The wave bivector formalism associated with circumferential leaky waves

It is shown that. the circumferential internal waves propagating around an elastic cylinder can be locally seen as plane evanescent waves, at any obse rvation point inside the surrounding fluid. This is done by direct calculat ion of the associated complex bivector. The exact anatomy of the wave is de tailed and the phase propagation paths are found to be curved, as expected. The transition to the plane interface is achieved. Polarization ellipses a ssociated with the acoustic displacement vector are described. The addition al low evanescence assumption leads to conventional ray interpretation with identification of the ray tube divergence coefficients, and the wavefront is found to be the involute of a circle. (C) 2000 Acoustical Society of Ame rica. [S0001-4966(00)03007-1].