Document
REPRODUCED BY NATIONAL TECHNICAL INFORMATION SERVICE U. S. DEPARTMENT OF COMMERCE SPRINGFIELD, VA. 22161
REPORT No. 633
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012
AIRFOIL WITH A SLOTTED AND A PLAIN FLAP
By CARL J. WENZINGER and JAMES B. DELANO
Langley Memorial Aeronautical Laboratory
74939--38--1 NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS HEADQUARTERS, NAVY BUILDING, WASHINGTON, D. C° LABORATORIES, LANGLEY FIELD, VA.
Created by act of Congress approved March 3, 1915, for the supervision and direction of the scientific study of the problems of flight (U. S. Code, Title 50, Sec. 151). Its membership was increased to 15 by act approved March 2, 1929. The members are appointed by the President, and serve as such without compensation.
SYDNEY M. KRAUS, Captain, United States Navy, JOSEPH S. AMES, Ph.D., Chairman, Bureau of Aeronautics, Navy Department.
Baltimore, Md.
CHARLES A. LINDBERGH, LL. D., DAVID W. TAYLOR, D. Eng., Vice Chairman, New York City.
Washington, D. C.
DENIS MULLIGAN, J. S. D., WILLIS RAY GREGG, Sc. D., Chairman, Executive Committee, Director of Air Commerce, Department of Commerce.
Chief, United States Weather Bureau.
AUGUSTINE W. ROBINS, Brigadier General, United States WILLIAM P. MACCRACKEN, J. D., Vice Chairman, Executive Army, Committee, Chief Matdriel Division, Air Corps, Wright Field, Washington, D. C.
Dayton, Ohio.
CHARLES G. ABBOT, Sc. D., EDWARD P. WARNER, Sc. D., Secretary, Smithsonian Institution.
Greenwich, Conn.
LYMAN J. BRIGGS, Ph.D., OSCAR WESTOVER, Major General, United States Army, Director, National Bureau of Standards.
Chief of Air Corps, War Department.
ARTHUR B. COOK, Rear Admiral, United States Navy, ORVILLE WRIGHT, Sc. D., Chief, Bureau of Aeronautics, Navy Department.
Dayton, Ohio.
HARRY F. GUGGENHEIM, M. A., Port Washington, Long Island,N. Y.
GEORGE W. LEWIS, Director of Aeronautical Research JOHN f. VICTORY, Secretary HENRY J. E. REID, Engineer-in-Charge, Langley Memorial Aeronautical Laboratory, Langley Field, Va.
JOHN J. IDE, Technical Assistant in Europe, Paris, France TECHNICAL COMMITTEES AERODYNAMICS AIRCRAFT STRUCTURES POWER PLANTS FOR AIRCRAFT AIRCRAFT ACCIDENTS AIRCRAFT MATERIALS INVENTIONS AND DESIGNS Coordination of Research Needs of Military and Civil Aviation Preparation of Research Programs Allocation of Problems Prevention of Duplication Consideration of Inventions OFFICE OF AERONAUTICAL INTELLIGENCE LANGLEY MEMORIAL AERONAUTICAL LABORATORY WASHINGTON, D. C.
LANGLEY FIELD, VA.
Collection, classification, compilation, Unified conduct, for all agencies, of and dissemination of scientific and tech- scientific research on the fundamental nical information on aeronautics.
problems of flight.
|I
REPORT No. 633
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH A SLOTTED
AND A PLAIN FLAP
By CARL J. WEN'ZIN'GER and JAMES B. DELAI_O SUMMARY (references 2 and 3) are available but, as the reported tests were not very comprehensive, the present investi- Pressure-distribution tests of an N. A. C. A. 23012 gation was undertaken to supply information applicable airfoil equipped with a slotted flap and with a plain flap to the structural design of slotted flaps. Similar data were made in the 7- by lO-foot wind tunnel. A test instal- are already available for the design of split, external- lation was used in which the 7-foot-span airfoil was airfoil, and Fowler flaps (references 4, 5, and 6).
mounted vertically between the upper and lower sides of Pressure-distribution tests were made in the 7- by the closed test section so that two-dimenslonal flow was 10-foot wind tunnel of an N. A. C. A. 23012 airfoil in approximated. The pressures were measured on the combination with a slotted flap. The optimum flap upper and lower surfaces at one chord section both on the path previously developed for this flap (reference 1) main airfoil and on the flaps for several different flap was used in these tests. Pressure-distribution tests deflections and at several angles of attack.
were also made over the same airfoil in combination The data are presented in the form o] pressure-distribu- with a plain flap for purposes of comparison and also to tion diagrams and as graphs of calculated section coe_- obtain additional information for the detailed structural cients ]or the airfoil-and-flap combinations and also for design of both flaps and ailerons.
the flaps alone. The results are useful ]or application to rib and flap structural design; in addition, the plain-flap APPARATUS AND TESTS data furnish considerable information applicable to the MODELS structural design of plain ailerons.
The models used in the present tests are the ones INTRODUCTION previously used in the force tests reported in reference 1. The main airfoil, made of laminated pine to the Up to the present time, many high-lift devices have N. A. C. A. 23012 profile, has a uniform chord of 3 been developed and investigated, but each appears to feet and a span of 7 feet. A removable full-span have some disadvantages. One of the most promising trailing-edge section permits the testing of different high-lift devices thus far developed is the combination full-span flaps in combination with the same main of a slotted flap with a main airfoil. Investigations of airfoil. Both a slotted flap and a plain flap made of this arrangement (reference 1) have shown that it is laminated pine were tested; each was supported on the capable of developing high lifts and that it gives lower main airfoil by three metal fittings, one located at mid-- drags at these high lifts than do external-airfoil, plain, span and one inboard of each flap tip.
or split flaps.
