Translations and Rotations Are Correlated in Granular Gases
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)Abstract
In a granular gas of rough particles the axis of rotation is shown to be correlated with the translational
velocity of the particles. The average relative orientation of angular and linear velocities depends on the
restitution coefficients -- the parameters which characterize the dissipative nature of the collision 1,2.
Using the Boltzmann equation and pseudo-Liouville operator technique 1,3 we derive a simple analytical theory
for these correlations. We also perform
numerical simulations for a wide range of coefficients of normal and
tangential restitution. Two different numerical methods were used:
Direct simulation Monte Carlo (DSMC) 4 and event-driven
molecular dynamics (MD). Surprisingly, the limit of smooth spheres was found to be singular: even
an arbitrarily small roughness of the particles gives rise to orientational correlations. The results of
the analytical theory are in a good agreement with the numerical simulations 5.
1) N.V. Brilliantov and T. Poeschel, Kinetic Theory of
Granular Gases (Oxford University Press, Oxford, 2004).\\
2) T. Poeschel, and N.V. Brilliantov (Eds.),
Granular Gas Dynamics,
Lecture Notes in Physics, vol. 624, Springer (2003).\\
3) T. Aspelmeier, M. Huthmann, and A. Zippelius, in
Granular Gases, S. Luding and T. Poeschel (Eds),
Lecture Notes in Physics vol. 425, Springer, Berlin,
(2000), p. 680.\\
4) T. Poeschel and T. Schwager, Computational Granular
Dynamics (Springer, New York, 2005).\\
5) N.V. Brilliantov, T. Poeschel, W.T. Kranz, and A. Zippelius,
Phys. Rev. Lett., 98, (2007) 128001.