Summary of Airfoil Data Page: 29 of 724
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NACA ACR No. L5Co5 CONFIDENTIAL 23
was obtained by scaling up and down the basic values of
the airfoil parameters 4 and E.
Teore ical- re ssure stribut ions indicated by ))
for a family of NACA 65-series airfoils covering a range
of thickness ratios are given in figure 5(a). This
figure shows the typical increase in the magnitude of
the favorable pressure gradient, increase in maximum
velocity over the surface, and increase in the relative
pressure recovery over the rear portion of the airfoil
with increase in thickness ratio. Figure 5(b) shows
the pressure distribution for a series of basic thickness
forms having a thickness ratio of 0.15 and having minimum
pressure at various chordwise positions. The value of
the minimum pressure coefficient is seen to decrease and
the magnitude of the pressure recovery over the rear
portion of the airfoil to increase with rearward movement
of the point of minimum pressure.
The pressure distribution for one of the basic
symmetrical thickness distributions at various lift coef-
ficients is shown in figure 6. At zero lift the pressure
distributions over the upper and lower surfaces are the
same. As the lift coefficient is increased, the slope
of the pressure distribution over the forward portion
of the unner surface decreases until it becomes flat at
a lift coefficient of 0.22 (the end of the low-drag range).
As the lift coefficient is increased beyond this value,
the usual peak in the pressure distribution forms at the
leading edge.
Rapid estimation of pressure distributions.- In the
discussntatEf ows, =t e term pressure stribution"
is used to signify the distribution of the static pres-
sures on the upper and lower surfaces of the airfoil
along the chord. The term "load distribution" is used
to signify the distribution along the chord of the
normal force resulting from the difference in pressure
on the upper and lower surfaces.
The pressure distribution about any airfoil in
potential flow may be calculated accurately by a
generalization of the methods of the previous section.
Although this method is notunduly laborious, the
computations required are too long to permit quick and
easy calculations for large numbers of airfoils. The
need for a simple method of quickly obtaining pressure
distributions with engineering accuracy has led to the
CONFIDENTIAL
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Stivers, Louis S.; Abbott, Ira H. & von Doenhoff, Albert E. Summary of Airfoil Data, report, March 1945; (https://digital.library.unt.edu/ark:/67531/metadc61319/m1/29/: accessed April 20, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.