Vibro-acoustic analysis of combined elliptical-cylindrical-elliptical shells immersed in acoustic medium

The vibro-acoustic behaviors of combined elliptical-cylindrical-elliptical shells (CECES) is studied by the spectral-energy boundary element approach. The Jacobian orthogonal polynomials and the variational principles are employed to establish the dynamic model of the CECES. The Kirchhoff-Helmholtz integral equation is used to calculate the exterior sound radiation of the CECES. The Chebyshev polynomials and the Fourier series are adopted to express the acoustic variables along the meridional direction and the circumferential direction of the CECES, respectively. In this case, the two-dimensional Helmholtz integral formulation is simplified to a one-dimensional problem. By using the spectral boundary element and Chebyshev collocation points to discretize the acoustic boundary, the mathematical difficulties of traditional boundary element method which needs physical points to integrate can be overcome. Furthermore, to solve the problem of singularity and frequency non-uniqueness in the acoustic solution, the CHIEF method is used. The full vibro-acoustic coupling model is established by considering the work due to the external field acting on the CECES surface. By comparing to the acoustic responses obtained by the coupled BEM/FEM, the present method is proved to have enough accuracy for predicting the vibro-acoustic behaviors of CECES. Furthermore, study on the influence of the circumferential wave modes, boundary condition and acoustic medium on vibro-acoustic behaviors of the CECES is made by several numerical examples, which contributes to the preliminary design of the CECES. (C) 2021 Elsevier Ltd. All rights reserved.