Scattering in the Time Domain from Submerged Elastic Shells at Coincidence Frequencies
NAVAL OCEANOGRAPHIC AND ATMOSPHERIC RESEARCH LAB STENNIS SPACE CENTER MS
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It is known that when scattering from elastic shells, a large resonance is produced at frequencies corresponding to values in which the flexural phase velocity is roughly equal to the speed of sound in the fluid. A systematic analysis indicates that the large response is due mainly to water born waves labeled A waves which have narrow half-widths and manifest themselves as pronounces spikes in the form function as well as weaker flexural resonances labeled AO which have rather larger half-widths and produce an envelop effect due to overlapping resonances over a broad frequency range. These results are analyzed within the context of a new time domain resonance scattering theory and are shown to produce characteristic transient return signals. From these signals it is possible to calculate both the half-width of the A waves as well as their group velocities.