A MODEL FOR THE VIBRO-ACOUSTIC RESPONSE OF PLATES EXCITED BY COMPLEX FLOWS

A model was developed and applied for predicting the vibration response of structures excited by complex vortical turbulent flows. Computational fluid dynamic (CFD) methods were utilized to model the flow over the structure. The computations allowed the general flow patterns to be identified and the mean properties of the flow field to be calculated. The spectral characteristics of the dynamic wall pressure fluctuations were obtained from an empirical database developed from genetically similar flows. The Corcos model was used to characterize the dynamic surface pressure cross-spectra. The power input into the structure was estimated accounting for the non-uniform dynamic pressure loading on the structure. The energy flow analysis (EFA) method was then used to predict the high-frequency structural vibration response and the radiated sound power. The frequency limit of the accuracy of the model was established. The model was applied to the case of a clamped rectangular homogeneous panel excited by vortical flows. The model predictions were verified experimentally for the case of an aluminium panel installed in a low-speed wind tunnel downstream of three-dimensional vortex generators. The wall pressure fluctuations, the plate transverse vibration velocity, and the acoustic pressure radiated from the plate were measured over a range of mean flow velocities. The measured surface pressure spectra beneath the coherent flow structures formed behind the vortex generators were found to be similar to those behind uniform fences at high frequencies. This confirmed that high-frequency wall pressure fluctuations depend on fine grain turbulence rather than on the large-scale flow structures. The measured panel vibration responses, and the radiated acoustic pressure levels were found to agree well with model predictions at frequencies above the model predictability threshold. The proposed modelling approach offers the opportunity to develop tools that could assist the vibro-acoustic design of complex flow-excited systems such as vehicles, or fluid machinery.