The slotted flap tested (fig. 1) is the one previously The force tests of reference 1, in which several com- developed by the N. A. C. A. and designated 2-h in binations of an N. A. C. A. 23012 airfoil with flaps of reference 1; it has a chord of 9.238 inches (25.66 per- different sections and with slots of several different cent of the over-all airfoil chord). A full-span fixed shapes were investigated, indicated that the best ar- lip made of strip brass is located on the upper surface rangement thus far obtained is a combination of an of the main airfoil over the flap-slot exit to seal the slot airfoil and a slotted flap, the flap having an airfoilshape when the flap is neutral and to direct the passage of and the slot an easy entrance; this combination is des- air downward over the flap when the flap is defleete(h ignated flap 2-h in reference 1. A survey of flap loca- The path of the nose point of the flap chosen (fig. 1) is tion with respect to the main airfoil was made to obtain the optimum one reported in the tests described in the best aerodynamic characteristics. It was also reference 1. The nose point of the flap is defined as found that some particular flap path would give opti- the point of tangency of a line drawn normal to the mum aerodynamic characteristics; the flap path airfoil chord and tangent to the leading-edge arc of the developed is reported in reference 1.
flap when neutral. The flap is arranged for locking at Very few data are available for application to the downward flap deflections between 0 ° and 60 ° in increments of 10% structural design of slotted flaps. Some recent data REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
outside the tunnel by rotating the torque tubes with a
The plain flap (fig. 1) has a chord of 7.20 inches
calibrated electric drive. Approximately two-dimen-
(20.0 percent of the over-all airfoil chord). The flap
sional flow is obtained with this type of installation,
gap was sealed for all flap deflections by interchange-
and the section characteristics of the model under test
able full-span brass lips on the upper and lower sur-
may be determined.
faces of the airfoil to prevent a flow of air through the
TESTS
gap. The flap is arranged for locking at flap deflec-
All the tests were made at a dynamic pressure of
tions between 45 ° up and 75 ° down in increments of
16.37 pounds per square foot, corresponding to an air
15 ° .
A single row of pressure orifices was built into the
upper and lower surfaces of both the main airfoil and
the flaps at a chord section 21 inches from one end of
!i!
the models (fig. 2). The orifices were located on the
models as listed in table I, the tubes from the orifices
being brought through the models and out at one end.
The pressures were photographically recorded by a
multiple-tube liquid manometer.
i i T I I /0'
I co
0 82 7c_ -- --L .. " _ , [
w,_ _ __...__
dzrecfzo ', , ,
_ ._0o788c_ lR=oO8#c j
asos/_, -------_" F-4 °<\', 1 , (al 60 ° Path of flop nose Horizon/a/ _ect/on (a) N. A. O. A'. 23012 airfoil with a 0.2566¢, slotted flap.
i-Balance frame [ {/ Mode/ support Path of flap nose for various flap deflec- _,]]fPressure tubes to oF/rices tions. Dtst anees measured from _//-- /.
lower edge of lip in 3! (deg.) percent airfoil chord
IWI"
c_ i i I l r i i , , , 2/" x y t i t --._-- ...... ,--. __¢: of 8.36 3.91 0 I ' I /2t-assure
i " 'Z
5.41 3.63 10 , I I Orl'fl'ce5 3.83 3. 45 i [ t 2. 63 3. 37 1. 35 2. 43 40 • 50 1. 63 50 i i • 12 1.48 60 I i I 1 I I I i
('" Gaps ueole(] 1 1" I I
i 5ZZ" .r 1
"= -----<VT ooos< I 32
=oo2 < ',\I /
Vertical section
(b) '_! ,_,: 75 °
':,y
FmUR_ 2.--Model installation for two-dimensional flow tests in the 7- by 10-foot t wind tunnel.
(b) N. A. C. A. 23012 airfoil with a O.2Oc, plain flap.
Fio, unE 1.--(;ross sections of model showing airfoil-flap combinations used in pres-
speed of about 80 miles per hour at standartl sea-level
sure-distribution tests.
conditions. The average test Reynolds Number, TEST INSTALLATION
based on the plain airfoil chord, was 2,190,000. This
test Reynolds Number, when converted to an effective
The model was mounted in the N. A. C. A. 7- by
10-foot closed-jet wind tunnel (references 1 and 7) as Reynolds Number (reference 8) that takes account
of the turbulence in the air stream, is 3,500,000. (Ef-
indicated in figure 2. The main airfoil was rigidly
fective Reynolds Number=average test Reynolds
attached to the balance frame by torque tubes, which
Number X turbulence factor; turbulence factor for the
extended through the upper and lower sides of the
tunnel is 1.6.)
tunnel. The angle of attack of the model was set from
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS The model was tested with the slotted flap set at chf=h-_f_, hinge-moment coefficient of plain flap about qvf angles of 0 °, 10 °, 20 °, 30 °, 40 °, 50 °, and 60 ° down; and flap hinge axis.
with the plain flap set at angles of 45 °, 30 °, and 15 ° __ Xf up, 0 °, and 15 ° , 30 ° , 45 ° , 60 ° , and 75 ° down. The ccf--_, chord-force coefficient of slotted flap alone.
angles of attack ranged from --14 ° to 20 °, and the lift (e. p.),o= 0.25- _-/N 100, center-of-pressure location cm_\ coefficients included those from approximately maxi- of main airfoil with flap mum negative to maximum positive. With the model in percent airfoil chord at a given angle of attack and with a given flap setting, from leading edge.
tunnel conditions were allowed to become steady before a record of the pressures at the orifices was
00, coo or-o - o =o
taken.
of flap alone in percent PRESENTATION OF DATA flap chord from leading PRESSURE DIAGRAMS edge of flap.
