Ray acoustics and vibration of immersed thin elastic cylindrical shells excited by an on-surface source

Abstract

Structural loadings, joints, and truncations of smooth shells act as equivalent forcings on such shells in the overall acoustic response and vibration. Choosing an on-surface phased line source as the acoustic source, this paper treats the ray synthesis of the pressure and displacement fields on a thin elastic cylindrical shell immersed in an acoustic fluid as well as the sound field in the far zone. The subsonic flexural waves and their strong resonances are observed at the shell surface, but not in the far field, thereby generating distinct field structures in these two regions. In the parameter region where the supersonic compressional and shear waves are cutoff, the surface fields are found to be represented completely by the shell guided flexural mode, while the far field is reduced to the modified geometrical acoustics field (essentially comprised of incident and reflected waves). The ray acoustic predictions prove to be accurate in comparison with the normal mode series data for ka ⩾ 2 or so (where a is the mean radius of the shell and k is the acoustic wavenumber of the fluid).