### ASA 126th Meeting Denver 1993 October 4-8

## 4pPA5. Attenuated leaky Rayleigh waves.

**Quan Qi
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*Dept. of Theor. and Appl. Mech., Univ. of Illinois, Urbana, IL 61801
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The attenuation of leaky Rayleigh waves due to viscous damping in a
boundary layer at the interface of an elastic solid half-space and a fluid
half-space is studied by matched asymptotic method. Viscosity of the fluid is
considered unimportant except in a thin boundary layer at the interface. By
keeping the leading order effect, shown by the inverse of square root of a
Reynolds number based on the shear velocity of the solid substrate, a new
characteristic equation is obtained. One of the numerically obtained solutions
gives the leaky Rayleigh wave speed and the attenuation coefficient due to both
radiation into fluid and viscous damping of the boundary layer. It is shown
that the viscous attenuation in the boundary layer may be as important as that
due to radiation into the fluid half-space for some fluid--substrate
combinations. These results may be used to improve our interpretation of
experimental results of acoustic signature of materials. Extension of the
analysis to a fluid layer instead of a half-space will be discussed. [Work
supported by the Hunt Fellowship.]