Cooling dynamics of a dilute gas of inelastic rods: A many particle simulation

We present results of simulations for a dilute gas of inelastically colliding particles. Collisions are modeled as a stochastic process, which on average decreases the translational energy (cooling), but allows for fluctuations in the transfer of energy to internal vibrations. We show that these fluctuations are strong enough to suppress inelastic collapse. This allows us to study large systems for long times in the truly inelastic regime. During the cooling stage we observe complex cluster dynamics, as large clusters of particles form, collide, and merge or dissolve. Typical clusters are found to survive long enough to establish local equilibrium within a cluster, but not among different clusters. We extend the model to include net dissipation of energy by damping of the internal vibrations. Inelastic collapse is avoided also in this case but in contrast to the conservative system the translational energy decays according to the mean field scaling law, E(t)proportional to t(-2), for asymptotically long times.