Wind-tunnel investigation of an NACA 23021 airfoil with a 0.32-airfoil-chord double slotted flap

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Material Information

Title:
Wind-tunnel investigation of an NACA 23021 airfoil with a 0.32-airfoil-chord double slotted flap
Alternate Title:
NACA wartime reports
Physical Description:
18, 35 p. : ill. ; 28 cm.
Language:
English
Creator:
Fischel, Jack
Riebe, John M
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Publisher:
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:

Subjects

Subjects / Keywords:
Flaps (Airplanes)   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: An investigation was made in the LMAL 7- by 10-foot wind tunnel of an NACA 23021 airfoil with a double slotted flap having a chord 32 percent of the airfoil chord (0.32c) to determine the aerodynamic section characteristics with the flaps deflected at various positions. The effects of moving the fore flap and rear flap as a unit and of deflecting or removing the lower lip of the slot were also determined.
Bibliography:
Includes bibliographic references (p. 17).
Statement of Responsibility:
Jack Fischel and John M. Riebe.
General Note:
"Report no. L-7."
General Note:
"Originally issued October 1944 as Advance Restricted Report L4J05."
General Note:
"Report date October 1944."
General Note:
"NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were previously held under a security status but are now unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003621366
oclc - 71367027
sobekcm - AA00006288_00001
System ID:
AA00006288:00001

Full Text
L-7


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





'WAl TIIE I REPORT
ORIGINALLY ISSUED
October 1944 as
Advance Restricted Report L4JO5

WIND-TUHNEL INVESTIGATION OF AN NACA 23021 AIRFOIL
WITH A 0.32-AIRFOIL-CHORD DOUBLE SLOTTED FLAP
By Jack Fiechel and John M. Riebe


Langley Memorial Aeronautical
Langley Field, Va.


Laboratory


WASHINGTON

NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of
advance research results to an authorized group requiring them for the war effort. They were pre-
viously held under a security status but are now unclassified. Some of these reports were not tech-
nically edited. All have been reproduced without change in order to expedite general distribution.


-L-7 DOCUMENTS DEPARTMENT
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!.ACa ARR No. L4J05 REST-CTED

NATIONAL ADVISORY COM!II TTEE POR AEROI'AUTICS


ADVANCE R-STFIC'TED REP ORTF


!JIiD-TUI;;EL IPIV.,TTGATITOI OF AN .IACA 25021 AIRFOIL

,ITH A 0.52-AIr-LFCIL-C0IORD DOuBLE SLOTTED FLAP

By Jack Fischel and John !';. Riebe


S U-MThiA71Y


An. investigation wvas made in the LI''LWL 7- b' 10-foot
wind- tunnel of an IIACA 2.021 airf,'oll with a double
slotted flap having a chord 5? percent of the airfoSl
chord ('0.52c) to dcter-mine the aerod:ayn-a:.Mic section charac-
teristics with the flaps deflected at various positions.
The effects of moving the fo-re flap and rear flap as a
unit and of deflecting or removing; the lower lip of the
slot 3"are also determined.

Three positions were select d for the fore flap and
at each position the m-:a:-.:mun lift of the airfoil was
obtained vith the rear flap at the i';ximlmr deflection
used at that fore-flap position. Th e section lift of
the airfoil increased as the e ore flao was extended and
ma.:imLun lift wes obtained with the fore flao deflected 500
in the ::.ost extended position. This arrangeatent provided
a maxii-umn section lift coefficient of 5.51, which vas
higher than the value obtained, with either a 0.25,60 or
a 0.L0Oc single-slotted-flap arran:.erient and 0.25 lss
than the value obtained with a O..Oc dozuble-slotted-flap
arran.e-.ent on the same airfoil. The values of the
profile-drag coefficient obtained with the 0.32c double
slotted flap were larer than those for the C0.2566 or
O.&,Oc single slotted flaps for section lift coefficients
between 1.0 and approximately 2.7. At all values of the
section lift coefficient above 1.0, the 0.40c double
slotted flap had a lower profile drag than the 0. 2c
double slotted flap. At various values of the : axiaimum
section lift coefficient produced. by various flap
deflections, the 0.52c double slotted flap gave negative
section pitching-Imomrent coefficients that were higher
than those of other slotted flaps on the same airfoil.
The O.52c double slotted flap gave approximately the same
max-.mumi, section lift coefficient as, but higher profile-


RESTRICT TEL







NACA ARR No. LlJ05


drag coefficients over the entire lift range than, a
similar arrangement of a 0.30c double slotted flap on an
NACA 23012 airfoil.


INTRODUCTION


The National Advisory Committee for Aeronautics has
undertaken an extensive investigation of various high-
lift devices in order to furnish information applicable
to the aerodynamic design of wing-flap combinations that
will improve the safety and performance of airplanes,
For use in take-off and initial climb, a high-lift device
capable of producing high lift with low drag is desirable.
For use in landings, however, high lift with variable
drag is believed desirable. Other desirable character-
istics are: no increase in drag with the flap neutral,
small change in pitching moment with flap deflection, low
forces required to operate the flap, and freedom from
possible hazard due to icing.

The results of various investigations on the
NACA 23021 airfoil are presented in references 1, 2, and
3. Results for the NACA 23021 airfoil with a single
slotted flap having a chord 25.66 percent of the airfoil
chord (0.2566c) are given in reference 1; results for the
same airfoil with a 0.40c single slotted flap and with a
0.40c double slotted flap are given in references 2 and 3,
respectively.

The present investigation, in which tests were made
of a 0.32c double slotted flap on the NACA 23021 airfoil
(fig. 1), is a continuation of the investigation reported
in reference 4 of a 0.30c double slotted flap on an IACA
23012 airfoil.


