仿鱼类表皮减阻研究现状与进展

Reducing energy consumption is consistently desirable, with the aim of avoiding aggravation of the global energy crisis. Creatures in nature have adapted to their surroundings as a result of biological evolution. Learning how nature creatures adapts to environmental challenges may help solve many challenges in engineering. Underwater drag reduction is a dominant functional strategy developed by the long-term evolution of high-speed swimming organisms such as fish, revealing the relationship between topography characteristics, material properties, and drag reduction functional mechanisms can provide a feasible reference scheme for solving the problem of high-friction resistance on high-moving surfaces. Based on this strategy, this review takes fish skin as a prototype, the unique structure characteristics of sharkskin and dolphin skin are briefly analyzed, before the topography characteristics and multilayered structure of tuna skin are revealed and summarized. The characterization results show that tuna skin has structural characteristics and mechanical properties that result from imbricated fish scales covered by a flexible epidermis layer and embedding in a flexible dermis layer. This structure could be one reason for tuna swimming faster than sharks and dolphins. As more topographical features of other fish skins have been discovered and characterized, some fish scales have been exhibited excellent drag reduction performance in varying conditions. The unique structure characteristics, material properties, and special function of fish skin can provide a useful source for scientific development, technological invention and creation, and engineering technological problems. Drag reduction surfaces inspired by these unique structures and material properties were fabricated using a variety of processing methods, and are summarized in this review. The drag reduction performance of different bionic surfaces differs due to various shapes which have been constructed on microscale or nanoscale surfaces, size dimensions, and material properties. Even so, the drag reduction mechanism of those bionic surfaces can be roughly divided into three categories. First, the drag reduction effect is brought about by the unique structure and its drag reduction mechanism is summarized as the structure effect. The unique structure has a direct influence on the characteristics of the near-wall flow field, such as the “water trapping” effect of the microcrescent array inspired by Ctenopharyngodon idelluse fish scales that can lower the velocity gradient and generate a fluid-lubrication film to reduce shear wall stress between solid and fluid interface. Second, the compliant mechanism is summarized in which the drag reduction effect is caused by a flexible or compliant surface. Typically, the compliant surface acts as a resilient energy-absorbing coating that can delay the boundary layer transitioning from laminar to turbulent flow. Finally, a composite mechanism type is proposed in which the drag reduction effect is brought by coupling of the flexible coating and the unique structure characteristics. The composite surface with unique structure coupling with functional coating not only has excellent drag reduction performance, but also has other useful functions such as antifouling and noise reduction. Those drag reduction mechanisms evolved in nature can provide new bionic drag reduction systems and provide inspiration for innovation to solve engineering problems. At the end of this review, the application of the bionic surfaces inspired by fish skin is briefly introduced. On this basis, the future development and application of bionic surface drag reduction technologies are prospected. Although has restriction development and application all sorts of factors, but with the continuous development of manufacturing technology and materials, infiltration and emergence of many scientific branches will become a trend in the field of bionic drag reduction. This review can serve as a foundation for an in-depth analysis of the hydrodynamic performance of fish as well as a new inspiration for drag reduction and antifouling.