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Quasi-gaussian velocity distribution of a vibrated granular bilayer system

Viot, P; Burdeau, A; Combs, K (UPMC)
Thursday 08 January 2009, 16:35-17:00

Seminar Room 1, Newton Institute


We present a Molecular Simulation study of a bilayer of vibrated granular bidisperse spheres which exhibits the striking feature that the horizontal velocity distribution of the top layer particles has a quasi-Gaussian shape, whereas that of the bottom layer is far from Gaussian. We investigate the relevance of all physical parameters (acceleration of the bottom plate, mass ratio, layer coverage) and compare our results to the experiments of Baxter and Olafsen. In addition, a microscopic analysis of the trajectories of the particles of the top layer as well as of the collision statistics provides information on the mechanism of randomisation at the origin of this effect. In collaboration with K Combs and J Olafsen, we have also found that the velocity statistics for a top layer consisting of a single particle are deeply modified in the presence of mobile defects in the first layer. We have developed a model which is able to capture the role of the defects.


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