EPJ Web Conf.
Volume 249, 2021Powders & Grains 2021 – 9th International Conference on Micromechanics on Granular Media
|Number of page(s)||4|
|Published online||07 June 2021|
Relative entropy of freely cooling granular gases. A molecular dynamics study
Departamento de Física, Universidad de Extremadura, E-06006 Badajoz, Spain
2 Instituto de Computación Científica Avanzada (ICCAEx), Universidad de Extremadura, E-06006 Badajoz, Spain
Published online: 7 June 2021
Whereas the original Boltzmann’s H-theorem applies to elastic collisions, its rigorous generalization to the inelastic case is still lacking. Nonetheless, it has been conjectured in the literature that the relative entropy of the velocity distribution function with respect to the homogeneous cooling state (HCS) represents an adequate nonequilibrium entropy-like functional for an isolated freely cooling granular gas. In this work, we present molecular dynamics results reinforcing this conjecture and rejecting the choice of the Maxwellian over the HCS as a reference distribution. These results are qualitatively predicted by a simplified theoretical toy model. Additionally, a Maxwell-demon-like velocity-inversion simulation experiment highlights the microscopic irreversibility of the granular gas dynamics, monitored by the relative entropy, where a short “anti-kinetic” transient regime appears for nearly elastic collisions only.
A video is available at https://doi.org/10.48448/qhse-yx22
© The Authors, published by EDP Sciences, 2021
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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