Scattering by tilted cylindrical shells in water above the coincidence frequency

Abstract

Experimental, theoretical, and computational results indicate that flexural waves on bluntly truncated tilted cylindrical steel shells are a major contributor to the backscattering of sound at high frequencies over a wide range of tilt angles. Important contributions are associated with meridional rays and with helical rays [S. F. Morse et al., J. Acoust. Soc. Am. 103, 785–794 (1998); S. F. Morse and P. L. Marston, J. Acoust. Soc. Am. 106, 2595–2600 (1999); S. F. Morse and P. L. Marston, IEEE J. Ocean. Eng. 26, 152–155 (2001)]. Successful development of a ray model for helical ray scattering contributions required the computation (at high frequencies) of the anisotropy of the flexural-wave velocity and radiation-damping parameters [F. J. Blonigen and P. L. Marston, J. Acoust. Soc. Am. (accepted for publication)]. In backscattering experiments with short and long tone bursts, the associated meridional and helical ray contributions are typically much larger than the scattering estimated for diffraction by a rigid tilted cylinder of the same size. The importance of the elastic response of shells was recognized in the early work of Junger [M. C. Junger, J. Acoust. Soc. Am. 24, 366–373 (1952)]. [Work supported by ONR.]