Research On Structure-acoustic Coupling Analysis And Associated Wave Based Method

It's very important to study the noise problem inside a cavity. The objects studied in this field include driving cabs of automobile, passenger compartments of a plane and cabins of a ship. The optimization of sound field based on the structure-acoustic analysis is developing rapidly. Based on the analysis about the advantages and disadvantages of the existing researches on structure-acoustic problems and indirect Trefftz method, a new method, wave based method (WBM), is brought forward for structure-acoustic studies in this paper. The WBM model of plate, cavity and structure-acoustic coupled system are deduced in detail, and the two key problems of WBM, namely wave function series and muti-domain calculation, are effectively handled. Then, a new structure-acoustic sensitivity calculation method is presented based on WBM. The WBM model of structure-acoustic coupled system under two coherent excitations is established and the principle of sound field distribution is studied in theory. Lastly, the validity of the proposed method is proved by experiments.Based on indirect Trefftz theory, the 3D structure-acoustic coupled system calculation model is deduced in detail using WBM, which is applied to palte and cavity coupled system under point force excitation. Using a cuboid cavity with random boundary conditions, deduced and proved a new wave function series. The validity of the WBM is confirmed by comparing the simulation results with the analytical and FEM results. At the same time, the great advantage of the method in convergence rate, calculation precision and calculation speed are proved and the method can extend the calculation range to mid-frequency. Focused on the flaw of the existing parameter indicating the strength of structure-acoustic coupling interaction, a new formulation is presented, which is more comprehensive and reasonable.Based on the continuity of boundary conditions, the method of domain decomposition is presented and the multi-domain calculation model of plate, acoustic cavity and structure-acoustic coupled system are established, which extend the application range of the method. The simulation result shows that the domain decomposition technique is valid and has negletable influence on convergence rate and calculation speed.The structure-acoustic sensitivity is discussed based on WBM. The structure-acoustic sensitivity formula is obtained by directly derivate on the structural and acoustic response expansion formula. Then, derivating on the system model gets the unknown parameter and forms the final structure-acoustic sensitivity expression. The sensitivity calculation model of plate, acoustic cavity and structure-acoustic coupled system are established. The principle of structural and acoustic response sensitivity comparing with design parameters are discussed through some examples.The WBM model of the structure-acoustic coupled system excited by two coherent inputs is established using plate, cavity WBM model and its coupling relationship. Based on a cuboid cavity example, the validity of the model is proved in theory. The influence of phase difference between inputs, damping of plate and absorption material of cavity surfaces on sound field distribution are discussed. The simulation result shows that the phase difference between inputs influence the sound field very much; suppressing the vibration of the plate can effectively reduce nearfield sound pressure, however, the influence on farfield sound pressure is very tiny; the using of absorption material can lead to the redistribution of sound power, in other words, the pressure near the absorption material decreased and the pressure of the opposite side increased.The proposed theory in this dissertation is tested by examples of a trapezoid structure-acoustic coupled system and the interior sound field of a real car.Lastly, the summarization and expectation are given.