CIRCUMFERENTIAL CREEPING WAVES AROUND A FLUID-FILLED CYLINDRICAL CAVITY IN AN ELASTIC MEDIUM

The dispersion behavior of circumferential creeping waves around a flu id-filled cylindrical cavity in an infinite elastic medium is analyzed by computational methods. Phase and group velocity as well as attenua tion curves are constructed by numerically solving the dispersion equa tion. A comparison of the corresponding modes for elastic and rigid ho sts is presented. The modes in both eases exhibit essentially the same series of cutoff frequencies corresponding to radial resonances at wh ich the phase velocity of the associated modes becomes infinite and th e group velocity assumes a limiting value of pi c(f)/2, where c(f) is the compressional wave velocity in the fluid. Attenuation of the circu mferential creeping modes in a cylindrical cavity is caused solely by losing energy to the surrounding elastic bulk. Therefore, for all mode s, the attenuation diminishes at high frequencies as leakage into the surrounding solid becomes negligible. This is in sharp contrast with t he case of leaky Rayleigh wave propagation along the plane surface of a solid-fluid interface where attenuation is caused solely by radiatio n of energy into the fluid, which causes the frequency to have an oppo site effect on the degree of leakage in these situations. (C) 1997 Aco ustical Society of America.