Relaxation of local density fluctuations in a fluidized granular medium

Abstract

Configurations of vertically vibrated, two-dimensional arrays of fluidized steel spheres have been recorded using high-speed photography. The resulting instantaneous particle positions have been used to extract statistical averages of the static structure factor and of the dynamical density autocorrelation function over a range of wave vectors. The local collective behaviour of this vibrated granular medium exhibits strong similarities with the density fluctuations in an atomistic fluid in thermal equilibrium, at the equivalent particle packing fraction.