Freely cooling granular gases with short-ranged attractive potentials
We treat the case of an undriven gas of inelastic hard-spheres with short-ranged attractive potentials via an extension of the pseudo-Liouville operator formalism. New evolution equations for the granular temperature and coordination number are obtained. The granular temperature exhibits deviation from both Haff’s law and the case of long-ranged potentials. We verify this departure using soft-sphere discrete element method simulations. Excellent agreement is found for the duration of the simulation even beyond where exclusively binary collisions are expected. Simulations show the emergence of strong spatial-velocity correlations on the length scale of the last peak in the pair-correlation function but do not show strong correlations beyond this length scale. We argue that molecular chaos may remain an adequate approximation if the system is modelled as a Smoluchowski type equation with aggregation and break-up processes.
This article is published as Murphy, Eric, and Shankar Subramaniam. "Freely cooling granular gases with short-ranged attractive potentials." Physics of Fluids 27, no. 4 (2015): 043301. DOI: 10.1063/1.4916674. Posted with permission.