Scattering enhancements for penetrable tilted circular cylinders in water: The computed evolution away from the meridional plane

Abstract

Significant contributions to the high-frequency backscattering by penetrable bluntly truncated solid circular cylinders include meridional leaky Rayleigh waves [K. Gipson, Ph.D. thesis, Washington State University (1998)] and the caustic merging transition [F. J. Blonigen and P. L. Marston, J. Acoust. Soc. Am. 102, 3088 (1997)]. The latter is important for plastic objects (where Rayleigh waves become subsonic relative to water) and is associated with merging transmitted and internally reflected rainbow rays. One way to explore the dependence of these processes on tilt is to compute the exact scattering by infinite circular cylinders away from the meridional plane. The meridional Rayleigh-wave feature for infinite metallic cylinders is a dip in the total scattering and a peak in the background-subtracted scattering [P. L. Marston, J. Acoust. Soc. Am. 102, 358–369 (1997)]. We find it evolves in a way bounded by the locus of those rays reflected with their local angle of incidence matching the Rayleigh-wave coupling angle. In the caustic merging case, the evolution of the rainbow enhancement is similar to optical observations [Mount et al., Appl. Opt. 37, 1534–1539 (1998)]. [Supported by the Office of Naval Research.]