Abstract
An active control strategy is applied to a circular air jet impinging on a plate with a hole of a jet axis, in order to suppress the self-sustained oscillation of the jet (Hole-tone phenomenon) and the associated noise. The jet shear layer is acoustically excited at the jet exit using six loud speakers installed in an excitation chamber, in a manner of sinusoidal mode. The jet responses have been investigated by the spectrum and wavelet analyses. It was found that the response characteristics were varied variously with the excitation frequency fe and amplitude, and were clearly classified into fe lock-in, fe/2 lock-in, and non folock-in regimes. The excitation condition for each regime was clarified. The periodic phenomenon with periodic vortex rings of uniform scale and the non-periodic phenomenon with the vortex rings of many different scales were visualized by the smoke-wire visualization technique of the jet and the wavelet analysis.
