Heterogeneous dynamics of a granular pack under vertical tapping
Résumé
The dynamics of a tri-dimensional dense granular packing under gravity and vertical tapping is numerically investigated in a stationary state. A slowing-down of the dynamics is observed close to the bottom of the packing with a correlation length of 5-6d. In this perturbed zone, the self-intermediate scattering function, decaying slower than exponentially, suggests the existence of a heterogeneous dynamics. A characteristic time scale of the dynamics depending on the distance from the bottom of the packing is extracted. Our numerical results open the way to a systematic study of the influence of external driving force and of boundary conditions on the heterogeneity of the dynamics of granular packings under gravity.