Modal coupling in the vibro-acoustic responses of submerged coupled shells

This paper presents a modal decomposition method for the sound power radiated by a coupled shell structure submerged in an infinite heavy fluid, by which physical insight into the self- and mutual-modal radiations of the in-vacuo modes can be provided. A fully coupled FE/BE model is developed for a simplified submarine hull, which is composed of a coupled spherical-cylindrical-spherical shell, ring stiffeners and bulkheads. The interactions of different circumferential modes of the hull are examined and the self-modal contributions of the circumferential modes to the acoustic responses are presented. A further study on the modal coupling among the n=1 grouped modes (with rigid body modes included) is implemented to reveal the cross-modal coupling characteristics of the modes in the axial direction.