Active control of flow oscillations in jet–wedge system by acoustic feedback

• DOI: 10.1016/j.jfluidstructs.2003.09.001
• Publication Date: 2003-12-16T06:02:18Z
• Authors: N. Fujisawa; Y. Takizawa; T. Kohno; S. Tomimatsu
• Keywords: 0103 physical sciences; 01 natural sciences

Abstract The performance and mechanism of an acoustic feedback control applied to flow oscillation in a jet–wedge system were investigated experimentally. The self-sustained oscillations were effectively suppressed by imposing velocity fluctuations near the nozzle exit, which were fed by the fluctuating pressure signal at the wedge with a certain phase lag and feedback gain. The optimum condition for the imposed velocity amplitude was found to be as small as 1.2% of the jet velocity. The variation of the flow field with and without control was studied by flow visualization with high-speed camera and by flow-field measurements with particle image velocimetry. These observations indicate that the primary mode of the jet oscillation in the jet–wedge system is weakened by the feedback control to a level of secondary mode. This is mainly due to the destruction of the synchronized flow structure of the jet–wedge system by the active control, which is found in the mean and fluctuating velocity distribution and the velocity correlation over the wedge and along the jet shear-layers.