RESONANCES AND SURFACE-WAVES IN THE SCATTERING OF AN OBLIQUELY INCIDENT ACOUSTIC FIELD BY AN INFINITE ELASTIC CYLINDER

The relationship between resonances and surface waves in the scattering of an obliquely incident acoustic wave from an infinite elastic cylinder is discussed. From the three-dimensional normal-mode solutions for a free cylinder, the resonance frequencies of the cylinder and, correspondingly, the phase velocities of helical surface waves and their relation to the helical angles are obtained. Furthermore, as the cylinder is excited by sound waves incident through ambient water, the dispersion of phase velocity for helical surface waves as a function of the angle of incidence has also been derived. Comparing the results of the present work with the results given by Flax et al. [J. Acoust. Soc. Am. 68, 1832 (1980) ], it was found that, for the case of oblique incidence, the resonance frequencies are basically in agreement with the frequencies of the minimum values of the form function, analogous to the case of perpendicular incidence. © 1990, Acoustical Society of America. All rights reserved.