Modal parameter estimation for a wetted plate under flow excitation: A challenging case in using POD

Abstract

In this paper some issues related to the use of the Proper Orthogonal Decomposition (POD) for the identification of the modal parameters of 2D structures are highlighted with reference to the experimental identification of the vibration modes of a plate excited on one side by a turbulent boundary layer. The poor convergence of the POD modes to the linear normal modes is explained analytically and provides also the theoretical framework to avoid these issues by applying band-pass filtering (BP-POD). The application of the POD with data pre-filtering has allowed for the evaluation of the modal damping from the proper orthogonal coordinates by using the Random Decrement Technique to obtain the corresponding free-decay function. Though the emphasis is about methodological aspects related to the POD, as a byproduct of the performed analysis some more physical insights concerning the damping sensitivity and the hydrodynamic added mass are finally carried out.