Effects of surface roughness periodicity and channel height in nano-channel flows

Abstract

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.One of important phenomenon's in micro and nano-devices is slippage. The concept of slip length has been introduced to compute slip at the solid surfaces. A large slip length decreases dissipation at the surfaces and results in changing pressure drop. In this paper, the effect of roughness periodicity has been studied, which deals with distances between corrugations, on velocity profile and slip length variations by molecular dynamics simulations. To have a perfect analysis, the channel walls was chosen to be rough and after that by increasing the distances between corrugations which result in increasing periodicity of roughness, its effect on variation of velocity profiles undergoing Poiseuille flow was investigated. Also, the slip length in each simulation which shows the magnitude of slippage was calculated. As the results showed, when roughness periods increased, velocity profiles were found to be the same as flat channel’s profile and slip length decreases. The outcomes also reveal a non-linear dependency of the slip length magnitude on the roughness period. Slip length profiles also showed that slip decreases by increasing the height of the nanochannel, because solid-fluid interface effects will disappear in channels with more height and slip length would have greater magnitudes as a result.