Phase transition
or Maxwell’s demon in Granular gas?

P. Jean, H.
Bellenger, P. Burban, L. Ponson & P. Evesque: Lab MSSM, UMR 8579 CNRS, Ecole
Centrale Paris, 92295 Châtenay-Malabry, France , **evesque@mssmat.ecp.fr**

**Abstract:** Dynamics of vibro-fluidised granular gas is investigated experimentally
using the transfer of grains from a compartment through a horizontal slit at a
given height h. It is demonstrated that the transfer rate j varies linearly
with the grain number N in the box when N remains small; however j(N) becomes
strongly non linear as soon as the number n of layers is larger than 0.3; dj/dN
becomes negative for n>0.4.It is found also that the maximum of j(N)
increases slightly with the acceleration aw² of the vibration which excites the granular gas. Using dynamical
system theory, dynamics equations are written, and a critical bifurcation is
found, which explains the existence of a condensation and of a phase
transition. This explains how the pseudo “ Maxwell’s demon” works in granular
gases. This experiments contradicts recent modelling .

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

*poudres & grains* **13**
(3), 27-39 (Juillet-Août 2002)