1、NATIONALADVISORYCOMMITTEE $FORAERONAUTICSiJTECHNICAL NOTE 2957SURVEYSOF THE FLOW FIELDS AT THE PROPELLER PLANESOF SIX 40 SWEPTBACK WING-FUSELAGE-NACELLE COMBINATIONSBy Vernon L. Rogallo andJohn L. McCloud IIIAmes Aeronautical LalmratoryMoffett Field, CaHf.AFMXWashingtonJune 1953Provided by IHSNot fo
2、r ResaleNo reproduction or networking permitted without license from IHS-,-,-TECHLIBRARYKAFB,NMIilllllllllllllllllil;llllilNATIONALADVISORYCOMMITTEEFORAERONAU. 0Ub575b. SURVEYSOFTEETECHNICALNOTE291FLOWFllHiOSATTHEPROPELLERPLANXSOFSIX40SWXPTBACKWING-FUSELAGE-NACELLECOMBINATIONSByVernonL.RogalloandJoh
3、nL.McCloudIIIHJMMA.RYTheflowfieldsatthepropellerplanesofsix40sweptbacksemi-spanwing-fuselage-nacelleconibinationsweresurveyedtoprovidedatatoenablethestudyofthecharacteristicsoftheflowfieldsandtheireffectonpropeller-oscillatingaerodynamicloads.Theresultsofthesurveysarepresentedintheformofanglesthatde
4、finethedirectionofthelocalvelocityrelativetothesurveydiskandastheratiosofthea71 localvelocitiestofree-streamvelocity.Theseparametersareshownasfunctionsoftheeagularpositionaroundthesurveydiskforgivenradialpositions.ical.propeller-oscillatingairloads,computedbythe.methodofNACATN2192usingmeasuredflow-f
5、ielddata,arepresentedtodemonstratethesignificanceofthe flowparameters.Alsoshownsrecomparisonsofmeasuredandpredictedupflowanglesforallmodelsataspecificangleofattack.Theresultsofthesurveysshowthatvsriati.onsoftheflowparam-eterswithangulsrpositionsxepredominantlyfirst-ordersinusoidalforthesixmodelstest
6、edand,thus,=e similsrtoresultsforanunswept-wingairplsnereportedinNACATN 2192.Therotational.flowangleisthemajorcontributortotheoscil-latingaerodynamicloadsandhasitsmaximumandminimumvaluesatthehorizontalcenterlineofthepropellerdisk,whereitsvalueisdeterminedby theupflowagle.Theupflowanglespredictedby t
7、hemethodsofNACATNts2795and2.894werefoundtobe ingoodageementwithmeasuredangles.INTRODUCTION*Vibratorystressesareintroducedinpropellerbladesby oscillating. aerodynamicloadswhichresultfromrotationofthepropeller(inclinedProvided by IHSNot for ResaleNo reproduction or networking permitted without license
8、 from IHS-,-,-2 NACATN2957a71ornoninclined)ina nonuniformflowfieldl(seeref.1). A detailedstudyoftheairflowatthepropellerplanesofa twin-engineairplanewitha unsweptwingwasreportedinreference2,anditwasdemonstratedthereinthattheupflowangle(sumofupwashandgeometricangles)atthehorizontalcenterlineoftheprop
9、ellerdiskwasthemajorcontrib-utortothepropeller-oscillatingaerodynamicloads.A methodforpredictingtheupwashcomponentsofthetotalupflowanglesatthehorizontalcenterlineofpropellerdisksforairplmeswithunsweptwingsispresentedinreference3, andeerimeatalverificationisgiventherein.Themethodofreference3 wasexten
10、dedinreferences4 and5 forapplicationtoairplaneshavingwingsofarbitraryplsmformwithnacellesatarbitraryverticallocations.Limitedexperimental.upflowdatawhichsubstantiatethemethodfortheswept-wingcaseme presentedinreference forseveralnacellelocations.Morecompleteexperimentaldataforthecaseoftheswept-wingai
11、rplaneareneededtodeterminethesignificanceoftheflow-fieldparameterswhichdeterminetheoscillatingaerodynamicloadsand,also,theextenttowhichtheseloadsaredependentontheupflowangles atthehorizontalcenterlinesofthepropellerdisks.Presentedhereinaretheresultsofdetailedflowmeasurementsatthepropellerples ofsixk
12、“ sweptback,semispsmwtig-fuselage-nacellecombinationswhichdifferinaspectratio,taperratio,smdnacellelocationandinclina-tion. Typicaloscillatingairloads,coutedby themethodofrefer-ence2 usingmeasuredflow-fielddata,arepresentedinordertodemonstratethesignificsmceoftheflow-fieldparameters.Inaddition,theme
