Recent progress in closed-loop control of cavity tones

Active flow control of cavity tones has been successful in controlling Rossiter tones in both subsonic and supersonic flows. While closed-loop control promises the lowest actuator power requirements and the ability to adapt to changing flow conditions, so far it has only been demonstrated on subsonic cavities. Suppression of Rossiter tones in supersonic cavities has been demonstrated using open-loop techniques. Progress and issues related to closed-loop control and controlling supersonic cavities are reviewed.