APPARATUS AND TE9TS

Models


An NACA 23021 airfoil with a 3-foot chord and a
7-foot span was the basic model used in these tests.
The ordinates for the NACA 23021 airfoil section are
given in table I. The airfoil was constructed of lami-
nated mahogany and tempered wall board and is the same








iTACA APR No. LI4JO5


airfoil previously used for the investigations reported
in references 1, 2, and 3. The trailing-edge section of
the model ahead of the flaps was equipped with lips of
steel plate rolled to the airfoil contour and extending
back to the rear flap in order to provide the basic air-
foil contour when the flaps were retracted (fig. 1).

The double slotted flap consisted of a fore flap
and a rear flap. The fore flap (0.1lhTc).tested was the
same one designated fore flap B in the investigation
reported in reference 4 and had an upper surface and
trailing-edge of dural and a lower surface of laminated
wood. The fore-flap profile is shown in figure 1 and
its ordinates are given in table I. The rear flap
(0.2566c) tested was the one used in the investigations
reported in references 1 ard 3. Its profile is also
shown in figure 1 and the ordinates are given in table I.

Both the fore flap and the rear flap were attached
to the main part of the airfoil by special fittings that
permitted then to be moved and deflected independently.
Each flap also pivoted about its own nose point at any
position; increments of 50 deflection were provided for
the fore flap and increments of 100 deflection for the
rear flap. The nose point of either flap is defined as
the point of tangency of the leading-edge arc and a line
drawn perpendicular to the flap chord. The deflection
of either flap was measured between its respective chord
and the chord of the main airfoil. The model was made
to a tolerance of 0.015 inch.


Tests

The model was mounted vertically in the closed test
section of the LMAL 7- by 10-foot tunnel and completely
spanned the jet except for s.iall clearances at each end.
(See references 5 and 6.) The main airfoil was rigidly
attached to the balance fr.me by torque tubes that
extended through the upper and lower boundaries of the
tunnel. The angle of attack of the model iras set from
outside the tunnel by rotating the torque tubes with a
calibrated electric drive. This type of installation
closely approximates twvo-dimeinsional flow and the
section characteristics of the model being tasted can
therefore be determined.







NACA ARR No.L4J05


A dynamic pressure of 16,57 pounds per square foot
was maintained for most of the tests but, as the flaps
were extended and the rear-flap deflection was increased
to 600 and 700, it was necessary to reduce the dynamic
pressure because of the limited power of the tunnel motor.
'jith the configuration for ma::im;um lift, a dynamic pres-
sure of 14.84 pounds per square foot was maintained.
These dynamic pressures correspond to velocities of 80
and 76.2 miles per hour under standard sea-level con-
ditions and to average test Reynolds numbers of approxi-
mately 2.245 x 106 and 2.140 x 106, respectively.
Because of the turbulence in the wind tunnel, the
effective Reynolds numbers Re (reference 7) were
approximately 3.6 x 106 and 3.4C2 x 106, respectively.
In each case, Re is based on the chord of the airfoil
with the flaps retracted and on a turbulence factor
of 1.6 for the LMAL 7- by 10-foot wind tunnel.

No tests were made of the plain airfoil nor of the-
model with the flaps completely retracted because the
characteristics of the plain airfoil had previously been
investigated and reported in reference 1.

The optim-um flap positions for the various flap
deflections were considered, for purposes of making the
best selection, to be the positions at which either
maximum lift, minimum drag, or minimum pitching moment
was obtained, although, as previously indicated, a
variable drag is desired for landing conditions.

Three positions of the fore flap were selected in
determining various extended positions of the flaps or
a possible path for the extension of the flaps. The
least extended fore-flap position, having a 50 deflection
(position 1), and the chordwise location of the inter-
mediate position (position 2) were chosen arbitrarily.
The location perpendicular to the chord and the 200
deflection for position 2 were optimum as determined from
a maximum-lift survey with the rear flap deflected 500
and 600. Because of the large number of tests involved
in determining the optimum-lift position of the double
slotted flap, a preliminary survey was made to determine
the optimum position and deflection of the most extended
position (position 3) of the fore flap with the rear flap
deflected 600 and 700 at various positions. Tests were
thereafter made with the fore flap at each of the three
selected positions in order to determine the maximum lift







TACA APR No. L4Jn5


and the optimum position of the rear flap at several
deflections. Data were obtained for rear-flap deflections.
of 100, 200, 30, and 40 at position 1; 350, 400, 500,
and 600 at position 2: and L0 500, (C, and 700 at
position 3. Inasmuch as it appeared likely that only
small rear-flap deflections would be used with the least
extended fore-flap position and that only large rear-flap
deflections would be used with the most extended fore-
flap position, the tests were confined to these configu-
rations. In order to determine the effect on the aero-
dynamic characteristics, tests were also made with the
lower lip of the slot in its normal position on the
contour, deflected 190 within the airfoil contour (at
fore-flap position 2), and completely removed (at fore-
flap position 5).

No scale-effect tests were made because the results
of earlier tests of the NACA 25021 airfoil with a slotted
flap (reference 1) are considered applicable to the
results of the present investigation.

An angle-of-attack range from -6 to the angle of
attack for maximum lift was covered in 20 increments over
most of the range for each test; however, when the stall
condition was approached the increne.nt was reduced to 10.
Very little data were obtained for angles of attack above
the stall because of the unsteady condition of the model.
Lift, drag, and pitching moment were measured at each
angle of attack.


