Vibrated granular media as experimentally realizable granular gases
S. McNamara1, 3 and E. Falcon2
1 Centre Européen de Calcul Atomique et
Moléculaire, 46 allée d'Italie, 69364 Lyon cedex 07,
France 2 Laboratoire de Physique, École Normale
Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon cedex
07, France 3 current address: Institute for Computer Applications 1,
Universität Stuttgart, 70569 Stuttgart, Germany
Reference:
in "Granular Gas Dynamics", Vol. 624
of Lectures Notes in Physics, T. Pöschel and
N.
V. Brilliantov (Eds.), Springer-Verlag Heidelberg, Berlin, p. 347 -
366 (2003).
ISSN: 1616-6361
Abstract:
We report numerical simulations of strongly vibrated granular materials
designed to mimic recent experiments performed both in presence [1, 2, 3] or absence [4] of gravity. We show that a
model with impact velocity dependent restitution coefficient is
necessary to bring the simulations into agreement with experiments. We
measure the scaling
exponents of the granular temperature, collision frequency, impulse and
pressure with the vibrating piston velocity.
As the system changes from a homogeneous gas state at low density to a
clustered state at high density, these exponents are all found to
decrease
continuously with the particle number. In absence of gravity, a loose
cluster
appears near the upper wall, opposite the piston, and acts as a buffer
for
fastest particles leading to unexpected non-extensive scaling exponents
;
whereas in presence of gravity, the cluster bounces as a single
inelastic
body. All these results differ significantly from classical inelastic
hard
sphere kinetic theory and previous simulations, both based on a
constant
restitution coefficient.
