A Universal Molecular-Kinetic Scaling Relation for Slip of a Simple Fluid at a Solid Boundary

TL;DR

This paper introduces a universal molecular-kinetic model for slip in simple fluids at solid boundaries, linking slip behavior to shear stress and molecular parameters, validated by molecular dynamics simulations.

Contribution

It develops a universal scaling relation for slip that unifies low and moderate shear rate behaviors and connects molecular parameters with macroscopic slip length.

Findings

Model accurately predicts slip dependence on temperature and interaction strength.

Simulation results agree well with the proposed molecular-kinetic relation.

The model generalizes the Navier-slip condition to a broader range of shear rates.

Abstract

Using the observation that slip in simple fluids at low and moderate shear rates is a thermally activated process driven by the shear stress in the fluid close to the solid boundary, we develop a molecular-kinetic model for simple fluid slip at solid boundaries. The proposed model, which is in the form of a universal scaling relation that connects slip and shear rate, reduces to the well known Navier-slip condition under low shear conditions, providing a direct connection between molecular parameters and the slip length. Molecular-dynamics simulations are in very good agreement with the predicted dependence of slip on system parameters, including the temperature and fluid-solid interaction strength. Connections between our model and previous work, as well as simulation and experimental results are explored and discussed.