RESULTS AND DISCUSSION

Coefficients and Symbols


All the test results are Tiven in standard section
nondimensional coefficient form corrected for tunnel-wall
effect and turbulence as explained in reference 6.

cl section lift coefficient (L/qc)

Cd section profile-drag coefficient (do/qc)
cm.. section pitching-moment coefficient about
(a.)o aerodynamic center of plain airfoil

ma.c.),/ c2 (fig. 2)







NACA ARR No. 14J05


Cma.c. ) o



Cd
o"max

omdin

where

I,

do

m(a.c. )o

q

c


V

P
and

Re

It



ao

6f


6f2


C7max
max


section pitching-moment coefficient
at maximum section lift coefficient


maximum section lift coefficient

minimum section profile-drag coefficient




section lift

section profile drag

section pitching moment about aerodynamic
center of plain airfoil (fig. 2)

dynamic pressure (1pV 2

chord of basic airfoil with flap fully
retracted

velocity, feet per second

mass density of air



effective Reynolds number

distance from aerodynamic center of airfoil
to center of pressure of tail, expressed
in airfoil chords

angle of attack for infinite aspect ratio

fore-flap deflection, measured between fore-
flap chord and airfoil chord

rear-flap deflection, measured between rear-
flap chord and airfoil chord

distance from airfoil upper-surface lip to
fore-flap-nose point, measured parallel to
airfoil chord and positive when fore-flap-
nose point is ahead of lip








NACA ARR !ro. L4J05 7


Y1 distance from airfoil upper-surface lip to
fore-flap-nose point, measured perpen-
dicular to airfoil chord and positive when
fore-flap-nose point is below lip

x2 distance from fore-flap trailing edge to
rear-flap-nose point, measured parallel
to airfoil chord and positive when rear-
flap-nose point is ahead of fore-flap
trailing edge

Y2 distance from fore-flap trailing edge to
rear-flap-nose point, measured perpen-
dicular to airfoil chord and positive
when rear-flap-nose point is below fore-
flap trailing edge


Precision

The accuracy of the various measurements in the
tests is believed to be within the following limits:

ao, degrees . . 0.1
max . . .. O.03

. . 0.003
Cdomi .* *.. 0.0003

Cdo(cj = 1.0) .. ......... o.ooo0006

c = 2 5) . 0.002
(o= 2.5)
8fl and 6f2, degrees . .. 0.2
Flap position . .. 0.001c

No corrections were determined (or applied) for the
effect of the airfoil or flap fittings on the section
aerodynamic characteristics because of the large number
of tests required. It is believed, however, that their
effect Is small and that the relative values of the
results would not be appreciably affected.








8 NACA ARR No. LJJ05


Plain Airfoil

The complete aerodynamic section characteristics of
the plain IIACA 23021 airfoil (from reference 1) are
presented in figure 2. Since these data have already
been discussed in reference 1, no further comment is
believed necessary.


Determination of Optimum Flap Configurations

Maximum lift.- The results of the maximum-lift inves-
tigation with the fore flap at each of the three selected
positions and with the rear flap deflected and located at
points over a considerable arsa with respect to the fore
flap are presented in figures 3 to 5. The results are
presented as contours of lift coefficient for various
positions of the rear-flap-nose point at various rear-
flap deflections. ITe results show that at each fore-
flap position, the contours dJd not close at the smaller
rear-flap deflections in 'estigated. At positions 1 and 2,
it is indicated that the open contours would close at
positions of the rear-flap nose that would be impracticable
because of the large gap between the two flaps.

At each of the three fore-flap positions, as the
flap deflection increased, the position of the rear flap
for miaxlmrniu section lift coefficient cLx generally
became more critical that is, a given movement of the
rear-flar-nose point caused a greater change in the value
of Z ax. Since the position of the rear-flap nose
for c, tends to move forward and up.'ard as its
cmax
deflection increases, the gap between the two flaps is
reduced. The values of ,ax obtained at each fore-
flap position and the approximate position of the rear-
flap nose with respect to the fore-flap trailing edge are
given in the following table:
Position of rear-flap nose
Fore-flap Ahead of lip Below lip C,
position (percent I (percent max
airfoil chord) I airfoil chord)
1 I 1 6 2.71
2 C i 2 5.06
3 i_ 3 3.?1








NTACA ARR No. LlTCO5


From the contours of rear-flap-nose position for
CZ max the best oath to be followed by the rear flap at
all deflections within the range investigated, from a
consideration of cma alone, can be determined. The
range of flap positions covered was considered sufficient
to allow for any deviations or compromises from the best
path. Complete aerodynamic section characteristics for
the optimum-lift and optimum-drag rear-flap-nose positions
at each selected fore-flap position are presented subse-
quently herein.

Minimum profile drag.- Drag data obtained with the
fore flap in the three selected positions and the rear
flap deflected at various positions over a wide region
are presented in figures 6 to 6. The data are presented
as drag contours for the rear-flap-nose position at
certain selected section lift coefficients and rear-flap
deflections. A comparison of the section profile-drag
characteristics of the plain airfoil (fig. 2) with the
prcfile-drag characteristics given in the contours of
figure L(a) and o(b) shows that the plain airfoil gives
the lower drag value at cL = 1.0.

Inasmuch as only a very few of the contours were
closed about indicated optimum-drag positions of the rear-
flap nose (figs. 6 to 3), it is obvious that a sufficient
range of rear-flap position was not covered and that the
true optimum values may exist at some other positions.
At each of the fore-flap positions, however, it is indi-
cated that the contours would close at positions of the
rear-flap nose which would be somewhat closer to the lip
of the fore flap than The positions tested. As the fore
flap was extended and as the rear flap was deflected, the
optimiil-drag rear-flap-nose position generally Irmo-/ed
forwar-: and up, closer to the fore-flap trailing edge.
More than one region of minimumin drag exists at various
values of section lift coefficient cl and various rear-
flan deflect:Ions and the minimum drag is seen to be prin-
cipally a function of section lift coefficient and rear-
flp electionn and relatively independent of the fore-flap
po03tion. In ea-h position of the fore flap, as the
setio:S lift coefficient or the rear-flap deflection
incre-jaed, the contours generally became more critical or
closely spavtd; tnat is, a given movement of the rear-
fl'a,..nose point generally caused a greater change in the
val-e of the section profile-drag coefficient cd.
(See figs. 6 to 8.)







NACA ARR No. L4J05


Inasmuch as the rear-flap-nose positions for maximum
lift and minimum drag generally do not coincide, a com-
promise is necessary. The curves for the complete aero-
dynamic section characteristics are therefore presented
for both conditions.

