The importance of roughness in the modeling of granular gases has been increasingly considered in recent years. In this paper, a freely evolving homogeneous granular gas of inelastic and rough hard disks or spheres is studied under the assumptions of the Boltzmann kinetic equation. The homogeneous cooling state is studied from a theoretical point of view using a Sonine approximation, in contrast to a previous Maxwellian approach. A general theoretical description is done in terms of $d_t$ translational and $d_r$ rotational degrees of freedom, which accounts for the cases of spheres ($d_t=d_r=3$) and disks ($d_t=2, d_r=1$) within a unified framework. The non-Gaussianities of the velocity distribution function of this state are determined by means of the first nontrivial cumulants and by the derivation of non-Maxwellian high-velocity tails. The results are validated by computer simulations using direct simulation Monte Carlo and event-driven molecular dynamics algorithms.

• Received 28 March 2023
• Accepted 13 June 2023

DOI:https://doi.org/10.1103/PhysRevE.108.014902