All diagrams of pressures over the upper and lower where the forces and moments per unit span are: surfaces of the airfoil-flap combinations are given as n_, normal force on main airfoil with flap (this force is ratios of the orifice pressure p to the dynamic pressure normal to chord of main airfoil and is equal to q of the free air stream for the flap deflections and for n,_-[-nf cos _f, neglecting the normal component the angles of attack investigated. Pressure diagrams of the flap chord force).
for the airfoil with the slotted flap are shown in figures n_, normal force on main portion of the airfoil without 3 to 15 and, for the airfoil with the plain flap, in figures flap (this force is normal to chord of main airfoil 16 to 24. The effect of the flaps on the pressure distri- and is equal to n,_--nf cos _s).
bution over the main airfoil is shown by a comparison n f, normal force on flap alone normal to chord of flap.
of the pressures over the plain airfoil with the pressures mr, pitching moment of main airfoil with flap about over both the slotted-flap and the plain-flap combina- quarter-chord point of airfoil.
tions at the same total normal-force coefficient and ms. pitching moment of slotted flap about quarter- also at the same angle of attack (figs. 25 and 26). In chord point of flap.
figures 3 to 9 and 16 to 26, the pressures over the main h f, hinge moment of plain flap.
airfoil are plotted normal to the airfoil chord and the xs, chord force on slotted flap alone.
and pressures over the flaps are plotted normal to a reference line which is parallel to the main airfoil chord when the q, dynamic pressure of free air stream.
flap is neutral but which deflects with the flap. c_, chord of main airfoil.
Figures 10 to 15 are included to show the pressures cl, chord of flap.
parallel to the chord of the slotted flap. These pres- The coefficients for the combination were derived sures are also given as ratios of orifice pressure to the from the normal forces alone, the chord forces of the dynamic pressure of the air stream; however, the flaps being neglected. In the case of the slotted flap, pressure values are plotted parallel to, instead of however, neglecting the flap chord-force component normal to, the flap reference line and are measured in the computation of the total normal-force coefficient from the maximum ordinates of the flap instead of of the combination reduces these coefficients by a from its reference line.
maximum of about 0.08.
COEFFICIENTS Because the model completely spanned the jet, the integrated results, which are given in coefficient form The pressure diagrams were mechanically integrated in figures 27 to 42, may be taken to be section charac- to obtain data from which section coefficients were teristics. The normal-force coefficients of the airfoil- computed. Where the term "flap alone" is used, refer- flap combinations include an experimentally determined ence is made to the characteristics of the flap in the correction for tunnel-wall effects, which was made as presence of the main airfoil. The section coefficients in reference 1.
are defined as follows: PRECISION normal-force coefficient of main airfoil with Cnw_ Tbw , No air-flow alinement tests were made in the wind qcw flap.
tunnel with the test arrangement used in this investiga- Cn¢_ fbf , normal-force coefficient of flap alone. tion, so the absolute angle of attack may be slightly in " qcr error; the relative angles are correct to within _0.1 °.
mw pitching-moment coefficient of main airfoil The flaps were set to specified angles to within _-0.1 °.
C m w ----"_w 2 , with flap about quarter-chord point of air- The orifice pressures, based on check tests in which foil.
both the angle of attack and the flap setting were independently changed, show that they agreed to pitching-moment coefficient of slotted flap alone about quarter-chord point of flap. within ± 2 percent, with the exception of upper-surface 4 REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 0 o 0 o W _o - -4 O ° c,_ = -0.23 _o = 12.0 ° C_= 1.30 _o = 0.0 ° c_= O./'q -4
p__
q -2
q
I -_- _o = 16.0 ° c,,_= 1.40 Upper- 5urfoce ........... £ ower b _o= 8.0 ° ao= 20.0 ° c._= 0.34 c,,_= 1.23 FIGURE &--Pressure distribution on the N. A. C. A. 23012 airfoil with a 0.2566c_ slotted flap, at various angles of attack. Flap set a_ 0%
PRESSURE DISTRIBUTION OVER AN N. A. C.A. 23012 AIRFOIL WITHFLAPS 5
/0 ° II _o = -4.0° e..: 0.03 _o 12 0 c,_,= 1.84 h' _o = 0"0° v c_= 0.59 _ - - _ _ _ _ - _ ta,, '._._- ao = /6.0 ° V,_,= 1. 60 .°= 4.0" _" Upper surfoce c._= 1.06 L owez- q -2 19-4 _._
\
,i '--- ao= 20.0" c._,= 1.51 ,..-" _o = 8.0 _ ; -- C..= 1.48 FIGURE 4.--Pressure distribution on the N. A. C. A. 23012 airfoil with a 0.2566c_ slotted flap, at various angles of attack. Flap set at 10% . REPORT NO. 633---NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS f
(
_--_o°
_o =-8.0" .__ _ ez ° = 8.0 ° C.== 0.10 C,_= 1..93
-° t
-6 P q c,.,= 0.5,.9 c._ = _2.23 i _ ao = 0.0 ° c..= /.07 "_"" " _a = 16.0" _'- ......
C._ = I. 78 UpDer surface L 0 wer ,,
\
0:-;; .......-_/-: J c.,. = 1,53 , ...... ,,,o = ao.o ° ;.- .....
c_,_= L66 FIGURE 5.--Pressuro distribution on the N. A. C. k. 23012 airfoil with a 0.2566c, slotted flap, at various angles of attack. Flap set at 20 °.
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS 7
•
c_= 0.02 -_"- - - _o = 8.0 ° "{- c,_= 2.23 -6
__p
q -4
.......... ..;,%..\
_" eQ =-4.0" L_ _. - c,,,_ = 0.38 "'-_ -2 k _ - _ _\_,"
/ - - % = -_ _.-o: - - -
c,._,= Z.43 Upper .surface ........... Lowe/" ,' l
................. -,._,,,_ \
._ _o= 4.0 ° "--. _ c,,_, = 1.86 _o= 16.0" .'----T_"2._ - ., c..= 1..99 FIGURE 6.--Pressure distribution on the N. A. C. A. 23012airfoil with a 0.256_c. slotted flap, at various angles of attack. Flap seL at 30° 74939---38--2 8 REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS c._= 0.,31 "'-."_ -12 6 o : -8.0 ° e.. : O. 78 -I0 -8 -6
p
q _o : _ 4.0 ° '- . _\ -4 c._= 1.24 _,. "x,__ -2 /.
, ..... ,,°: _£57- -/-.
