Analysis of Vibration and Radiated Noise of Circular Cylindrical Shell using Spectral Finite Element Method and Boundary Element Method

Abstract

The vibration characteristic of cylindrical shells is more difficult to analyze than those of plates because of 3-D coupling effects. Since it is difficult and complex to express the governing equations of motion of a cylindrical shell in exact form, many approximated forms of the governing equations have been presented based on reasonable assumptions. Based on Loves equation, the spectral finite element method (SFEM) is introduced to predict the frequency response function of finite circular cylindrical shells under simply supported – free boundary condition. In contrast to the FEM formulated in the time-domain and generally used in conjunction with the modal analysis method, the spectral finite element method (SFEM) is a frequency-domain solution method, in which the spectral element matrix formulated from the exact solutions of the governing differential equations are used in conjunction with the FFT-based spectral analysis method. To verify the results from structural vibration analysis, which is formulated with the spectral finite element method, comparisons of the results with those of NASTRAN, which is FEM based commercial code, are carried out. And for the radiated noise analysis of cylindrical shells, the boundary element method (BEM) is applied. The boundary element method is a numerical computation method used to solve linear partial differential equations that are formulated as integral equations. Specifically, the indirect boundary element method for a radiated noise analysis in open sound field is introduced and formulated using MATLAB program, with the out-of-plane displacements from structural vibration analysis as an input. And SYSNOISE, which is BEM based commercial code, is used to verify the radiated noise results. Finally, a full procedure that analyzes both structural vibration and radiated noise simultaneously is established.