G. Maze F. Leon J. Ripoche
LAUE, Univ. Le Havre, 76610 Le Havre, France
Univ. of Le Havre and Catholic Univ. of America, Washington, DC 20064
The real parts of the eigenfrequencies of an evacuated, fluid-immersed infinite cylindrical shell can be used to obtain the dispersion curves versus frequency of the phase velocities of families of circumferential waves. These waves are analogous to those of the families of Lamb waves on an elastic plate in vacuo, but contain an additional A wave corresponding to the Scholte--Stoneley wave in the fluid loading [see M. Talmant, Ph.D. thesis, Univ. of Paris VII (1987), or M. Talmant et al., J. Acoust. Soc. Am. 86, 278 (1989)], which is approximated by the first Franz wave [B. Clotteau et al., J. Acoust. 3, 213 (1990)]. Near the coincidence frequency, a repulsion phenomenon is obtained between the (Lamb wave) A[sub 0] and the A-wave dispersion curves, analogous to that in perturbed, quasidegenerate atomic levels. An analytic explanation is provided, using perturbation theory, for the form of the dispersion curves and the nature of the corresponding waves in the region of repulsion.