Scale-effect tests in a turbulent tunnel of the NACA 65(sub 3)-418, a = 1.0 airfoil section with 0.20-airfoil-chord split flap Page: 5 of 22
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NACA AGR No. L4I22 . ag g
. -_ Tests
The models were mounted vertically in the tunnel
so that the test section was spanned completely except
for a small clearance at each end. The models were rigidly
attached to the balance frame by torque tubes extending
through the tunnel walls. The angle of attack was set
by rotating the torque tubes by means of a calibrated
electric drive. This installation is thought to approxi-
mate closely two-dimensional flow, thus making it possible
to determine the section characteristics of the models
being tested. This setup is described in reference 3.
Each model was tested at dynamic pressures of 1.02,
4.09, 9.21, and 16.37 pounds per square foot, which
correspond to tunnel airspeeds of approximately 20, 40,
60, and 80 miles per hour, respectively. These air-
speeds correspond to test Reynolds numbers of 0.19,
0.37, 0.56, and 0.75 x 10, respectively, for the model
of 1-foot chord and 0.75, 1.50, 2.24, and 2.99 x 10 ,
respectively, for the model of 4-foot chord. The
turbulence factor of the LMAL 7- by 10-foot tunnel is 1.6.
Although the data are presented for various test Reynolds
numbers, the corresponding effective Reynolds numbers can
be obtained by multiplying the test Reynolds numbers by
the turbulence factor. The highest Mach number reached
was 0.10, so that no effect of Mach number on maximum
lift coefficient is thought to be present (reference 4).
At each tunnel airspeed, each model was tested both
as a plain airfoil and wtth the flap attached and
deflected 150, 30, and 60 . The flap deflections were
set by means of templets and were checked after each
test. The flap was sufficiently braced so that no
perceptible deflection occurred under load.
Balance readings were used to measure lift, drag,
and pitching moment, except for the drag of the plain
airfoil. Because of the insensitivity of the tunnel
balance system, particularly at low speeds, the drag of
the plain airfoil was obtained from wake-survey tests.
The angle of attack ranged from a negative angle
through the stall for each test. In most cases,
readings were taken at 20 intervals, with 10 increments
near the stall.
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Tucker, Warren A. & Wallace, Arthur R. Scale-effect tests in a turbulent tunnel of the NACA 65(sub 3)-418, a = 1.0 airfoil section with 0.20-airfoil-chord split flap, report, September 1944; (https://digital.library.unt.edu/ark:/67531/metadc61404/m1/5/: accessed March 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.