Active control of flow-induced acoustic resonance through surface perturbation

Flow-induced acoustic resonance inside downstream cavities was experimentally investigated. A controllable motion was imposed on the surface of an upstream vortex generator using embedded piezoceramic actuators. Experiments were conducted by using both open-loop and closed-loop control. Open-loop tests show that there was an optimum control frequency and control voltage which led to a significant reduction in the strength of the flow-induced acoustic resonance. This was directly resulted not only from an impairment of the vortex shedding strength, but also from a shift in the shedding frequency created by the control action. Due to the practical limitation of the actuators, closed-loop control based on the downsampled feedback signals was implemented and tested. A downsampling procedure for reconstructing the feedback signals was investigated. Performance of the closed-loop control was then assessed. Analyses were carried out to reveal the effects of the feedback gain and phase delay on the control performance.