Experimental Investigation of the Flowfield of a Symmetrical Airfoil in Ground Effect

In the present paper, results from an experimental investigation of aerodynamic ground effect on two airfoils are presented. The flow characteristics over a symmetrical airfoil (NACA 0015) and a cambered airfoil (NACA 4415) were studied in a low speed wind tunnel. Experiments were carried out by varying the angle of attack from 0° to 10° and ground clearance from zero to one chord length. Pressure distribution on the surface of the airfoil was obtained with the help of pressure tappings. Mean velocity distributions were obtained over the surface of the airfoil. Profiles of mean velocity and turbulence intensity were obtained in the wake region at 0.5 and 1.0 chord length downstream of the trailing edge. It is found that pressure increases on the lower surface as the ground is approached. The flow accelerates over the airfoil, and a considerably higher mean velocity is observed near the suction peak location. For the symmetrical airfoil, the mean velocity over the surface was found to increase by nearly 30%, while for the cambered airfoil, an increase of nearly 60% was recorded for an angle of attack of 7.5°. The flow was found to separate almost near the trailing edge for angles of attack upto 10°, resulting in a thinner wake region and lower turbulence intensities for the symmetrical airfoil; while for the cambered airfoil, an early separation for an angle of attack of 10° was observed. Measurements in the wake region showed a defect in mean velocity profile at the corresponding values of ground clearance. For lower angles of attack, turbulence levels were higher in the wake region for the symmetrical airfoil, while for an angle of attack of 10°, very large defect in velocity was observed for the cambered airfoil model and the minimum velocity reduced to 20% of the freestream velocity.

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Experimental investigation of the ground effect on the flow around some two-dimensional bluff bodies with moving-belt technique

Journal of Wind Engineering and Industrial Aerodynamics ◽

10.1016/s0167-6105(98)00046-4 ◽

1998 ◽

Vol 74-76 ◽

pp. 511-519 ◽

Cited By ~ 14

Author(s):

M.S. Kim ◽

D. Geropp

Keyword(s):

Experimental Investigation ◽

Ground Effect ◽

Bluff Bodies ◽

Two Dimensional

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Experimental Investigation of Various Winglet Designs for a Wing in Ground Effect

22nd Applied Aerodynamics Conference and Exhibit ◽

10.2514/6.2004-4720 ◽

2004 ◽

Cited By ~ 3

Author(s):

David Ogurek ◽

Jeff Ashworth

Keyword(s):

Experimental Investigation ◽

Ground Effect ◽

Wing In Ground Effect

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Experimental investigation of the aerodynamic characteristics of generic fan-in-wing configurations

The Aeronautical Journal ◽

10.1017/s0001924000002736 ◽

2009 ◽

Vol 113 (1139) ◽

pp. 9-20 ◽

Cited By ~ 5

Author(s):

N. Thouault ◽

C. Breitsamter ◽

N. A. Adams ◽

C. Gologan ◽

J. Seifert

Keyword(s):

Experimental Investigation ◽

Lift Coefficient ◽

Ground Effect ◽

Aerodynamic Characteristics ◽

Flow Visualisation ◽

Force Measurements ◽

Tunnel Model ◽

Image Velocimetry ◽

Flow Circulation ◽

Stereo Particle Image Velocimetry

Abstract This experimental investigation concentrates on the aerodynamic behaviour of a generic fan-in-wing configuration. The effects of the fan(s) on the flow circulation in a short take-off and landing or a transition flight condition without ground effect are evaluated. A wind-tunnel model has been constructed and tested to quantify the aerodynamic effects. Force measurements, surface pressure measurements, stereo-particle image velocimetry and wool tufts flow visualisation are performed. Different fan-in-wing configurations with the fans rotating in the wing plane, one fan either at the rear or front part of the wing and two fans are compared to the closed wing without fans set as reference. A fan placed near the trailing edge improves significantly the lift coefficient due to a jet flap effect on the wing lower side combined with enhanced suction on the wing upper side. The jet exiting the nozzle rolls up in a counter rotating pair of vortices affecting significantly the wing behaviour. This experimental investigation constitutes also a useful database for further CFD comparison.

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