Scattering of a narrow acoustic beam by a truncated fluid-filled cylindrical shell

Abstract

Previously a method of describing spherical acoustic waves in cylindrical coordinates was applied to the problem of point source scattering by an elastic infinite fluid-filled cylindrical shell [S. Dodd and C. Loeffler, J. Acoust. Soc. Am. 97, 3284 (A) (1995)]. This method is applied to numerically model monostatic oblique incidence scattering from a truncated cylinder by a narrow-beam high-frequency imaging sonar. The narrow-beam solution results from integrating the point source solution over the spatial extent of a line source and line receiver in the frequency domain. The cylinder truncation is treated by the method of images, and assumes that the reflection coefficient at the truncation is unity. The scattering form functions, calculated using this method, are applied as filters to a narrow bandwidth, high ka pulse to find the time domain scattering response. The time domain pulses are further processed and displayed in the form of a sonar image. These images compare favorably to experimentally obtained images [G. Kaduchak and C. Loeffler, J. Acoust. Soc. Am. 97, 3289 (A) (1995)]. The impact of the s0 and a0 Lamb waves are vividly apparent in the images.