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Updated: Jun 18, 2025

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Rotational and translational motions in a homogeneously cooling granular gas
Torsten Trittel1,2, Dmitry Puzyrev2,3, Kirsten Harth1,2
1Department of Engineering, Brandenburg University of Applied Sciences, Magdeburger Str. 50, Brandenburg an der Havel, 14770, Germany.
Abstract:
A granular gas composed of monodisperse spherical particles was studied in microgravity experiments in a drop tower. Translations and rotations of the particles were extracted from optical video data. Equipartition is violated, the rotational degrees of freedom were excited only to roughly 2/3 of the translational ones. After stopping the mechanical excitation, we observed granular cooling of the ensemble for a period of three times the Haff time, where the kinetic energy dropped to about 5% of its initial value. The cooling rates of all observable degrees of freedom were comparable, and the ratio of rotational and translational kinetic energies fluctuated around a constant value. The distributions of translational and rotational velocity components showed slight but systematic deviations from Gaussians at the start of cooling.
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