Prediction of flow -induced sound and vibration using the energy flow analysis method

The interaction between turbulent flows and flexible structures may cause structural vibration and noise emission. In this investigation, the energy flow analysis method (EFA) was used to predict the structural response and the radiated sound power from flow-excited structures. The objective of this study was to develop a model that would be applicable to complex flow excitations and complicated structures, and yield space- and frequency-averaged predictions at relatively high frequencies. A method, referred to as the infinite structure method, was developed to calculate the power input to structures for distributed random excitations using the cross-power spectral density of the excitation field and the approximate transfer mobility of the structure. A model based on the infinite structure method and the energy flow analysis method was developed and used to predict the structural vibration response and the radiated sound power of the plate excited by turbulent boundary layer flows and separated-reattached flows. The predictions were compared to the measured data. The model was then improved and applied to predict the responses of structures to more complex turbulent flows. Computational fluid dynamic (CFD) methods were utilized to identify the flow Patterns and predict the mean flow properties of the flow field over the structures. Spectral features of wall pressure fluctuations were obtained from a pre-developed empirical database. The non-uniform loading on the structures was accounted for using the power density input method. The energy flow analysis method was used to predict panel vibration and acoustic radiation. The predictions using the model were verified experimentally for the case of a homogeneous panel downstream of two different three-dimensional wedges which were used as vortex generators. The measured panel vibration response, and the radiated acoustic pressure levels were found to agree reasonably well with the predicted results at frequencies where the modal density of the panel was sufficiently high. The results of this study suggest that the proposed approach, which combines computational fluid dynamic techniques, the infinite structure method, and the energy flow analysis method, will be a useful tool in predicting the behavior of complex flow-excited structures