Effect of surface roughness on rate-dependent slip in simple fluids

TL;DR

This study uses molecular dynamics simulations to explore how molecular-scale surface roughness affects slip behavior in thin liquid films, revealing the impact of surface properties and thermal fluctuations on slip length and rate dependence.

Contribution

It demonstrates how surface roughness and thermal fluctuations influence slip length and its shear rate dependence in molecular-scale fluid-solid interfaces.

Findings

Slip length increases linearly with shear rate on smooth walls.

Thermal fluctuations induce effective roughness, reducing rate dependence.

Rougher surfaces decrease slip length and its shear rate dependence.

Abstract

Molecular dynamics simulations are used to investigate the influence of molecular-scale surface roughness on the slip behavior in thin liquid films. The slip length increases almost linearly with the shear rate for atomically smooth rigid walls and incommensurate structures of the liquid/solid interface. The thermal fluctuations of the wall atoms lead to an effective surface roughness, which makes the slip length weakly dependent on the shear rate. With increasing the elastic stiffness of the wall, the surface roughness smoothes out and the strong rate dependence is restored again. Both periodically and randomly corrugated rigid surfaces reduce the slip length and its shear rate dependence.