Document
.
REPORT No. 742
WIND-TUNNEL INVESTIGATION OF AN NACA 23012 AIRFOIL WITH 30-PERCENT- CHORD VENETIAN-BLIND FLAPS By F. M. ROGALLO and 13AETHOLOMFIW S. SPANO VENETIAN-BKNDPLAH SUMMARY AU the venetian-blind flap arranganents had an An imwtigation b been mm-h in the NACA 7- @ over-all ohord of 30 percent of the wing chord and a 10-foot n“nd tunnel of cm NA.@4 MOM a~’-l wii!h ilap-hinge axis at the tiailhg edge of the wing with the SO-percent-chord wwtian-blindjiaps king one, ium,three, flap fully extended. This smangement was considered and four 81at8of Clark Y 8ection. The three-idat arrange- optimum from the tests of refetknee.1.
nwnt w aerodynamically the beet of “those teded bui The first alat of eagh combination was hinged below - dtm.wd practically no improvement owr the comparable the trailing edge of the w@g and the successive slate arrangement wed in the prelirninq t2.et8published in were hinged on the premding ones. A slat chord NACA Report No. 689., The multiple-dat J%ps gare L..
spacing (distance between stat-hinge axes) of one sIat 81ightly higher li$ caejicient8 thun the o-n.-e+lat (Foder) chord Ie@h, ~ncIuded w optinkn in reference ],” &p but gare considerably greater pitching+noment coefi and a aIatAinge axis ‘at the slat nose (3.5 percent of the m“ents. An anal@a of te8tdata indicalea thut eubh”iuh”on slat ohord above the slat chord line) were used for aU ‘ of a thicker and more cambered sectionfor tlu Clark Y the tests. The sIat deflections were measured between 81at88hotdd improre the aerodynamic and h 8irwtural the wing chord Iine gnd the chord lines of the slats.
diarmtetitim of the renetian-blindj?ap.
All the slats were made of wood and conformed “to - INTRODUCTION the Clark Y profile. They were seeured ta the wing with four sets of ela&inge &kings located spanwise The NACA is undertaking an extensive investigation to give minimum slat bending deflection. Each skit 4 of various wing-flap combinations for improving safety required a sepexate set of hinge fittings.
and performance in flight. One promising oombirtation The combinations teeted (~. 1) were: The one-slat developed to’ date by the NACA is the ventkian-blind (Fowkr) flap composed of one 30-percent-chord slat, flap (reference 1), which gave higher maximum Iift coefficients and lower drag coefficients at modcmd.dy high M coefficients than any flap previoudy tested by the NACA (referenc~~1 and 2].
A further development of the 30-percen&chord venetian-blind flap hinged at the trailing edge of the wing appeared pmmising. ” In the present investigation various arrangements were tested b determine the effect of number of the slats and chords of the sIata used tn form the flap, of the slot gap between the slats, and of the position of the slats with respect to each other and to the wing.
The characteristics of an NACA slotted flap and of a plain wing me iduded for comparison.
MODELS MAINAIBFOIL The basic wing, or plain airfoil, was budt to the NACA 23012 profile and has a chord of 3 f&t and a span of 7 feet. The wing was constructed of laminated mahogany and tempered wallboard with a sti trailing- edge pIate. It was specially made for these tests.
(s) One .OJOc slat (Fowkc).
(0) Tlyen O.Ioc RInL% (b) Two OMc SIBts.
(cU Fuu O.(mc data.
The cut-out required for the retraction of the one-dat FIOUM L—&ctiomM NACA =12 fLrfdI with sevfd srrauements d O.ZOC (l?owler) 30-pert.en&ehord venetian-blind flap was venethmblhd &. Test bingeaxescddata (4 at 0.(@2i!G 0.016G and 0.0Z3C Mow retained in all the models.
tmIUncedgesnd~dkmlarto chorduneofm@Mm Ma !241 l 242 REPORT NO. 742—NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS the two-slat combination composed of two 15-percent- section lift coefficient (1/qc) chord slats, the three-slat combination composed of effective section maximum lift Omefficien t for three 10-percent-chord slats, and the four-sIat combi- complete airplane nation composed of four 7%percent-chord slab. In section profile-drag coefficient (ddqc) the tests the one-slat (Fowler) flap is considered to be section pitching-moment coefficient about aero- the limiting case of the venetian-blind flap.
