APPROXIMATE MERIDIONAL LEAKY RAY AMPLITUDES FOR TILTED CYLINDERS - END-BACKSCATTERING ENHANCEMENTS AND COMPARISONS WITH EXACT THEORY FOR INFINITE SOLID CYLINDERS

Leaky waves propagating on cylinders in (or close to) a meridional pla ne have been found to significantly enhance the high-frequency acousti c visibility of the ends of tilted cylinders [G. Kaduchak et al., J. A coust. Sec. Am. 100. 64-71 (1996)]. The meridian of interest is in the plane containing the incident wave vector and the cylinder's axis, A ray model for this enhancement is developed along with a ray model for a canonical test case: scattering by an infinite circular cylinder. T o isolate a single high-frequency leaky wave contribution, numerical e xamples are shown for generalized Rayleigh waves on a solid circular c ylinder. Partial wave series (PWS) calculation show that the meridiona l Rayleigh wave contribution is maximized when the tilt angle is close to the flat-surface coupling angle. The ray model approximates the su perposition of leaky waves excited by the incident acoustic wave as a simple integral that accounts for the phase shift and attenuation for propagation from each illuminated surface point to a surface point of interest, While the model gives the spatial evolution of the leaky wav e amplitude as would be measured by acoustic imaging, it also approxim ates the far-field amplitude. Important features of the canonical PWS calculation are reproduced by the model. The far-field magnitude of th e end contribution can be larger than for reflection off a rigid spher e having the same radius as the cylinder, The end is assumed to be fla t and perpendicular to the cylinder's axis. (C) 1997 Acoustical Societ y of America.