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

## 4pSAa3. Adaptive multi-level substructuring for computing acoustic
radiation and scattering from complex structures.

**Jeffrey K. Bennighof
**

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Paul D. DSouza
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Matthew F. Kaplan
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Murugan Subramaniam
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J. Christopher Tutt
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**
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*Dept. of Aerosp. Eng. and Eng. Mech., University of Texas at Austin,
Austin, TX 78712-1085
*

*
*
An adaptive method for computing acoustic radiation and scattering from
complex structures is presented. The method uses a multi-level substructuring
decomposition of a structure's finite element model, in which the structure is
partitioned into several substructures, and each of these is partitioned into
its own substructures, and so on. For each substructure, the finite element
representation is transformed to a new one in terms of a quasistatic dependence
of internal degrees of freedom on interface and excited ones, complemented with
response in substructure fixed-interface modes of vibration. This allows for
model reduction in the form of modal truncation for substructures on various
levels. The order of the model is reduced to the number of degrees of freedom
excited by either the acoustic fluid or applied excitations, plus the number of
modes included. An adaptive procedure is used to determine which substructure
modes should be included in the structure model. The acoustic fluid is
represented with a boundary element model, and the procedure for coupling the
structure and fluid models is described. The method is demonstrated on
numerical examples in three dimensions. [Work supported by ONR.]