13、asuredandpredictedupflowgles togetherwiththepredictedupwashcomponentsarepresentedforeachmodel.A totalupflowangle,andthedirectionNOTATIONanglebetweenthe_gropellerthrustaxisofthelocalflow, aG+ e,degb spanofwingmeasuredperpendiculartotheverticalplaneofsynmetry,ftCL liftcoefficient,totalliftqsc localcho
14、rdofthewingattheinboardnacelle,2ftOscillatingairloadsmayalsobe introducedby rotatingapropeller_ inclinedina uniformflowfield.a71Measuredina planeparalleltothemodelplaneofsymmetry.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN2957. Ct. ActDLMn
15、QrsV.vl=.v#?o.VtYaG%7E?9.sectionthrustcoefficient?sectionthrustpn=D4incrementalsectionthrustcoefficientctO- ct= propellerdismeter,ftbodylength,ftfree-streamMachnuderpropellerspeed,rpsfree-streamdynemicpressweyPVO=/27lb/sqftdistmcealonganyradiallinefrompropellerthrustsxis,ftwingsrea,sqftfree-streamve
16、locity,ft/seclocslvelocityatanypoint(r,Q) atthesurveydisk,ft/sec(Directionofthisvelocityisdefinedby theangles9 =dV- Seefig.1.)velocityratioatanypoint(r,Q) atthesurveydiskcomponentofthelocalvelocityintheplaneperpendiculartoa radialline,ft/secdistancefrommodelplaneof symmetry,ftanglebetweenthepropelle
17、rthrustaxisandthedirectionoffree-streamvelocity,2 deg(Seefig.1.)snglebetweenwing-rootchordanddirectionoffreestream)2degpropellerthrust-sxisinclinationasmeasuredfromthewing-rootchord(negativebelowwing-chordline)2degsngleofupwash=measuredfromthefree-streamdirection,degdimensionlesslateralcoordinate,se
18、mispsmsangleofoutflow,measuredfroma linepsralleltotheTrapel-lerthrustaxisinaplanethroughthepropellerthrustaxis,deg(Seefig.1.)zSeefootnote2,p. 2.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4,gtAAPTNACATN2957angleatwhichthelocalvelocityatanypointon
19、thesurveydiskisinclinedtotheplaneperpendiculartotheradiallinethroughthatpoint,deg(Seefig.i.)sweepofthewingdegwingtaperratio,quarter-chordline,positiveforsweepback,tipchordrootchordmassdensityofairinfreestream,slugs/cuftdimensionlesslongitudinalcoordinate,distanceaheadofwingquarter-chordline,2semispa
20、nsangleofrotationalflow(anapparent,notanactualrotation),measuredfroma lineparalleltothepropellerthrustaxisina planeperpendiculartoa radialline,deg(Seefig.1.)angularpositionaboutthepropellerthrustaxis,measuredcounterclockwisefromtheupperverticalpositionasseenfromthefront,deg(Seefig.1.)MODELSANDAPPARA
21、TUSThesixsemispan-model,k“ sweptbackwing-fuselage-nacellecombi-nationsusedinthisinvestigationsreshowninfigure2, togetherwithpertinentinformationconcerningeach. Themodeldesignationsindicatedinfigure2 areusedthroughoutthisreport.Itmaybenotedthatthemostimportsmtdifferencesbetweenmodelsarethechordwisean
22、dverticallocationsandinclinationofthelongitudinalaxisofthenacelles.3PhotographsofmodelsB,D, andE mountedintheAmeshO-by 80-footwindtunnelareshowninfigure3. Thevariousmodelconfigurationshavebeenmadebymodificationofabasicmodel,thegeneralarrange-mentandpertinentdimensiomofwhichareshowninfigure4. Thefuse
23、lageandnacellecoordinatesareshowninfigure.Thesurveyrakeconsistedofsixdirectionalpitot-statictubesmountedatvariousintervalsalonga steeltube.Detailsofthesurveyrakeareshowninfigure6. Therakeis6hownmountedonthemodelsinfigure3.2Seefootnote2,p. 2.3Thepropellerthrustaxeswereassumedtobe coincidentwiththenac
24、ellelongitudinalaxes.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN2957 5* TFSTCONDITIONSTheflow-fieldmeasurementsandforcetestsweremadeintheAmes40-bytherefore,crossplotsoffigures7,8,and9 couldbeusedforattainingtheradialvariationoftheflowparam
