1、 _k. 7_!,i_ _ /_ !. _ _ _ _ !_ i _ k_ H . / -“TECHNICAL NOTESNATIONAL ADVISORY COMMITTEE FOR AERONAUTICSNo. 808WIND-TUNNEL INVESTIGATION OF AN NACA 23012 AIRFOIL WITHSEVERAL ARRANGEMENTS OF SLOTTED FLAPS WITH EXTENDED LIPSBy John G. LowryLangley Memorial Aeronautical LaboratoryPle eReturntoWashingto
2、nMay 1941Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NAT 0NAL ADVIS0RY COMM E FORATECHN c LNOTENO.SO8WIleD-TUNNEL INVESTIGATION OF AN NACA 23012SEVERAL ARRA_GEI,E_TS OF SLOTTED FLAPS WITH EXTENDED LIPSBy John G. Lok_rylSUMMARY _An investigation w
3、as made in the NACA 7- by 10-footwind tunnel to determine the effect of slot-lip locationon the _aerodynamic section characteristics of an NACA23012 airfoil with.a 30-percent-chord Slotted flap.Tests were made with slot llps located at 90 and 100 per-cent of the airfoil Chord and with two differen%
4、flapshapes.The results are compared with a slotted flap previ-ously developed by the National Advisory Committee forAeronautics with a slot lip located at 83 percent of theairfoil chord, The extension of the slot lip, to the rearincreased the section lift and pitching-moment coefficients.Comparisons
5、 made on a basis of pitching moment fora glve n tail length show that the Fowler type flap, lipextended to trailing edge of the airfoil, has the greatestsection lift coefficient. For moderate tail lengths, 2to 3 chord 1.engths, there was only a slight differencebetween the_previQusly developed slott
6、ed flap and the slot-ted f%ap with zslot lip extended to 90 percent of the air-foil chord. Of the three flaps tested, the Fowler flaphad the lowest drag coefficient at high_iift coefficients.The extenslon, of the lower surface at the leading edge ofthe slot:had a negligible effect on the profile dra
7、g ofthe airfoil-flip arrangemen t witl_ the flap deflected whenthe lip terminate _ at 90 percent of the airfoil chord,N ODUCT _I I0NThe Nati0nal iAdVisory Committe_ for Aeronautics hasundertaken an extensive investigation of high-lift devicesto furnish information applioable to the design of moreeff
8、icient and safer airplanes. Some of the desirable aero-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 , . NACAi, Techn.ical,?Note_,N,Q., ._808“,dynamic features of high-l_fto eViceS are: high liftwith variable drag for landing, high lift with low
9、dragfor take-off and initial climb, no increase in drag withthe device neutral, and small change in pitching momentwith the device in operation. One of the most promisingdevices developed up to the present time is an airfoil _in combination with a slotted_flap. Aerodynamic and loaddata are available
10、 o_ 12-p_rcent thick airfoil-flap com-binations in references 1 to 8; references 1 and 2 giveaerodynamic data for slotted flaps with a short lip exten-sion developed by the NACA; and references 3 and 4 giveaerodynamic data for Fowler flaps on which the slot lipextends to the trailing edge of the air
11、foil. Load dataare given in reference 5 for one of the slotted flaps andin reference 6 for the Fowler flap.The present te_ts broad ened_the investigation to in-clude slotted flaps with slot-lip extensions between slot-ted flap 2-h (reference l) with the slot lip extended to83 percent of the airfoil
12、chord and the Fowler type flap.MODELSThe airfoil model used in these tests has a chord of3 feet and a span of 7 feet; it conforms to the NACA 23012airfoil profile (table I) and is/made of mahogany andwaterproofed wallboard. The basic model is provided witha removable trailing-edge section that allow
13、s easy chang-ing of slot-lip length andslot shape. Three flap arrange-ments were used in the tests: Two of them have slot lipsterminating at 0._0c (90 percent of the basic airfoil withflap retracted) and will be called slotted flaps 1-a andl-b; the third one has the slot lipterminating at 1.00cand i
14、s a Fowler flaP. (See fig. i.)The full,span flaps were built of laminated mahoganywith a cher_ of 0.30c (10,8 in.) and were fastened to theairfoil with seweral thin-steel fittings. The Fowler flap(fig. l) conforms to the Clark Y airfoil profile (table I).The two slotted flaps (fig. l) have a Clark Y
15、 profile modi-fied to conform to the NACA 23012 airfoil back of the slotlip with the flap in the fully retracted position andfaired to the nose radius of the flap by progressive vari-ation of the Clark Y _ppe_r s?urfa_ce_ ordinates (table I_.All the flaps could be_ mo:ve for slotted flap l-a, how-ev
16、er, the lower surface of the airf011 extended 0.020cback of the slot entry for slotted flap l-b, forming aseal when the flap was fully retracted. (See fig. )The slot shape for the Fowler flap is made to clear theflap in the fully retracted position, as shown in figure 1.TESTSThe models were so mount
