A numerical study of drag reduction of superhydrophobic surfaces in shipping industry

As energy-conservation and emission-reduction become more and more severe, the concept of Green Ship has been proposed. And drag reduction is a realizable method to achieve this goal. Superhydrophobic surfaces (SHSs) whose contact angle is greater than 150° have attracted much attention because of the ability of realizing drag reduction in turbulent flows. However, few researchers focus on the application of SHSs in shipping industry. In this paper, a numerical study of turbulent channel flows and turbulent boundary layers developing over SHSs are performed. In the simulation, the VOF multiphase flow model is used for the gas-liquid phase flow, and a superhydrophobic surface microstructure grid with local encryption technology is adopted. The results show that within the range of ship economic speed, a stable gas vortex can form in the upper part of microstructure, and the drag reduction ratio of SHSs has a close relationship with size of velocity, gas-liquid contact area, and soaking time.