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Wind-Tunnel Investigation of the Horizontal Motion of a Wing Near the GroundBy the method of images the horizontal steady motion of a wing at small heights above the ground was investigated in the wind tunnel, A rectangular wing with Clark Y-H profile was tested with and without flaps. The distance from the trailing edge of the wing to the ground was varied within the limits 0.75 less than or = s/c less than or = 0.25. Measurements were made of the lift, the drag, the pitching moment, and the pressure distribution at one section. For a wing without flaps and one with flaps a considereble decrease in the lift force and a,drop in the drag was obtained at angles of attack below stalling. The flow separation near the ground occurs at smaller angles of attack than is the case for a great height above the ground. At horizontal steady flight for practical values of the height above the ground the maximum lift coefficient for the wing without flaps changes little, but markedly decreases for the wing with flaps. Analysis of these phenomena involves the investigation of the pressure distribution. The pressure distribution curves showed that the changes occurring near the ground are not equivalent to a change in the angle of attack. At the lower surface of the section a very strong increase in the pressures is observed. The pressure changes on the upper surface at angles of attack below stalling are insignificant and lead mainly to an increase in the unfavorable pressure gradient, resulting in the earlier occurrence of separation. For a wing with flaps at large angles of attack for distances from the trailing edge of the flap to the ground less than 0.5 chord, the flow between the wing end the ground is retarded so greatly that the pressure coefficient at the lower surface of the section is very near its limiting value (P = 1), and any further possibility of increase in the pressure is very small. In the application an approximate computation procedure is given of the change of certain aerodynamic characteristics for horizontal steady flight near the ground.
Document ID
20050019459
Acquisition Source
Langley Research Center
Document Type
Other - NACA Technical Memorandum
Authors
Serebrisky, Y. M. (Tsentralni Aerogidrodinamicheskii Inst. Moscow, USSR)
Biachuev, S. A. (Tsentralni Aerogidrodinamicheskii Inst. Moscow, USSR)
Date Acquired
August 22, 2013
Publication Date
September 1, 1946
Publication Information
Publication: Report of the Central Aero-Hydrodynamical Institute, Moscow
Subject Category
Aircraft Design, Testing And Performance
Report/Patent Number
NACA-TM-1095
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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