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Turbulence Mechanisms in a Supersonic Rectangular Multistream Jet with an Aft-Deck

Stack, Cory M.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1560352886647369

Abstract Details

2019, Doctor of Philosophy, Ohio State University, Aero/Astro Engineering.
Over the last 80 years, high-performance military aircraft have relied on increasingly sophisticated jet engine technologies to enable performance and fulfill mission requirements. To satisfy these engineering demands, several reliable technologies are often combined into one composite engine configuration. Although the behavior of these composite configurations is fairly well known at the engineering level, their rapid advancement is constrained by a lack of knowledge of the fundamental fluid dynamics, particularly the dominant unsteady turbulent mechanisms. This has in turn limited the effectiveness of design tools. Nozzle designs are also becoming more exotic as they conform to increasingly complicated emerging engine architectures, such as variable-cycle engines, whose flowfields are inherently complex due to the multitude of compressible shear layers that evolve in the presence of pressure gradients. The flowfield complexity is further exacerbated for supersonic flight where the engine is integrated into the airframe, and the turbulent, high-speed, shock-containing exhaust interacts with proximal surfaces of the aircraft. In this work, high-fidelity Large-Eddy Simulations are employed to examine the fluid dynamics of a nozzle configuration relevant to emerging airframe-integrated variable-cycle engine architectures. The nozzle comprises two rectangular streams; the upper (core) Mach 1.6 single-sided expansion ramp stream is separated by a splitter plate from a sonic, lower (deck) stream issuing in a wall-jet arrangement over an aft-deck. Simulation results are validated with available experimental measurements performed at Syracuse University, and are probed using a variety of techniques to characterize the composite flowfield. Even at design conditions, the asymmetry induced by the single-sided expansion and the aft-deck results in a highly three-dimensional shock train, whose interactions with the bounding shear layers influence numerous aspects of the flowfield, including local separation of boundary layers developing on the expansion ramp and aft-deck, as well as the downstream plume development. During this downstream development, three-dimensional features become prominent, including corner effects and asymmetric entrainment. The unsteady flowfield exhibits numerous complicated phenomena, including shock train and shear layer unsteadiness. Notably, the signature of a shedding instability initiated at the trailing edge of the splitter plate that separates the two streams is shown to be directly related to the primary tone observed throughout the computational and experimental domains. In conjunction with the unsteadiness of the shock train, the unsteadiness associated with the various shear layers are shown to be the predominant sources of unsteady loading on the aft-deck. Numerical experiments are performed on a simplified configuration to examine the effect of the splitter plate thickness on the evolution of the shear layer between the two streams. In particular, as the splitter plate thickness is reduced, the nature of the dominant instability in the near-wake region is shown to transition from an absolute instability associated with shedding mechanisms, to a convective instability associated with non-shedding mechanisms. As this transition occurs, the amplitude of the turbulent fluctuations decrease, and the most energetic structures become less efficient at mixing the two streams, while also exhibiting a reduced signature throughout the domain. The analyses within this disseration provide valuable information on the fundamental fluid dynamics in emerging airframe-integrated nozzle designs, particularly regarding the dominant unsteady phenomena, and inspire future work in controlling these processes through active or passive methods.
Datta Gaitonde, PhD (Advisor)
Jen-Ping Chen, PhD (Committee Member)
Mei Zhuang, PhD (Committee Member)
231 p.
Aerospace Engineering
supersonic, multistream, airframe-integrated, jet, nozzle, aft-deck, rectangular, unsteady, Large-Eddy Simulations

Recommended Citations

Citations

  • Stack, C. M. (2019). Turbulence Mechanisms in a Supersonic Rectangular Multistream Jet with an Aft-Deck [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1560352886647369

    APA Style (7th edition)

  • Stack, Cory. Turbulence Mechanisms in a Supersonic Rectangular Multistream Jet with an Aft-Deck. 2019. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1560352886647369.

    MLA Style (8th edition)

  • Stack, Cory. "Turbulence Mechanisms in a Supersonic Rectangular Multistream Jet with an Aft-Deck." Doctoral dissertation, Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1560352886647369

    Chicago Manual of Style (17th edition)

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