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

## 4pSA4. Diffraction effects from the joining of two curved plates.

**Douglas Rebinsky
Andrew Norris
**

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*Dept. of Mech. & Aerosp. Eng., Rutgers Univ., P.O. Box 909, Piscataway, NJ
08855-0909
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Acoustic scattering from a fluid-loaded shell consisting of two joined
curved plates is considered. Asymptotic approximations are made based upon the
assumption that the fluid wavelength is much shorter than the smaller radius of
curvature. A plane wave in the fluid incident upon a line weld at which the
shell properties and curvature are discontinuous, but the tangent is
continuous, is considered. The problem simplifies by first assuming that the
angle of incidence with respect to the tangent plane at the weld is not near
the critical angle for supersonic membrane waves on either side of the weld.
The discontinuity then generates a diffracted wave field in the fluid which is
determined by solving a Wiener--Hopf problem. This background wave field in
turn forces the ordinary differential equations describing the membrane waves.
From their solution, diffraction coefficients are obtained for the membrane
waves generated on each curved plate by the incident acoustic field. When the
incident wave is close to one of the critical angles it couples directly to the
shell waves via curvature, and the interaction of this launched membrane wave
with the discontinuity results in scattered membrane wave fields with
diffraction coefficients determined in a manner similar to the previous case.
[Work supported by ONR.]