c. ruan

Superhydrophobic surfaces have garnered attention for their ability to decrease fluid resistance, which can significantly reduce energy consumption. This study aims to accurately capture critical flow phenomena in a microchannel and explore the internal drag-reduction mechanism of the flow field. To achieve this, the three-dimensional (3D) superhydrophobic surface flow field with conical microstructure is numerically simulated using the gas–liquid two-phase flow theory and Volume of Fluid (VOF) model, combined with a Semi-implicit method for the pressure-linked equation (SIMPLE) algorithm. The surface drag-reduction effect of the conical microstructure is investigated and compared it to that of the V-longitudinal groove and V-transverse groove surfaces. Additionally, the changes in the drag-reduction effect during the wear of the conical microstructure were explored. The numerical results reveal that the drag-reduction effect improves with a larger period spacing of the conical microstructure, the drag reduction rate can reach 25.23%. As the height of the conical microstructure increases, the aspect ratio (ratio of width to height) decreases, and the dimensionless pressure drop ratio and the drag-reduction ratio increase. When the aspect ratio approaches 1, the drag reduction rate can reach over 28%. indicating a more effective drag-reduction. The microstructure is most effective in reducing drag at the beginning of the wear period but becomes less effective as the wear level increases, when the high wear reaches 10, the drag reduction rate decreases to 3%. Compared to the V-shaped longitudinal groove and V-shaped transverse grooves, the conical microstructure is the most effective in reducing drag.

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.