D'Andrade Souto C., Pavanello R.

The modal approach is commonly used in structural dynamics to save computational effort on dynamic analysis. The same method can be used in the analysis of structure-acoustic systems and some techniques were developed for this purpose in the last three decades. This kind of systems can be modeled using different finite element formulations. The most frequently used have displacements and pressures as nodal variables for the structure and acoustic fluid respectively. However, this formulation leads to non symmetric matrices. In this paper we implemented and study the performance of a modal reduction method that uses a symmetric formulation. The method was implemented in a C++ finite element code developed in the Computational Mechanics Department. Natural frequencies and mode shape analysis of a test problem are performed and compared with the results obtained by the multipurpose versatile code ANSYS 7.0 by direct solution to demonstrate the efficiency and versatility of the proposed method.