The Research Of The Acoustic Stealthy Technology Based On The Transformation Acoustics And The Scattering Cancellation

Acoustic stealth technology is one of the key technologies to improve the survivability and penetration ability of underwater equipment.With the development of multi-level,omnidirectional,and wide-band stereoscopic detection technology,the sound stealth technology based on the sound absorption mechanism cannot meet the stealth requirements of current underwater equipment.Therefore,the development of sound stealth technology based on the new principle can break through the bottleneck of sound-absorbing stealth technology,counter new type of detection technology,and bring leap-forward development to stealth technology.At present,the sound stealth technology of the new principle is mainly based on the sound stealth cloak.This kind of sound stealth cloak can make the hidden object neither scatter nor leave the sound shadow area due to sound absorption.In an ideal situation,the state of the sound wave over the invisible object is exactly the same as the direct sound,the sound field does not change,and any hidden means cannot find the hidden object.In summary,the non-sound-absorbing stealth technology can overcome the theoretical defects inherent in the sound-absorbing stealth technology and improve the acoustic stealth performance of underwater equipment.In this paper,the acoustic stealth technology based on the new principle is studied,and the research on stealth mechanism,calculation method,structural optimization design and experimental verification is carried out.The main work of the thesis is as follows:The theory of using Bezier scatterers to design the scattering cancellation acoustic cloaking is proposed.Based on the method of foundamental solutions,a method for solving the acoustic scattering coefficient of a single arbitrary shape scatterer is established.Combined with the theory of multiple scattering theory,the scattering calculation model of the acoustic cloaking based on Bezier curve is established.The new optimization algorithm GASA(Genetic Algorithm Simulated Annealing)made of Genetic Algorithm and Simulated Annealing is built and this new optimization algorithm can achieve the global optimal solution while maintaining high efficiency.A design of acoustic cloaking based on multiple scattering theory and GASA is established.Simulation and experimental results show that the acoustic cloaking with Bezier scatterers can greatly simplify the design while achieving good acoustic stealth effect compared with the traditional acoustic cloaking composed of cylindrical scatterers.The optimal design theory of the transformation acoustic device with non-ideal continuous parameters is proposed.Based on acoustic transformation,the design formula based on density and modulus regulation is derived,and the key factors for acoustic wave regulation are analyzed.The variation theory of the acoustic characteristics of the acoustic transformation acoustic device when deviating from the ideal design are deeply studied.The intrinsic mechanism of the acoustic stealth effect of the layered discrete acoustic cloaking with the coordinate transformation equation,and the optimization design method are proposed.The difference between continuous transformation and finite embedded transformation is deeply studied.The relationship between the designed acoustic wave manipulation effect and the boundary impedance matching is proposed.The theoretical and experimental results show that the control effect on the acoustic wave of the acoustic device can be significantly improved.A comparative system with pentamode material based on acoustic transformation is established.Based on Gibson’s formula,the analytical expressions of equivalent acoustic parameters of pentamode material are obtained,which solves the problem of using pentamode materials to design acoustical metamaterials with single anisotropic density,single anisotropic modulus anisotropy and both anisotropic density and modulus.The influence mechanism of the surface acoustic state of the acoustic device on the acoustic manipulation ability is analyzed,and the boundary constraint design is proposed.Combined with the GASA optimization algorithm and the improved design scheme,the function,parameter distribution and structure integration method based on the acoustic design of underwater transformation of pentamode materials are established.The acoustic cloaking and acoustic bending are designed by this method.The simulation and experimental analysis show that the designed acoustic transformation devices have good acoustic wave manipulation capability and wide frequency characteristics.