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TECHNICAL PAPERS

Aspects of Shear Layer Unsteadiness in a Three-Dimensional Supersonic Wake

[+] Author and Article Information
Alan L. Kastengren1

Energy Systems Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439akastengren@anl.gov

J. Craig Dutton2

Mechanical & Aerospace Engineering Department,  The University of Texas at Arlington, 500 West First Street, Arlington, TX 76019

1

Postdoctoral Research Scientist.

2

Professor and Chair.

J. Fluids Eng 127(6), 1085-1094 (Jul 05, 2005) (10 pages) doi:10.1115/1.2062727 History: Received August 02, 2004; Revised July 05, 2005

The near wake of a blunt-base cylinder at 10° angle-of-attack to a Mach 2.46 free-stream flow is visualized at several locations to study unsteady aspects of its structure. In both side-view and end-view images, the shear layer flapping grows monotonically as the shear layer develops, similar to the trends seen in a corresponding axisymmetric supersonic base flow. The interface convolution, a measure of the tortuousness of the shear layer, peaks for side-view and end-view images during recompression. The high convolution for a septum of fluid seen in the middle of the wake indicates that the septum actively entrains fluid from the recirculation region, which helps to explain the low base pressure for this wake compared to that for a corresponding axisymmetric wake.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

Example global end-view Mie scattering images at various axial locations

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Figure 2

Schematic of the test afterbody with added nomenclature

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Figure 3

Schematic of side-view imaging locations

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Figure 4

Flapping processing example: (a) processed image; (b) average intensity profile, with shear layer inner and outer edges, as well as position for flapping calculations

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Figure 5

Convolution processing example, lateral plane, position A; (a) processed image; (b) threshold image; (c) image showing all pixels within 4pixels of the interface

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Figure 6

Example side-view Mie scattering images

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Figure 7

Trends in side-view image shear layer flapping and thickness. (a) Standard deviation in the shear layer position (flapping), normalized by local shear layer thickness; (b) average shear layer thickness normalized by base radius

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Figure 8

Example side-view image shape factor histograms: (a) leeward, position G; (b) windward, position J

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Figure 9

(a) Trends in the average shape factor for the symmetry plane, lateral plane, and axisymmetric base flow. Uncertainty bars show one standard deviation on either side of the mean. (b) Intermittency in the occurrence of supersonic fluid, as a function of transverse position for the developing shear layer.

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Figure 10

Example end-view images, showing the unsteadiness of the wake core area (a), (b) x∕R=1.6; (c), (d) x∕R=2.0

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Figure 11

Trends in global end-view wake core area: (a) average wake core area, normalized by base area; (b) wake core area standard deviation normalized by base area and local wake core area

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Figure 12

Centroid displacement plots: (a) distribution of wake core centroid positions for global end view, x∕R=1.6; (b) standard deviation of the wake core centroid displacement from the mean position in the lateral and symmetry planes for the global end views

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Figure 13

Example end-view shape factor histograms: (a) x∕R=0.6; (b) x∕R=1.2

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Figure 14

End-view shape factor trends. Uncertainty bars denote one standard deviation on either side of the measured mean value.

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