Vibroacoustic radiation and propagation properties of slender cylindrical shell in uniform shallow sea

Abstract

Shallow sea, especially the reflection and absorption of seabed, have significant influence on the vibroacoustic radiation and propagation properties of underwater structures. An FEM/BEM algorithm based on modal summation is adopted to calculate the modal source strengths and modal coordinate responses of a slender cylindrical shell, in which the Green function of sound field is obtained via virtual source chain model. Using the modal source strengths and modal coordinate responses obtained, the near/far field radiated sound pressure level (SPL) of the slender cylindrical shell in uniform shallow sea is calculated adopting the 3-parameter seabed model. By comparing the radiated power of all modal shapes, the modes with greater contribution can be acquired. Results show that seabed parameters have influence on the far field acoustic radiation of the slender cylindrical shell, mainly on the modal shapes with large grazing angle waves due to larger bottom loss; while the small grazing angle waves are less susceptible to the seabed and propagate much farther.