Density profiles of a colloidal liquid at a wall under shear flow

TL;DR

This paper uses a modified dynamical density functional theory to study how shear flow affects the density profiles of colloidal liquids near a wall, revealing shear-induced structural transitions and energy changes.

Contribution

It introduces a physically motivated correction to standard theory to account for shear-induced interparticle forces, enabling accurate prediction of nonequilibrium density profiles.

Findings

Shear flow enhances density oscillations near the wall.

High shear rates induce a transition to layered particle arrangements.

Shear increases the potential energy of particles under gravity.

Abstract

Using a dynamical density functional theory we analyze the density profile of a colloidal liquid near a wall under shear flow. Due to the symmetries of the system considered, the naive application of dynamical density functional theory does not lead to a shear induced modification of the equilibrium density profile, which would be expected on physical grounds. By introducing a physically motivated dynamic mean field correction we incorporate the missing shear induced interparticle forces into the theory. We find that the shear flow tends to enhance the oscillations in the density profile of hard-spheres at a hard-wall and, at sufficiently high shear rates, induces a nonequilibrium transition to a steady state characterized by planes of particles parallel to the wall. Under gravity, we find that the center-of-mass of the density distribution increases with shear rate, i.e., shear increases the potential energy of the particles.