Volume 79, Number 2, July 2007
Article Number 24003
Number of page(s) 5
Section Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics
Published online 03 July 2007
EPL, 79 (2007) 24003
DOI: 10.1209/0295-5075/79/24003

An invariant distribution in static granular media

T. Aste1, T. Di Matteo1, M. Saadatfar1, 2, T. J. Senden1, Matthias Schröter3 and Harry L. Swinney3

1  Department of Applied Mathematics, Research School of Physical Sciences and Engineering, The Australian National University - 0200 Canberra, ACT, Australia
2  Trinity College - Dublin, Ireland
3  Center for Nonlinear Dynamics and Department of Physics, University of Texas at Austin Austin, TX 78712, USA

received 23 March 2007; accepted in final form 6 June 2007; published July 2007
published online 3 July 2007

We have discovered an invariant distribution for local packing configurations in static granular media. This distribution holds in experiments for packing fractions covering most of the range from random loose packed to random close packed, for bead packs prepared both in air and in water. Assuming only that there exist elementary cells in which the system volume is subdivided, we derive from statistical mechanics a distribution that is in accord with the observations. This universal distribution function for granular media is analogous to the Maxwell-Boltzmann distribution for molecular gasses.

45.70.-n - Granular systems.
45.70.Cc - Static sandpiles; granular compaction.
81.05.Rm - Porous materials; granular materials.

© Europhysics Letters Association 2007