Evolution of coherent structures and feedback mechanism of the plane jet impinging on a small cylinder

The dynamics of coherent structures and their instability evolution of the small cylinder impinging plane jet are extensively studied in this paper. The hot-wire measurements are conducted to investigate the physical flow properties and relevant flow field behaviors. The jet exit velocity is operated between 2–26 m/s, with the Reynolds number range from 2.1×103 to 2.7×104 based on the initial jet width. The acoustic excitation is applied to verify the instability evolution mechanism and is introduced at the jet nozzle exit with two arrays of small loudspeakers. A modified feedback mechanism is proposed to successfully explain the interaction between the cylinder and the plane jet. The competition between the jet and wake shear layer instabilities is significantly revealed in comparison with the standing wave number measured in the self-sustained oscillating flow. The augmentation effect of acoustics excited at the resonant frequency on the impinging flow with the small cylinder is also explored in detail to substantiate the feedback mechanism.