Pitching moment.- Contours of section pitching-
moment coefficient for the rear-flap-nose positions at
selected section lift coefficients and rear-flap deflec-
tions are given for each of the three fore-flap positions
in figures 9 to 11. These contours indicate that an
increase in the negative value of m(a..)o at a

given c7 was obtained with increased rear-flap deflection
and that the maximum negative values of m(a..) were

usually obtained at or near the position of the rear-flap-
nose point for maximum lift at each rear-flap deflection
(compare with figs. 5 to 5). At 6f2 = 500, 60, and 700
at position 3, however, a decrease in the value
of cm( ) was indicated when ct increased.
(a.c.)o z

At a given lift coefficient and rear-flap deflection,
the negative values of pitching moment also increased as
the fore flap was extended from position 1 to position 3.
It appears desirable therefore to use the minimum flap
deflection or extension necessary to obtain any given lift
coefficient. In addition, the contours indicate that the
position of the rear-flap nose becomes more critical with
increased rear-flap deflection and lift coefficient.

With these contours of flap location for cm(a..)
in figures 9 to 11, the designer can determine or antici-
pate the values of cm( to be encountered at a
m(a.c.)
given value of c within the range of position and
deflection indicated.


Aerodynamic Section Characteristics of Selected

Optimum Configurations

The complete aerodynamic section characteristics of
the airfoil with the rear flap at the optimum-lift and








NACA ARR No. L4J05


optimum-drag positions at each flap deflection and at
each of the three fore-flap positions are presented in
figures 12 to 1i. The consecutive flap-nose positions
as 6f2 increases are indicated in the figures by those
key symbols that are connected by dashed lines. The
lift-curve slopes decreased with increased rear-flap
deflection, although at rear-flap deflections below 500,
the lift-curve slope was sometli.ies as much as 0.05 greater
than that of the plain airfoil. At each fore-flap
position, the angle of attack for maximum lift usually
decreased with increased rear-flap deflection but in some
instances remained fairly constant.

At position 5 (fig. 1-) and 5f2 = 500, the position
of the rear flap for maximum lift and minimum drag coincide.
Irregularities in the curves at the larger flap deflec-
tions (figs. 12 to 1l) indicate changing flow conditions.

At the small rear-flap deflections and lift coeffi-
cients, the slopes of the pitching-r'-otIent curves were
negative and, at high flap deflections and lift coeffi-
cients, were usually positive: s..aller negative values
of cma..)o were therefore soretimres obtained with a
large flap deflection than with a small one at high lift
coefficients. (See figs. 15 and 14.)

Increment of maximum section lift coefficient.- The
increment of the maximum section lift coefficient Acmax,'
based on the value of cZax of the plain airfoil,
increases as the rear flap is deflected and as the fore
flap is extended (fig. 15). At each fore-flap position,
the values of Acya are higher for the optimum-lift
position than for the optimum-draq rear-flap position, as
was anticipated.

'The maximum increment of lift coefficient obtained
was at position 5 with 5f2 = 700, where a value of 1.96
is indicated. The scale effect on the values of AZmax
max
was not investigated but it is expected that the values
would increase slightly with leynolds number with the
0.52c double slotted flap as did the values for the
single-slotted-flap arrangements of references 1 and 6.







NACA ARR No. LLJO5


Envelope polar curves.- The envelope polars of
section profile-drag coefficient co at each fore-flap
position, obtained from figures 12 to 14 for the optimum-
lift and optimum-drag configurations, and the polar of
the plain airfoil are presented in figure 16. These
curves indicate the cd available at any c, when
min
the rear flap is located to give cmax (fig. 16(a))
max
and cd (fig. 16(b)).
min
For both the maximum-lift and minimum-drag configu-
rations (fig. 16), the plain airfoil gives the lowest cd
for values of ct less than 1.3, and for values of c,
above 2.6 the lowest value of Cdo indicated at
position 3.

Comparison of Flap Arrangements

When the lift-drag characteristics of the 0.2566c
and O.0LOc single slotted flaps (references 1 and 2) and
the 0.40c double slotted flap (reference 3) are compared
with those of the optimum-lift and optimum-drag configu-
rations of the 0.52c double slotted flap (fig. 17), it
is apparent that the 0.lOc double-slotted-flap arrange-
ment produced the highest lift coefficient (cL = 3.56)
on the .TAOA 25021 airfoil. The c, obtained with
max
the 0.52c double slotted flap is considerably higher than
that obtained with either single slotted flap but it is
approximately 0.25 less than that of the 0.40c double
slotted flap.

The 0.52c double slotted flap had a larger cd
o
than either single slotted flap for values of ct
between 1.0 and approximately 2.7 and had a larger
Cdo than the 0.L-Oc double-slotted-flap arrangement at
all values of ct above 1.0.

The 0.32c double-slotted-flap arrangement had values
of Cd for the envelope polars that differed by








ITACA ARR No. LLLJ0O


about 0.02 for the optimum-drag and optimum-lift configu-
rations at a value of c, of about 2.5. At values of c7
less than 1.3 and greater than 5.1, however, the two polar
curves practically coincide.

When the polars of the 0.52c double-slotted-flap
arrangement on the NACA 23021 airfoil are compared with
a similar arrangement of a 0.30c double slotted flap on
the NACA 23012 airfoil (reference 4), it is apparent that
the c, obtained with each is approximately the same
fig. ax
(fig. l8). The values of Cdo, however, are higher at
all values of c, for the arrangement on the 21-percent-
thick airfoil than for that on the 12-percent-thick air-
foil but the relation between optimum-lift and optimum-
drag configurations is about the same for each arrangement.

A further comparison of the various slotted-flap
arrangements on the NACA 23021 airfoil indicates that a
fairly linear variation exists for each arrangement at a
given flap configuration between the cm and
"max
the [cm(a.) (fig. 19) and this variation

max
appears dependent on the flap arrangement. The 0.32c
double slotted flap gave higher values of [mc lcj

max
at any value of ct than any of the slotted flaps.

