Abstract: Efficient oscillating jet systems need actuators with excellent oscillation characteristics, which requires reduction of the internal flow losses in the actuator to increase the outflow velocity, reduction of the stagnation time of the jet at 0° deflection angle to generate unsteady vortexes in the flow field, increase of the jet deflection angle to enlarge the control area, and the ability to effectively adjust the oscillation frequency to approach the optimal control frequency. This study takes the suction and oscillatory blowing actuator, which can significantly reduce the gas flow of the high-pressure gas source, as the research object. The characteristics of the start-up, discharge and frequency of the actuator with different geometric shapes are examined by numerical simulation. The results show that only when the throat height after deducting the jet width is larger than 1.2 times of the feedback channel width, the length of the feedback section is sufficient and the expansion angle is appropriate, the jet will oscillate stably and be tangent to the wall of the expansion section. The truncated expansion section can increase the velocity of the jet center at the exit by 67.3% maximally, and reducing the aspect ratio of the separated vortex in the expansion section can maximally increase the jet sweep angle up to ± 110°. Changes in the width and length of the feedback channel will alter the flow rate by changing the flow area and the losses along the channel, thus affecting the frequency.

Key words: suction and oscillatory blowing, control efficiency, start-up characteristics, discharge characteristics, frequency model