Wind-tunnel investigation of an NACA 23012 airfoil with several arrangements of slotted flaps with extended lips Page: 4 of 21
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NACA Technical. Note No. 808 ! 3
the. slotted flaps along a line 0.0025c ahead of the slot
lip and the, Fowler. flap along a line at the 1.00c station.
Flap deflections of 600 in 100 increments were possible
with all arrangements, No arrangement was made for fully
retracting the flaps,
The slot shapes for the two slotted flaps follow the
same general profile (table I); for slotted flap 1-a, how-
ever, the lower surface of the airfoil extended 0.020c
back of the slot entry for slotted flap 1-b, forming a
seal when the flap was fully retracted. (See fig. 1.)
The slot shape for the Fowler flap is made to clear the
flap in the fully retracted position, as shown in figure 1.
TESTS
The models were so mounted in the closed test section
of the NACA.7- by 10-foot wind tunnel that they completely
spanned the jet except for small clearances at each end.
(See references 1 and 7.) The main.airfoil was rigidly
attached to the balance frame by torque tubes extending
through the upper and the lower boundaries of the test
section. The angle of attack was changed from outside the
tunnel by a calibrated electric drive connected to the
torque tubes. Approximately two-dimensional flow is ob-
tained with this test installation and the section charac-
teristics of the model under test can be determined.
For all the tests a dynamic pressure of 16.37 pounds
per square foot was maintained; this pressure corresponds
to a velocity of about 80 miles per hour under standard
conditions and to an average test Reynolds number of about
2,190,000. Because of turbulence in the air stream the
effective Reynolds number, based on the chord of the air-
foil with flap retracted and a turbulence factor for the
tunnel of 1.6, was approximately 3,500,000, (See refer-
ence 8,)
Tests were made with the Fowler flap and slotted flap
1-a to determine the optimum gap for conditions of low
drag .coefficient throughout the lift range and for maximum
lift coefficient. Tests were made on slotted flap 1-b
with the flap located at the optimum position for slotted
flap 1-a. Lift, drag, and pitching moment were measuredfor the slotted flaps throughout the lift range from ap-
proximately zero lift to the stall and for flap deflection
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Lowry, John G. Wind-tunnel investigation of an NACA 23012 airfoil with several arrangements of slotted flaps with extended lips, report, May 1941; (https://digital.library.unt.edu/ark:/67531/metadc56962/m1/4/: accessed March 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.