C_,: 2.67 Upper Surfoce -Lower a o = 16.0 ° c,,,., = Z.08 c_= 2.06 FIGURE 7.--Pressure distribution on the N. A. C. A. 23012 airfoil with a 0.2566cw slotted flap, at various angles of attack. Flap set at 40 °.
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS 9
C
I J
_o: o..s "--.\b
-12 -I0 -8 -6
p_
o c _o = -4.0 ",, q e,,,, = 1.26 -4 -2 o_ o = 0.0 ° c._= 1.66 • upper .surfoce I 0 We/" "
L
___ _ - _o = /_i0 ® c._= 2.04 FIGURE 8.--Pressure distribution on the N. A. C. A. 23012 airfoil with a 0.2566cw slotted flap, at various angles of attack. Flap set at 50%
10 REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
<i
4"
i i 6 o = 8.0 ° c._= B.30 -/Z -I0 cQ = -8.0 ° \,, C_= 0.82 -8
__P
q -8 ..... _ J c,,_,= /./3 -2 / I / _f -_-- /11 \\\ Upper Surfoce ..........
._ ° ....... Lower ,,
L
:--'" .°= T_; _,
_..- '_" "'..\5
FIGURE 9,--Pr_ure distribution on the N. A. C. A. 23012 airfoil with a 0.2566c_ slotted flap, at various angles of attack. Flap set at 60 °.
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS \\ t i ...... _%:, _,, = -8.0 ° , \..-_ _° = _%'Y/ \"-.
do = - 4.0 ° do = 12.0 ° % =-0.08 ",22_, o_, = 0.01 co, =0.04 Aheod Aheqd of maxi- \\\ FnOXl'- mum oro'i- mum ordl'- no/e_ \\\\ no(es of "_ of -- 2 R-_ of flop N \ flop "N clo "_ G=/ .-_ %: -a/o _--. :-o.oG -_\'", v4 =0.0 ° % =O.02 . _,J vt o =16.0 o e_, =O..08 /. To reor To mox/- "_.__....._ reor 2% o, of _0 =4.0 °
o. o%m 2,='%G l
co_ =-O.OS \-Z__. notes moxi- e_, =o.oa of mum ordi- flop no_es of Mop --,. \\%_ o',o ,..ofo,.. _ "\ / _',oc_ ,. \ ), / F/°° ,'-e P@,_
" "
2,
o
f I 9' I do = 8.0 ° _o =200 o _o= 4.0 ° 04=8O0° e_, = O.0.3 % = a/2 c_, =-0.0.8 ¢_, =00.1 FIGURE 10.--Chord pressure distribution on a 0.2566c_ slotted flap mounted on tho FIGURE ll.--Chord pressure distribution on a 0.2566c_ slotted flap mounted on the N. A. C. A. 23012 airfoil, Flap set at 10 °. N. A. C. A. 23012 airfoil. Flap sot at 20 °.
i2 REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
%
' j "
"%../\
_'o:-/_._ -..,-...\ _o: 4._o_°_ "-,L:_,\
%:-o._8 , -..\.. _o,:-03o '"C_
-%\.. -..
--\._
• \_ _ of _ ', _ moxi- ') ; .... ) \ mum ' -- _ ordl- \\ \ / nares \, c_ Ah_oo , , \',. \ / of '"_"_ L'\ I_ flap
">.>:X
do%:-aO °_d3o """J"- .%.-. t c:, :-O2m ' "-._L
r ear -" - - - " of , .
max/- t \, ordi- _, '_t _ To nares _, _ -ear
\,, _ of "'V of \
. - _) _ max/- _ _ mum
,.).\ /.,o. ,.%
. \ i ordi- "\ \ / notes _: V of a,o - -<o o ", ..,.,. % - 120 o ", c.. : -O 44 , c_. : "0.36 , " _.-.._.. , I \ flop
i
"c.-.. /
\
<<o:-_o: "-!_..\ d.o:m.9: ^ "_..\
c<, -(230 J "","_c-.
c_, :-026 ' -.,_\.
..\-
..\-..
/ 0 • .,.._ _ / •
/
",,,]):)_ _/ "><,..m
_,o: ao
_o: 16.o°'-._.
FIGURE 12.--Chord pressure distribution on a 0.2566c, slotted flap mounted on the FIGURE 13.--Chord pressure distribution on a 0.2566e_ slotted flap mounted on the N. A. C. A. 23012 airfoil. Flap set at 30 °. N. A. C. A. 23012 airfoil. Flap set at 40 °.
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS 13 /1 /" t \\ "-,.. ....
\ ,,, \ _"x \ \..
\ \\ \ k "x \ ", \ \\ \\\\ \ \ \\ \ a,o = 40 o
co,: -2{35 _I
Ahead \\"- too\l- \ " _ \ \ \\ \\ mum \ "\ \ \ ordi- \\ \ \ \\ o:Ts ,,\ ,
(
04 : 8.0 ° \\ "\ Co, = -0"36 \_,, _ oo__o,, ",.\ \ -.
To \ ____ \ "% reor \\ "...
of \ %,.
too\l- \ x\ \ \ \ x \ x, ordi- notes \\\ x\ mum \\ of flop
""_'%. /
\\" % _ -0.3(9 "\>_ c_,= -0.40 ',_,_ %% -....
,,....... ...
',,, -..... ?_ ,,_,_ ""3>
\,, -. \\__ ( ' \ .
_o- O0 ,,, \ c_, =-0.4.1 \\ ('- c_ =-cZ.31 \ \_x • ..' _\,_ \
_- aa" \',"%/_ _o-l_.O' \',,_
' _ _ ',, ,-__.
Ftougm t4.--Chord pressure distribution on a 0.2566c,_ slotted flap mounted on the FIGUR_ 15.--Chord pressure distribution on a 0.2566c_ slotted flap mounted oa the N. A. C. A. 23012 airfoil. Flap set at 50 °. N.A.C.A. 23012 airfoil. Flap set at 60 °.
