1、.i,$,-FORAERONAUTICS TECHNICALNOTE 2445WIND-TUNNEL TESTS AT LOW SPEED OF SWEPT AND YAWEDWINGSHAVINGVARIOUSPLAN FORMSBy Paul E. Purser and M. Leroy SpearmanLangley Aeronautical LaboratoryLangley Field, Va.WashingtonDecember 1951.-.- -.-. CD and Cy betweenmglesofyawof,5and-5.Theyawedwingsweretestedthr
2、oughthe.angle-of-attackrangefrombelowzerolifteithertoabove liftortoanangleofattackofabout55measuredinaplanenosltotheleadingedgejwmcheverwassmaller. - .-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Thedataarepresentedinfigures6to43inthreegeneralgro
3、ups-force-testdata,tuftsketches,andcomparisonplots-and areindexedintableII.THEORETICALRELATIONSHIPThebasictheoryforsweptandyawedwingsasdevelopedbyBetz(reference2)isbasedontheconceptthatonlythecomponentofvelocitynormaltothewingleadingedgedeterminesthechordwisepressuredis-tribution.Amongthesimpliingas
4、sumptionsmadebyBetzare:Thespanwiseloaddistributionisrectangular,thetwosemispnsofa sweptwingmaybeconsideredindependentlyasyawedwings,andthewingissweptbyfirstsettingthepaelsatanangleofattackandthensweepingthewinginsuchamannerthattheleadingedgesofthepanelsremaininahorizontalplane.Thelastassumption,sinc
5、eitintroducesageo-metricdihedral,primarilyaffectstherollingmoments,and,since “maintainingthepanelleadingedgesinaplaneisnotapracticalarrange-ment,a seriesofequationswasdevelopedfromBetzsworkwithoutsuchanassumption.Thenormal-component-of-velocityconceptandtheassumptionsofindependetisemispansandrectang
6、ularspanloading,however,wereretainedinthedevelopmentofthefollowingequations,wl+charenotallusedinthepresentpaperbutarepresentedforfuturereference:Yawedwings:()cLa= cLa CO+*w (1)(3).- . - - -. -. . - - - .- .-. -.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
7、 IHS-,-,-_ - - -.- -8 IIUCATN 2U5Sweptwingswithoutflapsorcamber:c = c (%) COS A COS%A=IJ4c%;=p-) COS A COS +A=O .()cza= %8 COS A COS%a A.+=(II Swept wings withfull-spanflapsorcsmiber:( )-C%f= C%fA+a co”Acosflaps)(,)cL=o COS2ACOE2$ (canber).()= cos AA=-I .()ACcZ=2L t2mAtan*+-c Ltanr tally+(4)(5)(6)(7
8、) (8)(9) .(lo)(11)(12) “ “1,tI(r. - . .- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2H.,.t .NACATN25orsince()0.00!k CL tan A9(13)(14)(15)Equations(1)to(15)take no accou(2)byuseofchartsdevelopedbyMutterperl(reference6) whichgivethespanloadingandt
9、otalliftofsweptbackwingscalculatedbyamethodbasedonWeighardtsextensiontolifting-linetheory(reference7);(3)byuseoflifting-surface-theorycomputations(reference8). Foreffectivedihedral,inordertoaccountforaspectratioandtaperratio,thefollowingitemsmsybenoted:(1)equations(7), (13), and(15) actuallyprovideo
10、nlyincrementsin Cz causedby sweepanddihedral;(2)thebasicvaluesof CzW beo$tainedfromWeissinger(reference9) byusingthevaluesof“aspectratioandtaperratioactuallyexist onthesweptwings.DISCUSSIONLongitudinalStabilityofSweptWingsEffectofaspectratio.-Ashasbeenshowninreferences3 and10,thepitching-momentcurve
11、sbecomeincreasinglynonlinearasthesweepangleisincreasedandtendtobecomeunstablenearthestall.DecreasingProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-10 NACATN244theaspectratiogenerallyreducesthenonlinearityandtendstomakethepitching-momentcurvestablene
12、axthestall.(Seefigs.6,7,9,and36forexample.) Thedataforallthewingsincluded-inthepresentinvestigationbothsweptbackandsweptforwsrd,agreeverywellwiththesunmarychartofreference10astotheeffectsofsweepanglemd, aspectratioonthepitching-momentcharacteristicsnearthestall.Asshowninfigure36,increasesinaspectrat
