Effects of non-axisymmetric internal structures on vibro-acoustic characteristics of a submerged cylindrical shell using wavenumber analysis

Non-axisymmetric structures (foundations, equipment etc.) have been extensively arranged in axisymmetric shells and proved to change the mechanism of vibration and sound radiation of the shell. To study the effect of non-axisymmetric internal structures, a hybrid analytic-numerical method is developed for vibro-acoustic characteristics analyses of a submerged cylindrical shell. The wave based method (WBM) and finite element method (FEM) are respectively employed to model the shell and internal structures. A precise coupling is carried out to assemble the shell and internal structures, which fully considers all six degree of freedoms (DOFs) at junctions between the two substructures. The acoustic pressure is described by the Helmholtz integral equation. According to the axisymmetric property of the shell, the surface integral is reduced into the curve integral. Subsequently, the final vibro-acoustic model is obtained by introducing the acoustic pressure into the dynamic equation of the coupled structure. The high accuracy of the present method is firstly demonstrated by FEM and boundary element method (BEM). Then by comparing vibro-acoustic responses of the shell with and without internal structures in wave domain, the effects of non-axisymmetric internal structures on vibro-acoustic characteristics of the shell are discussed.