dynamic center of phiin airfoil {?n~~,t,j~q~) EquaI slot gaps of )4, 1!4, and 2?4percent of the wing chord were used. Theee slot gaps were measured from section lift the slat nose-hinge point to the chord line of the imme- section profile drag diately preceding slat or main airfoil. The slot gap section pitching moment defined is not ‘the minimum air gap between two ad- jacent slats or between the first slat and the main airfoil L 172 dynamic pressure Zp but is the distance between the slat-hinge axis (at the () slat nose) and the chord line of the preceding slat or chord of basic airfoil with flap retracted main airfoiL TESTS angle of attack for infinite aspect ratio The models were mountad in he closed test section deflection of individual slats of the NACA 7- by 10-foot wihd tumml so aa b span The subscript carried by j refers to the number of the the jet cornpletdy except for small clearances at each slat, counting as 1 the slat hinged to the wing trailing end, (See referenca 3.) The main airfoil waa rigidly edge.
attached to the bahmce frame by torque tubes, which PIU3C!MION extended through the upper and the lower bounda&s The accuracy of the various measurements in the of the tunnel. The angle of attack of the modeI was tests is believed to be within the following limits: set from outside the tunnel by rotating the torque q------------ +0. 10 C% .------ &o.0006 tubes with a Calibrakd drive. Approximately two- (Cld.m dimemional flow is obtained with this type of instal- cam= ---------- ko.03 C% ------- *O. 002 lation and the section cha.racteristkaof the model under (Cl -9 .5) test may be determined. ------- +0. 003 af-----------.- +0.2° % .C.)o A dynamic pressure of 16.37 pounds per square foot cqmtm ------------ +0..0003 Slat position .-. *O. 001a was maintained for all the taste, which corresponds ta The accuracy of t$frefers to the deflection of the slat a velocity of 80 miles per hour nnder standard atmos- pheric conditions and b an average test ReynoIds relative to the preceding slat and may be an additive number of about 2,190,000. B6cauae of the turbulence error for succwsive tdata, giving a maximum possible in the wind tunneI, the effective ReynoIde number error of + 0.8° for dfi in the fourdat combination.
R, was approximately 3,500,000. For alI tests, R, is No tare tests were run to determim the effect of based on the chord of the airfoil with the flap fully eIat&inge fittinga on profile drag and the data are not retracted and on n turbulence factor of 1.6 for the corrected for this effect. Each slat required a aeparak tunnel.
set of fittings and the tare drag probably incrmscd tith Each venetian-blind flap combination was tested the numkr of slat8.
through a complete range of slat deflections with 1.5-percent+hord slot gaps. The optimum slat deflec- VENEITAN-BIJND FLAP ARRANGEMENT tions were then tested again with equal slot gaps of Maximum-lift characteristics.-~n order to determine 0.5- and 2.5-percent chord. An angle-of-attack range the optimum venetian-blind flap arrangement from from – 6° to the angle of attack for maximum Iift was consideration of maximum lift, the various arrange- covered in 2° increments for each test. Lift, drag, ttnd ments have been compared in f@re 2 on the basis of pitching moment were measured at each, angle of attack.
increase of section maximum lift coefficients ACJW duc No tests were made of a pIain wing; the p$in-wing to slat deflections. The value of Ac’- is the difference data used hereiq are taken from reference 3.
between the section maximum Hft coefficient of the wing with the flap extended and the section maximum lift RESULTS AND DISCUSSION coefficient of the plain wing, STMBOLS The values of Acl_ for the two- and tho three-skd Test results are presen~d in standard section non- arrangements increase almost linearly over the one-slaL dimensional coefficient form, corrected as in reference 3.
arrangement giving Act- of 1,75, 1.80, and 1.85 for The following symbols are used: TTINIITIAN-BLINR FLAPS 243 NACA 23012 AIRFOIL WITH 3CWERCENT-CHORB proiiledrag coe&ient and lowest maximum lift the one-, the tw-o-, and the three+lat arrangements, re.spectivdy. The thre~at arrangement was the ooefioient.