13、iomovedtheaerodynamiccenteratlowliftcoefficientsslightlybackfortheunsweptandswept-forwarwingsandslightlyforwardforthesweptbackwings.-Effectoftaperratio.-Inagreementwiththedataofreference10,thepresentinvestigationshowedlittleornoeffectoftaperonthe :.=pitchi-momentcharacteristicsnearthestallforsweptba
14、ckwings.(Seefigs.13 and14.)Forsweptforwardwings,however,increasingtheratioofrootchordtotipchordproVideda slightstabilizingeffectonthepitching-momentcurvenearthestall.(Seefigs.26to28.)Increasesintheratioofrootchordtotipchordmovedtheaerodynamiccenteratlowliftcoefficientsbackforsweptbackwings,verylittl
15、eforunsweptwings,andforwardforsweptforwsrdwings.(Seefig.37.) ,Effectofhigh-liftdevices.-Theuseofa full-spansplitfla .atthetrailingedgeorofa spoilerextendingfromthenoseonanuntapered600sweptbackwing(figs.7, 8, and38) hadlittleeffectonIthepitching-momentcurveexceptfora changeintrimproducedbythetrailing
16、-edgeflap.Fortheinverse-tapersweptbackwing(figs.14and38) theuseofa half-spancenter-sectionsplitflapatthetrailingedgeandahalf-sparetipslatorflapat-theleadingedge- either .Cseparatelyorincombination- delayedtheexcessivestabilityathigh-liftcoefficientsandhadlittle,effectonthestabilityatlowliftcoefficie
17、nts.Allcombinationsproducedsomechangeintrim,andinthe -orderofincreasingthenegativevalueof Cm at CL= O thedevicesare: leading-edgeslat,trailing-edgeflap,trailing-edgeflapandleading-edgeslat,trailing-edgeflapandleading-edgeflap,andleading- “ edgeflap., Effectoftipmodification.-Cuttingoffthetipnormalto
18、theleadingedgeonanuntapered60sweptbackwinghadlittleeffectonthenonlinearityofthepitching-momentcurveoronthestabilitynearthestall(figs.6and10)butdidmovetheaerodynamiccenterbackatlowliftcoefficients(fig.39).Whentheouter40percentofthewingpanelswassweptforward,however,thepitching-momentcurvebecsmenearlyI
19、-inesrandindicatedstabilitynearthestall.(Seefigs.6,H,and39.) .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN2445 IL.EffectiveDihedralofSweptWingsEffectofaspectratio.-Forunsweptwingstheslopeofthecurveof clv againstCL isincreasedpositivelyasthe
20、aspsctratioisdecreased.(Seefig.36.) Thessmeeffectisshowninfigure36foruntaperedsweptbackwings.Althoughinsufficientdataareavailabletoshowdirectlytheeffectofaspectratioon()Cq(CLforsweptforwardwings,theagreementbetweenexperimentandcalculationshowninthesectionentitled“Comari60nwithTheory”supportstheargum
21、entthat .aspect-ratioeffectson)ClvcareindependentofLvalueof Cl forthesweptbackwings(fig.36)wasvastheaspectratiowasreduced.sweep.Themaximum =increasedslightlyiEffectoftaperratio.-AccordingtothecalculationsofWeissinger(reference9)anincreaseintheratioofrootchordtotipchordshouldgivea reductionintheposit
22、ivevalueof()”Cz ThatthisresultCL-istrueisindicatedbythedataoffigure37forbothaweptbackadsweptforwardwings.Theapparentdiscrepancyfortheunsweptandfortheapproximatelyunsweptwings(fig.37)isattributabletothefactthatthetaperedwingbuiltwitha straighttrailingedgehadenoughsweepbacktocounteractthesmalltaper-ra
23、tioeffect.Forswetbackwings,increasesintheratioofrootchordtotipchordapparentlyincreaaedthemaxbmmpositivevalueof c andtheliftcoefficienttatwhichthismaximumvalueoccurred.Effectofhigh-liftdevices.-Thedataoffigure38 showthattheuseofhigh-liftdevicescangreatlyincreasethemaximumvaluesof *c1$obtainedwithswep
24、tbackwings.Theuseofa full-spansplitflapatthetrailingedgeofanuntaperedwinghavinga600sweepbackgaveanincrementinthevalueof C1?$at CL= O,anincrementinthemaxhumvalueof Cz,andanincrementinthevalueofV CL atwhichthemaximumvalueof CZV occurred.Fortheinverse-tapersweptbackwing, .ahalf-spancenter-sectionsplitf