14 REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
_ -45 Ll \ \ \ cco = /2.0 ° c,,_,= 0.19 L'_ (=o = -4. 0 ° C.,_ = -LJ3 N. ....... .
f
_o= 0.0" c,_, = -/.06 _,o = 16.0" C,,_, = 067 Upper _¢urfoc_ ............. Lower _xo= 4.0 ° c._,= -0.67 q sl-,_ , 0 / _ _" _o= ZO.O ° c,_,= L 04 o¢o= 8.0 ° c,_, =-O.Z4 FIUURE 16.--I'ressure distribution on the N. A. C. A. 23012 airfoil with a 0.20cw plain flap, at various angles of attack. Flap set at --45 °.
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS ] a \ x f .°..,o.
c._ = -/./5 = 0.0 ° c ,, _, = - 0..73 i___ _ s _ u o = 16.0 c,_,= 0.81 Upper ,surface _o= "if'O° Lower ,, c._=-0.4Z _61 -4 q -2 I -_ 0 - _e 8 0 I "_-_ _ _o = 20.0" e._ffi-O.08 e._= 0.83 FIeUR_ 17.--Pressure distribution on the N'. A. C. A. 23012 airfoil with a 0.20c_ plain flap, at various angles of attack. Flap set at --_0 ° 74939--38--3
16 REPORT NO. 633_-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
-C
_-_ -/5° ___ " -..1_ -.'_ _ I _ = 12.0 ° c,,_,: 0.70 O:o = -40" c._ = -0.30 _:o = O. 0 ° ¢,_= -0.53 t_ 6 o = I6.0 ° e,_, = 0.34 (_o= 4.0" c._ :-0.14 Upper _urfoce ........... Lower" ,, -2 P -4 L • X).
(_o = 8.0" 0 V,,,_= 0.28 '- ao= 20.0" c,,,_ = /.0/ FIc, Vl¢l_ 18,--Pressure distribution on the N. A. C. A. 23012 airfoil with a 0.20c_ plain flap, at various angles of attack. Flap set at --15 °.
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS :17 f 0 ° 0 o _I o =-4.0 ° c._ = -0.33 eQ = 12.0" c._= 1.31 c_o = 0.0 ° c._= 0.12 3, _i - 6o = 16.0 ° Cn_,= 1.37 Upper ._urf oce ....... Lowet- _o= #.0 ° c._= 0.55 -4
p
q -g _o= £0.0 ° C,.,,.,= /.25 o_ o . 8.0 ° c.,_ = O. 95 FIGURE 19.--Pressure distribution on the N. A. C. A. 23012 airfoil with a 0.20c_ plain flap, at various angles of attack. Flap set at 0%
18 REPORT NO. .633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
f
C
=- , o ao 80 c ,,,, = -0.02 a o = IZ.O ° C,,w= 1.73 o_ o= 0.0 ° C.,.= 0.77 "_ .... _ " cto = 16.0" C,,=,= 1.63 Upper- ._urfoce Lower" "
6 f
-2
P.P_q -4
-" at= 20.0" c_. l L41 FIGURE 20.--Preseure distribution on the N. A C. A. 23012 airfoil with a 0.20c,, plain flap, at various anglos of attack. Flap set at 15°.
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS 19
a o : -8.0 ° cn_: 02/ '.,L_"" ,_o = 8.0" c_,= 1.74
[-_ -___ __
[ oo= --
c._= 0.60 Upper ._urfoce .......... Lower -6
p
V / - _o= IG.O ° C,_,, = /. 7,.9 FIGURE 21.--Pressure distribution on the N. A. C. A. 23012 airfoil with a 0.20c_ plain flap, at various angles of attack. Flap set at 30% REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
2O
a o =-12.0 c..= 0.06 _--- _o = 8.0"
--._%)
c.,,= 1.97 e% =- &O" c,_,= 0.4,9 -6 --4 P ,,- .................... q,, 'Y'o = -4"0° -Z c,_= 0.83 0 i //I c..,= 2.20 Upper ,surface ao= 0.0 ° L owel" /' _ _ _ _o = 16.0 ° _x_ ,, C._= 1.86 FIGURE 22.--Pressure distribution on the N. A. C. A. 23012 airfoil with a 0.20e_ plain flap, at various angles of attack. Flap set at 45°.
PRESSURE DISTRIBUTION OVER AN N. A. C.A. 23012 AIRFOILWITHFLAPS 21
a o = -/2.0 ° cn_, = 0.20 ,., ___ i
"-_ --- e..:a°= z/4so: - ..... _-L_"
QB = -8-0 ° \,, \ \ C,,_,= O. 70 " " "-__J
__p-sq/
-4 c.,,= ZlO -2 i _ 12.0 ° c..= 2.38 ._ Upper _urfoce c,,,,: 1.48 / OWeF ......... ( I .... _ _'o = 16.0" \..
C.,,,= /.92 FIUUa_ 23.--Pressure distribution on the N. A. (.'. A. 23012 airfoil with a 0.20c, plain flap, at various angles of attack. Flap set at 60 °.
REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 75 ° 75" c_= 0./6 '__ ) 1 ..... % _x - - ......... T -- J \ c_= e.17 \ _ .)
V ao =-/a.O ° ', c,,w:0.37 '.. __ _.)
_o=-8.o o I \ \
c_= o 78 ',. \_)
-6
p
__ ....... T'-- l c._= Z17 "_ __ )
/ ...... /2 o _, J
. _ 0.0 ° /.53 UppeF 5urfGce ............... LOWeF ........ L,:-;_o- .... r , C,,,,= /..93
; ----- .o= 4.o: ...... '_
e,_,= /.88 FIGURE 24.--Pressure distribution on the N. A. C. A. 23012 airfoil with a 0.20c_ plain flap, at various angles o[ attack, Flap set at 75 °,
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS 23
/
/
/ / /
///
//
//
% Lo I t,D .Plain airfoil -- - -- Airfoil with flop, _ -15 ° © ............ 30 ° -5 ..... 45" ©
\
© p
\
q © ©
S
(a) At the same lift, Cnw=l.3l. (b) At the same angle of attack, a0=8 °.
