Numerical Study on Laminar Drag Reduction for Superhydrophobic Surfaces with Continuous V-Shaped Microstructures

Abstract

Superhydrophobic surfaces have attracted great attention owing to their capacity of reducing fluid resistance. Most of the previous numerical simulations on drag reduction of the superhydrophobic surfaces have concentrated on the rectangular microstructures, whereas few studies have focused on the continuous V-shaped microstructures. Based on the gas–liquid two-phase flow theory and volume-of-field model, combined with the semi-implicit method for pressure-linked equations algorithm, the effects of laminar drag reduction for superhydrophobic surfaces with continuous V-shaped microstructures were numerically studied. Three different sizes of superhydrophobic microchannels with continuous V-shapes were simulated according to the experimental data. Results showed that the drag reduction effects of continuous V-shaped microstructures were mainly determined by the width of adjacent microstructures, with the height of the microstructures only having minimal influence. At the same time, the effects of drag reduction for superhydrophobic surfaces with continuous V-shaped microstructures were compared with those with V-shaped and rectangular microstructures. The results indicated that the effects of drag reduction for superhydrophobic surfaces with continuous V-shaped microstructures were obviously better than for those with V-shaped microstructures, whereas the superhydrophobic surfaces with rectangular microstructures were more effective in reducing their drag than those with V-shaped microstructures under the condition of the same shear-free air–water ratios. Therefore, in the preparation of superhydrophobic materials, the continuous V-shaped microstructures are recommended; in addition, increasing the microstructure width should be emphasized in the preparation of superhydrophobic materials with continuous V-shaped microstructures.

Keywords

• superhydrophobic surface
• laminar flow
• drag reduction
• v-shaped microstructure
• flow field