Behavior of lower-order moments in a dense vibrofluidized granular material

The behavior of the lower-order moments of the velocity distribution function for a system of inelastic granular disks driven by vertical vibrations is studied using simulations and kinetic theory. A kinetic theory is developed on the lines of the Enskog correction to dense gases to account for the high-density corrections in granular materials. Using a perturbative expansion for the distribution function, a numerical solution to the lower-order moments is obtained for the high-density case. Event driven simulations are carried out on a system of granular disks, driven by a vibrating wall, to investigate the profiles of the moments. An approximate and simple method to deal with a vibrating wall in an event driven algorithm is presented. Theoretical predictions of the lower-order moments of the velocity distribution function from low- and high-density kinetic theory of vibrofluidized granular materials are compared with the simulation data. In both dilute and densecases the theory shows a good agreement with the simulation results