Orientational order and alignment of elongated particles induced by shear

Phys Rev Lett. 2012 Jun 1;108(22):228302. doi: 10.1103/PhysRevLett.108.228302. Epub 2012 May 30.

Abstract

Shear induced alignment of elongated particles is studied experimentally and numerically. We show that shear alignment of ensembles of macroscopic particles is comparable even on a quantitative level to simple molecular systems, despite the completely different types of particle interactions. We demonstrate that for dry elongated grains the preferred orientation forms a small angle with the streamlines, independent of shear rate across three decades. For a given particle shape, this angle decreases with increasing aspect ratio of the particles. The shear-induced alignment results in a considerable reduction of the effective friction of the granular material.