Séminaire Liquides/Mat. molle

Mardi 30 Septembre 2014 à 14h00.

Limit to the universal Beverloo's scaling for the flow rate of particulate matter

''The Beverloo's scaling for the flow rate of granular materials through orifices has two distinct universal features. On the one hand, the flow rate is independent of the height of the granular column. On the other hand, the flow rate does not depend on the material properties of the grains (Young's modulus, Poison's ratio, friction coefficient, effective restitution coefficient, etc.). Although the first is widely recognized, the latter is rarely highlighted in the literature and yet not understood. We show compelling evidences that this universality holds if and only if an effective inelastic collapse is at play during the flow of the granular sample. In particular, we show that this universality with respect to the material properties can cease if work is done on the system at a high rate and the number of grains in the container reduces. Under such conditions, the flow rate depends on material properties and increases while the amount of the material reduces in a silo; in striking contrast with fluids.''