A Model for Wall Slip Prediction of Confined n-Alkanes: Effect of Wall-Fluid Interaction Versus Fluid Resistance

Abstract

It is shown via molecular dynamics simulations that the occurrence of wall slip for linear alkanes confined between geometrically smooth surfaces depends on the wall-fluid interactions and the chain length of the lubricant molecules. A wall slip model based on the competition between these two factors is introduced. A surface parameter accounts for the wall-fluid interaction and commensurability, and is valid for both canonical and complex crystal lattices: this quantity is then linked to the shear stress transferred to the fluid molecules. The lubricant internal cohesion under confinement is described by a bulk viscosity term. Finally, a semi-analytical law for wall slip prediction including both the fluid viscosity and the surface characterization parameter is proposed.