Simulation Analysis Of Drag Reduction Of Super-Hydrophobic Microstructure Surface Under Water

With the proposal of the national strategy of maritime power,there is a higher demand for underwater drag reduction in recent years.With its excellent self-cleaning and strong hydrophobicity,superhydrophobic materials can also reduce energy dissipation,which provides a good research direction for underwater drag reduction.In order to better apply the underwater super-hydrophobic groove drag reduction technology to coastal and submerged structure areas,this paper systematically studies the drag reduction performance of different super-hydrophobic surfaces,and the main research contents are as follows:1.In this paper,a series of super-hydrophobic microstructure sizes are selected by empirical formula,and the microstructure is combined with Clark-Y airfoil,and the SpaceClaim software is used for modeling,and the Ansys-Icem software is used for meshing hydrofoil with microstructure surface.The basic control equations required for Ansys numerical simulation calculation in this paper are explained and introduced.At the same time,the definition of boundary layer and the thickness calculation formula of boundary layer are explained in detail,and the drag reduction characteristics of groove are studied by Reynolds time average method.The underwater simulation is carried out by Ansys-Fluent software,and the lift resistance and rent reduction rate of hydrofoil are numerically analyzed.2.In this paper,polydimethylsiloxane(PDMS)was used as the film material,and the superhydrophobic film was prepared by its excellent physical properties.In the preparation process,the required test materials and processing flow are introduced,and how to etch the surface of PDMS film with laser etcher to manufacture rectangular groove microstructures with different spacing is introduced.Finally,the superhydrophobic film was characterized and observed by microscope,which proved that the superhydrophobic film had excellent properties.3.Based on the principle of water tunnel experiment,the water tunnel test device is built,and the water supply system and test system design of the water tunnel test device are completed.Different super-hydrophobic hydrofoils were designed to carry out comparative tests,and the hydrodynamic characteristics of different super-hydrophobic hydrofoils under water were measured by a force balance with lifting resistance.The results show that the surface of PDMS film with rectangular microstructure can play a certain drag reduction effect.The contact angle of untreated PDMS film with grooves can reach 110 degrees,while the contact angle of superhydrophobic PDMS film with rectangular grooves can reach 153 degrees.Among them,the drag reduction effect of hydrofoil is the most obvious on the surface of rectangular microstructure with 100μm spacing and width.By analyzing the flow field around hydrofoil,it is found that "micro-air bearing" is the main factor to reduce drag in micro-grooves,and the flow field of hydrofoil affected by microstructure is also an important factor to improve the lift of hydrofoil.In the water tunnel test,the hydrofoil covered with microstructure PDMS film shows higher drag reduction stability and more lasting drag reduction effect than the hydrofoil treated with superhydrophobic coating.