Flow Control of Large-Scale Coherent Turbulence to Reduce Jet Noise

Dr. Steven Miller | University of Florida



This project will investigate the reduction of the dominant noise from commercial engines of military fighter aircraft through a new type of feedback control system. An upstream microphone will be used to simulate a wing-mounted microphone to measure the noise from the nozzle exhaust. A new technique will be developed to extract the portion of the noise due to the large-scale instability waves and turbulent structures within the jet flow. This portion of the signal is highly correlated with the large-scale structures and the dominant noise that occurs in the downstream direction of the jet. The project will explore the use of this signal to actuate control within the nozzle that will alter the behavior of the large-scale turbulent structures, and in turn, reduce the greatest noise source of the jet. The unique contribution of this approach is a new method to extract the highly correlated noise statistics from the large-scale turbulent structures. The research team will also examine the effectiveness of controlling large-scale structures through actuation within the divergent section of the nozzle. The project will focus on the core technology of statistical separation of mixing noise sources and potential integration into a control system operating on a supersonic off-design jet. This approach will lead to lowering both the nearfield and far-field dominant noise source

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Technical Approach

The project will explore reduction of large-scale mixing noise through an actuation mechanism using actuators within the nozzle divergent section. The actuators will be controlled using a decomposed signal consisting of the noise that propagates upstream from large-scale turbulent structures within the jet shear layer. A combination of analytical methods will be used to examine the source, decomposition approaches including the proper orthogonal decomposition, large-eddy simulation to study the turbulence, and an experimental implementation in the laboratory environment. At the end of the one-year period of performance, the project plans to demonstrate elements of this noise reduction technology (in the laboratory environment) for the noise associated with large-scale coherent turbulence within high speed off-design jets. The technologies currently reside within technology readiness levels one through three. At the end of the project, TRL three will be achieved for these technologies. The eventual application of this technology in the fleet of aircraft is foreseen as a modification to existing engines. Actuators will be added to the engine, a small flight computer will perform the control and decomposition, and multiple microphones will be placed within the trailing edge of the airframe near the engine

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This project will allow for increased understanding of noise reduction technology and physics for the dominant noise producing turbulent structures within high-speed jet flows. An increased understanding of the upstream traveling noise and associated statistics will be obtained through the decomposition approach. The research team plans to quickly transition the technology to higher TRL levels if successful. The research will be communicated to industrial and government partners through the Strategic Environmental Research and Development Program (SERDP), Department of Defense (DoD), National Aeronautics and Space Administration (NASA), and major engine manufactures. Success of this research will eventually lead to technology that reduces hearing loss of the Warfighter within Aircraft Carrier operations. The project will lead to technology to reduce community annoyance near airfields. Finally, sonic fatigue of aircraft components and nearby structures could be reduced.

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Points of Contact

Principal Investigator

Dr. Steven Miller

University of Florida

Phone: 352-392-0886