Investigation of the effects of profile shape on the aerodynamic and structural characteristics of thin, two-dimensional airfoils at supersonic speeds Page: 3 of 61
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NACA RM A54BO8a 0143344
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
RESEARCH MEMORANDUM
INVESTIGATION OF TE EFFECTS OF PROFILE SHAPE ON THE
AERODYNAMIC AND STRUCTURAL CHARACTERISTICS OF
THINX TWO-DIMENSIONAL AIRFOILS
AT SUPERSONIC SPEEDS
By Elliott D. Katzen, Donald M. Kuehn,
and William A. Hill, Jr.
SUMMARY
In order to determine the effects of thickness, trailing-edge blunt-
ness, boattailing, and forward profile on the aerodynamic characteristics
of thin airfoils, and to provide a check on the available theoretical
methods, 31 airfoils were tested. The airfoils were 2, 4, and 6 percent
thick and were tested at Mach numbers of 1.45 and 1.98 at Reynolds numbers
of 1.0, 2.0, and 3.5 million in a clean condition and at a Reynolds number
of 3.5 million with transition fixed.
The aerodynamic advantage of very thin airfoils was shown by a rapid
increase of maximum lift-drag ratio (e.g., from 5.8 to 14.4 at M = 1.45
and a Reynolds number of 1.0 million) as the airfoil thickness ratio was
decreased from 6 to 2 percent. Increased trailing-edge bluntness of the
6-percent-thick airfoils caused a small decrease in maximum lift-drag
ratio but a large increase in section modulus; for the 2--percent-thick
airfoils, increased bluntness caused a large decrease in maximum lift-
drag ratio with only a small increase in section modulus. This has spe-
cial significance for propeller designers in that it indicates that
propellers whose blade elements operate at supersonic speeds should have
blunt trailing edges for the thick sections near the hub and relatively
sharp trailing edges for the thin sections near the tip. The importance
of maintaining a laminar boundary layer on very thin airfoils was shown
by the decrease of maximum lift-drag ratio from 14.4 to 11.9 caused by
fixing transition at the leading edge of a sharp-trailing-edge 2-percent-
thick airfoil at a Mach number of 1.45. The effects of the different
forward profiles and changes in boattailing were generally such that a
reduction in profile area reduced the minimum drag coefficient. The
center of pressure of the airfoils moved forward with increased thickness
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Katzen, Elliott D.; Kuehn, Donald M. & Hill, William A., Jr. Investigation of the effects of profile shape on the aerodynamic and structural characteristics of thin, two-dimensional airfoils at supersonic speeds, report, May 7, 1954; (https://digital.library.unt.edu/ark:/67531/metadc60484/m1/3/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.