Numerical characterization of laminar bulk flow over textured surfaces

Abstract

Textured surfaces have been fabricated in the past using several methods and were characterized for relatively simple texture geometries and especially with static drops on them. Numerical tools may provide an effective alternative to understand the effect of complex texture geometries and help understand the effect of texturing on flowing liquids. This work focuses on the numerical simulation of laminar bulk flow of water through microchannels with textured surfaces and provides a comparison with their smooth counterparts. The interpillar spacing on the textured surfaces is found to influence the pressure drop. This is because the trapped air is able to exit the surface cavities at a relatively high rate for larger interpillar spacings. A decrease in channel height increases the percentage pressure drop reduction because of an increase in the ratio of slip length to channel height. The probability of water penetrating the surface cavities increases with flow velocity. Pressure drop measurements on microchannels with textured surfaces, fabricated using two-step photolithography, show that the theoretical pressure drop for smooth microchannels is marginally closer to the experimental value than those observed with textured microchannels. The study therefore helps understand the effect of individual parameters on the overall flow field and engineering parameters such as wall shear stress.