optimum of those tested and its value of Ac* was The three-slat arrangaent with optimum sIat de- SIightly above that of the comparable three-slat fkotiions and with a set of differential slot gaps con- arrangement of reference 1, which gave a vahe of sisting of a 0.015c slot gap between the main wing and of 1.80 for slightly diflerent slat Ioeations and Acl= the first slat and 0.00% sIot gaps between the other —l-n--r!
r 1 r r , P 2.8
d-h’ ,~
I
Ill i .cL4A~4: 4’.4 ~4.% HI
# I t 1 dm
m deq
*
I I f I I ——-
- a%% 1 !aa — 2a40—--+f2 Q-O— 2.6
—— --
Lu 410 ----—– 3Q30— -- -La a~o---:----: ~$.$
—— ---
am}o-— - ‘la [0—-—- m,@ —— -- ,,, ,
m
—— ..-
*Z4 1 Iazo ---- 40,40 ——--- — - 10.la/0 ~—-— 2f24a.40
L J #.50 ——— – - la IQ20———— 2Q4c/50 —— ---- a?,20—-- ~~- ----, /0. 2Q20----L 2Q5Q50 ———- I [ 1 I I @ “2Q2L?20------3aQ30 –—— r “’’’’’’’’’’’’’’’’’’’’’’’’’” 118.11, 1 1 1 I 111111111111 [ e —— n- f.+ d -++?k7T,w@~ y–,–-; I I I I I I t I I I I t I I I I I I I I I I L $,0 .8 -8 .4 .2 0 102U .340506070 102U.7040 5O8O7OO fo20.m40m 800 ~ fm one Shf Lusf sla~.deffecfrnn, dj,, deg Losf slof c&kdh , & + .bsf da’ &fkcfitn ~z . ~ ~fo~= .* { 1 (b)‘rhIww. ((0 Fm slak.
(s) tie and tWOL4WS.
rmum z-rnuemmtsofmartmnm m coemcfenb km varim mmwmm- tiO.&k venetk-hlhd firm with o.imcgaps.
deflections. The Acb of the four+dat optimum ~ ~o arrangement was 1.84, indicating that a further inmease ~ in the number of eIats would probably give no improv+ ~ /.6 ment in high-lift characteristics.
.! {,= Differential deflection of slats with the kst slat set at the three-, and t-he 50° proved optimum for the two-, gei.
& four-slat arrangements and, as the number of slata .G.u J composing the flap increased, the dHerentieI defhtion ,UG !ys between slats deoreased for optimum arrangemmts.
B The effeot of slot gap on the increment of maximum Iift coefficient is shown in @ure 3. The effeot of slot ~ ‘4 * gap on other aerodyntic section characteristics is ehowm in figure 4. For alI arrangants the 0.015c !
o fs 20 25 .5 sIot gap was optimum formaximum lift and low profde ‘ SIof ga~~ercenf whq chord drag; the 0.005c slot gap ww next best; and the 0.025c mum %-EM of dot w on maxkanm Ilft MW veuetinn-btid fim ti slot gap was leaat desirable with large increases in Optimnmdenecucas A7gle of ottti.
Sectlm pltchlng—mimm t ~.okg sccfio~ p-of~le-hag mt?(fickq c~o .- Coef fiu”a-it, 0“-.
i WI K b.
REPORT NO. 742—NATIoNAL ADVISORY COMMITTEE FOR AERONAUTICS Slotted flap 2-h of reference 3 gave considerably lower coefhcient of 2.5, the two-slatarrangement had the leastdrag,giving 27 percent less drag coefficient than effective cl~~ than the venetian-blind flap arrangements the beat slotted flap of reference 3 at the same CZ;and, shown. Although the slotted flap had a chord of only at a c1 of 3.0, the thre~slat arrangement had the lowest 0.2566c as compared with 0.30c for tho vcnetian-blind the four-, and the one-slat drag coefficient, the two-, flap, the comparison is vaIid in view of the fact that combinations, respectively, giving successively higher tesh have shown a chord of about 0.25c to prod ucc very As an exampk of the high variable drag coefficients. nearly the same cl- as a chord of 0.40c for Lho.slotted profile-drag coefficient at high lift coefficient, the flap. (See reference 5.)
profile-drag coefficient of the three-slat combination 1 I I I I I increased 31 percent for an increase in lift coefficient of only 0.1 in going from c1of 3.3 h 3.4.
