High-Speed Measurements on a Swept-Back Wing (Sweepback Angle phi = 35 Deg) Page: 4 of 34
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NACA TM No. 1102
normal position of maximum thickness. The Reynolds number
based upon the mean chord of the swept-back wing. was ......
.yaried- from.Re -=- -i3-- x 106 to- 2.6 7x .106, which is higher
than the Reynolds number at which transition from the
laminar to turbulent boundary layer takes place on a flat
plate (fig. I).
The longitudinal moments of the swept-back wing were,
as usual, based upon the geometric mean chord Z, = fLy2dy
and were referred to a moment axis which corresponds to
the 1/-line of a rectangular wing. In the case of the
.swept-back wing it corresponds to the neutral-point position
of the so defined 1/-line of the rectangular wing with
a rectangular lift .distribution along the span. The
location of the moment axis defined in that manner is at
a distance AxE = 243mm = 1.19Zm behind the point of the
At various angles of attack and stream velocities,
three-comionent force measurements were conducted at
various Mach numbers as well as were measurements of total-
head loss behind the wing, and optical observations using
the schlieren method.
II. LIFT, MONTT AND DRAG OF THE SWEPT-BACK WING
The curves of lift coefficient ca as a function of
angle of attack are shown in figure 2 for several Mach
numbers. While at the small Mach number M = 0..30
and 0.55 the curves are straight up to the highest measured
angle of attack a = 8o, there occurs in the regions of
higher lift coefficients, at higher Mach numbers, a
continuously increasing curvature which decreases the slope
of the lift curve. This curvature begins at the Mach
number M = 0.70 .and is slightly pronounced at lift
coefficients of about ca = 0.6, but is stronger at higher
Mach numbers where simultaneously a decrease is brought
about in the lift coefficient. at- which. bending occuts ; ...
for example, the bending of the lift curve at the Mach
number M = 0.87 begins at lift coefficients as low as
about ca = 0.5. This loss of lift indicated by the bending
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Göthert, B. High-Speed Measurements on a Swept-Back Wing (Sweepback Angle phi = 35 Deg), report, March 1947; (https://digital.library.unt.edu/ark:/67531/metadc64276/m1/4/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.