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oai:www.ideals.illinois.edu:2142/19118 2023-07-10 col_2142_5131 col_2142_14787 com_2142_5130 com_2142_9630 com_2142_234

Dutton, J. Craig Smith, Kenneth Michael 2011-05-07T11:57:30Z 2011-05-07T11:57:30Z 10000-01-01 1996 Time-resolved, planar imaging was employed to study the spatial organization of large-scale structures within the shear layers, at reattachment, and in the wake region of a supersonic base flow. Single-pulse side and end views were obtained at several streamwise locations to characterize the evolution and three-dimensionality of the large-scale motions. From statistically significant ensembles, spatial correlation fields were computed to quantify the mean size, eccentricity, and orientation of the large structures. Double-pulse visualizations were also performed to capture an accurate time history of individual structures and to measure the local streamwise convection velocity. Visualizations confirm that large-scale turbulent structures exist at all stations in the shear layers and interact vigorously with the recirculation region. Mach and/or shock waves are frequently seen emanating from within the shear layers which may be indicative of eddy shocklet formation. The embedded turbulent structures are elliptical in shape and usually appear inclined to the mean flow direction. A distinct flattening and tilting in the streamwise direction occurs as the coherent eddies negotiate shear layer formation, recompression, and reattachment processes. Spatial statistics indicate that the structures have a streamwise and spanwise spatial extent on the order of the local shear layer thickness. Examinations of spatial correlation fields suggest that the embedded structures are thoroughly three-dimensional at all streamwise stations. Furthermore, the structures appear to degrade in their spatial organization during the recompression and reattachment processes. Time-correlated images indicate that the individual structures evolve primarily through an elongation and rotation toward the streamwise direction. The structures possess a limited temporal coherence, typically of the order of one eddy roll-over time. Convection velocities near the base are higher than the isentropic prediction, in agreement with previous compressible shear layer studies. During recompression and reattachment, the structures slow considerably, apparently in response to the adverse pressure gradient. Downstream of reattachment, the structures accelerate as the mean flow accelerates. Made available in DSpace on 2011-05-07T11:57:30Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9712439.pdf: 7529350 bytes, checksum: 5ff2c499e47f2d86353bc4541224a47c (MD5) Previous issue date: 1996 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:34:47Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:13:26-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only 9780591199963 AAI9712439 (UMI)AAI9712439 http://hdl.handle.net/2142/19118 eng Copyright 1996 Smith, Kenneth Michael Engineering, Mechanical An experimental investigation of large-scale structures in supersonic reattaching shear flows text Mechanical Science and Engineering Mechanical Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.