Mean field theory for a driven granular gas of frictional particles

We propose a mean field (MF) theory for a homogeneously driven granular gas of inelastic particles with Coulomb friction. The model contains three par ameters, a normal restitution coefficient r(n), a maximum tangential restit ution coefficient r(t)(m), and a Coulomb friction coefficient mu. The param eters can be tuned to explore a wide range of physical situations. In parti cular, the model contains the frequently used mu --> infinity limit as a sp ecial case. The MF theory is compared with the numerical simulations of a r andomly driven monolayer of spheres for a wide range of parameter values. I f the system is far away from the clustering instability (r(n) approximate to 1), we obtain a good agreement between mean field and simulations for mu = 0.5 and r(i)(m) = 0.4, but for much smaller values of r(n) the agreement is less good. We discuss the reasons of this discrepancy and possible refi nements of our computational scheme. (C) 2000 Elsevier Science B.V. All rig hts reserved.