Compaction of granular materials: experiments and contact dynamics simulations

We present an original experimental study of the slow compaction dynamics for two dimensional isotropic granular systems. Compaction dynamics is measured at three different scales : the macroscopic scale through the normalized packing fraction , the mesoscopic scale through the normalized fraction of domains ideally ordered in the system, and the microscopic scale through the grain mobility µ. The domains ideally ordered are found to obey a growth process dominated by the displacement of domain boundaries. We present also preliminary results of three-dimensional simulations with a model of contact dynamics. These results allow to discuss the difference between the two-dimensional and the three-dimensional cases.