FIGURE 26.--Comparison of the pressure distribution on an N. A. C. A. 23012 airfoil and a 0.20c_ plain flap with that on the plain airfoil.
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS 25
-4 An_/e of ottock, _o, deg.
0 4 8 12 /6 _0 0 4 8 I_ I_ ZO -4 z 0 4 8 I_ o L2 L6 20 .P4 4 .8 /2 LG _0 24 coeffic/ent of (a) Airfoil with flap. (a) Airfoil with flap.
(a) Airfoil with flap.
(b) Flap alone.
(b) Flap alone. (b) Flap alone.
FIGURE 27.--Section characteristics of the FIGURE 28.--Section characteristics of the FIGURE 29.--Section characteristics of the N. A. C. A. 23012 airfoil with a 0.2566c_ N. A. O. A. 23012 airfoil with a 0.2566¢. N. A. C. A. 23012 airfoil with a 0.2566co slotted flap set at 0 °.
slotted flap set at 10 ° slotted flap set at 20% REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 8O IO0 -.4 .4 .8 I.Z L6 2.0 _.4 .4 .8 1.2 /.6 _.0 24 Z coefficient of c._ (a) Airfoil with flap. (a) Airfoil with flap.
(a) Airfoil with flap.
(b) Flap alone. (b) Flap alone.
(b) Flap alone.
FIGURE 31.--Section characteristics of the FIOURZ 32.--Section characteristics of the FmURE 30.--Section characteristics of the N. A. C. A. 23012airfoil with a C.256,_c_ N.A.C.A. 23012airfoil with a 0.2566cw N. A. C. A. 23012 airfoil with a 0.2566cw slotted flap set at 40°. slotted flap set at 50°.
slotted flap set at 30 ° ,
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS 27
pressures near the leading edges, which, at high angles of attack, checked to within :E 5 percent. The dynamic pressure recorded was accurate to within :E0.25 per- cent for all tests. Pressure orifices were not sufficiently numerous to determine accurately the peaks of pres- sures on the airfoil nose, but this deficiency should not materially affect the results.
RESULTS AND DISCUSSION SECTION PRESSURE DISTRIBUTION The distributions of air loads on the main airfoil and on the two types of flap are shown in figures 3 to 26. These pressure diagrams may be applied to the structural design of ribs and flaps and, in addition, figures 16 to 24 are useful in that they supply consid- erable detailed information for the structural design of plain ailerons. The pressure diagrams also serve to -.4 2..8 illustrate some important effects of the action of flaps on the distribution of pressures over the airfoil.
A comparison of the pressures over the upper surface of the slotted flap (figs. 3 to 9) with those of the plain flap (figs. 16 to 24), or with those of either the external- airfoil flap (reference 5) or some Fowler faps (refer- ence 6), indicates certain differences, the most obvious of which is a double-peak negative pressure region near the nose. These peaks may be interpreted as indicat- ing the existence of relatively high-velocity regions with a low-velocity region between them.
An analysis of figures 4 to 7 shows that this region of decreased velocity, or increased pressure, moved for- ward on the flap as the flap deflection was increased.
For flap deflections of 10 ° , 20 °, 30 ° , and 40 ° this region was located at approximately 2, 1_I, 1, and _ percent of the main airfoil chord, respectively, behind the leading edge of the flap. Because of its path, the nose of the flap moved back correspondingly greater increments when the flap was deflected; therefore the resultant movement of the region of decreased velocity was back- ward toward the edge of the lip as the flap deflection was increased. The double-peak pressures finally dis- appeared at high angles of attack for a flap deflection of 30 ° (fig. 6) and at low angles of attack for a flap de- flection of 40 ° (fig. 7). As the angle of attack was in- creased for a given flap deflection (figs. 4 to 7), the double-peak pressure distribution slowly approached a single-peak pressure distribution. It is interesting to note that these peak negative pressures on the slotted flap extended over a greater portion of the flap chord than did corresponding peak pressures Over other flaps (references 5 and 6).
The peak pressures over the upper surface of the slotted flap are not so high as the corresponding peak pressure's over an external-airfoil flap, but they arc FIGURE 33.--Section characteristics of the N. A. C. A. 23012 airfoil with a 0.2566c.
much higher than those over the plain flap (figs. 16 slotted flap set at 60 ° .
to 24). No data are available, however, for the ex- ternal-airfoil flap for flap deflections above 40 °, but it is peak pressures because it can be set at higher flap deflec- believed that the slotted flap would develop higher tions before completely stalling. The upper surface of REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
I
Angle of attack, do, deg.
/2 /6 0 4 8 12 IG 20 -,¢ 0 4 8 12 16 EO -4 0 4 I00 -/.2 :8 =4 0 -.8 :4 0 .4 .8 /.Z coefflc/ffn¢ of c,,.
(a) Airfoil with flap. (a) Airfoil with flap.
(a) Airfoil with flap.
(b) Flap alone. (b) Flap alone. (b) Flap alone.
FIGURE 35.--Section characteristics of the FIGUEE 36.--Section characteristics of'the FIGURE 34.--Section characteristics of the N. A. (]. A. 23012 airfoil with a 0.20c. N. -4.. C. A. 23012 airfoil with a 0,20c.
N. A. C. A. 23012 airfoil with a 0,20¢.
plain flap set at -30% plain flap set at -1_ °.
plain flap set at --45 ° .
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS 29 -:4 0 .4 .8 L2 L6 0 .4 8 LZ 4 ._ LZ 16 2.0 2.4 coeff,;cient of c.. i (a) Airfoil with flap. (a) Airfoil with flap. (a) Airfoil with flap.
(b) Flap alone. (b) Flap alone. (b) Flap alone.
