50 / 2021-03-27 22:43:53

Prediction of the flow-induced tones of an open cavity with a flexible wall using the describing-function method

Flexible cavity, Fluid excitation, Oscillation frequency, Describing-function method, Patch-mobility method

Wind induced vibration in structures

Shear flow past a cavity involves a complex fluid dynamic process. From an acoustical point of view, it is important to determine the conditions under which self-sustained oscillations occurs as inherent feedback mechanism often results in significant tones. Extensive efforts have been made to investigate the underlying mechanisms of such a simple yet compelling system as well as to predict the noise generated. However, less efforts were dedicated to the more realistic case, that is, when the wall of the cavity is flexible. Indeed, a flexible wall will complicate the interaction between the hydrodynamic and the vibro-acoustic fields of the system. In this work, a method is developed to predict the tones generated by the shear flow past an open cavity with a flexible wall. In view of the feedback process involved within the system, a describing-function method which decomposes the system into a non-linear part and a linear part is used. The former part is associated with the response of the flow instability to vibro-acoustic excitation while the latter is the vibro-acoustic response to the fluid excitation. The oscillation frequency calculated by the proposed model is in good agreement with the results measured using a flow duct.