Experimental study of the compaction dynamics for 2D anisotropic granular materials

TL;DR

This experimental study investigates the compaction dynamics of 2D anisotropic granular materials across multiple scales, revealing the roles of grain translation and rotation in different stages of compaction.

Contribution

It provides a multi-scale analysis of compaction, highlighting the impact of grain rotations on late-stage dynamics in anisotropic granular systems.

Findings

Discontinuity observed in macroscopic compaction curve

Formation and growth of aligned grain domains

Grain translation initiates compaction, rotation dominates later stages

Abstract

We present an experimental study of the compaction dynamics for two-dimensional anisotropic granular systems. Compaction dynamics is measured at three different scales : (i) the macroscopic scale through the packing fraction $\rho$, (ii) the mesoscopic scale through both fractions of aligned grains $\phi_{a}$ and ideally ordered grains $\phi_{io}$, and (iii) the microscopic scale through both rotational and translational grain mobilities $\mu_{r,t}$. The effect of the grain rotations on the compaction dynamics has been measured. At the macroscopic scale, we have observed a discontinuity in the late stages of the compaction curve. At the mesoscopic scale, we have observed the formation and the growth of domains made of aligned grains. From a microscopic point of view, measurements reveal that the beginning of the compaction process is essentially related to translational motion of the grains. The grains rotations drive mainly the process during the latest stages of compaction.