Research On Stealth And Microstructure Drag Reduction Of Flying Target Based On Metamaterial Structure

Metamaterials are periodic array structures based on various materials in nature.The radar absorber designed based on metamaterials can effectively reduce the radar signal reflectivity of the aircraft surface and enhance the stealth ability;The microstructure surface based on metamaterials can reduce the flight resistance,improve the flight efficiency and enhance the cruise ability.Aiming at the two key problems of radar absorption and drag reduction of aircraft,the main research contents of this paper are as follows:1.Firstly,Thesis makes a theoretical research on the absorber based on frequency selective surface,discusses the design idea and working principle of frequency selective surface and the theoretical conditions for the absorber to realize perfect absorption,and then introduces two research methods: full wave simulation method and equivalent circuit method.Combining the two research methods,a separated sector absorber working in the X-band is designed.The absorber realizes the-10 d B absorption standard in the range of 7.78GHz-12.68 GHz.The absolute bandwidth is 4.9GHz and the relative bandwidth is 49%.It has the maximum absorption rate at 9.82 GHz and the maximum absorption rate is 99.998%.At the same time,the designed absorber is not sensitive to the polarization mode of incident wave;In TE mode,when the incident wave angle is0-20°,the absorber has X-band full band absorbing ability,and the-10 d B bandwidth coverage of X-band is 96% at 30°;In TM mode,when the incident wave angle is0-20 °,it has X-band full band absorbing ability.At 30 °,the-10 d B bandwidth coverage of the absorber in X-band is 94.5%.Then,by analyzing the surface power loss and electric field vector distribution at different frequency points,the results show that the loss of incident wave in the absorber mainly occurs at the lumped resistance loaded on the surface of the absorber,and the current distribution at the resistance is obviously more dense than other parts,so more energy can be lost.Finally,the real object is made and the experiment is carried out.The experimental results are basically consistent with the simulation results.2.using the numerical calculation method of Reynolds average NS model(RANS),this paper comprehensively studies the variation of turbulent friction resistance on the surface of flat plate and flat plate with transverse small rib microstructure.Through the simulation results of smooth plate under different turbulence models,it is determined that the optimal simulation model is SST-k-w model,and then the influence of microstructure shape and distribution parameters on drag reduction effect is analyzed by changing the structural parameters of microstructure on the surface of the plate.The results show that the small rib microstructure achieves the best drag reduction effect when the shape is isosceles triangle,the height is 0.05 mm,the width is 0.1mm,the spacing is 0.25 mm and the incoming flow velocity is 15m/s.at this time,the microstructure resistance is 0.062303 N.Compared with the plate resistance of0.067884 N,the resistance is reduced by 0.05581 N,and the drag reduction rate is8.22138%.Finally,the drag reduction mechanism is discussed through the analysis of microstructure streamline and wall shear stress.The results show that the existence of small ribs makes the fluid flow appear vortex,and the existence of vortex reduces the viscous resistance,so that the total resistance of microstructure is less than that of flat plate.In Thesis,two kinds of metamaterial structures are designed,one is to achieve the goal of broadband and high absorptivity in X-band,and the other is to achieve the effect of turbulent drag reduction.Combined with the simulation results,the working mechanisms of the two are discussed respectively,which has a certain reference significance for the follow-up Research of wave absorption and drag reduction.