Document
‘ ‘ ‘“-MA’l&26 NAT IONAII ADVISCRY CCLWITTEE FCRAERONAUTICS No. 243 I THE CEIRACTZRETICS OF T’HE N; A. (I. A. M-12AIRFOIL SEOTION 3Y George J Higgins Langley Memori.al Aeronaut icalLaboratory .
..*- Washington Au~st, 1926 .- —.
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A,,.....= ~ __ — NATIONAIJ ADVISORY CCMMITTZX FORAERONAUTICS.
TECHNICAL NOTENO. 24.3.
TEE CHARACTERISTICS OF THEN.A.C.A.
U-12AIRFOIL SKWIW. ~ T3y George J. Higgins.
Summary Thedataobtained on theN.A.C.A. M-12airfoil, tested at twenty atmospheres density in theNational Advisory Committee forAeronautics variable density windtunnel, havebeenextend- ed by additional testsat oneandat twenty atmospheres under improved conditions.
The results of thesetests are given.
Considerable scaleeffect. was found.
The Tests The dataon theN.A.C.A. M-12airfoil wereextended for comparison and to determine scaleeffect by testing ther.odel in theNational Advisory Committee forAeronautics variable density windtunnel at oneatmosphere density.As theoriginal testat twenty atmospheres wasmade sometimeagoundercondi- tionswhichhavesince been improved, a re-test at thatdensity was alsomade. The latter represents a Reynolds Numberof 3,480,0G0, whichis aboutthe condition of fulldynamic scale.
The original duralumin airfoil -model of theN.A.C.A. ?.!-12 (Table I),withan aspectratio6 andwitha planform secti”on, t of 5 in.by 30 in.wasused. It wasmounted in the tunnel in t N. A.C.A.Technical Note ITO. 243 ?
.
J theusualmanner as described in Reference 1. Fairings wereadd- ed, covering theloderhalfof thestreamlined supports, thus reducing thetaredragby half. The angleof attack wasvaried from-3° to +24°withobservations takenat l~!’ intervals.
Result s The results of thetestsare givenin Tables11 ad 111, and areplotted in Fig.1.
Curves are alsoplotted representing the lift, moment, andminimum induced dragcoefficients as cal- culated frm,theory (References,2 and 3).
Whenacomparison is madeof the highReynolds Number test withthelow,itmay be seenthatthereis a big delayin the angleat whichburbling occurs, andalsoa largeincrease in themaximum liftcoefficient. Theangleof zeroliftis in b agreement withthe theoretical valuein bothtests. The slope of theliftcurveat thehigher density is normal and hasa valueof 0.0710.Thisis about86.per centof the theoretical slopeforan airfoil of the sameaspectratio, a usualfigure for thistunnel.However, theliftcurveslopeat thelower For a portion of its range(3°) density is very irregular.
itsvalueis wellabovethatfor the theoretical slope (. 0960/. 0822),indicating thata peculiar typeof flowis crest- y occurrence hasbeennoticed in ed at those angles.A similar testsmadeat lowdensities on other airfoils of thissamegen- & of theliftcurveis normal, though eralshape. The remainder t N. A.C.A.Tcchni@lNoteNo. 243 the slope is low.
Thisincrease in liftcoefficient at oneat- mosphere eqlainswhy thepolarcurveof thattestisbetter through itsmid-portion.
The dragcharacteristics are sligntly improved at thehigher Reynolds Number. Thereis alsoa slight change in stability; the twenty-atmosphere moment,coefficient agrees verywellwith thatcalculated.
Fordetermining airfoil characteristics, testsat high Reynolds Numbers are of greatimportance.
References 1. Munk,Max M. TheVaziable Density WindTunnel of the .
and National Advisory Committee forAero- Technical R~ort No.” Miller, Elton??. “ nautics.N.A.C.A.
Fig.10.
227 - 1926. Part II,pp. 14-15, : 2. Munk, ~ELXM. Tho Determination of theAnglesofAt- tackof ZeroLiftand of ZeroMoment, IT.A.C.A.
