Microgravity† and Dissipative Granular Gas in a vibrated container: a gas with an asymmetric speed distribution in the vibration direction, but with a null mean speed everywhere
P. Evesque , Lab MSSMat, UMR 8579 CNRS, Ecole Centrale Paris, 92295 CHATENAY-MALABRY, France, email@example.com
The main topic of this paper (part 4) is the interpretation of data from extended simulations published in previous Poudres & Grains (see P&G 17, #1 to #18) concerning† the dynamics of N equal-size spheres in a 3d rectangular cell excited along Oz in 0 gravity.(N=100, 500, 1000, 1200, 2000, 3000, 4000, 4500). Different Oz excitation kinds have been used (symmetric and non symmetric bi-parabolic, symmetric and non symmetric saw teeth, thermal wall). No rotation is included, dissipation is introduced via a restitution coefficient e= -Vín/Vn , where Vín and Vn are the relative ball speed along normal to ball centres after and before collision. It is proved that the local speed distribution along z† is fundamentally dissymmetric in most part of the cell while the mean local speed is 0. This demonstrates the inability of a model based on a thermal bath (with a single local temperature) to describe this dissipative-granular-gas-system, even when assuming that this temperature varies in space. The other (1-3) parts sum up few results obtained in the very low density regime.
Pacs # : 5.40 ; 45.70 ; 62.20 ; 83.70.Fn
poudres & grains 18 (1), 1-19 (Juin 2010)