High Drag Reduction by Spontaneous Capture and Transportation of Bubble

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 covering area and insufficient drag reduction efficiency. Here, we developed an underwater superaerophilic pattern composed of a serial structure and brachistochrone profile to spontaneously capture and transport gas bubbles, which effectively hindered the bubble escaping, expanded the gas covering 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, the two-phase flow simulation showed that superaerophilic pattern still work and could realize a drag reduction rate of 13.25% even under a large flow velocity of 10 m•s-1. Moreover, the flowing gas layer on superaerophilic pattern also endowed an excellent corrosion resistance and marine antifouling. This high and eco-friendly underwater drag reduction method will will minimize the energy consumption required for ship navigation and greenhouse gas emission, which has a strong implication for the sustainable human development.