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

## 2pSA5. Acoustic scattering from flexible bodies with discontinuities using
analytic/numerical matching.

**Donald B. Bliss
**

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Rickard C. Loftman
**

**
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*Mech. Eng. and Mater. Sci., Duke Univ., Durham, NC 27706
*

*
*
Analytical/numerical matching (ANM) is a hybrid scheme combining a
low-resolution global numerical solution with a high-resolution local
analytical solution to form a composite solution. ANM is applied to scattering
from a fluid-loaded cylindrical membrane with a discontinuity, e.g., a point
impedance. This coupled fluid/structural problem utilizes the addition and
subtraction of canceling distributed forces at the discontinuity. The problem
divides into one with the point force and distributed force in opposition, and
another with only a distributed force. Conditions are imposed on the problem
with the distributed force opposing the point force, leading to a structural
response with only local motion and minimal radiation. This local problem can
be solved analytically in simplified form. The remaining problem with only a
distributed force is a low-resolution global numerical problem and can be
solved efficiently. The local and global problems are dynamically coupled in
the composite solution. The scattering problem revealed sensitivity to whether
the discontinuity was a point force or a narrowly distributed force. This
sensitivity is explained, and implications for accurate modeling of scattering
from structures with discontinuities are discussed. Application of the method
to multiple discontinuities and general geometry is described. [Work supported
by ONR.]