Inasmuch as there will be a tail load required to
trim the negative pitching moment of the wing of an air-
plane, the loss in maximum section lift coefficient in
trimming the airfoil section pitching-moment coefficient
has been calculated, for the case when the center of
gravity is at the aerodynamic center of the plain airfoil,
from the following expression and is indicated in figure 19:

) max
Loss of c = t
max Zt

The loss in cma has been presented for tail lengths
of 2, 5, and 5 airfoil-chord lengths and, by means of the
curves of figure 19, the effective cm can be
dmax
determined.








:TACA ARR to. LIJO5


Effect of Various Modifications on the Aerodynamic

Section Characteristics

Effect of moving the two flaps as a unit.- The
effect on the aerodynamic section characteristics of
moving the fore flap and rear flap as a unit perpendicular
and parallel to the airfoil chord is shown in figures 20
and 21, respectively. A 0.01c displacement downward of
the flaps, perpendicular to the chord, was quite critical
in that a large decrease in lift and an increase in drag
resulted (fig. 20). Figure 21 indicates that a movement
of the flaps parallel to the airfoil chord had a consid-
erable effect on the aerodynamic characteristics; that is,
at positions of the fore flap downstream from xi = 0.70
(position 3), large decreases in lift and increases in
drag resulted and unsteady flow conditions existed. A
comparison of figures 20 and 21 with the contours of
figures 4 and 7 and 5 and 8, respectively, indicates that
the position of the fore flap is more critical than the
position of the rear flap.

Moving the two flaps approximately as a unit from
position 1 to position 2 and then to position 5 along two
different paths, A and B, gave an increase in lift,
drag, and pitching moment. (See figs. 22 and 23.) Since
the model fittings only allowed increments of 100 for the
deflection of the rear flap, it was not possible to have
a 6f2 of 550 for figure 22 and a 6f2 of 450 for
figure 23 at position 1. Although motion of the two
flaps as a unit is only approximately simulated, figures 22
and 23 are thought to be sufficiently illustrative.

Effect of the airfoil lower lip.- The effects of
deflecting the lower lip of the airfoil from its normal
position at fore-flap position 2 and of removing the
lower airfoil lip at position 3 are shown in figures 24
and 25, respectively. Deflecting the lip upward 190
decreased c, and increased do over most of the
angle-of-attack range, possibly because of the poorly
shaped slot entry ahead of the fore flap when the lip is
deflected. On the other hand, removing the lip at the
extended fore-flap position (fig. 25) had a slightly
favorable effect on the aerodynamic section character-
istics at low values of cG, by causing a reduction in
the profile drag, and a slightly adverse effect at high








;iACA ARR No. L4JO5


values of cI. Such a result indicates that a smoother
slot entry ahead of the flaps may be desirable, provided
it does not reduce the values of c max available.
Although no data were obtained at small flap deflections,
it is probable that the smoother slot entry would be even
more favorable under such conditions.


CONCLUSI OiS


An investigation was made in the LMAL 7- by 10-foot
tunnel of an :IACA 2.021 airfoil with a double slotted
flap haviIng a chcrd ri po-cent of the airfoil chcrd (0.52c)
to deter.-irne the aerodynT:amic section characteristics with
the flaps dcfi-cted at ve.ious positions. The results of
this inrestigaticen shove; hat:

1. The 0.52c double slotted flap on the NA'CA 25021
airfoil gave a ma-:iin ,-i sect :on lift coefficient of 3.51,
which was larger than the vLalue obtained with the 0.2566c
or 0.kOc single slotted flaps and 0.2f, less than the value
obtained with the 0.4Oc double slotted flap on the same
airfoil.

2. The values of the profile-drag coefficient obtained
with the 0.32c double slotted flap were larger than those
for the 0.2566c or O.L0, single slotted flaps for section
lift coefficients between l.C and approximately 2.7. At
all values of the section lift coeffiefent above 1.0, the
present arrar.ngaemt had a higher profile drag than the
0.4Oc double slotted flap.

5. At a given valu..e of the maximum section lift
coefficient pro.i.ed ,l y various flap df'le:hions, the
0.52c doub-F sl.it.? flap ara negative section pitching-
moment coieffiicients tli.t were higher than those of other
slotted flaps on the cas.e airfoil.

4. The 0.52c double slotted flap gave approximately
the sar~e lma-imium lift ccefficient as, but higher profile-
drag coefficient over the entire lift range than, a
similar arrangement of a 0.30c double slotted flap on an
NACA 25012 airfoil.

5. Moving the flaps slightly front their optimum
positions sometimes proved critical and resulted in a








16 NACA ARR No. L4JO5


large increase in drag and a reduction in lift. The
position of the fore flap appears to be more critical
than that of the rear flap.

6. Deflecting the lower lip of the airfoil 190
upward generally decreased the section lift coefficient
and increased the section profile-drag coefficient over
most of the angle-of-attack range; removing the lip at
the extended fore-flap position reduced the profile drag
slightly in the lower-lift range but was slightly
unfavorable at high section lift coefficients.


Langley F'emorial Aeronautical Laboratory
National Advisory Committee for Aeronautics
Langley Field, Va.








ITACA ARR No. L4J05


REFLRENICES


1. denzincer, Carl J., and HarriLs, Thomas A.: 'Jind-Tunnel
Investigation of an F.A.C.A. 25021 Airfoil with
Various Arrangements of Slotted Flaps. ETACA Rep.
No. 677, 1959.

2. .Duschik, Frank: V.ind-Tunnel Investigation of an
N.A.C.A. 25021 Airfoil with Two Arrangements of a
40-Percent-Chord Slotted Flap. [TACA TN !o. 728,
1959.

