Decoupling procedures for fluid-structure interaction problems (Q1108126)

Methods for decoupling of acoustoelastic fluid-structure interaction problems in the frequency domain are developed and discussed in a systematic way. Rayleigh-Ritz transformations of the four condensed symmetric forms of the initial nonsymmetric system are obtained, using full and reduced basis vector sets. The reduced transformations are then compared to the Guyan-Irons reduction (first-order approximation) of the full transformations, establishing some necessary conditions for the choice of the basis vectors. Eigenvectors from various structure and fluid eigenproblems are then considered as special choices for the Rayleigh-Ritz basis vectors. Finally, effective decoupling computational procedures are proposed, that can be implemented using standard black-box structural analysis codes. They utilize the eigenvalues of the in vacuo and acoustic eigenproblems and allow the solution not only of the fully coupled eigenproblem, but also of the other limit case eigenproblems encountered (the incompressible fluid being just one of them). In the appendices, modal transformations of the second added mass matrix are derived and relations between the eigenvalues of several eigenproblems are established.