Comparison of pitching moments.—-The veneti2n- blind flap arrangements gave large pitching-moment coeficien ts, which increased with the number of slats.
The four-slat arrangements, however, gave orily slightly higher pitching-moment coefficients than tbe three- The optimum three-slat arrange- slat arrangement.
ment gave a pitching-moment coefficient of —0.76 at ci~a, which was 10 percent greater than the pitching- moment caeflicient of the one-slat (Fowler) flap at its maximum Iift coefficient.
In order to givo a more comprehensive comparison
.----
— : /.6
–---– FW l J-wii
of maximum lift coefficients of flaps with different —-
l-. D i%w 2-h {refqmce 3) ~
!=’1 I
values of pitching-moment coefficient, the eflect of tail loads required ta bsJance the pitching-moment coefficients should be considered in determining the net or the effective maximum Iift coefficient. Figure 6 gives a comparison of the tiective maximum lift co- efficients of several flaps for varying tail lengths. For simplicity in the computation of Cltm, the center of gravity was assumed to be at the aerodynamic center of the wing with the flap fully retracted. The following formula was used: @%c.,o) Clma Clem= C{ma+ — tail Iengt
[ h]
Toil l~th , uk~oil dorc% FIOFEE6.—EEwtIvesectionmnxlmumIUtmeIWIcnfsd NACA 23312drfofl Wth The largo pitching’moment coefficients of the venetian- Mvcrd naps.
blind flaps made no difference in relative valuea of Aerodynamic section characteristics of optimum qg- of the various flaps and, for tail lengths of 1 to 5 arrangements.-The aerodynamic section characteris- airfoil chord Iengths (conventional length is about 2% to tics of the highest lift arrangements of the one-,the 3 chord lengths), the three-slat arrangement was stiLI two-, the thret+, and the four-slat combinations with optimum and the two- and the four-slat arrangements the l-t slats of the tw~, the three-, and the four-slat gave slightly higher values of c’,- than the one-slat, combination deflected through a short rango aro or Fowler flap, arrangement, presented in figure 7.
Ml
!5
-, I ., 248 REPORT NO. 74%NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
H=
I I I I I I I t I I I
Cl&i i ~ t+ H7X+?Tl
. .
-b!,
tH -
.- Airplanea Designed Primariiy for High Cruking SpcedB.
LANGLEY MEMORIAL AERONAUTICAL LABORATORY, Jour. Aero. Sei., vol. 7, no. 5, March 1940, pp. 185-13% NATIONAL ADVISORY COMMI~EE FOR A ERONAUWCS, 3. Wenzinger, Carl J,, and Harris, Thomaa A.: Wind-Tunnel LANGLEY FIELD, VA., September 17,1941.
lnveatigation of an N. A.C.A,23012 Airfoil with VmIoun hrangement& of Slotted Flaps. Rep. No. 664, NACA, REFERENCES 1939.
4. Jacobs, Eaatman N., and Sherman, AIkt: Ahfoil Section 1. Wenainger, Carl J., and Harriu, Thomaa A.: Preliminary Characteristke as Affected by Variations of the Reynolds Wind-Tunnel Investigation of an N. A. C. A. 23012“Airfoil Number. Rep. No. 5S6, NACA, 1937.
wkh Varioua Arrangements of Venetian-Blind Flaps. Rep. 5. Harm Thomas A.: Wind-Tunnel Invest [gation of an No. 039, NACA, 1940. N. A. C. A. 23012 Airfoil with Two Arrangements of a 2. RogalIo, Francis M“.: Application of High-LMt Devices to Wide-Chord Slotted Flap. T. N. No. 715, NACA, 1939.