Dynamically induced effective interaction in periodically driven granular mixtures

TL;DR

This paper investigates the microscopic origins of pattern formation and segregation in oscillating granular mixtures, revealing an effective anisotropic interaction that explains observed phenomena and can be modeled with a modified Cahn-Hilliard equation.

Contribution

It uncovers the effective interaction between particles in driven granular mixtures and demonstrates its role in pattern formation, using molecular dynamics simulations and a modified theoretical model.

Findings

Effective short-range attraction between like particles.

Anisotropic interaction with a long-range repulsive shoulder.

Modified Cahn-Hilliard equation captures the dynamics.

Abstract

We discuss the microscopic origin of dynamical instabilities and segregation patterns discovered in granular mixtures under oscillating horizontal shear, by investigating, via molecular dynamics simulations, the effective interaction between like-particles. This turns out to be attractive at short distances and strongly anisotropic, with a longer range repulsive shoulder along the direction of oscillation. This features explain the system rich phenomenology, including segregation and stripe pattern formation. Finally, we show that a modified Cahn-Hilliard equation, taking into account the characteristics of the effective interaction, is capable of describing the dynamics of the mixture.