The generalized Stoneley and Rayleigh waves on cylindrical shells.

Abstract

This paper dealt with acoustical scattering resulting from a plane harmonic wave normally incident upon an infinite elastic circular cylindrical shell immersed in water and filled with air. Various circumferential surface modes have been experimentally and numerically observed. The so called l=0 and l=1 circumferential waves are considered. A numerical study of their behavior at high frequency, when the relative thickness of the shell remains constant, is achieved in the complex wave-number plane. The results are presented in the form of trajectories in the complex wave-number plane and of curves of phase velocity and attenuation by reradiation in water plotted as function of reduced frequency. At low frequency, the trajectory of the circumferential waves on shells depends strongly on the value of the relative thickness of the shell. Nevertheless, it is shown that, at high frequency, the effect of the internal interface becomes negligible and, for all values of the relative thickness considered, the l=0 wave (respectively, l=1 wave) on cylindrical shells tends toward the Stoneley wave (respectively, Rayleigh wave) on solid cylinder and, in the limit of very high frequency, when the curvature becomes negligible, their common limit is their flat-surface counterparts.