Energy Decay Rate in Free Cooling Process of Inelastic Hard Sphere System
Abstract: The energy decay rate is examined carefully in the homogeneous cooling state of the free cooling of the inelastic hard sphere system. It is shown that the decay rate obtained from numerical simulations is slightly smaller than the one obtained from the assumption of random collision with the Maxwell-Boltzmann velocity distribution. The difference is small, but much larger than the one that can be explained from the Enskog-Boltzmann equation that takes into account of the deviation of the velocity distribution. This implies the velocity correlation ignored in the theory is responsible for the difference even though it starts from the very early stage of the homogeneous cooling state.