Implementing Resonant Enhanced Pulsed Micro-Actuators for the Control of Supersonic Impinging Jets

Recent work at the Advanced Aero-Propulsion Laboratory (AAPL) at Florida State University has produced a micro-actuator design utilizing micro scale cavity resonance phenomena for active control of various high-speed flowfields such as supersonic impinging jets and cavity flows. These micro-scale actuators are capable of producing pulsed supersonic microjets over a wide range of design frequencies which can be chosen depending on the frequencies that are relevant to the application. Pulsed microjet control has the potential to produce improved flow and/or noise control as has been shown with steady microjet control, while introducing less mean momentum into the system by actuating at the natural frequency of the system. This study focuses on the design, characterization, and implementation of these actuators into the STOVL impinging jet flowfield. The results of this implementation are compared to the no control case, steady control, and the first generation implementation of pulsed microjets into our STOVL facility. By operating these pulsed microjet actuators at 6.1 kHz, impinging tones were reduced by up to 23 dB, and overall sound pressure levels were reduced by up to 7 dB as compared to the baseline flow. Compared to steady microjet control, pulsed control showed improved reduction of discrete tones of about 5 dB and overall sound pressure levels within 2 dB of those found in the steady case. Additionally, this second generation implementation does not exhibit the new peaks generated by first generation control, and further reduces OASPL by about 5 dB.