### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 3aSA4. Acoustic scattering from a hemicapped cylindrical shell with
substructures.

**Weiping Zhang
**

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*Component Products Group, Motorola, 1301 E. Algonquin Rd., Schaumburg, IL
60196
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**Takeru Igusa
**

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Jan D. Achenbach
**

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*Northwestern Univ., Evanston, IL 60208
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This paper extends the study on acoustic radiation of axisymmetric
submerged shells of finite length to the scattering problem. A modal-based
method is developed to determine the scattering from finite shells insounified
by plane incident waves. A surface variational principle provides the acoustic
impedance relationship between the surface pressure and displacement fields,
which are expanded into a series of shape functions. Lagrange multipliers are
introduced in a Lagrange formulation of the dynamic analysis to account for the
interaction between the shell and internal substructures. Surface and far-field
pressures scattered from the elastic shell are calculated. It is found that, at
certain angles, the scattered pressure field has pronounced peaks, particularly
as the incident frequency increases. A wave number domain analysis is performed
on the surface displacement field. A dominant wave number is found which
accounts for the high directivity pattern of the far field. The effect of
substructures on the far field is also investigated.