25、etersforallmodels,ifdesired.Figure13 showstypicaloscillatingairloadsfora propeller-bladeelementoperatingintheflowfieldsofseveralofthesweptbackwing-fuselage-nacelleconibinations Foreachofthecombinations,a compar-ison is shownoftheoscillatingairloadcomputedusingthecompleteflow-fielddatawiththatcompute
26、dusingonlytherotationalfloweagles. andassumingthatvl/vo Cos (3!= 1Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 I?ACA 2957(ThisiBtantamounttoassumingVZ/Vo.1 ande .0 forLQl Qs.)Themethodofreference2 wasusedforthesecomputations.Measm-edandpredicted
27、upflowmgles forallmodelsareshowninfigure140 Thepredictedupwsshanglesshowninfigure14 (computedby themethodsofrefs.4 and5)arepresentedtofacilitatethediscussionoftheeffectsofnacellelocationandinclination.Liftcurvesofthesixmodelsareshowninfigure15 forsllmodels.No correctionshavebeenappliedtotheflowmeasu
28、rementsortheliftcurve,sincetheAmes4.0-by 80-footwcbd-tunnel-wallcorrectionsarenegligiblefora semispanmodelofthissize.DISCUSSION “PropellerFlowFieldsFromexaminationoffigures7,8,and9,itisseenthatthevsria-tionoftheflowparameters,4,8,andV2/Vo,withaDgularpositionsxepredominantlyfirst-ordersinusoidal.Theo
29、utflowangleandvelocityratiome approximatelyinphasewitheachothermd 90outofphasewiththerotationalflowangle.Thesecharacteristicsaresimilertothosefoundfortheunswept-wingairplaneasreportedinreference2.Forallmodels,themaximumandminimumvaluesof occurwhenQ isproximatelyequalto90aad270. Thesevaluesof Q estab
30、lishthehorizontalcenterlineofthepropellerdiskforwhich+ = “(aG+ %0) -ho7+(aG + 2T00 ) = +A2700OscillatingAerodynamicLoadingTheoscillatingairloads,asindicatedby thevariationofthethrustcoefficientwithangularposition(showninfig.13), werecomputedby useoftheentireflow-fielddataandby useofonlythemeasuredro
31、tationalflowangle?. Alsoshowninfigure13 aretheflow-fieldparametersusedinthecomputations.Comparisonoftheload-ingsshowsthat X isthemajorcontributortotheoscillatingairload.Foreachmodelthemagnitudesofthevariationsarenotgreatlydifferentforthetwocases;hence,themagnitudeoftheoscillatingairloadduetothecompl
32、eteflowfieldcanbe estimatedwithgoodaccuracyifthe 6maximumandminimumvaluesof $ areknown.4Thesethrustcoefficientswerecomputedby themethodofreference20Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN2937 7. Onthebasisofalltheforegoing,thetotslupfl
33、owanglesatthehorizontalcenterlineofthepropellerdiskprovidea rationalbasisforcomparisonofthemodelswithrespecttothemagnitudeofthe. oscillatingairload.TheUpflowAnglesattheHorizontalCenterLinesofthePropellerDisksThemeasuredmd predictedupflowmgles areshowninfigure14.A wingangleofattackof10waschosenforthe
34、comparisonsasrepre-sentativeofa clfmbingattitudewherethemagnitudeoftheropellervibratorystresseswouldbe large.At thismgle ofattack,allmtielshavearoximatelythesaneliftcoefficient(seefig.15). Whencom-psringthemodels,itisbportanttoconsiderboththelevelandasyrmnetryoftheupflow.A highlevelofupflowisindicat
35、iveofalargefirst-ordercomponentoftheoscillatingairload;theasymmetryoftheupflowdistributionisprimarilyassociatedwithhigher-ordercomponentsoftheoscillatingairloads.Thepredictedupwashcomponentswillbe usedinexplainingthedifferencesintheupflowforthemodelsbecause,asmaybe seeninfigure14,theagreementbetween
36、themeasured.andpredictedupflowangleswasofthesameorderatvsriouspointsalongthehorizontalcenterlineofthepropellerdisksandforthe. differentnaceelocationsata givenangleofattack.TheeffectofchordwiselocationofthepropellerdisksisshownintheupflowandupwashvariationsofmodelsA andB (fig.14). ModelA,whichhasitsn
37、acelles(hence,propellerdisks)farthestforward,hasa somewhatlowerlevelanda lesseramountofasymmetryofupflowthanmodelB. However,thesereductionsexeinsiificantinthattherewouldbe no sizabledifferencesintheoscillatingairloadofpropel-lerslocatedwithinthelimitsofthechordtisepositionsinvestigated.Theeffectsofs
