The Design Of Micro-structure Functional Surface And Study Of The Underwater Drag Reduction Characteristics

The energy consumption of spaceflight vehicle,underwater vehicle and high-speed train during operation is mostly used to overcome the surface resistance.It seems to have reached the bottleneck by optimizing the shape to speed up and reduce energy.Relevant studies have found that when the surface of the object distributes a specific shape of the micro-structure,it can reduce the operating resistance,improve the speed and efficiency of operation,achieve energy saving and emission reduction.In this paper,by analyzing the drag reduction effect of microstructures under water,the drag reduction effect of microstructures applied to underwater vehicles was explored,the drag reduction mechanism of microstructures were analyzed,the microstructures were milled by a carving machine and analyzed of the influence of processing parameters on micromorphology.Four microstructures,V-shaped,M-shaped,trapezoidal and semi-circular,were designed.CFD was used to mesh in the flat computing domain.Fluent fluid simulation platform was used to simulate the resistance of smooth surface and microstructural surface in turbulent state.By analyzing the contour of velocity,turbulent energy and shear force,the drag reduction effect of microstructures was qualitatively and the theory of "outburst height" was verified.It is believed that microstructures can reduce the drag by slowing down the process of turbulent burst and reducing the intensity of turbulent burst.The factors affecting the drag reduction of microstructures were discussed.The effects of velocity,microstructural size and number of microstructures on the drag reduction of four microstructures were compared under different inflow directions.It is found that the drag reduction effect under longitudinal inflow is better than that under transverse inflow for the four microstructures;The drag reduction effect of microstructures generally increases first and then decreases with the increase of velocity;The dimension parameters(angle and height)of the microstructures have the drag reduction effect within a certain range;The larger the number of microstructures is per unit area,the better the drag reduction performance is.The reliability of the simulation results was verified by comparing the simulation results with the experimental ones.By comparing and analyzing the comprehensive performance of drag reduction,V-shaped and M-shaped microstructures have better comprehensive drag reduction performance.The V-type and M-type microstructures were applied to the underwater vehicle model and the drag reduction in the calculation domain of the external flow field was further studied to provide the simulation basis for its underwater application.The results showed that the two microstructures still have drag reduction effect in the underwater vehicle model and the drag reduction rate of M-type is higher.The drag reduction rates of the two microstructures are reduced compared with those of the flat panel model,however the simulation results are more with the actual complex underwater environment.In the end,micro-milling V-shaped micro-structure with CNC engraving machine was used.The micro-morphology was processed and then observed under electron microscope.The influence of machining parameters on the surface quality of microstructure was analyzed.And the methods to improve the processing quality were put forward,such as minimizing edge collapse and burrs.The research on drag reduction and micro-structure processing of underwater microstructures has important reference and guiding significance for further research.