Effective slip boundary conditions for flows over nanoscale chemical heterogeneities

TL;DR

This paper investigates how nanoscale chemical heterogeneities on surfaces affect slip boundary conditions for simple fluids, providing effective boundary models and analyzing their implications for experiments and surface design.

Contribution

It introduces a perturbative method to derive effective slip boundary conditions for fluids over chemically heterogeneous surfaces at the nanoscale.

Findings

Effective slip boundary expressions match numerical solutions in specific limits.

The study discusses implications for experimental measurements of slip.

Design strategies for surfaces with large slip lengths are considered.

Abstract

We study slip boundary conditions for simple fluids at surfaces with nanoscale chemical heterogeneities. Using a perturbative approach, we examine the flow of a Newtonian fluid far from a surface described by a heterogeneous Navier slip boundary condition. In the far-field, we obtain expressions for an effective slip boundary condition in certain limiting cases. These expressions are compared to numerical solutions which show they work well when applied in the appropriate limits. The implications for experimental measurements and for the design of surfaces that exhibit large slip lengths are discussed.