Effect of solid properties on slip at a fluid-solid interface

Abstract

The dependence of velocity slip at a liquid-solid interface upon the character of the solid is studied using atomistic simulation methods for Lennard-Jones model systems. The effect of the thermostatting mechanisms, often used in such simulations, is also investigated. The solid atom vibrational frequency is shown not to have a significant effect on the slip length for the range of parameters investigated; however, it is found that application of a thermostat to the fluid changes the slip length at low shear rates and results in an unphysical divergent slip behavior at high shear rates. On the other hand, removing the generated heat through the walls, which is more analogous to a laboratory condition, results in a nonlinearly decreasing slip length with shear rate that asymptotes to the no-slip limit at high shear rates. This effect is due to viscous heating, which increases the fluid temperature and pressure. A nonlinear relationship between the slip length and the shear rate collapses the shear-rate-slip-length dependence onto a single curve for a range of cases when heat is more realistically removed through the walls.