3. Harris, Thomas A., and Recant, Isidore C.: Wind-Tunnel
Investigation of WACA 25312, 25021, and 25050
Airfoils Equipped with [p0-Percent-Chord Double
Slotted Flaps. NACA Rep. ?io. 725, 1941.

-. Purser, Paul E., ischel, Jack, and Riebe, John M.:
"lind-Tunnel Investigation of an TIAA .012 Airfoil
with a 0.50-Airfoil-Chord Double Slotted Flap.
FACA ARR No. 5L10, 1945.

5. Harris, Thomas A.: The 7 by 10 Foot '7"nd Tunnel of
the Iational Advisory Coriittee for Aeronautics.
NACA Rep. No. 412, 1951.

6. Jenzinger, Carl J., and Harris, t'homas A.: "'~nd-Tunnel
Investigation of an N.A.C.A. 25012 Airfoil with
Various Arrangements of Slotted Flaps. NACA Rep.
iTo. 664, 1959.

7. Jacobs, Eastman N., and Sherman, Albert: Airfoil
Section Characteristics as Affected by Variations
of the Reynolds Number. IACA Rep. No. 586, 1937.

























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00


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mo


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1








NACA ARR No. L4J05


NAROgM ADVISOM
coMInIEE FOR ALRONAU11CS


Figure /- Sections of the ,VA CA 2302/
airfoil and the 0.32c double slotted
flap.


Fig. 1






NACA ARR No. L4J05


-F













II
--- -













.3t)1
-5; -0i:.0. -~ -5- __- -- : j ,
t7..
Li .. ..
-1







)C ---- 7














r Io~r/f n? :
I U,







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IC
^^ER~E~i TFF^rE^EEE^i
5
P g- -- --.- -- -4--- -- -4 -- -- c_ _.--_e- _I-
23D2r" n .attd lik^nL EN 2cel ~l1 ~^ ^~


Fig. 2









NACA ARR No. L4J05


1r



,..-









4 -
?:I- c.2.*.


(:-_ ---- r 1


J i .' '-
c^,'-v', Qi'iij c ",aW
lul if f.V


. .........


Fig. 3







NACA ARR No. L4J05


-L : e ii z"
6 4 28 0- -4 -6 6 6 4 Z 0 -2 -
Percent oirfoi chord Percentairfol chrd
(a) S 3o (Wfb)4'440!



RIIAHUliAL ADVISOi Y
ICDMITIE FOR AERONAUTICS














IJ/ I 6 I
/0
4o tA
-. 2 <* ___ __ __ 9


) 456o.


&&- To 0


Figure 4.-Contours of .a-- a 'o position for c, Position 2 4, =20, x,=2 70 y, e.45.(//ues ofxy, are
given inpercent r r,..' chord)"


Fig. 4









NACA ARR No. L4J05


6 ,- 6


4 a o -e -+ 6 0 2 -B -4 -6
Percent airfoil chord Percentairfoilchord
(a) A. 400 ?b) S0









NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


C,'.rcc r o .c *,, c-ark, tr/cc^o'a
Ri- 3,, 6- ia.; Cf *e m 70'


,,L,'reo .- L ;... r r '6 Cor-'f.jp cs to, f ; ,". "::- '.'O : r- L/O'Vo .- .-"<,
oar g;,e- .n percent Oa/r'l// chord.,


Fig. 5








NACA ARR No. L4J05


Percent airfoil chord
(a) c 1.0 s-/O:


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


6 4 2 o -4-6 -8" 6 4 0 -Z -4 -e
Percent airfoi/ chond Percent airfoilchord
(b) c =/-.0; -20, (c0 cel/.5 ,O"


Fipf.re6.-Confours of rear-flap pos/f//n for cd. Positionl ;f- z,=~5 70;y,=445.
(Va/ues of2,,y, are giYn in percent airfoi/ chord.) '


Fig. 6a








NACA ARR No. L4J05


.3ercen oirfi' c/ or
td) c;i.s, Sf =30'


'mI uhAL D VAisoR
CIAMMi llE i i ARalOLiLICS


F go r 6.- ,Co.rc/o lej.


Fig. 6b


te) c, 1.5 40".


ce it ~~~ r'







NACA ARR No. L4J05


(a) c, -'/5 = 5o*.


NAlIONAL ADVISORY
Cu;MMITIEE FOR AERONAUTICS


6 -4' 0 --P -4 -6-8 6 B 0 -o-4--6-8
Percent airfoil cord Percent a-rfoil chord
(b) c: = .0; 30o. (c) c, z.oj; ,- 40:


Figure 7- Confours of rear- flap pos/'fit / for C Pos/'ton 2- f,6 0 o*;L,=e.70!.y2,4S.
(Va/ues ofx,,y, are Yiven in p ercenf /r;fo /~ cord) 4


Fig. 7a








NACA ARR No. L4J05


(d) c 3 40-


.uUMIllIm I OR ALEORAUTICI


Percent ai/ri/ chord
ge)urc 7-rt 4C50o


,,gure 7- Concluded.


(f) C:Z5; &, 60:


Fig. 7b








NACA ARR No. L4J05


()Cfz .O- 5, 40!


(b}c-&g.5 3-=40:


NALIUNAL DAVISORY
COMMITTEE FOR AERONAUTICS


Percent airfoil chord Percent airfoil c/ord
(c) ce Z.&5; S3o: (d)C-.aO,.4 =- .


Fgfare d- Confours of reor-f/lap pos/i/'on for Cd0 PFsitionJj 6f=JO.xLO.S7O ,.4S../Vlo/ues of
,,y, are ,iVen /n lpercenlr e orfo/7 chord)


Fig. 8a








Fig. 8b


. :- 't rfo,.'c. ,ord Perc, it .yr~o(' Ctr
{'ei C. A *. ; -. 0. ff)c,.* O. 60'.