25、lapatthetrailingedgeproducedpracticallynochangeinthevalueof Cz at CL= O,probablybecauseTatcL=() thewingtipswerecarryinga negativeload;inturnproduceda negativevalueof Czw tocounteractthisloadin -thepositiveProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,
26、-,-12 NACATN2445incrementprovidedbytheflap.Theuaeoftheflapdid,however,extendthecurveof C enoughtoproduceanappreciableincreaseinthe+maximumvalueof C7 andintheliftcoefficientatwhichthemaximumtvalueof Cttioccurred.Fortheinverse-tapersweptbackwingtheuseofthehalf-spantip-sectionleading-edgeslat(orflap) e
27、itheraloneorincombinationwiththetrailing-edgeflap resultedinlittlechangeinthevalueof C2$ at CL= O butdidincreasethemax-IUUmvalueof Cz andtheliftcoefficientatwhichthemaximum+valueoccurred,probablybecausetheleading-edgedeviceBimprovedtheflowoverthetipsathighliftcoefficietis.Theuseoffull-spanandhalf-ep
28、antip-sectionnosespoilersextendingforwardfromthechordplaneonthe600sweptbackwingapparentlyimprovedtheflowconditionsoverthewingouterpanelandslightlyincreasedthemaximumvalueof Cz.+Effectoftipmodiffcation.-Cuttin.goffthetipnormaltotheleadiuqedgeonanuntapered60sweptbackwingreducedtheS1OF.Softhecurveof Cz
29、 againstv CL atlowliftcoefficientsbutdidnotchangethemaximumvalueof Cz . Sweepingforwardtheouter40percent4ofthespan, however,markedlyreducedboth ()cZCL andthemaximumvalueof Czv. (Seefig.39.)InducedDrag,w-ruMaxtiumLift,andStallingofSweptWings vratio.-Curvesinfiwes 19ml36indicatetheEffectofaspect. . ef
30、fectofasDectratioontheinduceddrag;them“thisflowresultsinathickeningoftheboundarylayerandcausesseparatedflowoverthewing.Thisconditionapparentlybecomesmoreaggravatedatthehighersweepanglesasthespanisincreasedandresultsina dragincrementlargeenoughtooffsetw decreaseininduceddragcausedbyincreasingtheaspec
31、tratio.Aspect-ratiochangeshavea pormaleffectonsweptforwardwings,asseeninfigures25and34.Theeffectissimilartothat“forunsweptandfor30sweptbackwings,buttheincreaseindragandthelossin L withdecreasesinaspectratioappearlargerforthesweptforwardWiIlgS.Effectoftaperratio.-Forunsweptwingsfigure37 showsthat ani
32、ncreaseoftaperreducedtheinduceddrag,buttheapparentincreaseinc forthewingwithtaperratioof3.0isprobablya falseeffeetsince”thetaperedwingsaxecthenthetipstallsandthestallmovesprogressivelytowsrdthecentersection.Chamgesintaperdidnotappreciablyaffectthegeneralpatternofthestall.Effectofhigh-liftdevices.-Th
33、evseoffull-spansplitflapsonthetrailingedgeofanuntapered600swebackwing(fig.7) increasedCL onlyslightlybutdidreducetheangleofattackforC%lax”Thedragwasincreasedovermostofthelift-coefficientrangeandbecamelessthanfortheplainwingonlyslightlybelowC*. Thefull-spannosespoilertestedonthe60sweptbackwing(fig.8)
34、gavea slightlylargerincrementof Cb thandidthesplitflapbutindicatednochangeinthe,stallangle.Thedragwasincreaseduptoa liftcoefficientofaboutwingaboveCL=0.6.Deflectinga half-spansweptbackwing(fig.14)or0.6 butwaslessthanthedragoftheplain,splitflaponaddhgeitherthetrahingedgeofaa leading-edgeslator37a71 5
35、flap.- - .-.- .-. - . . . -. -. . -. - -.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-,. . -14 “ NACATN2445.nheip Eased C%ax”Deflectingtheflapincreasedthedraguptoaliftcoefficientof0.65andthengavelessdrsgthantheplainwingupto c=.Theadditionofeithert
36、heleading-edgeslatorflapfurtherreducedtheag fromaliftcoefficierrtof0.65upto Ck.Theadditionofeithertheleading-edgeslatorflapwiththetrail-edgeflapunreflectedreducedthedraginthehigherliftrangebyanamountaboutequaltothatcausedbydeflectingthetrailg-edgeflapalone. Deflectingthesplitflaphadlittleeffectonthe
