A numerical methodology for resolving aeroacoustic-structural response of flexible panel

Fluid-structure interaction problem is relevant to the quieting design of flow ducts found in many aeronautic and automotive engineering systems where the thin duct wall panels are directly in contact with a flowing fluid. A change in the flow unsteadiness, and/or in the duct geometry, generates an acoustic wave which may propagate back to the source region and modifies the flow process generating it (i.e. an aeroacoustic process). The unsteady pressure arising from the aeroacoustic processes may excite the flexible panel to vibrate which may in turn modify the source aeroacoustic processes. Evidently there is a strong coupling between the aeroacoustics of the fluid and the structural dynamics of the panel in this scenario. It is necessary to get a thorough understanding of the nonlinear aeroacoustic-structural coupling in the design of effective flow duct noise control. Otherwise, an effective control developed with only one media (fluid or panel) in the consideration may be completely counteracted by the dynamics occurring in another media through the nonlinear coupling. The present paper reports an attempt in developing a time-domain numerical methodology which is able to calculate the nonlinear fluid-structure interaction experienced by a flexible panel in a flow duct and its aeroacoustic-structural response correctly. The developed methodology is firstly verified able to capture the acoustic-structural interaction in the absence of flow where the numerical results agree with theory very well. A uniform mean flow is then allowed to pass through the duct so as to impose an aeroacoustic-structural interaction on the flexible panel. As a result, the nonlinear coupling between the flow aeroacoustics and panel structural dynamics are found completely different from the case without mean flow. A discussion of the new physical behaviors found is given.