17、ed in the closed test sectionof the NACA7- by 10-foot wind tunnel that they completelyspanned the jet except for small clearances at each end.(See references I and 7.) The main.airfoil was rigidlyattached to the balance frame by torque tubes eitendingthrough the upper and the lower boundaries of the
18、 testsection. The angle of attack was changed from outside thetunnel by a calibrated electric drive connected to thetorque tubes. Approximately two-dimensional flow is ob-tained with this test installation and the section charac-teristics of the model under test can be determined.For all the tests a
19、 dynamic pressure of 16.37 poundsper square foot was maintained; this pressure correspondsto a velocity of about 80 miles per hour under standardconditions and to an average test Reynolds number of about2,190,000. Because of turbulence in the air stream theeffective Reynolds number, based,on the cho
20、rd of the air-foil with flap retracted and a turbulence factor for thetunnel of 1.6, was approximately 3,500,000, (See refer-ence 8.)Tests were made with the Fowler flap and slotted flap1-a to determine the optimum gap for conditions of lowdrag coefficient throughout the llft range and for maximumli
21、ft coefficient. Tests were made on slotted flap 1-bwith the flap located at the optimum position for slottedflap 1-a. Lift, drag, and pitching moment were measuredfor the slotted flaps throughout the lift range from ap-proximately zero lift to the stall and for flap deflectionProvided by IHSNot for
22、ResaleNo reproduction or networking permitted without license from IHS-,-,-4 NACA_Technica! N.ote _o_ 808from 0 to the deflectlon fo_ maxim_m lift at I0 incre -ments. On the F6wler flap similar,data were Obtainedthroughout t_e angle-of-attack range from -6 to the stalland for flap deflections at 100
23、 increments_ No tests _eremade above the stall because of unsteady conditions of themodel.- RESULTS AND DISCUSSION_ COefficient sAll test results are given in standard nondimensionalsection coefficient form corrected as explained in refer-ence i.c IC do:Cm(ac“ )0“whereaom(a.C.)oqCandsection lift coe
24、fficient (_/qc)section profile-drag coefficient (do/qc)section pitching-moment coefficient aboutaerodynamic c,enter of.plain airfoil(m(a.C.)o/qC _) , section liftsection profile dragsection pitching momentdynamic pressure (I_2 pV2) chord of basic airfoil with flap retractedO_o8fangle of attack corre
25、cted to infinite aspectrat_io.flap deflection, measured between airfoilchord line an_d flap chord l_neProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA Technical Note No. 808 5PrecisionThe _ccuracy of the various measurements in the testsis believ
26、ed to be within the following limits:_o _0“lC%max. . . . , _0.03. . _0.003Cm(a.C.)o“_ 0. 0003Cdomi n . _0.0006Cd(c = 1.0)“. . _0.002Cd(c = 2.5)“6f 0.20Flap position. _0.001cNo attempt was made to determine the effect of hingefittings because the effect is believed to be small. Therelative merits of
27、the several flap arrangements shouldnot be appreciably affected by hinge-fitting drag becausesimilar hinge fittings were used for all.Plain AirfoilThe complete aerodynamic section characteristics ofthe plain NACA 23012 airfoil are given in figure 2. Thesedata have beeH discussed in reference 1 and t
28、herefore re-quire no further discussion here.Fowler FlapThe aerodynamic section characteristics of the NACA23012 airfoil with a 0.30c Fowler flap at the optimum gapare given in figure 3. The maximum lift coefficient,C_max = 3.30, is much higher than that reported in refer-ence l, where the flap was
29、also of NACA 23012 profile. Thepitching moment of this flap arrangement is very high andmight limit the use of this flap in some designs.The effect of slot gap on the aerodynamic sectioncharacteristics of the NAC_ 23012 airfoil with a 0.30cFowler flap is given in figure 4,_ The effect of eitherincre
30、asing or decreasing the gap from 0.015c was to de-crease the maximum lift and increase the profile drag.These results show the optimum gap to be smaller than forthe arrangement reported in reference 1.No tests _rere made to determine the adverse effect ofProvided by IHSNot for ResaleNo reproduction
31、or networking permitted without license from IHS-,-,-6 NACA Technical Note No. 808a break in the lower surface with flap retracted becausea simple member could be made to cover this gap and sealthe slot.Slotted FlapsThe aerodynamic section characteristics of the NACA23012 airfoil with the two arrang
32、ements of slotted flapswith extended lips are given in figures 5 to 10. Figures5 to 8 give the characteristics for the airfoil-flap ar-rangements tested and figures 9 and l0 are comparisons ofthe different arrangements.The effect of the slot gap on the maximum sectionlift coefficient of these arrang
33、ements is given in figure9. The maximum values of AClmax for slotted flap 1-awith the 0.01c gap were about the same as for flap 1-awith the 0.02c gap; with the 0.01c gap a flap deflectionof 50 was required, whereas a deflection of only 40o wasrequired with the 0.02c gap. Flap 1-a with the 0.30c gapg