Basedon M.uQcts Integrals.
Technical NoteNo. 122- 19230 : 3. Munk,Max M* Preliminary WingModelTestsin the Variable Density WindTunnelof the National Advisory Committee forAeronau- tics. N.A.C9A* Technical Report No.
217 - Appendix-1925.
TableI.
Ordinates of theN. A.C. A. M-12Aizfoil Section in Per Centof Chord.
7.5 20 Sta. 1.25 2.5 10 15 o 5~o 6061 7*3O 2.86 4.01 4.89 5*59 Upper (3.00 2.03 -3.60 -3.80 -3.07 -3b 31 Lower -Q.
oo -1.65 -2914 -a. 72 /..
Sta.
25 30 40 100 50 60 70 80 90 95 Upper 7,74 7.95 7.86 7.25 6.27 4,98 3.50 1.89 1,07 0,20 * Lower-3.92-3.98-3.96-3.82-3.50-3*OO-2 l 31 -1*37-o*81-O*2O i .
N.A. C-.1. Technical NoteNo. 243 Table11.
Airfoil LS-12 Span- 30 in. 76.2 ‘cm { AVCZWC TankPressure - I atrn. Chord - 5 in. 12.7cm 1 Avera~ec Dynar~ic Prsssure - 28.5kg/mz Aspect %tio :“6 - Average Reynol~.s Number - 17~,000 Date- April9, 1926.
Average temperature - 25°C.
lJ~-~* Angleof Lift 1) rag atzack Cocf ficient Coefficient 3ocfficient degrees CD CM
CL
-3 -,090 .0151 -.168 l 030 ,030 -1*5 8007 .0128 1.83 . ..
o .0122 ,060 ,104 ~ 117 ,, ,050 1.5 l 245 ,0135 .055 -,040 3 ,391 .0189 .048 l 030 4.5 ,477 .0234 l 049 ,010 6 ,0317 ,055 .578 ,.
,050 7.5 l 0401 .060 .0,50 9. ~0486 ,064 ,760 ~060 ~ 069 10.5 00568 ,, .080 .076 12, *899 . ~0687 l 100 .0817 .087 13*5 .936 ,100 .1020 l 108 15 l 947 ,. ., .g90 16,5 ,875 .1740 ,199 ,312 ,070 18 ,77g ,2402 . ~40 19.5 .730 .2705 .371 .070 .721 .3013 .417 .32$3 .463 l 110 22.5 .703 .678 .3496 l 517 .120 2’4 N..A. C..’i. Technical I;ote No. 243 ]63-2 Table111= 76.2W) Span- 30 in.
Airfoil H-12 G) Chord - 5 in. 1207 Average TankPressure - 20 atm. 1 Average Dynanic Pressure, q, - 617k~m2 AspectIWtio-- 6 Date- April9, 1926.
Average Reynolds Number - 3,480,000 Average temperature - 40°C.
Drag Ratio Uonent Angle of Lift Coefficient Coefficient D/L attack, Coefficient Cjj degrees -,022 ‘“”- l 0119 -.1035 -3 -.115 -.024 1.030 .0103 -1.5 .010 -.020 .0108 l 1039 0 l 104 -.023 .0603 .0129 1.5 .214 -.018 .0159 .0497 3 .320 -.030 .0231 .0537 4.5 .430 -F 029 .0567 l 0304 6 .536 -.039 l 0594 .0382 7.5 .643 -,002 .0466 .0622 l 749 -.030 .0644 .0549 .852 10.5 -.005 .0669 .0640 .956 12 “ -,002 .0756 l 0794 1,050 13.5 -.003 .0823 l 0940 15 1:142 -.019 . 092?
l 1114 16.5 1.208 -.029 .1180 .1449 1022s - l 019 l 1344 .1684 1.253 19.5 .
-.013 .2026 .1627 1?245 -.075 .2643 .2314 22.5 1.142 t -.048 .3001 .2831 24 1.061