Dynamic Rearrangements and Packing Regimes in Randomly Deposited Two-Dimensional Granular Beds

TL;DR

This paper investigates how two-dimensional granular packings formed by random deposition undergo structural rearrangements and exhibit different packing regimes, using dynamic and geometrical models to analyze their properties.

Contribution

It introduces a dynamic simulation approach based on rolling friction to study packing stability and identifies four distinct packing regimes based on solid fraction.

Findings

Dynamic method yields higher solid fractions than geometrical models.

Packings exhibit four regimes with different growth mechanisms.

Structural properties vary systematically across regimes.

Abstract

We study the structural properties of two-dimensional granular packings prepared by random deposition from a source line. We consider a class of random ballistic deposition models based on single-particle relaxation rules controlled by a critical angle, and we show that these local rules can be formulated as rolling friction in the framework of dynamic methods for the simulation of granular materials. We find that a packing prepared by random deposition models is generically unstable, and undergoes dynamic rearrangements. As a result, the dynamic method leads systematically to a higher solid fraction than the geometrical model for the same critical angle. We characterize the structure of the packings generated by both methods in terms of solid fraction, contact connectivity and anisotropy. Our analysis provides evidence for four packing regimes as a function of solid fraction, the mechanisms of packing growth being different in each regime.