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TECHNICAL PAPERS

A Quantitative Comparison of Delta Wing Vortices in the Near-Wake For Incompressible and Supersonic Free Streams

[+] Author and Article Information
Frank Y. Wang

 USDOT John A. Volpe National Transportation Systems Center, Cambridge MA 02142

Ivana M. Milanovic

 University of Hartford, Department of Mechanical Engineering, West Hartford CT 06117

Khairul B. Zaman, Louis A. Povinelli

 NASA John H. Glenn Research Center at Lewis Field, Cleveland OH 44135

J. Fluids Eng 127(6), 1071-1084 (Jul 12, 2005) (14 pages) doi:10.1115/1.2060732 History: Received December 02, 2004; Revised July 12, 2005

When requiring quantitative data on delta wing vortices for design purposes, low-speed results have often been extrapolated to configurations intended for supersonic operation. This practice stems from a lack of database in high-speed flows due to measurement difficulties. In the present paper an attempt is made to examine this practice by comparing data from an incompressible flow experiment designed specifically to correspond to an earlier experiment in supersonic flows. The comparison is made for a 75° sweptback delta wing at angles of attack of 7° and 12°. For the incompressible flow, detailed flow-field properties including vorticity and turbulence characteristics are obtained by hot-wire and pressure probe surveys. The results are compared, wherever possible, with available data from the earlier Mach 2.49 experiment. The results indicate that quantitative similarities exist in the distributions of total pressure and swirl velocities. Qualitative similarities also exist in other properties, however, many differences are observed. The vortex core is smaller and rounded at low speed. At high speed, it is elongated in the spanwise direction near the trailing edge but goes through “axis switching” within a short distance downstream. The vortex is located farther outboard, i.e., the spacing between the two legs of the vortex pair is larger, at low speed. The axial velocity distribution within the core is significantly different in the two flow regimes. A “jet-like” profile, observed at low speed, either disappears or becomes “wake-like” at high speed. The axial velocity characteristics are examined in the light of an analytical model.

Copyright © 2005 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Top-view schematic of the planform and the illustration of coordinate notations

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Figure 2

Low-speed vortex wake at α=12°; contour labels indicate total pressure loss coefficient (P0−P0,∞)∕q, at the following locations: (a) (x∕c=0; x∕s=0), (b) (x∕c=0.06; x∕s=0.22), (c) (x∕c=0.13; x∕s=0.49), (d) (x∕c=0.25; x∕s=0.93), (e) (x∕c=0.5; x∕s=1.87), (f) (x∕c=0.64; x∕s=2.39)

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Figure 3

Low-speed vortex wake at α=12°; contour labels indicate turbulence intensity, u′∕u∞, at the following locations: (a) (x∕c=0; x∕s=0), (b) (x∕c=0.06; x∕s=0.22), (c) (x∕c=0.13; x∕s=0.49), (d) (x∕c=0.25; x∕s=0.93), (e) (x∕c=0.5; x∕s=1.87), (f) (x∕c=0.64; x∕s=2.39)

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Figure 4

Low-speed vortex wake at α=12°; contour labels indicate normalized streamwise vorticity, ωxc∕u∞, at the following locations: (a) (x∕c=0; x∕s=0), (b) (x∕c=0.06; x∕s=0.22), (c) (x∕c=0.13; x∕s=0.49), (d) (x∕c=0.25; x∕s=0.93), (e) (x∕c=0.5; x∕s=1.87), (f) ( x∕c=0.64; x∕s=2.39)

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Figure 5

Low-speed vortex wake at α=12° contour labels indicate normalized total velocity, (u2+v2+w2)1∕2∕u∞, at the following locations: (a) (x∕c=0; x∕s=0), (b) x∕c=0.06; x∕s=0.22, (c) (x∕c=0.13; x∕s=0.49), (d) (x∕c=0.25; x∕s=0.93), (e), x∕c=0.5; x∕s=1.87), (f) x∕c=0.64; x∕s=2.39)

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Figure 6

Evolution of minimum and maximum values of various properties of the vortex core, normalized by respective values at the trailing edge

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Figure 7

A comparison of transverse profiles at the trailing edge; ◻ α=7° ▵ α=12°

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Figure 8

The same as in Fig. 7

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Figure 9

The same as in Fig. 7

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Figure 10

A comparison of spanwise profiles at the trailing edge; ◻ α=7°, ▵ α=12°

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Figure 11

The same as in Fig. 1

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Figure 12

The same as in Fig. 1

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Figure 13

A comparison of transverse profiles at half-chord downstream; ◻ α=7°, ▵ α=12°

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Figure 14

The same as in Fig. 1

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Figure 15

The same as in Fig. 1

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Figure 16

A comparison of spanwise profiles at half-chord downstream; ◻ α=7°, ▵ α=12°

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Figure 17

The same as in Fig. 1

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Figure 18

The same as in Fig. 1

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Figure 19

Near-wake vortex core trajectories from low-speed and supersonic experiments. Cited references are (MK) Milanovic and Kalkhoran (32) and (LP) Povinelli (49).

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Figure 20

The leeward vortex sweep angle, λ, for both supersonic and low-speed data, illustrating the core locations at the trailing edge. Cited references are (LH) Lee and Ho (46), (MW) Monnerie and Werlé (18), (MK) Milanovic and Kalkhoran (32), and (LP) Povinelli (49).

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Figure 21

Near-wake vortex core shape from low-speed and supersonic experiments. Cited references are (MK) Milanovic and Kalkhoran (32), (LP) Povinelli (49), and (GS) Ganzer and Szodruch (24).

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