**Evidence for**** speed-symmetry breaking
in steady state of dissipative
granular gas in 0g**

P. Evesque, R. Liu, M. Hou , pierre.evesque@ecp.fr

Lab MSSM, UMR 8579 CNRS, Ecole
Centrale Paris, 92295 Châtenay-Malabry, France &

Dept of Physics,
Chinese Acad. Sc.,

**Abstract: **The main topic of this
presentation 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= -V’_{n}/V_{n} , where V’_{n} and V_{n}_{ }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.

This oral presentation was presented
at Powders & Grains 2009, Golden, Co,

**Pacs**** # : **5.40 ;
45.70 ; 62.20 ; 83.70.Fn

*poudres**
& grains ***17**(19) 564-576 (August
2009)