Identification and Closed-Loop Control of a Backwards Facing Step by Opposite Side Acoustic Excitation

This paper demonstrates that it is possible to use opposite side acoustic actuation to dynamically control the reattachment length/recirculation bubble size of a backwards facing step flow. It is shown experimentally by proxy of total pressure measurements that pure-tone acoustic actuation is able to reduce reattachment length, and that the extent of reduction can be controlled by amplitude modulation of the pure tone. Maximum reduction in reattachment length is estimated to be as much as 18% compared to baseline flow. An integral controller is then applied to closed-loop control of pitot probe measured pressure, and it is shown that a response time of around 0.2s is achieved.