Ming Ming Z., Li C., Yu Z.

Closed-loop control of flow-induced noise, which was generated by the vortex shedding behind a cylinder in a cross flow, was experimentally investigated in this paper. The noise was caused by the acoustic resonance, where the frequency of vortex shedding from the cylinder coincided with one of the acoustic modes of the wind tunnel. Based on a newly developed perturbation technique, a local surface perturbation was created on the cylinder surface using embedded piezo-ceramic actuators to impair the vortex shedding behind the cylinder and subsequently the acoustic noise. Two closed-loop control schemes were investigated, which deployed the streamwise fluctuating flow velocity (u) measured by a single hot wire and the acoustic pressure signal (p) measured by a microphone as the feedback signals, respectively. The control effect on the acoustic noise and flow were assessed using different flow and noise measurement techniques. It was found that the control scheme based on the feedback signal u led to a significant impairment in the vortex strength and subsequently an effective reduction in the noise level, outperforming the control scheme based on the feedback signal p. The underlying physics behind the observations is discussed.