Acoustic Field With The Structure Of The Coupled System Modal Analysis And Sensitivity Calculations

The acoustic design for a passenger compartment of the vehicle, ship, and plane is very important to improve the carborne acoustic comfort and to enhance the competitiveness for the products in market.The research work in this dissertation involves the theories of interior noise analysis for the cavity, the sensitivity analysis of dynamic optimization, and the modal analysis of acoustic-structural coupled system with proportional damping. Main contents of dissertation are as follows:(1) The finite element method is demonstrated to apply for the solution of the wave equation. If rigid walls are assumed in the finite element model for the boundary panels, an eight node, isoparametric acoustic finite element model is developed for calculating the acoustic modes of cavities. Initially a rectangular enclosure is analyzed in order to study the convergence of the results. The element is then used to analyse an irregular shaped cavity. A semi-analytic method, in which the derivatives of stiffness matrix and mass matrix are obtained by the difference technique, for sensitivity analysis in dynamic shape optimization is presented in this dissertation.(2) Based on the wave equation in the acoustic fluid space and the theory of thin-wall structure, the non-symmetrical coupled structure-acoustic dynamic equation without damping is studied. The non-symmetric system of the finite element model for coupled structure-acoustic response is solved by the conjugate subspace iteration method. The numerical methods have been implemented in a finite element software system - JIFEX.(3) Introducing the proportional damping, the finite element formula of structural-acoustic coupled system lined with sound absorbing materials is obtained. Mode-superposition technique for modal frequency response analysis of coupled structure-acoustic systems is also used to deal with the sensitivities of the eigenvalues and eigenvectors of coupled systems for the purpose of reducing cavity interior noise in theory.The research of this dissertation is part of the projects supported by the National Natural Science Foundation of China (No. 10032030) and the Special Funds for National Key Basic Research of China (No.G1999032805).