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)