Characterization of the stationary states of a dilute vibrofluidized granular bed - art. no. 041303

This paper reports two phenomena in an event driven simulation of a dilute vibrofluidized granular material in two dimensions. Both phenomena show inh omogeneity in the horizontal direction. They are convection rolls similar t o the Rayleigh-Benard thermal convection in fluids, and a clustering instab ility, where the bed spontaneously phase separates into coexisting dense an d dilute regions. Detailed investigations show that these are different fro m the known instabilities in a vibrated granular medium. Characterization o f these instabilities is carried out with a phase diagram using suitable pa rameters from the kinetic theory of vibrofluidized beds.