Homogenization Method For Laying Acoustic Coating Structure And Its Application In Acoustic Scattering

Laying the sound absorbing cover layer on the surface of the submarine is an important means to reduce the target strength and improve the concealment of the submarine.The resonant cavity type sound absorbing layer has a good sound absorbing effect and is the mainstream structure of the submarine sound absorbing cover layer.There are many theoretical solutions or approximate solutions for the study of acoustic scattering characteristics of regular structures,and the finite element method is a more common method for the study of acoustic scattering characteristics of complex structures.When the finite element method is used to calculate the sound scattering characteristics of the structure covered with cavity sound absorption layer,it is necessary to divide the fine grid and consume a lot of computing resources.In order to reduce the amount of calculation,the homogenization method is used to study the sound scattering of the structure with cavity sound absorption layer.The homogenization method is to use uniform medium to replace the structure with cavity for finite element modeling,which can reduce the amount of calculation caused by cavity and improve the efficiency of calculation.The equivalent method of acoustic parameters is the main method for homogenization of structures.According to the principle of equal sound absorption coefficient,the equivalent parameters of the corresponding homogenization model of infinite plate structures are obtained by genetic algorithm.The same equivalent parameters are applied to the homogenization model with more complex geometry.The equivalent method of structural parameters is a supplement to the equivalent method of acoustic parameters.The equivalent structural parameters of the homogenization model are obtained based on the equality of stiffness.In this paper,the acoustic scattering characteristics of plate,cylindrical shell and command room enclosure under different backing conditions are discussed.The target strength is calculated by direct modeling and homogenization model respectively,and the applicability of homogenization method is analyzed.The calculation results show that for the infinite plate,the same reflection coefficient and sound absorption coefficient can be obtained by using the homogenization model and the direct modeling calculation in the calculated frequency band.For the water-filled cylindrical shell,the target strength calculated by the homogenization model is basically consistent with the results of the direct modeling calculation,and for the vacuum cylindrical shell,it is also consistent in the high frequency band.And in the low frequency band,the results of the homogenization model established by the equal stiffness method are better than those of the acoustic parameter equivalent method.For the finite plate,when the sound wave is normal incident,the target strength changes little after the steel plate is stiffened,and the corresponding homogenization model is in good agreement with the results of the direct modeling calculation.The target strength curve of the homogenization model fluctuates around the result curve of the direct modeling calculation,and the valley point moves forward.When the command room enclosure is filled with water,there is little difference between the homogenization model and the direct modeling calculation.When the command room enclosure is vacuum,the homogenization model is quite different from the direct modeling calculation,because the cavity resonance is more obvious.