Performance Analysis Of Insulation Structure For Low Frequency

As the improvement of detection range of active and passive sonars, vibration and noise reduction of submarine has become an important problem. As the key point of the sound reflection and sound transmission, the acoustic coupling analysis received extensive concern. The structural vibration and the sound field coupling problems relate to the vibration theory and the analysis of sound field.In this paper, we use the finite element method to study the structural vibration and the sound field coupling problems in order to analyze the sound absorption and sound insulation of submarine. We analyze the sound absorption and sound insulation problems under the condition of the air backings and water backings respectively, based on which we study the spherical cavity in fluid. Sound absorption coating is assumed as an infinite layer which contains some distribution of structures such as cavities, and a unit cell is analyzed.The unit cell to be considered which contains structure and fluid region is meshed into hexahedron elements by ANSYS. We obtain the equation which describes structural vibration and acoustic field. Then we analyze the condition of structural stress and velocity continuum and establish balance equation to get the structure-fluid coupling matrix. The acoustic coupling equations are established considering the case that the plane wave is normally incident. For the conditions of air backings and water backings, reflection coefficient and transmission coefficient are solved and compared with the theoretical data. And then we analyze spherical cavity arrangement in fluid. We change the parameters to get corresponding regularity in order to design sound absorption and sound insulation structure. FORTRAN language is used to implement the arithmetic, and the adaptability is considered to the program. The comparison between the FEM results and analytical results shows the validity of the proposed method. The paper provides a effective method for design of complicated insulation structure.