34、ave maximum lift at a flap deflection of 30 but with aloss of 0.17 in Clmax from the values for the smallergaps. Slotted flap 1-b with a gap of 0.02c gave a slight-ly lower value of maximum section lift coefficient thanslotted flap 1-a with the same gap.A comparison of profile-drag characteristics f
35、or thevarious arrangements of slotted flaps with extended lipsis given in figure 10. Figure 10(a) shows that, through-out the lift range of slotted flap l-b, there is no appre-ciable difference in the profile drag for the two flapsbut that the profile drag of slotted flap 1-a increasesrapidly above
36、the maximum lift of flap 1-b. Figure 10(b)shows that slotted flap 1-a with a gap of 0.O2c appearstobe most desirable if the criterion of low drag and highlift is used. Slotted flap 1-a with the 0.03c gap hadapproximately the same profile drag as with the 0.02c gapfor values of the lift coefficient l
37、ess than 2.3. Slottedflap 1-a with the 0.01c gap gave lov_er profile drags forvalues of the lift coefficient above 2.8 but had muchhigher profile drag than the arrangements with larger gapsover the lift range from cl = 1_4 to c_ = 2.8.No tests were made to determine the effect of thebreak in the low
38、er surface of the airfoil with flap re-tracted because the effect is thoughtto be small forProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA Techn_ical Note No,. 808 7slatted flap 1-a, as the lower surface _ould be sealed un-der such conditions. I
39、nasmuch as the _change in slotshape had no adverse effect on the airfoil-flap charac-teristics,; such tests wo_ld have little value.From the results of these tests it would appear_that the Fowlez ty_e flap could have a similar seal withno adverse effects on the aerodynamicsection character-istics.Co
40、mparison of Three Slotted FlapsA comparison of increments of section maximum liftcoefficients is given in figure ll for the two flapstested and for a 0.2566c slotted flap 2-h. (See refer-ence 1.) For the arrangements tested, the maximum liftcoefficient increases as the slot lip is moved toward there
41、ar, reaching a maximum value of 3.30 for the Fowlerflap.In order to get a more comprehensive comparison ofthe three flaps, the value of pitching moment should beaccounted for because the pitching moment also increasesas the slot lip is moved toward tile trailing edge. Tailloads necessary to compensa
42、te for the adverse pitchingmoment were therefore computed, and the effective sectionmaximum lift coefficients as a function of tail length %are shown in figure 12. The tail length in this paper isthe distance fromthe aerodynamic center of the airfoil%o theL center of pressure of the tail, expressed
43、in air-foil chords. These values are based on a theoretical cen-ter of gravity at _the aerodynamic center of the wing withthe flap fully retracted. If the center of gravity isahead of the aerodynamic center of the _irfoil, the tailload will increase as some function of the_ increase intail length an
44、d the lift of the w_ing; but, if the centerof gravity is back of the aerodynamic center of airfoil,the tail load will decrease by a similar function. Withthis method of comparison the Fowler flap also givesgreater maximum effective section lift coefficients thanthe other two flaps, but %he slotted f
45、lap with extendedslot lip ,is _not_ appreciably better than slotted flap 2-h(reference l) for a tail length of 2 airfoil chords. Fortail lengths of 2.5 chords or more the slotted flap withextended slot lip gives a greater maximum effective sec-tion lift coefficient than slotted flap 2-h. It might be
46、possible with a flap of different camber and a gap ofProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 NACA Technical Note No. 8080.015c to obtain higher maximum effective section liftcoefficients with the extended-lip slotted flap.A comparison of pr
47、ofile-drag characteristics for thethree flaps is given in figure 13. The plain airfoil hasthe lowest profile-drag coefficients for lift coefficientsless than 0.90. The slotted flap 2-h (reference l) hasthe lowest profile-drag coefficients for values from cl =0.9 to c I = 1.9. Above a value of c_ = 1
48、.9, the Fowlerflap has the lowest profile-drag coefficients. In caseswhere high lift with high drag is needed to make safelandings, the slotted flap with extended lip would be themost satisfactory. Here again by changing the camber andthe gap, it might be possible to obtain values of profile-drag co
49、efficient lower than those shown for the slottedflap with extended lip.CONCLUSIONSFor the arrangements tested, the extension of theslot lip to the rear increased the section coefficientsof lift and pitching moment of an NACA 23012 airfoil withslotted flap. The Fowler arrangementgave the largesteffective maximum lift coefficient
