An experimental investigation of the two-stream, supersonic, near wake flowfield behind a finite-thickness base
Amatucci, Vincent Andrew
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Permalink
https://hdl.handle.net/2142/20306
Description
Title
An experimental investigation of the two-stream, supersonic, near wake flowfield behind a finite-thickness base
Author(s)
Amatucci, Vincent Andrew
Issue Date
1990
Doctoral Committee Chair(s)
Addy, A.L.
Dutton, J. Craig
Department of Study
Mechanical Science and Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, General
Engineering, Aerospace
Engineering, Mechanical
Language
eng
Abstract
The interaction region generated by separation of two supersonic streams past a finite-thickness base occurs in high-speed flight and characterizes the aft-end flowfield of powered missiles in supersonic flight. In order to examine fundamental mechanisms and interactions ongoing in this near-wake region, an experimental investigation was conducted to obtain mean and turbulence data in a wind tunnel. The test section produced a Mach 2.56 upper stream and a Mach 2.05 lower stream which both undergo geometric separation past a finite-thickness plate and experience strong expansion and mixing processes before eventual recompression, reattachment, and redevelopment of the wake flow. This near-wake flowfield is characterized by strong velocity and density gradients, viscous interactions, high turbulence levels, and energetic recirculation. The data was obtained using Schlieren photographs, stagnation and static pressure measurements, and laser Doppler velocimeter (LDV) measurements. The primary tool was a two-color, two-component LDV system. The data was analyzed in component approach consistent with the Chapman-Korst model.
The interactions within the wind tunnel correctly modeled the missile aft-end flowfield. The flow regions included Prandtl-Meyer expansions, shear layer mixing and recompression, recirculation, and wake redevelopment. The shear layer mixing regions were characterized by initially constant-pressure mixing and by evolution of velocity profiles from truncated boundary layer forms to wake-like profiles farther downstream. While self-similarity of mean velocity data was achieved, the turbulence field did not reach that state before recompression began. The separated flow region was characterized by vigorous recirculation, negative velocities reaching 23 percent of freestream values, and strong interaction with low-velocity regions of both shear layers. Turbulence intensities, Reynolds stresses, and triple products increased in the latter portions of both shear layers and in the recompression/reattachment region, indicating the presence of large-scale structures. The turbulence field near reattachment was strongly anisotropic, and transverse diffusion of turbulence energy agreed with existing correlations. Recovery of the mean velocity field in the redeveloping wake occurred quickly, while the turbulence field remained perturbed. These data are valuable for use in validation and improvement of computational schemes.
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