High drag reduction by spontaneous capture and transportation of bubbles

Abstract

Gas lubrication is globally recognized as an effective technology for reducing drag. However, the injected gas bubbles are prone to escape, resulting in a low gas coverage area and insufficient drag reduction efficiency. Herein, we developed an underwater superaerophilic pattern composed of a serial structure and a brachistochrone profile to spontaneously capture and transport the gas bubbles, which effectively hindered bubble escape, expanded the gas coverage area, and increased the drag reduction rate. The maximum drag reduction rates at a horizontal sample surface and an inclined sample surface under a water velocity of 0.6 m s⁻¹ were as high as 31.8% and 18.5%, respectively. In addition, two-phase flow simulation showed that the superaerophilic pattern could still work and achieve a drag reduction rate of 13.25% even under a high flow velocity of 10 m s⁻¹. Moreover, the flowing gas layer on the superaerophilic pattern endowed an excellent corrosion resistance and marine antifouling ability. This high efficient and eco-friendly underwater drag reduction method will minimize the energy consumption required for ship navigation and greenhouse gas emission, which has a strong implication for sustainable human development.