Inversion Of Equivalent Parameters Of Sound-absorbing Covering Layer Based On Genetic Algorithm

Sound absorption overlay is an acoustic structure laid on the surface of underwater vehicle in direct contact with water,which plays an important role in improving the vibration and noise reduction of underwater vehicle.Of underwater target installation simple acoustic covering layer of the structure of the sound absorption performance issues for a lot of research,the key scientific problems of this study is based on the genetic algorithm with the cavity of the structure of the equivalent sound absorption layer structure inversion,the complex cavity layer structure model is simplified to homogeneous solid layer model,and the acoustics performance analysis,in order to simplify the calculation problem,improve the computational efficiency.First of all,this article introduces the acoustic theory of underwater flat structure and spherical structure separately,and then builds a model of underwater plane structure and elastic sphere with plane waves perpendicularly incident based on the finite element software COMSOL.Furthermore,the sound absorption coefficient of the underwater flat structure and the target strength of the elastic spherical structure were calculated separately.Among them,the calculation results of reflection coefficient of plate structure were compared with the research results of other scholars,and the numerical calculation solutions of spherical structure were compared with the theoretical solutions,which verified the effectiveness of the simulation method based on finite element COMSOL to calculate the acoustic performance of plate structure and spherical structure,and provided a theoretical basis for the later research.Then,compared with the uniform solid overburden structure,the modeling of the cavity overburden structure laid by the underwater target and the calculation of the relevant acoustic performance are more complicated.In this paper,in addition to calculating and analyzing the sound absorption coefficient of different structural cavity coverings(referred to as "cavity covering-elastic plate and shell")laid on the elastic plate shell,the underwater elastic spherical shell laying cavity cover(abbreviated as It is a "cavity cover-elastic spherical shell")composite structure model.This part is one of the innovations in this chapter,because the principle of mechanical balance is used in this paper to obtain the coordinates of points evenly distributed on the center spherical surface of the cover,and then embedded in the coordinate position Cylindrical cavity,build a composite structure model.Finally,based on the genetic algorithm,the complex reflection coefficient of the cavity overburden composite structure is equivalent inverted,and the material parameters obtained from the inversion are applied to the homogeneous composite structure,so as to realize the homogenization of the cavity overburden without changing the acoustic performance of the structure.Firstly,the "cavity overburden-elastic spherical shell" composite structure model is homogenized,which is another innovation of this paper.Building with "cavity cover-elastic spherical shell" same physical parameters(cavity ratio,structure parameters and material parameters)of the cavity cover-elastic plate and shell "composite structure,based on the genetic algorithm the complex reflection coefficient of plate and shell composite structure equivalent parameter inversion,by comparing the inversion of the reflection coefficient of the composite structure before and after test and verify the reliability of this method,then the application of the material parameters of inversion is to" uniform coating-elastic spherical shell structure,and compared before and after the analysis of the target structure inversion of target strength,to realize the homogenization of spherical cavity cover structure.In addition,the reflection coefficient of the composite cavity overburden structure with underwater elastic plate and shell laying is calculated.