Tests of Six Symmetrical Airfoils in the Variable Density Wind Tunnel Page: 3 of 27
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2 N.A.0.A. Techh'ical Note No. 385.,
fits of a systematic investigation of airfoil profiles at
large values of the Reynolds Number are so self-evident
that it is .hardly necessary to point them out. Not only
do the restits of such investigations greatly facilitate
the choice of the most satisfactory airfoil for a given
application but, because the results may be correlated to
indicate the trends of the aerodynamic characteristics
with changes of shape, they may point the way to the de-
sign of new shapes having better characteristics.
Airfoil profiles may be considered as made up of
certain profile thickness forms disposed about certain
mean camber lines. The major shape variables then be-
come two: the thickness form and the mean camber line
form. The thickness is of particular importance from a
structural standpoint. On th6 other hand, the form of the
mean camber line determines almost independently some of
the most important aerodynamic properties of the airfoil
section, e.g., the pitching moment characteristics and the
angle of zero lift.
The related airfoil profileswere obtained for this
investigation by changing systematically these shape vari-
ables. A single basic thickness variation was chosen for
the first group of airfoils. Sections having a different
maximum thickness were obtained by the application of a
factor to all the basic ordinates. The following ratios
of maximum thickness-to-chord were chosen: 0.06, 0.09,
0.12, 0.15, 0.18, and 0.21. The cambered profiles were
then obtained by combining these thickness forms with dif-
ferent mean camber lines. Since this report does not deal
with the cambered airfoils, it will be sufficient to state
that the various mean camber line forms are obtained by
varying the maximum camber and by varying the distance
from the loading edge to the position of the maximum cam-
ber. The airfoils so produced are designated by a number
of four digits; the f-irst indicates the maximum mean cam-
ber; the second, the position 6f the maximum mean camber;
and the last two, the maximum thickness. Thus the N.A.C.A.
2315 airfoil has a maximum mean camber of 2 per cent of
the chord at a position 0.3 of the chord from the leading
edge, and a maximum thickness of 15 per cent of the chord;
the N.A.C.A. 0012 is a symmetrical airfoil having a maxi-
mum thickness of 12 per cent of the chord.
This note presents in preliminary form the results of
the tests of the first group of six airfoils. These tests
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Jacobs, Eastman N. Tests of Six Symmetrical Airfoils in the Variable Density Wind Tunnel, report, July 1931; (https://digital.library.unt.edu/ark:/67531/metadc54117/m1/3/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.