Year: 2026
Type: article
Abstract: We revisit the properties of quasi two-dimensional mono-disperse granular gases under micro-gravity conditions using an air table. The air flow provides a microgravity-like environment and homogeneously injects energy into the system. The energy supplied to the particles is dissipated through aerodynamic drag and by collisions between particles,thus leading to a steady state. The horizontal components of the translational velocity and the vertical component of the angular velocity $\omega$ of the particles are found to follow remarkably well Gaussian distributions except at very low surface fraction. We independently varied the particle size $d$, the surface coverage $C$, and the air flow speed $U$, and found that the variation of the mean square horizontal velocity of the particles can be well described by a simple scaling law: $ \langle V^2 \rangle \propto U^{2/5} d^{-4/15} C^{-2/3}$. Importantly, the dependence of the scaling exponents on $d$ and $C$ can be inferred from the kinetic theory of granular gases, combined with the experimental determination of the collisional friction coefficient $\mu$ and the normal restitution coefficient $e_p$ in particle--particle collisions. Additionally, we show that the power injected per particle $\Gamma_{in}$ by the air flow is independent of the surface coverage and particle size. $\Gamma_{in}$ solely depends on the air flow speed as $\Gamma_{in} \propto U^{3/5}$. Interestingly, our quasi 2D granular system behaves similarly to a two-dimensional gas of hard disks and the measured mean free path and self-diffusion coefficient agree perfectly with the prediction of the kinetic theory. However, the analysis of the rotational granular temperature $\Theta$ of this two-dimensional gas indicates that it is much smaller than its translational granular temperature $T$, and that energy equipartition between translational and rotational degrees of freedom is therefore not satisfied.
Language: English
Subfield: Computational Mechanics
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,580
OpenAlex ID: W7164933647