FIGUaE 37.--Section characteristics of the FIGURE 38.--Sectiov characteristics of the FIGURE 39.--Section characteristics of the N. &. C. A. 23012 airfoil with a 0.20c_ N.A.C.A. 22012 airfoil with a 0.20c_ N:. A. C. A. 23012 airfoil with a 0.20c.
plato flap set at 0% plain flap set at 15 °. plain flap set at 20 °.
REPORT NO. 633--NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
3O
/_ An:_ le of" o/lack 8 /2 -8 -4_ 0 4 8 12 - -8 -4 O 4 -8 -4 0 4 I00 zl .8 AZ A6 2.0 Z4 .4 .8 /.2 A6 20 2.4 .4 8 A2 /.6 2.0 2.4 28 coeff_c/enl of c,, (a) Airfoil with flap. (a) Airfoil with flap. (a) Airfoil with flap.
(b) Flap alone. (b) Flap alone. (b) Flap alone.
FIGURE 40.--Section characteristics of the Fmva_ 41.--Section characteristics of the FXOURE 42.--Section characteristics of the N. A. C. A. 23012 airfoil with a 0.20c_ N.A. (3. A. 23012 airfoil with a 0.20c_ N.A.C.A. 23012 airfoil with a 0.20c_ plain flap set at 45 ° . plain flap set at 60 ° . plain flap set at 75 ° .
PRESSURE DISTRIBUTION OVER AN N. A. C. A. 23012 AIRFOIL WITH FLAPS of positive pressure were practically constant; whereas, the slotted flap (figs. 3 to 9) was only partly stalled for for the plain-flap combination, the magnitudes of both high angles of attack at high flap deflections; whereas positive and negative pressures were increased as the the upper surface of a.n external-airfoil flap (reference 5) flap deflection was increased.
was completely stalled for angles of attack above 3 ° at The flaps also obstructed the flow of air below the a flap deflection of 40 °. The slotted flap taken as a airfoil and caused the pressures to build up on the lower whole was completely stalled (no increase in flap load surfaces. The air flowing through the slot produced a with flap deflection) for a flap deflection between 40 ° high average velocity and increased the negative pres- and 50 ° (figs. 8 and 9), and the external-airfoil flap sure on the upper surface of the slotted flap; the nega- previously tested (reference 5) was completely stalled tive pressures on the upper surface of the plain flap for a flap deflection between 30 ° and 40 °.
The chord pressure diagrams for the slotted flap changed very little.
The slotted flap had a pressure distribution similar (figs. 10 to 15) are included because it is believed that to that of the plain airfoil, except for the double-peak relatively large forces probably existed that acted in a direction to retract this flap from its maximum-lift pressures, indicating that, as long as the flap remains unstalled, it would have a small wake, as would the setting. As shown by these diagrams, the negative and positive components act in the same direction for nearly plain airfoil. Near the stall, however, the wake of the combination would still be small because of the slot all of the arrangements tested except the 10 ° setting, so that the total chord pressure force is directed forward effect, which permitted the attainment of high lifts with in practically all cases. These diagrams are consider- relatively low drag. This effect is absent for the plain ably different from those of some Fowler flaps previously flap on account of the large wake, especially near the stall.
tested (reference 6), in which the negative and positive components acted in opposite directions and tended to Comparison of pressure diagrams for the plain airfoil counteract each other. It should be noted that the and for the airfoil-flap combinations at the same angle chord pressure forces do not include the sldn-friction of attack (figs. 25 and 26) shows that the flaps increased forces, which act nearly parallel to the chord and in the negative pressure over the entire upper surface of the main airfoil and increased the positive pressure such a way as to decrease the magnitude of the total on the lower surface of the main airfoil except near the chord force if negative or to increase it if positive.
No pressure-distribution tests were made to deter- leading edge. The pressure gradients remained about the same except at the trailing edge of the main portion mine the effect of slight deviations of the flap from its of the airfoil for the slotted-flap combination, where optimum path. An analysis of the data presented in the adverse pressure gradients were decreased on the reference 1 and in this report, however, indicates that upper surface and increased on the lower surface. The slight deviations from the optimum flap path would pressures on the upper and lower surfaces of the flapg not be expected materially to affect the magnitudes increased with flap deflection but more so for the slotted and the distribution of the pressures over the flap. Any flap. The important effect of the flap, as shown by appreciable deviation from this optimum path would affect the total lift and the total drag of the airfoil-flap these diagrams, was its ability to influence the air flow around the main airfoil so that the airfoil carried combination as noted in reference 1.
a much greater load without stalling than was possible The distribution of pressures over the plain flap (figs.
16 to 24) is similar to that of a symmetrical plain flap without the flap. The slotted flap was superior to the reported in reference 9. High negative pressures for plain flap in this respect.
practically all angles of attack were found on the lower SECTION LOADS AND MOMENTS surface at the flap nose for flap deflections of --30 ° and --15 ° and on the upper surface for a flap deflection of The section coefficients are plotted in figures 27 to 15 ° . For flap deflections above 15 ° , high negative 42. Flap loads build up slowly for most lifts of the combination. The loads on the slotted flap increase pressures appeared on the upper surface at the flap nose. For flap deflections of 30 ° to 75 ° (figs. 21 to 24), more rapidly with flap deflection (figs. 27 to 33) than the upper surface of the flap was stalled. do the loads both on the plain flap (figs. 34 to 42) and Comparison of pressure diagrams for the plain airfoil on the external-airfoil flap (reference 5). The highest and for the airfoil-flap combinations at the same lift flap loads seem to be obtained with the slotted flap, the maximum normal-force coefficient being about 30 (figs. 25 and 26) shows the effect of the flaps. Increas- ing the flap angle and decreasing the angle of attack percent higher than for the external-airfoil flap. It is to maintain constant lift had the following effects: At believed that slight deviations of the flap from its the leading edge of the main airfoil, for both combina- optimum path would not materially affect the flap tions, the magnitudes of the peak pressures were loads. The greater part of the increment of normal- force coefficient of the combination due to deflecting progressively reduced. At the trailing edge of the main the flaps downward, however, arises from the increased airfoil, for the slotted-flap combination, the magnitudes load carried by the main airfoil.
