Research On Vibration And Acoustic Scattering Characteristics Of Elastic Target With Acoustic Black Hole Structure

As the basis of detection,identification and localization for active sonar device and underwater weapon,the characteristics of underwater target structure vibration and acoustic scattering have significant theoretical research value.Besides the relating factors of acoustic wave frequency,waveform and so on,the characteristics are also related with the geometric shape,materials of the target itself,when the geometric shape of the target changes,it will also influence the structure vibration and acoustic scattering.This study mainly researched the regulation mechanism of Acoustic black hole(ABH)in the plate vibration and acoustic scattering of cylindrical shell though the finite element method.This study firstly explained the basic theory of Acoustic black hole effect by approximate geometric acoustics method,and introduced the specific form of one and two-dimensional Acoustic black hole and their derived structures.The following is utilizing finite element software COMSOL Multiphysics to establish a numerical calculation model of plate vibration including the two-dimensional Acoustic black hole structure as well as the ABH array and ABH slot structure.According to the comparisons of the harmonic response with the ordinary plate and the absorption layer plate,Acoustic black hole obviously shows the regulatory effects to the structural vibration,it can decrease the climax of resonant frequency effectively,and restrain the fluctuation of structural vibration;comparing with the traditional damping method of laying sound absorption layer,it has better damping effects,as well as lighter in weight and smaller in volume.Then we led the Acoustic black hole theory into the research of underwater target broadband echo characteristics,simply introduced the numerical calculation method of underwater target acoustic scattering characteristics.Through the two-dimensional finite element method of axial symmetry target,we acquired the target strength of ABH slot cylindrical shell,and compared it with the cylindrical shell and absorption cylindrical shell,the result indicates that the Acoustic black hole effect also has the regulation mechanism to the underwater target broadband echo characteristics.Finally,through the acoustic scattering experiment,we measured the broadband echo characteristics of cylindrical shell and ABH slot cylindrical shell in the frequency range of 10kHz-40 kHz,verified the correctness and effectiveness of the numerical calculation method,and preliminary revealed the regulatory effects of Acoustic black hole on the scattering sound field frequency features and echo characteristics of underwater target.