Leaky wave scattering contributions for tilted thick cylindrical shells in water above the coincidence frequency: Ray theory and computational models

Abstract

Scattering measurements [Morse, Marston, and Kaduchak, J. Acoust. Soc. Am. 103, 785–795 (1998)] and sonar images [Kaduchak, Wassmuth, and Loeffler, J. Acoust. Soc. Am. 100, 64–71 (1996)] demonstrate that above the coincidence frequency, the responses of tilted cylindrical shells associated with leaky antisymmetric Lamb waves can give major contributions to the scattering of sound. Thin-shell dynamics is not applicable for the modeling of the shell’s response and an approximate ray formulation has been developed for situations where exact solutions are unavailable. Relevant contributions include meridional [P. L. Marston, J. Acoust. Soc. Am. 102, 358–369 (1997)] as well as helical [P. L. Marston, J. Acoust. Soc. Am. 102, 1628–1638 (1997)] leaky rays. The present research emphasizes computational tests for situations where helical antisymmetric Lamb wave contributions are important. These include situations where contributions from the broad meridional ray enhancement interfere with helical ray contributions. The results are helpful for interpreting features of the scattering. [Work supported by the Office of Naval Research.]