of negative pressures were increased and the magnitudes
32 REPORT NO. 633---NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
The chord-force coefficients of the slotted flap (figs.
effective in this respect than the plain flap or an 28 to 33) are nearly all negative in sign; that is, the external-airfoil flap.
pressure forces parallel to the flap reference line are directed forward. The magnitudes of these forces are relatively high and considerably greater than those of some Fowler flaps of N. A. C. A. 23012 section that LANGLEY _V[EMORIAL J_.ERONAUTICAL LABOR&TORY, were recently tested (reference 6). The chord forces NATIONAL ._kDVISORY COMMITTEE FOR AERONAUTICS, should be taken into account in design when consider- LANGLEY FIELD, VA., March 17, 1938.
ation is being given to the resultant air loads acting on REFERENCES the slotted flap. As mentioned previously, the magni- tudes of these forces would be somewhat decreased by 1. Wenzinger, Carl J., and Harris, Thomas A.: Tests of an N. A.
the skin-friction forces that have not been included.
C. A. 23012 Airfoil with Various Arrangements of Slotted The pitching-moment coefficients of the slotted flap Flaps in the Closed-Throat 7- by 10-Foot Wind Tunnel, to be published at a later date.
alone about its quarter-chord point were slightly 2. Kiel, Georg: Pressure Distribution on a Wing Section with tfigher than the pitching-moment coefficients of the Slotted Flap in Free Flight Tests. T.M. No. 835, N. A.
external-airfoil flap (reference 5) for flap deflections C. A., 1937.
up to about 30 ° (figs. 27 to 30). The pitching-moment 3. Ruden, P.: Versuche an einem Diisenfliigel. Jahrbuch, 1937 center for both flaps was at about the same location.
der Deutschen Luftfahrtforschung. S. 1 75-186.
4. Wenzinger, Carl J., and Harris, Thomas A.: Pressure Distri- For a flap deflection of 40 ° (fig. 31), the pitching- bution over a Rectangular Airfoil with a Partial-Span Split moment coefficients for the slotted flap were much Flap. T.R. No. 571, N. A. C. A., 1936.
smaller than they were for the external-airfoil flap.
5. Wenzinger, Carl J.: Pressure Distribution over an N. A. C. A.
For higher flap deflections, the pitching-moment co- 23012 Airfoil with an N. A. C: A. 23012 External-Airfoil efficients increased quite rapidly (figs. 32 and 33). The Flap. T.R. No. 614, N. A. C. A., 1938.
hinge moments for the plain flap were high and in- 6. Wenzinger, Carl J., and Anderson, Walter B.: Pressure Dis- tribution over Airfoils with Fowler Flaps. T.R. No. 620, creased rapidly with an increase in flap deflection (figs.
N. A. C. A., 1938.
34 to 42).
7. Harris, Thomas A.: The 7 by 10 Foot Wind Tunnel of the CONCLUSIONS National Advisory Committee for Aeronautics. T. R.
No. 412, N. A. C. A. 1931.
1. These pressure-distribution tests show that, as 8. Platt, Robert C.: Turbulence Factors of N. A. C. A. Wind with other types of flap, the greater part of the incre- Tunnels as Determined by Sphere Tests. T.R. No. 558, ment of total maximum lift due to deflecting the N. A. C. A., 1936.
slotted flap downward arises from the increased load 9. Jacobs, Eastman N., and Pinkerton, Robert M.: Pressure Distribution over a Symmetrical Airfoil Section with Trail- carried by the main airfoil.
ing Edge Flap. T.R. No. 360, N. A. C. A., 1930.
2. The maximum normal-force coefficient for the slotted flap investigated had a higher value than that TABLE I.--ORIFICE LOCATIONS ON AIRFOIL-FLAP attained by other types of flap, and the magnitudes of COMBINATIONS TESTED the pressure chord-force coefficient were relatively N. A. C. A. 23012 36- large.
inch airfoil with a N.A.C.A. 23012 36-inch airfoil with a 3. The pitching-moment coefficients for the slotted 0.20c_ plain flap i 0.2566cw slotted flap flap alone were slightly higher than the pitching-moment upper and lower upper and lower Orifice locations on coefficients for an external-airfoil flap alone (moment surfaces in percent surfaces of main upper and lower Orifice locations on I Orifice locations on chord from leading portion of airfoil in surfaces of flap in centers had approximately the same location) for flap edge percent chord from percent flap chord leading edge from leading edge deflections up to 30 ° .
I 4. The pressure diagrams showed that, when the Orifice Location Orifice Location Orifice I Location I plain airfoil and airfoil-flap combinations were com- pared at the same total normal-force coefficient, the flap 0 0. 00 0 0. 00 0 0. 00 1 1.25 1 1. 25 1 1.25 reduced the adverse pressure gradients and the tendency 2 2. 50 2 2. 50 2 2. 50 3 5. 00 3 5. 00 3 5. 00 of the main airfoil to stall. The slotted flap was more 4 10. 00 4 10. 00 4 10. 00 5 2O. 00 5 20. 00 5 18.00 effective in this respect than the plain flap or an ex- 6 30. 00 6 30. 00 6 30. 00 40. 00 7 7 40. 00 7 45. 00 ternal-airfoil flap.
8 50. 00 8 50. 00 8 62. 50 9 60. 00 9 60. 00 9 72. 50 5. The pressure diagrams showed that, when the 10 70. 00 10 67. 00 10 82. 50 ll 75. 00 11 70. 00 11 92, 50 plain airfoil and the airfoil-flap combinations were com- 12 78. 00 • 12 74. O0 ....................... i 13 80. 00 13 78. O0 .......................
pared at the same angle of attack, the flap influenced the 14 82. 50 14 81.50 ..........
15 85. 00 flow of air around the main airfoil so that the airfoil 16 90. 00 17 95. 00 ...............................
carried a much greater load without stalling than was 18 98. 00 .......... i ................ ! .............
possible without the flap. The slotted flap was more