Statistics of the contact network in frictional and frictionless granular packings

TL;DR

This study analyzes contact force distributions and network structures in simulated granular packings with varying friction, revealing force decay patterns, weak force correlations, and anisotropic contact networks with minimal role for force chains.

Contribution

It provides a detailed comparison of force distributions and contact network properties in frictional and frictionless granular packings, highlighting weak force correlations and anisotropic contact networks.

Findings

Force distributions decay exponentially at large forces.

Force correlations decay rapidly beyond three diameters.

Contact network is anisotropic and weakly dependent on friction.

Abstract

Simulated granular packings with different particle friction coefficient mu are examined. The distribution of the particle-particle and particle-wall normal and tangential contact forces P(f) are computed and compared with existing experimental data. Here f equivalent to F/F-bar is the contact force F normalized by the average value F-bar. P(f) exhibits exponential-like decay at large forces, a plateau/peak near f = 1, with additional features at forces smaller than the average that depend on mu. Computations of the force-force spatial distribution function and the contact point radial distribution function indicate that correlations between forces are only weakly dependent on friction and decay rapidly beyond approximately three particle diameters. Distributions of the particle-particle contact angles show that the contact network is not isotropic and only weakly dependent on friction. High force-bearing structures, or force chains, do not play a dominant role in these three dimensional, unloaded packings.