Research On The Design Of Bionic Hydrophobic Structure On Metal Surface And Its Underwater Anti-drag Performance

Nowadays,with the increasingly serious global energy crisis,drag reduction technology has been paid more and more attention in various fields.How to reduce the navigation resistance more efficiently has become a hot topic.Superhydrophobic surface drag reduction technology is one of the important methods to alleviate the bottleneck of drag reduction technology.The superhydrophobic surface uses its rough surface structure to capture the air and change the contact mode between the surface of the vehicle and the fluid medium,so as to achieve the purpose of drag reduction.However,the traditional superhydrophobic surface has some limitations in the field of vehicle drag reduction,and its performance is not satisfactory.It is difficult to achieve the synergistic performance of excellent durability and hydrophobicity.Therefore,there is still much room for improvement in the design and R ? D of superhydrophobic drag reduction surfaces.The rapid development of engineering bionics provides a new way to break through the problems existing in the design and R ? D of superhydrophobic drag reduction surfaces.In the face of hundreds of millions of years of natural selection,organisms in nature have evolved special functional structures that could almost perfectly adapt to the environment.The functionality and drag reduction ability of these structures are far beyond the materials currently used by humans.Imitating nature and starting from the special structure evolved by these typical organisms,an in-depth study on the mechanism of biological drag reduction will provide new ideas and inspiration for the research and development of new bionic drag reduction materials.Starting from the concept of engineering bionics,aiming at two common marine environments,including ordinary navigation environment and crude oil leakage environment,this paper takes water spider(Argyroneta aquatica)and butterfly Trogonoptera brookiana as biological prototypes.A variety of characterization methods were used to observe the structural characteristics of the drag reduction function of the two biological prototypes.Optimize the structural parameters of drag reduction function in different environments: the "nest" structure and ciliary structure on the body surface of water spider can effectively capture bubbles,improve its own buoyancy and reduce the walking resistance in the water.The butterfly reduces its weight by relying on the ridge vein and pore structure of the butterfly wing skeleton.In addition,the nonwettability of butterfly wings and the micro nanostructure with low surface energy endow the surface with super lipophilic characteristics,which makes it possible for butterflies to shuttle in the rainforest with high humidity and high oil pollution.Based on the special structures of the above two organisms,combined with the principle of bionics,this paper reveals the drag reduction mechanism of the two organisms in different environments by using experimental characterization and theoretical analysis.On this basis,three bionic superhydrophobic drag reduction surfaces were designed,prepared and characterized.The main research contents of this paper are as follows:1.Characterization of surface microstructure and analysis of drag reduction performance of water spider: on the macro scale,dense cilia are distributed on the legs,abdomen and back of water spider,and the cilia completely cover the original body surface;On the micro scale,these ciliary structures have a multi-scale hierarchical structure,the overall structure is similar to the "feather duster" structure and the cilia are conical from the root to the top,and the ciliary root has a protective "nest" structure.The ciliary structure and the nest structure at the bottom jointly build the superhydrophobic surface of the water spider body surface and confirm the key parameters of the multi-scale hierarchical structure of the water spider body surface.The bubble trapping characteristics of feather duster-like ciliary structure and the function of the nest structure to capture and store bubbles were verified.Relying on the combination of its superhydrophobic structure and the characteristics of capturing bubbles,the water spider has the drag reduction characteristics of rapid underwater travel.2.Characterization and determination of the multi-scale hierarchical structure of the wings of the butterfly.The multi-scale micro/nano hierarchical structure of the butterfly wing skeleton shows superhydrophobic performance,and the hydrophobic and lipophilic characteristics of ridge structure,groove structure,and pore structure show drag reduction characteristics.The bionic superhydrophobic drag reduction surface is designed and prepared according to the above multi-scale hierarchical structure,which shows excellent drag reduction characteristics at the oil-water mixing interface.The characteristic structure and key parameters of the butterfly wing scale were characterized by a variety of microscopes,super depth of field imaging systems,and other instruments.It was found that ridge vein structure and pore structure distributed in the middle of ridge vein structure was distributed on the surface of butterfly wing scale,and groove structure was distributed on the surface of ridge vein structure.It is confirmed that these multi-scale hierarchical structures play a special role in the construction of nonwetting drag reduction surfaces.3.Preparation of bionic metal-based multi-scale micro/nano hierarchical structure and characterization of its underwater drag reduction performance: Based on the above water spider surface multi-scale micro/nano hierarchical structure,two bionic superhydrophobic drag reduction surfaces were prepared,and the characteristic morphology and structure of the two surfaces were characterized.The experimental results show that the bionic superhydrophobic anti-drag surface realizes the bionic preparation of water spider surface microstructure.In addition,for the purpose of bionic manufacturing in an ordinary navigation environment,a bionic drag reduction surface test device is designed and built.The test results show that the bionic superhydrophobic drag reduction surface has excellent drag reduction performance.4.Preparation and performance study of bionic superhydrophobic drag reduction synergistic functional surface: the nonwetting characteristics of the surface are verified.The results show that the bionic drag reduction surface could quickly get rid of the interference of water and oily media and maintain the surface characteristics at all times.In addition,for different application scenarios,the drag reduction conditions of the surface in the pure water environment,oil-water mixed environment,and pure oil are verified.The test results show that the surface shows excellent drag reduction performance in three environments.