The influence of substructure modeling on the structural-acoustic response of a plate system

Changes in the vibro-acoustic response of a fluid-loaded plate due to variations in some of the modeling details associated with an attached substructure are examined. The attached substructure consists of a smaller plate supported by springs along each edge. To examine the important modeling issues, three studies are performed. In the first study, discrete changes in the system response due to discrete changes in the size of the region over which the spring elasticity is distributed are examined. In the second study, substructure modeling issues are examined by varying the number of degrees-of-freedom included in the substructure model. Finally, sensitivity relationships that express changes in the system response to changes in the scale of the spring elements are developed. These relationships are used to examine changes in the system response due to small variations in the scale of the distributed elasticity. Both the combined system response and acoustic radiation are computed using the Acoustic Surface Variational Principle and Hamilton's Principle. For the example cases considered, it is shown that details associated with the scale of the spring are only important for frequencies near or below the resonances of the isolated subsystem. Furthermore, only the dynamics of the substructure including rigid-body type motions are important.