To my peers. Granular Gas & 2nd principle of thermodynamics:

a "hard" gas, a "quarrel" gas, a gas of missed debate

P. Evesque, Lab MSSMat, umr 8579 cnrs, ECP, 92295 Châtenay-Malabry, France , pierre.evesque@ecp.fr :

Abstract :

This paper explains within simple arguments why the physics of granular gas has to be understood in a new way, different to the one proposed by P. Haff, and able to describe the energy delivered to it and dissipated by it. This requires to take into account the difference in the mean particle speed in the + and – ways of the excitation direction. These different means V+ (Sum(mv+) /sum(m) and V-(= exist mainly everywhere in the sample as shown in P&G17, 577 (2009) and P&G18, 1,(2010). In steady excitation, which imposes ( m v++ m v-) =0, this generates the existence of a new force │P+│-│P-│, where P± (Sum( m v_±²) are the mean kinetic pressures in the two ± directions , due to the fact that the “pressures” P± on the two sides of a fixed plane are different. This new force was not taken into account; it is due to the speed asymmetry, combined with a particle-particle restitution coefficient e smaller than 1. In the scientific literature, everything is treated has one did want to deliver energy to the granular gas: the granular system at a local uniform temperature at the boundary, so that it cannot make any work (second principle of thermodynamics. It gets heat only from the boundary. If this was true, it would help mining excavation and treatment. This article tries to understand how we arrived there there. So the paper proposes a new writing of dissipation in granular fluid (liquid or gas).

Pacs # : 5.40 ; 45.70 ; 62.20 ; 83.70.Fn ; 45.35i ; 45.70.Mg; 83.80.fg ; 46.80.Ff ; 05.20.-y

poudres & grains 21, 1-19 ( Janvier 2013)