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Effects of Compressibility on the Flow Past Thick Airfoil SectionsSix, 3-inch-chord symmetrical airfoil sections having systematic variations in thickness and thickness location were tested at Mach numbers near flight values for propeller-shank sections. The tests, the results of which are presented in the form of schlieren photographs of the flow past each model and pressure-distribution charts for two of the model, were performed to illustrate the effects of compressibility on the flow past thick symmetrical airfoil sections. Representative flow photographs indicated that at Mach numbers approximately 0.05 above the critical Mach number a speed region was reached in which the flow oscillated rapidly and the separation point and the location of the shock wave were unstable. Fixing the transition on both surfaces of the airfoil was effective in reducing these rapid oscillations. The pressure distributions showed that the section normal-force coefficients for thick airfoils were very erratic at subcritical speeds; at supercritical speeds the section normal-force coefficients for the thick airfoils became more regular. Drag coefficients showed that considerable drag decreases can be expected by decreasing the model thickness ratio.
Document ID
20050071700
Acquisition Source
Langley Research Center
Document Type
Other - NACA Research Memorandum
Authors
Daley, Bernard N. (National Advisory Committee for Aeronautics. Langley Aeronautical Lab. Langley Field, VA, United States)
Humphreys, Milton D. (National Advisory Committee for Aeronautics. Langley Aeronautical Lab. Langley Field, VA, United States)
Date Acquired
August 22, 2013
Publication Date
January 30, 1947
Subject Category
Fluid Mechanics And Thermodynamics
Report/Patent Number
NACA-RM-L6J17a
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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