Model of coarsening and vortex formation in vibrated granular rods

Phys Rev E Stat Nonlin Soft Matter Phys. 2003 Feb;67(2 Pt 1):021305. doi: 10.1103/PhysRevE.67.021305. Epub 2003 Feb 26.

Abstract

Neicu et al. observed experimentally spontaneous formation of the long-range orientational order and large-scale vortices in a system of vibrated macroscopic rods. We propose a phenomenological theory of this phenomenon based on a coupled system of equations for local rods density and tilt. The density evolution is described by the modified Cahn-Hilliard equation, while the tilt is described by the Ginzburg-Landau type equation. Our analysis shows that, in accordance with the Cahn-Hilliard dynamics, islands of the ordered phase appear spontaneously and grow due to coarsening. The generic vortex solutions of the Ginzburg-Landau equation for the tilt correspond to the vortical motion of the rods around the cores which are located near the centers of the islands.