Theory of rheology in confinement

TL;DR

This paper develops a theoretical framework for understanding fluid viscosity under confinement using density functional theory, focusing on the effects of wall separation on rheological behavior.

Contribution

It introduces a novel approach to rheology in confined geometries based on the many-particle diffusion equation and classical density functional theory.

Findings

Viscosity varies with wall-to-wall distance in confined fluids.

Theoretical predictions align with known behaviors of confined colloidal suspensions.

Provides a foundation for future studies on nanoscale fluid dynamics.

Abstract

The viscosity of fluids is generally understood in terms of kinetic mechanisms, i.e., particle collisions, or thermodynamic ones as imposed through structural distortions upon e.g. applying shear. Often the former is less relevant, and (damped) Brownian particles are considered good fluid model systems. We formulate a general theoretical approach for rheology in confinement, based on the many particle diffusion equation, evaluated via classical density functional theory. We discuss the viscosity for the situation of two parallel walls in relative motion as a function of wall-to-wall distance.