38、panwiselocation ofthepropellerdisks(asasso-ciatedwithswept-wingairplanes)areapparentintheupflowandupwashvariationsofmcdelsA,B, C,andD. Themagnitudeandasymmetryoftheupflowsresomewhatgreaterattheoutbosxdsurveydisksthanattheinboardsurveydisk. Comparisonofupflowandupwashcharacteristicsattheinboardsurvey
39、diskofmodelC withthoseatthesurveydiskofmodelD (modelD hasonlyaninbosrdnacelle)showsthattheoutbo=dnacelleofmodelC inducesnosignificantupwashattheinboardsurveydisk.* TheeffectofverticsllocationofthenacellesisshownintheupflowandupwashcharacteristicsofmodelsD, E, andF (fig.14). Thepylon-mountednacelleso
40、fmodelsE andF havelittleorno asymnetryof.upflowanda lowerlevelofupflowthanmodelD. Thesereductionssresignificantinthattheyindicatea sizablechangeintheoscillatingProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 NACATN2957airloadmayberealizedfromchange
41、sintheverticalpositionofthehorizontalcenterlineofapropellerdisk.Theeffectofnacelleandthrust-axisinclinationisshownintheupflowandupwashcharacteristicsofmodelF whichhasconsiderablylessnacelle-inducedupwashthanallothermodels.Althoughonlya slightreductionintotslupwashresultedfromtiltingthenacelledownwar
42、d,thelargereductioninthethrust-isinclinationconsiderablyreducedthemagnitudeoftheupflowangles.Sincetherateofchangeoftheupflowanglewithangleofattack,dA/da,isindependentofthrust-axisinclination,57,minimumupflowanglesatthehorizontalcenterlineofaTropellerdiskcanonlyoccurata givenaLe ofattack.A methodispr
43、esentedinpendixB ofreference4 forselectionofthrust-andnacelle-axi5inclinationforminimizingoscillatingairloads.CONCLUSIONSFrcnntheresultsofsurveysofthepropellerflowfieldsofsixko sweptback,semispanwing-fuselage-nacellecombinations,thefollow-ingconclusionsmaybe drawn:1. Variationsoftheflowparameterswit
44、hangularpositionarepredominantlyfirst-ordersinusoidalforthesixmodelstestedand,thus,similsrtoresultsforanunswept-wingairphnereportedinNACA 2192.2. Therotationalflowangleisthemajorcontributortotheoscillatingaerodamicloadsandhasitsmaximumandminimumvaluesatthehorizontalcenterlineofthepropellerdisk,where
45、itsvalueisdeterminedby thethrust-axisangleofattackandthetotalupwashsingle.3. Fromthe upflow characteristicsofthemodelstested,itwasfoundthatsignificantreductionsintheupflowangleswereobtainedbyloweringthehorizontalcenterlineofthepopellerdisk.4. TheupflowanglespredictedbythemethodsofNACATNTs2795and2894
46、werefoundtobe ingoodagreementwithmeasuredangles.AmesAeronauticalLaboratoryNationalAdvisoryCommitteeforAeronauticsMoffettField,Calif.,Ma. 31,1953“If a chsmgeinthepositionofthehorizontalcenterlineofthepro-pellerdiskresultsfrominclinationofthethrustaxis,dA/da maybe altered.Provided by IHSNot for Resale
47、No reproduction or networking permitted without license from IHS-,-,-NACATN2957 9. REFERENCES. 1. Rogallo,VernonL.,Roberts,JohnC.,andOldaker,MerrittR.:VibratoryStressesinPropellersOperatingintheFlowFieldofaWing-Nacelle-FuselageCombination.NACATN2308,1951.2. Roberts,JohnC.,andYaggy,PaulF.: A Surveyof
48、theFlowatthePlsmeofthePropellerofa Twin-EngineAirplane.NACATN=92, 1950.3. Yag?g,PaulF.: AMeth 45 90 /35 /80 225 270 3/5 360,4ngu/or position, Q, oeg(o) Mode/A, inboordsurveyoH.fgureZ Vuriutionof the mgle of rotationalflow withanguh positionfor severalangles of uttack.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN2957 2120100-10-20lx / a, dwI “o -4nor = 256 feet 04A8k /p201 I I1001-/0-20 0 45 90 /35 /80 225 270 3/5 360Angular position, , oegb) Ml A, owbmrdsurveydisk.Fgure Z - Cmti