.. MMitl AI uh.AUllCS


! 6 4 i. 0 -4 -6 0 6 4* i: -Z -4 -f
-rcEc -' r .-. C/crrd Frcr t i,' 0i cho'rd
;'g>c, &s Tr) I'ti c( .. <, J 76 o


NACA ARR No. L4J05


F~g,~re6- ICe-rr .Oe







NACA ARRNo. L4J05


6 4 2 O -2 -4 -6 -8
Percent airfoil coard
(aj Ce /o:








NAlllItNAL ADVISORY
COMMITTEE FOR AERONAUTICS


6 4 0 -2--4 -6 -
Percent airfoil chord
(b) Cf ,/.O ^Z -20.


6 Z 0O -8 -4 -6 -
Percent airoilchord
(c)Y C /.5; 64,-.o0:


Figure 9.- Con tours of rear- flap position for c~, Position /, =5 =. 70. yJ.4V.ao/ues
ofx,,y, are giren in percent airfoi/ chord,)


Fig. 9a







NACA ARR No. L4J05


hAlluuL AOlVISUR
.UOMMIIIEE FOR AUROtIUIICs


(e) c 40 e (4f c, 4 0; 40'


*iaureC9.- Conr'c eod'.


Fig. 9b


"d) c:/.- b, -o 3







Fig. 10a


NACA ARR No. L4J05


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


I I I I I I I I I I -4
8 6 4 o--4-6-e 8 6 4 0 -2---6
Percent airfoil chord Percent ai'foil chord
(b) C q ;. 0; 5= o30. (c)c -.0; S=40*



Figure /0.- Con tours of rear-f/op posif/on for c I, Poslfion 2; c,=-ZOer= 70Aj-.4.
(ialc/es of x,,, ore giren in percent a/rfoilchord] & "


(6) C /-, j '=/30t







NACA ARR No. L4J05


d C, C t s; 4 40-


IrlIONlAL ADVIStRY
rnuMlllEtl FOR IIONAUIICS


Percent aor 6. chor d
(ec) c 5f so.


oc.'re ./C.- Cr'rc,'cded


Percent ,rfo/ cord
(f) c .5 60.


r I
_ "-crTI


Fig. 10b








NACA ARR No. L4J05


Fig. lla


(a) c o.0, Sf,- 40.


(cbi =. % -i -


iuwfInAL A*VISURY
COMMITTEE FOR AERONAUTICS


6 6 *' z 0 o- -4---- 6 a 0 o-a-- -0
Percent Oairfoil chord Percent a/rfo// c/ord
(c) c, ; f Fo (d) cf, 3.0,; so.

Fiyure /1- Con ours of rear-f/a osition for ,. Pas/f/on3 Sj 30',=70.7y, -e45.fJ'//ues ofz_,,
r1e gir/n in percent a/ rfoi/ chord.)








NACA ARR No. L4J05


Fig. 11b




















oP


Percent airfoil chord
(e) c,-Z.s; S- 60'.


Percent airfoilchord
(ff)J c.o; S 60.


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


, 0. "-', c -0,, s ^ ,... C o r/ ,'i _'C.*,.-o
,/;; Y ,: ..: :r 'V ;,. > .. ."C .'


,r ,', Cc.'C jc,.2







Fig. 12a


NACA ARR No. L4J05







NACA ARR No. L4J05


Sf- itf tH


4.1. K iL 4
...


I : -- i






IF


}7 T^ T'


S "!7- ih j


m m- tt m II-r-1 --


fh..Ffi!ItT..I..*TflI4u jj,, ,,,,..{j-


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1- L f I- if ri;FTsl


L' I i -- -- 1


I 1 I


7 L I I I -14 J~E 7IE 4H-,F~bf,-r-+


. t i-' 4 -1 t- I -I. I I ---4-- I --I -I -- I I i i .- ~ -


pry5.7.2

^.^^^^::::^:^ ^t A


^rt- f1 &1--it- -


EI- l4 fI L 1 -1 1L


t--.. -t


-. -- --I P ~


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^t"N^-


m


~=1~3~t~-~


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-- L-' LK7-.f-^-bl


I-


-Y


-rL=f


r


T=_-:_- Z-


Tl -


it-r-tT Iy--


i^MI'


" Y1"' '


- LL3 : LL


Fig. 12b






Fig. 13a


NACA ARR No. L4J05







*NACA ARR No. L4J05


- Ar .. -


- =;.


. I. 1-3


I-i -T*Y

-MTm


* -= I ~Ii '
I I I.:I .I. J -


.-H Nr a ^t ld 7 I 14 I :M -x.i 1 ri :l:. l :1I


*1AL. ILLltIlItiEIIi *.: iLEILLIEI


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T"T-TA 0


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la^E


-sF -p z^P- i--E


,,jff-UY-gUlat-,


itt~ rl__


I ~ : 4- 1-I


~:~f~-t~t'F~T~;4Fs~~


4 -Fi


1- -1


t-i t t-L --


,-E ,- A -t .f.. .. .


Fig. 13b


1. I








NACA ARR No. L4J05


Fig. 14a


-- --- --




A_ -A_-I


















-~ -j -Z --'S -S -^ i--- --- --- -f .* ^ .... ...5m


? 1 n^_L '*~c- 'L 3t 3X= :-^ ~: ~. ~.~ ^ -
.. ----- --
t 741: -.V-' --A.-
J L-:: I-lbZ -
-j X A N -



I I F.
rl 1

I





i. I F-' _F


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mI



ipht fi- T I


4o- od ziAn'











I Q::Ec i=_||
-^ ^ -j i - -^ ^ ^ ; g E .I: t^ | i
u iID~ipri~izi~^z^^S~~eSS
^_-.- 11 ?JlI Jaiflfl Z ^Bf ^^ ^4;mMIS ^i^ ^
__ _;_ _! I 1 t r .ir m L! ^ B!B SJ ; _
_i ^ ^ 'Jb ^ ^ ;'5*-lr? _L _^ _^ ^
^ ^_ _L _J ^ 1 Y ". i ::* :*- -
_-LI -.-^^ ^ ^ -fi~^ ^ s4 ^ '~ ~ b,^
-L-____dfe-.-,', //1|?J c^2^aL^^ a~^ ^ !4^^ ^ l:,_:g^^ ias:^
-. -- -La I5. r4^ ^ g^L a gi^