37、stallpatternbutuseofthetipslatconsiderablydelayedthesta3Jatthewingtip(figs.35(c)=d 35(d).Estimatesbasedonafierondata(fig.30)weremadetodeterminetheeffestivenessofa splitflaponthetipofsweptforwardas.Theincremerrtofliftat a =O forthehalf-spansplitflaponthetipofa 45sweptfomardwingwasslightlygreaterthant
38、hatforantioardhalf-spansplitflapona 45sweptbackwing(reference3)andahuosttwiceasgreatasthatforahoutboardhalf-spansplitflapona 45sweptbackwing(references3 and13). Littledifferencewasnotedh ae iCmmetif C%laxprovidedbythesplitflaponsweptforwardandsweptbackwings.Effectoftipmodification.-Cuttingoffthetipo
39、fa sweptbackwingnormaltotheleadingedgecausedareductionindr fromaliftcoefficientof0.50uptomaximumliftsincethetaperratiowaseffectimlyincreased(fig.39). Sweepingtheouter40percentofthewingforwardincreasedthedragfromaliftcoefficietiof0.80to Ch andslightlyreducedC*, probablybecauseoftheincreasedinter-fere
40、ncebetweenthesweptforwszdsmdthesweptbackpanels.AileronEffectimnessforSweptforwardWingsDatafortwo45sweptforwardwingsoftaperratio1.0and4.0equippedwithhalf-spansplit-flap-typeO.20ctieronsdeflectedoneleftwingonlyarepresentedinfigmes30and33. .Comparisonswhichaccountedfortherelati=effestivenessofplainands
41、plitflaps(reference13)indicatethattheaileroneffectiveness .cz ata liftcoefficierrtof0.2forthe45untaperedsweptforwardawingwasabout10percentgreaterthanthevaluethatwouldbeobtainedforthe45Untaperedsweptbackwingofreference3. Thisret isprobablycausedbythethinnerboundarylayerandthelessturbulentflowexisting
42、onthetipsofsweptforwardwings. . . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACAnessTN“25 15Thedatashowedthatthelossinaileronrolling-momenteffective-resultingfromincreasedtaperwasgreaterforthesweptfoardthanthelossindicatedforunsweptwingsinrefer
43、ence14.COMPARISONWITHTHEORY“ ,Yawed-WingLift-curveSlopeThetestsoftheyawed.wingsweremadeprimarilytoprovidearelativelyquickpreliminarycheckonBetzsconceptoftheeffectofyawonthelift-curveslope(reference2). Asshownbyfigurek(lthedatafortheNACA0012wingofaspectratio6 agreedalmoste=ctlywiththecosinelaw. Tests
44、of NACA0012wingofaspectratio3,however,showedlesseffectofyawon CL thanisindicatedbythecosinelaw. Inanefforttoexplainthediscrepancy,testsweremadeoftwoflatplateshayingaspectratiosof3,onerectsmgularandoneofinfinitetaper.Asshownbyfie b theinfinite-tapermodelshowedmoreeffectofyawthanthecosinelawandtherect
45、angularplateshowedlesseffect.Additionaltestsofa flatplatehvinganaspectratioof1.27showedanincreaseratherthana decreasein C%, asthemodel wasyawed. Theseresultsmaybepartlyexplainedbythefactthatasa rectangleisyawedthespannormaltotheair-streamdirection-andthustheaspectratio- increasesforpartoftheyaw rang
46、e.Theamountofincreaseandtheanglesofyawoverwhichthisincreaseappearsarefunctionsoftheaspectratioandthetapsrofthebasicmodel.Correctionsappliedonthisbasisindicatethatallthedatawouldgroupaboutthecurvefortheinfinite-taperplatehavinganaspectratioof3. Theresultingcurveshoweda slightlygreatereffectofyawthani
47、sindicatedbythecosinelaw.Swept-WingLift-CurveSlopeThedataofreference3 indicatethatinthecomputationoflift-curveslopeofsweptwingsthecosinelawisvalidprovidedthethe aspectratiousedisthatofanunsweptwinghavingthesamepanelsasthesweptwing.Onthisbasisandbyuseofhelifting-surface-theoryequationforthelift-ceslo
48、pe(reference15)figure41wasderived.Byuseoffigure41anda valueof0:099forthesectionlift-curveslopethevaluesof C werecomputedforalltheswept-wingtests.Themeasuredandthecomputedvaluesof Ck areshowninfigure42.Theageementisreasonablygoodbutindicates,asdidtheyawed-wingdata,thatthecosinelawdoesnotindicatequiteeno-”dropin Cas A isincreased. - .- . . . . - . . ._. .- Provided by IHSNot for ResaleNo reproduction or networking permitted without licen
