Parametric Analysis And Optimization Of The Acoustic Overlay Under Oblique Incidence Of Plane Waves

Anechoic coating(HC)is an important acoustic structure laying on the outer shell of underwater vehicle,which is between the shell and sea water.It is used to absorb external detection signals,reduce the intensity of underwater targets and ensure the navigation safety of underwater vehicle.In this paper,based on the finite element method(FEM),the sound absorption performance of the acoustic coating under oblique of plane wave has been analyzed.Optimization algorithms in COMSOL software has been applied to optimize the structural and material parameters of anechoic coating,and the optimum value which maximizes the sound absorption coefficient in a certain low frequency range is obtained.Firstly,based on the waveguide finite element-transfer matrix method(WFEM-TM)and the oblique incidence theory of plane wave,the sound absorption coefficient of the anechoic coating under oblique incidence has been deduced theoretically.At the same time,the problems of viscoelastic material loss,periodic boundary conditions and semi-infinite waters in finite element analysis are dealt with accordingly.Based on the theoretical model,the corresponding finite element model has been established,the accuracy of this model has been validated via the comparison between the FEM and the theoretical results.And it lays a theoretical foundation for the subsequent analysis of acoustic coatings with more complex structures.Secondly,FEM models of the anechoic coating with double plates under oblique incidence condition have been established,and the effects of parameters changes such as structural parameters and material parameters of the coating on its sound absorption performance under oblique incidence have been studied.The sound absorption mechanism of the anechoic coating with air holes has been analyzed more clearly by using the efficient post-processing module in COMSOL,which will provide reference value for subsequent related practical applications.Then,the calculation and the derivation of the dispersion curve of periodic infinite local resonance unit based on FEM have been introduced.The accuracy of the established local resonance unit dispersion curve has been verified by comparison with the existing literature.At the same time,the FEM model of local resonance anechoic coating with double plates under oblique incidence condition has been established,and the sound absorption characteristics of the established model are parametrically analyzed.Finally,under the condition that the material structural parameters are close to each other,the sound absorption performance of local resonance anechoic coating has compared with the one of anechoic coating with air holes.Finally,the acoustic coating with air holes has been taken as the research object,and the maximum of sound absorption coefficient in the low frequency range of 1000~2000 Hz has been taken as the optimization objective.The optimization analysis has been carried out by using optimization algorithms in the optimization module of COMSOL.By comparing optimization results of different algorithms,the applicability of different algorithms to the optimization analysis of the acoustic coating has been analyzed.It provides a reference value for the design of acoustic coating with specific sound absorption requirements in a specific frequency range.