### ASA 127th Meeting M.I.T. 1994 June 6-10

## 1aSA3. Acoustic scattering from rigid shells of revolution using the
generalized internal source density and SVD method.

**P. R. Stepanishen
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*Dept. of Ocean Eng., Univ. of Rhode Island, Kingston, RI 02881
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Acoustic harmonic nonaxisymmetric scattering from rigid shells of
revolution is addressed using the generalized internal source density and SVD
method. The development of the generalized ISD/SVD method, which entails the
use of various internal multipole source distributions along the axis of the
shell, will be presented. The approach is based on first expanding the incident
pressure and associated velocity field into circumferential harmonics about the
axis of the shell. Integral equations of the first kind are developed for the
unknown source distributions. A least-mean-squared error formulation of the
solution naturally leads to using the SVD method to determine the source
distributions. The blocked surface pressure for each circumferential harmonic
is then readily evaluated by simple quadrature methods and the associated
far-field scattered pressures are shown to be simply related to the Fourier
transforms of the source distributions. Numerical results for some selected
problems are presented and some limitations of the method as a function of
azimuthal wave number and shape of the shells are noted. These limitations are
discussed and are readily interpreted in light of the above-noted Fourier
transform relationship.