High-Order Perturbation Expansion for the Spectral Analysis of Fluid-Loaded Vibrating Structure

This paper deals with vibroacoustic under heavy fluid-loading conditions. The aim is to show how the high-order perturbation expansion approach described yields a very simple approximation of the spectrum of a heavy fluid-loaded structure. When the fluid-loading is "light" (e.g. metallic structures in contact with air) perturbation methods have been classically used to compute the spectrum of a fluid-loaded structure. Because of the computational efficiency of the expansions involved, it is now necessary to extend this method to heavy loading problems, such as those involving a metallic structure in contact with water. As we will see, although direct high order expansion methods yields unrealistic results, a judicious re-ordering of the various terms leads to surprisingly simple and efficient analytical results. Numerical examples are given in the simple case of a clamped rectangular plate under various fluid-loading conditions.