Design And Manufacturing Of Biomimetic Surface Structure With Characteristic Of Underwater Drag Reduction&Anti-fouling

Drag reduction and anti-fouling under water have an important impact on the speed and energy consumption of the underwater vehicle,which is directly related to the operating efficiency of the underwater vehicle and to whether it has an effect on energy-saving and emission reduction.Applying the principle of bionics,designing and manufacturing biomimetic groove structure on the surface of underwater vehicles is an important measure to achieve drag reduction and anti-fouling.In view of the problems of the designed biomimetic groove in the current research,such as the single structure,the unsatisfactory drag reduction effect,the impossibility of processing and failure to verify in the actual experiment,this research focuses on the structure of dolphin skin ridge and mosquito mouthparts to design a novel biomimetic micro-nano composite structure with characteristic of underwater drag reduction&anti-fouling,and the size parameters of biomimetic structure is optimized applying the fluid simulation software.Taking 316L stainless steel fish dart as the research object,the designed composite structure was prepared on the surface with fiber laser,and its drag reduction&anti-fouling properties were studied by underwater experiments.(1)According to the requirements of bionics theory,to improve the underwater drag reduction&anti-fouling performance of fish dart,this research uses dimensionless method and Carmen vortex theory to design a series of micro-nano structure of drag reduction elements,such as transverse groove,longitudinal groove and sawtooth structure.The drag reduction elements are distributed on the surface of the fish dart model according to periodic arrangement,periodic progressive arrangement and quasi-periodic arrangement to form a composite structure,which can achieve a good effect of underwater drag reduction&anti-fouling.(2)The Reynolds average method was used for numerical simulation,and the biomimetic composite structure was simulated under water in an ideal state.Through the analysis of flow field velocity,flow field pressure,turbulent kinetic energy and surface shear stress,the distribution position and size parameters of the surface groove structure of the fish dart model are determined and optimized.The results are showed as follows:the sawtooth structure and progressive transverse groove structure are used in the head of the fish dart;the sawtooth structure is used in the transition part of head and body;the periodic transverse groove structure is used in the body;the periodic longitudinal groove structure is used in the tail.The friction coefficient of the composite structure surface is reduced,and the drag reduction effect is 89.49%when the groove width is 380?m,the depth is 100?m,and the spacing is 0?m.(3)The surface anti-fouling performance of biomimetic micro-nano structure fabricated by fiber laser on a 316L plate was studied.The experimental show that the surface hydrophobicity is the best and the wetting effect is poor when the groove width is 340?m,the depth is 80?m,and the spacing is 0?m.Moreover,the adhesion area of marine fouling organisms can be reduced,and the resistance to fouling is effective;and the surface friction coefficient under water lubrication is 0.2,the drag reduction effect is excellent.(4)Taking the fish dart as the research object,a novel biomimetic micro-nano structure is machined on its surface,and the underwater shooting experiment is carried out by using the modified shooting device.Based on the difference in the underwater running distance of the fish dart under different groove size parameters,the groove size parameters obtained from the simulation and the size parameters obtained from the experimental verification of the plate were continuously verified and optimized.As a result,the drag reduction effect can reach 43.20%when the groove width is 380?m,the depth is 100?m,and the spacing is O?m.The research results show that there are external non-ideal factors such as air resistance,friction between the fish dart and the shooting device during the shooting experiment.The drag reduction rate calculated in the simulated environment is not the same as the one obtained in the actual experiments,but the regulation of change is same and the regulation is that the effect of drag reduction is consistent with the change of groove size.The biomimetic composite micro-nano structure prepared through this study has a good drag reduction effect,poor wettability,which can reduce biological adhesion,and improved surface anti-fouling performance.The research results provide a certain theoretical and practical basis for biomimetic drag reduction&anti-fouling,which can effectively alleviate the problems of slow speed,short-range and large energy consumption caused by underwater vehicles due to resistance and marine attachments in the water.