NACA ARR No. L4J05


Fig. 14b


titr


I IIl E ITZT.T Il{
I I A 1 1 V I 1 1 RL-L. 1 l 1 T'


-mI


FM--


. I I i I i I I V 1 I 1 I I .. .1-I .. -l


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4 ri
I



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44
. ... 1 I -
|^r |=:| ^^E^i|^

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: '___ 1 .^ x /g / "l J /.d e, I i ] i j L J _. 4 -


-I Fcs


I,-4z-L--


I n I I


4-- i





NACA ARR No. L4J05


- 4
0


0







o

oe
S,
J;


Sh.
i'l)



0 -%
-< i=


(a ~



o co
-$ o ~
ct- *^ <
'*F
0 t, <0 ^

B .


xmu 4uepi^9QG) V// !9!s. uo, q wnuflxvw ,O 4U~W.~*ulau


Fig. 15







NACA ARR No. L4J05


.44





.36 -- 1-




-Fore-flap position 3


c6-- -----------------------4---- ---
-, deg
Z4
.4eo ---------- -------- ,Q 40 --- --------------------------------------- -___^_1_______
/0
30
zo -__ 40
S50 I
S60 ------ __
S70
.16------- I||-------------^--------------I,


.T



.1r --- 1^- 1
() R fa f
.05-------------------I-----------
.--------------------^------------------- -- -

.04
,/il R


4 0 .4 .8 1/2 1.6 .0 .4 2.8 3.2 3i
Section lift coefficient, c
(a) Rear flap posiTions for ctx.
/'qure i6.- Prof/'e-a'rg enve.'pe po/or curves for the /VACA 2.302/
a/rfo// wv/ith ao C.c aouble s.cttea f/op.


Fig. 16a







Fig. 16b


NACA ARR No. L4J05


Section lift coefficient, c,
(b) Rear-flap positions for cdoi.
F7yure /6- Conc/uded.






NACA ARR No. L4J05 Fig. 17










SI






-. A__ .. 4..>,
Q NO

'P 9 ') I _'


\..


-, -- i_ i

-------






___ |JQ o I .




i'L I I '.1




0 o o .

'"/'fISIJpr2I JI3 tilKp .llIJCd ULOuij






NACA ARR No. L4J05


.44-----------------





36--


--- -- 0.30 c Double slotted flap on NACA 301 airfoil (referen ce 4)
S0.32 c Double lotted flap on NACA 30,1 airfoil


2e deg
0 10
S0
o -0
> 50
0 60
70
Rear-flap positions //I
-IC ---_ -Optimum lift-
Optimum drag











-4 O .6 / 16 .0 ,O .4 Z.8 3. Z 3
Section lift coefficient, cq
.1-----------------------^-----

--------------------------------------------------^^--------------









250/2 alddNACA 2O-3/ alrfoils.
?.3O/e cand A/AlCA ?30ZI a~rfo,/s.


Fig. 18







NACA ARR No. L4J05


x I. I
X r ^ U93j^04>9Wt-LHf4CfU19


c)
Q -~ ^
SZ -F


Fig. 19


"sk
FR






I..'
(^












.
5^











-r,,




4:z
(fS
















Ii-.
o i~







Fig. 20 NACA ARR No. L4J05









S- .- . --
















thl;~ -r








-101










L-A ere F t ri r




LTL
L1 L -4!9)
AL?_ 44
-- --'- -2 F- --- --F- --- -- --- --- .-^ -=-:- t *"-' -- j:--' a--.-i- ---"----t .---





-- -T 1:' *4_._ ~ vr:i--]- -- .I- +-'t -_ ,-* i1'- "-i-
:~r~aaa4H~


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r/ / 4rfak4I


x< .brs l-nvVyAa


Sio" 2.!.P. z & /1 z /,R9


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V I


. 1 ; "


v / 2


/


SffeTerf- ^-\ 84 .&t
e '*'" rt//-7t / ^^s? f:F pr 1=i


-- _. _- t








NACA ARR No. L4J05


I 4W41-I ~{1 4


I 1---


K-'[ i w 14-11 i t4..t W- -i y _l-4.M _--4


V-I 4 -1I


I. Y99- -












77
LX 0


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I --_I J7






















I~~~ ~ is YA JtV,4 ;t
:4 -
I Ij 1 yt 7 -"? = ?'*















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I LL





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IL- .
|g- i ^ ;I i 1 |i......._:_^~ l L:
^SL~l^ ^ 'a^Z^IS i^:]^^
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a|;:';:;t:::::::|-is~s~s;;2i^:::
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_i_ ___.L..---___ 4-.. .__^ Em ^Sz~~~~~~fi^'zb~~~ ~ ~ if ~ ~ ^ &^^ ~e iia''4S^i';(^S.:-/_
_!__^ _2z^ J~^^-^^^^^ if^^d^^4^ci1 j'L^ a^-l
1 _- Zt ^ ^ ija 2L2 ^ 2^ ia /-:l!' _L
=tL! ^ '^^^-'^ ,^ ^ ?-'>/j5 >? 4_I L ^~~ __

^^^^^ ^^^^py^--- .-n--v--.n


i
"'


I i
I


Fig. 21


I- I- i -L- i-:


I- -.I


L---








NACA ARR No. L4JO5


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UNIVERSITY OF FLORIDA I

31262081049719



I i',IvERSITY OF FLORIDA
DOGiCUMENTS DEPARTMENT
1 0 MARSTON SCIENCE UBRARY
P.O. BOX 117011
GAINESVILLE, FL 32611-7011 USA