STUDY OF FLOW-INDUCED VIBRATION AND SOUND OF A FLEXIBLE STRUCTURE

Numerical and experimental studies on flow-induced vibration and sound from a flexible structure in the flow are carried out. In addition, effect of flow velocity on the dynamics of flexible structure is also investigated. A test model of a cantilevered elastic plate with an upstream square bluff body is considered. For the simulations, a computational aeroacoustic (CAA) hybrid method is used, wherein the flow field is computed with a two-way fluidstructure coupling and acoustic propagation is calculated by using a linearized Euler equation based method. A surface injection based coupling is implemented between the flow and acoustic region. The numerical results demonstrate that for a certain value of flow velocity, plate remains steady. Beyond that velocity, the cantilevered plate exhibits vibration in first bending mode of the cantilevered plate. The frequency of vibration is observed close to the fundamental frequency of the plate. The vibration amplitude observed first increases, reaches a maximum value and then decreases with increase in the flow velocity. However, the frequency increases monotonously. For a particular value of flow velocity, the coupled system shows a resonance type behavior. The character of far-field acoustic pressure calculated is correlated with the observed vibration of the plate. The radiated sound field showed a dipole type of pressure field. The experiments have been conducted in a 200mm x 200mm wind tunnel at different flow velocities. A similar test model as considered in the numerical study is used. The Reynolds numbers of the flow (based on the frontal body) are maintained in a range of 1000 to 20000. The results revealed interesting facts about the vibration of the flexible structure under the interaction of the flow field. The numerical and experimental results are found to be in good agreement qualitatively.