Disruption of flow-induced noise from a bluff body

The suppression of flow-excited acoustic resonance from a circular cylinder in cross-flow is investigated experimentally over a Reynolds number range of 3.3 × 1 0 4 to 1.7 × 1 0 5 . The effectiveness of several passive flow-control techniques in mitigating resonance excitation is examined, including a splitter plate, a sweeping jet, a continuous jet, and a small control rod. Aeroacoustic measurements show that these control strategies can suppress flow-excited acoustic resonance associated with the first acoustic cross-mode of the duct, achieving reductions in sound pressure levels of approximately 19–22 dB. Flow visualization highlights the key role of the interaction between clockwise and counterclockwise vortical structures in driving flow-induced noise and sustaining the acoustic resonance. Disrupting this interaction, or convecting the vortical structures further downstream away from the cylinder base, weakens the feedback mechanism and substantially reduces the acoustic response. In addition, proper orthogonal decomposition (POD) analysis shows that the introduction of passive control devices significantly reduces the energy associated with the antisymmetric shedding mode, which is dominated by the first two POD modes, while enhancing the contribution of higher-order POD modes that are generally associated with a symmetric vortex-shedding process.