Near- and far-field radiated acoustic pressures from a vibrating three-dimensional cylindrical shell in an underwater acoustic waveguide

The vibroacoustic behavior of a vibrating infinitely-long thin three-dimensional cylindrical shell immersed in a perfect underwater acoustic waveguide is predicted using an analytical method. Vibration is induced by a point force excitation on the surface of the shell that is ingested into the equations of motion modeled using Flügge's shell theory. Radiated acoustic pressures are then investigated in relation to an influence from the acoustic boundaries of an underwater acoustic waveguide. The waveguide, which simulates a simplified shallow water environment, is composed of an upper free surface and a lower rigid floor. Its influence is modeled with the image-source method. Graf's addition theorem is employed to reconcile the coordinate systems of the infinite image sources in the fluid–structure coupling analytical expressions. Predictions of the near-field acoustic pressure are obtained by a direct numerical evaluation of the inverse Fourier integral, while the far-field acoustic pressure uses the stationary phase method. Axial directivities are of interest as the longitudinal length of the 3D shell imposes an additional dimension to the most commonly used 2D models in the literature to which radiated acoustic waves can dissipate energy. The far-field sound propagation from the shell in different fluid domain configurations is also shown.