Modal parameter estimation for fluid-loaded structures from reduced order models

A model reduction method is developed to estimate modal parameters of fluid-loaded structures. The method uses a matrix-free formulation of rational Krylov projection to construct reduced order models of the fluid-loaded structures from forced responses at selected interpolation frequencies. Due to small sizes of the reduced order models, eigenpairs of the associated eigenvalue problems are available at a very low computational cost. Resonance frequencies, modal damping ratios, and mode shapes of the original systems are recovered from the forced responses and the eigenpairs of the reduced order models. Nonphysical modes introduced by the model reduction process are filtered out by a modal damping ratio test and double checked by the condition number of the dynamic stiffness matrix. Efficiency and accuracy of the present method are demonstrated on a benchmark model of a water-loaded plate clamped in a baffle. (c) 2006 Acoustical Society of America.