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Understanding and Control of Coupling of Supersonic Twin Jets Using Localized Arc Filament Plasma Actuators

Cluts, Jordan Dean
http://rave.ohiolink.edu/etdc/view?acc_num=osu152555508900912

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Aero/Astro Engineering.
A twin-jet consists of two jet engines that are close enough to one another on an aircraft for the plumes to interact and merge downstream of the nozzle exit. This interaction can cause the noise generated by twin jets to be louder than an equivalent single jet under certain operating conditions. The noise of all jets is a health concern for communities near airports and personnel on aircraft carrier decks, but twin jets are of particular concern due to their increased noise levels. Additionally, the coupling of twin jets can cause strong near field pressure fluctuations that have the potential to damage airframes of military aircraft through sonic fatigue as occurred on both the F-15 and the B-1A during their development. Previous research into twin jets has studied a variety of twin-jet nozzle configurations. This study focuses on round converging-diverging nozzles with a center-to-center spacing of 2.0 nozzle diameters---close to that found in military aircraft. Localized arc filament plasma actuators (LAFPAs) are perturbation-based flow control devices that excite jet instabilities with small energy input and alter their characteristics. They have been used to control the noise generated by single jets. These actuators can alter the dominant mode (the shape of the large-scale turbulent structures) present in the jet plume by creating small thermal perturbations near the nozzle exit. LAFPAs were applied to test their efficacy at altering the dominant mode and as a diagnostic tool to study the behavior of the different modes in the twin-jet. Regardless of the naturally dominant mode in the twin-jet at a given operating condition, the LAFPAs can change the mode present to match the excited mode. This includes eliminating the strong coupling at modes and conditions where it normally occurs. Far field and near field acoustic measurements show that when the flapping mode is dominant in the twin-jet, the resulting coupling causes higher noise and near field pressure fluctuations than other modes. Axisymmetric and helical modes synchronize the large-scale turbulent structures so that they are generated simultaneously, but do not amplify one another to create the higher noise and pressure fluctuations of the flapping mode. The identities of these modes were confirmed using phase-averaged schlieren imaging which reveals the shape of the different modes in the twin-jet, both naturally occurring and excited using LAFPAs Both schlieren images and screech tone frequencies were captured for a twin-jet at elevated temperatures. These images revealed that the flapping mode disappears in the twin-jet as the temperature increases and is replaced by the helical mode. A theoretical model in the literature designed to predict the screech tone frequency in single jets was applied to the twin-jet. This model accurately predicted the tones present in the twin-jet and was able to predict a shift from one frequency to another when a mode shifts from the flapping mode to the helical mode due to increased jet temperature. The screech tones of the twin-jet closely match the feedback loop of the single jet.
Mo Samimy (Advisor)
Igor Adamovich (Committee Member)
Jeffrey Bons (Committee Member)
Datta Gaitonde (Committee Member)
Brenda Henderson (Committee Member)
127 p.
Acoustics; Aerospace Engineering; Fluid Dynamics
Twin-jet; Jet Noise; Jet Screech; Flow Control; Screech Modes; LAFPA; Localized Arc Filament Plasma Actuator; Acoustics

Recommended Citations

Citations

  • Cluts, J. D. (2018). Understanding and Control of Coupling of Supersonic Twin Jets Using Localized Arc Filament Plasma Actuators [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu152555508900912

    APA Style (7th edition)

  • Cluts, Jordan. Understanding and Control of Coupling of Supersonic Twin Jets Using Localized Arc Filament Plasma Actuators. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu152555508900912.

    MLA Style (8th edition)

  • Cluts, Jordan. "Understanding and Control of Coupling of Supersonic Twin Jets Using Localized Arc Filament Plasma Actuators." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu152555508900912

    Chicago Manual of Style (17th edition)

osu152555508900912
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This open access ETD is published by The Ohio State University and OhioLINK.