Effects of Channel Scale on Slip Length of Flow in Micro/Nanochannels

The concept of slip length, related to surface velocity and shear rate, is often used to analyze the slip surface property for flow in micro- or nanochannels. In this study, a hybrid scheme that couples molecular dynamics simulation (used near the solid boundary to include the surface effect) and a continuum solution (to study the fluid mechanics) is validated and used for the study of slip length behavior in the Couette flow problem. By varying the height of the channel across multiple length scales, we investigate the effect of channel scale on surface slip length. In addition, by changing the velocity of the moving-solid wall, the influence of shear rate on the slip length is studied. The results show that within a certain range of the channel heights, the slip length is size dependent. This upper bound of the channel height can vary with the shear rate. Under different magnitudes of moving velocities and channel heights, a relative slip length can be introduced, which changes with channel height following a logarithmic function, with the coefficients of the function being the properties of the fluid and wall materials. [DOI: 10.1115/1.4001619]