vertically (St-Venant). This model can be tested on stationary flows, but also on transients, such as avalanches. To cite this article: S. Douady et al., C. R. Physique 3 (2002) 177–186.