Sound Scattering by Resonantly Excited, Fluid-loaded, Elastic Spherical Shells.(Reannouncement with New Availability Information)

摘要

The scattering of sound waves by an air-filled, elastic, spherical shell in deepwaters, in the frequency domain is analyzed. This exact analysis is based on the classical formulation of three-dimensional elastodynamics, for fluid-loaded spherical shells of arbitrary thickness. Form functions, residual responses, and the partial-wave expansions of both, are determined. Results are displayed in relatively wide frequency bands for various increasing shell thicknesses. The resonance features in the sonar cross sections (SCS) are isolated by means of a new hybrid modal background that substantially improves the results found with the earlier (rigid/soft) backgrounds of the resonance scattering theory (RST). The resonance features in the SCSs that correspond to each mode, and also to each of the various shell waves that propagate around its periphery are isolated. There seem to be over half-a-dozen shell (generalized Lamb and Stoneley) waves manifesting their influence in the SCSs within the examined band. Three large-amplitude features are most noticeable. There is a (slow) wave due to the double curvature of the shell which is responsible for a large, spiky feature at low frequencies.