2022 Volume 65 Issue 5 Pages 221-229
An experimental study is performed to investigate the feasibility of success in controlling supersonic boundary-layer flows using a device to discharge the jets flapping at several tens of kilohertz (kHz). In the experiments, a shadowgraph image velocimetry (SIV) technique is applied for measuring the velocities in a supersonic boundary-layer flow with a freestream Mach number of 2.05. Five operations in the device are tested (i.e., the operation of discharging no jet, non-flapping jets, and jets flapping at 15 kHz, 17 kHz, and 30 kHz). The experimental results reveal that the flapping jets work so as to effectively increase the boundary layer fullness in the near-wall region as compared to that of the non-flapping jets. In addition, the operation of discharging the jets flapping at 30 kHz displays the most remarkable increase in the boundary layer fullness among the five operations. These experimental results illustrate that the device to generate a high-frequency flapping jet can be a practicable actuator for controlling supersonic boundary-layer flows.
