SIMPLIFIED PREDICTION OF SOUND RADIATION DUE TO BENDING MODE RESONANCES OF SUBMERGED CYLINDERS

The aim of this work is to explore the nature of radiation from bending modes of a submerged tube with variation in mass distribution along the length of the tube. The bending modes of a fluid-loaded tube are initially predicted using a simple finite element shell model, where the effects of water loading are modelled by adding mass to that of the tube itself. The sound radiation is then predicted using an array of transverse dipoles whose strengths are proportional to the local cross-sectional area and vibration amplitude. The effects of retarded time are taken into account for directions that are not normal to the tube. For comparison with the semi-analytical approach, a fully coupled finite element/boundary element model of the fluid-loaded tube was also developed. Results from both techniques show that variation of the mass distribution of the fluid-loaded tube has a large impact on the radiated sound power and directivity of the radiated sound pressure due to low order bending modes.