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Research Papers: Flows in Complex Systems

Aerodynamics of Large-Scale Vortex Generator in Ground Effect

[+] Author and Article Information
Joseph Katz

Department of Aerospace Engineering, San Diego State University, San Diego, CA 92119

Frederic Morey1

 San Diego State University, San Diego, CA 92119

1

Visiting Student from Institut Français de Mécanique Avancée (IFMA).

J. Fluids Eng 130(7), 071101 (Jun 25, 2008) (6 pages) doi:10.1115/1.2948361 History: Received February 26, 2007; Revised January 15, 2008; Published June 25, 2008

The aerodynamic performance of several vortex generators (VGs) of the type used on the lower surface of race cars was tested in a low-speed wind tunnel. In this particular application, the vortices emanating from the VGs create a suction force between the vehicle and the ground, thereby improving tire adhesion and the vehicle’s cornering∕traction performance. Since the size of these devices is much larger than the local boundary layer thickness, they are termed “large scale” in this study. Results of the wind tunnel tests indicate that the aerodynamic adhesion forces increase with reduced ground clearance while the corresponding drag increase is much smaller. The parameters investigated in this study are the VG length, shape, and the effect of incidence angle. Amongst the various shapes tested, the traditional rectangular VG created the largest forces while the simple triangular design was the most efficient in terms of the incremental lift to drag ratio.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic description of “large-” and “small-scale” VGs

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Figure 2

Typical application of large-scale VGs on the lower surface of an open-wheel race car

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Figure 3

The flat-plate model with the VGs mounted upside down at the center of the test section. Ground clearance variations were simulated by moving the thin ground plane down, toward the stationary model. Dimensions are in inches (meters).

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Figure 4

The wind tunnel model consists of a horizontally placed flat plate with four VGs. Dimensions are in inches (meters) and the spacing d was kept constant at d=2in.(0.05m) throughout the whole test. Note the schematic description of the vortices emanating from the left side.

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Figure 5

Variation of the lift coefficient versus ground clearance h∕c and comparison with previously published data (rectangular VGs at β=20deg). Note that uncertainty in CL is represented by the vertical error bars (which are hardly visible)!

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Figure 6

Variation of the drag coefficient versus ground clearance h∕c and comparison with previously published data (rectangular VGs at β=20deg). Note that uncertainty in CD is represented by the vertical error bars!

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Figure 7

Dimensions of the rectangular∕triangular long∕short VGs. Dimensions in inches (meters).

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Figure 8

Variation of the lift coefficient versus ground clearance h∕c for rectangular and triangular VGs, and the effect of larger incidence, β (β=20∕20 means all VGs are at 20deg, and β=20∕30 stands for outer VGs at β=30deg)

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Figure 9

Variation of the drag coefficient versus ground clearance h∕c for rectangular and triangular VGs, and the effect of larger incidence, β (β=20∕20 means all VGs are at 20deg, and β=20∕30 stands for outer VGs at β=30deg)

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Figure 10

Variation of the lift coefficient versus ground clearance h∕c for short rectangular and triangular VGs, and the effect of larger incidence, β (β=20∕20 means all VGs are at 20deg, and β=20∕30 stands for outer VGs at β=30deg)

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Figure 11

Variation of the drag coefficient versus ground clearance h∕c for short rectangular and triangular VGs, and the effect of larger incidence, β (β=20∕20 means all VGs are at 20deg, and β=20∕30 stands for outer VGs at β=30deg)

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Figure 12

Lift coefficient comparison for short∕long and rectangular∕triangular VGs at β=20∕20

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Figure 13

Additional VG shapes evaluated during this test. Note that only the “short” versions were tested (e.g., length=3in. and height is 1in. or 0.08×0.026m2)

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Figure 14

Variation of the lift coefficient versus ground clearance h∕c for several short VGs (β=20∕20 means all VGs are at 20deg)

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Figure 15

Variation of the drag coefficient versus ground clearance h∕c for several short VGs (β=20∕20 means all VGs are at 20deg)

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Figure 16

Variation of the lift coefficient versus ground clearance h∕c for several short VGs (β=20∕30 stands for inner VGs at β=20deg, and outer VGs at β=30deg)

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Figure 17

Variation of the drag coefficient versus ground clearance h∕c for several short VGs (β=20∕30 stands for inner VGs at β=20deg, and outer VGs at β=30deg)

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Figure 18

Variation of incremental lift to drag ratio versus ground clearance h∕c for the four most efficient VGs (β=20∕20deg)

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