Two-dimensional chord-wise load distributions at transonic speeds Page: 2 of 43
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SNACA RM L5.107 3 1176 01436 4567 9
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
TWO-DIMENSIONAL CHORDWISE LOAD DISTRIBUTIONS
AT TRANSONIC SPEEDS
By Walter F. Lindsey and Richard S. Dick
From tests on the NACA 16-009 airfoil and on eight airfoils of the
'NACA 6A series, results are presented to show that the chordwise loading
due to lift at a Mach number of 1.0 is insignificantly affected by thick-
ness distribution within the range of airfoil shapes presented and only
slightly affected by thickness. In addition, a method of estimating the
pressure distributions for lifting symmetrical airfoils at a Mach number
of 1.0 which seems applicable to profiles of the type considered herein
is presented. The possibility is indicated that the effects of camber,
thickness, and angle of attack may be treated separately at a Mach number
of 1.0 as they are at low subsonic Mach numbers and at supersonic Mach
The chordwise loadings on airfoils in incompressible two-dimensional
flow can be predicted by available theoretical means to a high degree of
accuracy at moderate angles of attack and lift coefficients where the
effects of viscosity are small (references 1 and 2). The changes in
loading due to the effects of compressibility can be estimated by simple
velocity-correction formulas such as those derived in papers by Prandtl
and Glauert, Karmen and Tsien, Kaplan and Garrick, and others. Generally,
as a result of assumptions used in the derivations, the velocity-correction
formulas are limited in application to purely subsonic or subcritical
flow. Comparisons at subcritical Mach numbers between experimentally
determined loadings and the loadings derived theoretically, with the
effect of compressibility estimated by velocity-correction formulas, show
agreement within sufficient accuracy for usual engineering purposes.
At supercritical or low transonic Mach numbers, the occurrence of
both subsonic and supersonic regions of flow, together with shocks and
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Lindsey, Walter F. & Dick, Richard S. Two-dimensional chord-wise load distributions at transonic speeds, report, February 18, 1952; (digital.library.unt.edu/ark:/67531/metadc58975/m1/2/: accessed January 16, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.