Radiated power and acoustic convergence zone properties of the vibration of the shaft-hull system in an ocean acoustic channel

Abstract

To compute the vibroacoustic radiation of the shaft-hull system in an ocean acoustic channel, we apply the finite element method/boundary element method. For the convergence zone effect, we use the beam displacement ray normal mode to examine the profile of the speed of sound in seawater. To evaluate the radiation property of the system, we propose the concept of effective radiated acoustic power, where only reversing acoustic rays and seabed totally reflected rays are included. We reveal that the far-field radiation can be approximately inferred from the effective radiated acoustic power. Effective radiated acoustic power can be utilized to extract the main radiating modes, which dominate the far-field radiation. The axial force induces vibration, including breathing and bending modes, resulting in the highest peak of the radiated sound pressure level (SPL). The lateral and vertical excitation results in horizontal and vertical bending modes, respectively, and the SPL in convergence zones induced laterally are higher than those induced vertically.