Study on vibro-acoustic performances of coupled orthogonally stiffened cylindrical shell-inner foundation system using wavenumber analysis method

Abstract

The present work intends to provide physical insights into the vibro-acoustic performances of coupled orthogonally stiffened cylindrical shell-inner foundation system, which have seldomly been conducted from the perspective of wave propagation. A semi-analytical method integrating the modified variational method and Kirchhoff-Helmholtz integral equation is first proposed for the vibro-acoustic responses of the model. The displacements and acoustic pressure are analytically expanded by Fourier series along circumferential direction, which reduces the structure-fluid coupling to a one-dimensional problem. The accuracy of the theoretical method are demonstrated by numerical method. Then the vibro-acoustic performances of the model are analyzed using wavenumber analysis method, by which the wave spectrum and supersonic intensity are obtained. The study indicates that the inconsistency between structural vibration and acoustic radiation results from the discrepancy in radiation efficiencies of helical wave components, and the subsonic helical wave close to the radiation circle can radiate to the far-field more efficiently than the wave away from the circle. Further, compared to the stiffened cylindrical shell, the foundation strengthens the coupling effect of helical waves, induces more abundant helical waves near the radiation circle, and further leads to more acoustic resonance peaks, which shows negative effects on acoustic performances of the model.