### ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

## 4aPAa4. Implementation of a ray tracing algorithm to calculate the
acoustic scattering from fluid loaded, doubly curved shells.

**Douglas A. Rebinsky
**

**
Andrew N. Norris
**

**
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*Dept. of Mech. and Aerosp. Eng., Rutgers Univ., P.O. Box 909, Piscataway,
NJ 08855-0909
*

*
*
**Yang par
**

**
**
*SFA, Inc., Landover, MD 20785
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*
*
Ray tracing is used to calculate the acoustical and structural response of
smooth, elastic shells of nonseparable shape. The frequency range of interest
is below flexural coincidence but still high enough that asymptotic methods are
applicable. The structure and development of ray-like solutions on arbitrarily
doubly curved shells is reviewed with a discussion of two mechanisms: (1) a
``background'' response determined by the local inertial impedance, and (2)
phase matching to longitudinal and shear waves. The background response can be
approximated by specular reflection, but the membrane waves require global
treatment over the whole structure. After first calculating the coupling
curves, which are the closed loci defined by phase matching with the incident
wavefield, ``pressure'' rays are then sent out over the shell with each ray and
its amplitude evolving according to a ray equation and a transport equation.
Illustrative examples of ray paths and ray-tube areas will be presented for
ellipsoidal and quasicylindrical shells. The use of the Gaussian beam summation
method to describe the wavefields will be discussed. Numerical comparisons are
made with the exact results for the canonical geometries, and extensions to
nonseparable shapes and discontinuous shells will be shown and discussed. [Work
supported by ONR.]