The effects at transonic speeds of thickening the trailing edge of a wing with a 4-percent-thick circular-arc airfoil Page: 3 of 44
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2 ' NACA RM A5lJ11
INTRODUCTION
At supersonic Mach numbers, the airfoil section having minimum
drag for a prescribed structural strength or stiffness may have a blunt
trailing edge, as has been shown through theoretical considerations by
Chapman in reference 1. The two-dimensional characteristics of such
airfoils of moderate thickness as compared with a more conventional
airfoil having a sharp trailing edge have been investigated experimen-
tally at subsonic Mach numbers (reference 2). Although the results of
that investigation indicated higher minimum drag for the blunt-trailing--
edge airfoil, gains in maximum lift were observed and the lift-curve
slope increased at Mach numbers where the lift-curve slope decreased
for the sharp-trailing-edge airfoil. Thus, it would seem that blunt-
trailing-edge airfoils may be of some practical value at both subsonic
and supersonic Mach numbers.
Thea present investigation was undertaken to evaluate the effect
of an increase in trailing-edge thickness on the aerodynamic character-
istics of a thin three-dimensional wing in the transonic Mach number
range. For this investigation, the thick trailing-edge airfoils were
formed by building up the trailing edge to the desired thickness and
then fairing to the original airfoil by straight lines. The forward
portion of the circular-arc section remained intact and the resulting
airfoil was not one of the optimum sections derived in reference 1.
NOTATION
CD drag coefficient t~~~e semis pan drag)
CL lift coefficient (twice semispan lift)
Cm pitching-moment coefficient, referred to 0.25 c
(twice semispan pitching moment )
E amplitude of total-pressure ,fluctuation, pounds per
square foot
L
r- lift-drag ratio
_.';.Wr
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Cleary, Joseph W. & Stevens, George L. The effects at transonic speeds of thickening the trailing edge of a wing with a 4-percent-thick circular-arc airfoil, report, December 11, 1951; (https://digital.library.unt.edu/ark:/67531/metadc59200/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.