Drag reduction performance and mechanism of flexible conical microstructure film inspired by pufferfish epidermis

Flexible bionic drag reduction surfaces have attracted increasing attention in recent years owing to its potential to address the daunting energy crisis. Inspired by the skin of pufferfish, a flexible conical microstructure film with effective drag reduction is designed. The film has the advantages of cost-effective and tensile-bending resistance to meet commercial applications. The low price of raw materials and rapid solidification at room temperature are the core of cost reduction, and the manufactured film can withstand a maximum tensile force of 70 N and a strain of 484%. The practical application effect of the film has been confirmed by model ship tests, and it still has stable drag reduction ability after multiple stretching and bending. The water tunnel experiment results show that the drag-reducing efficiency of the flexible conical microstructure film is 10.65%–12.04% compared to the rigid plane, in which the conical topography suppresses turbulence burst, whereas the flexible surface has the effect of absorbing turbulent energy to buffer the near-wall fluid. The coupling effect enhances drag-reducing efficiency. Therefore, the flexible conical microstructure film in this work provides a practical and commercialized fluid drag reduction approach for ships, underwater vehicles, and pipeline transportation.