1、NATIONAL;.TECHNICALNOTE3615ANEXPERUVIENTALllW7ESTIGATIONOFTHESCALERFJATIONSFORTHEIMPINGINGWATERSPRJIYGENERATEDBYA PLANINGSURFACEByEllisE. McBrideLangleyAeronauticalLaboratoryLangleyField,Va+WashingtonFebruary1956_-. - -. . . . . . . - - - . .Provided by IHSNot for ResaleNo reproduction or networking
2、 permitted without license from IHS-,-,-TECHLIBRARYKAFB,NMlL NATIONALADVISORYCOMMITTEE llllllllllMmlIllFORAJ3RONAUT13X 01JLL440TECHNICALNoTE3615ANExPERIMENnuINVESTIGATIONOFTEESCAIERELATIONSIK)RTEEIMPINGINGWATERSPRAYGENERATIIDBYA PL4NINGSURFACEIthus,aReynoldsnumbereffectonspraydragwastidicated.Byusin
3、ganempiricalmethodforcorrectingthesprayfrictiondragcoefficientsonaReynoldsnunberbasis,reasonableagreementwiththeSchoenherrlinewasgenerallyobtained._. . .- -. - - - -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 NACATN3615IIIJTRODUXIIONb thepast,s
4、eaplanesprayinvestigationswereprimarilyconcernedwiththedefinitionsadreductionofsprayimpingingonthepropellers,horizontal-tailswfaces,smdflapsbecausethoseregionsoftheair-craftweremostsusceptibletospraydamage.Recentdevelopments,how-ever,havealteredthesprayconsideration,smnewhatsincemodernsea-planedesig
5、nsutilizejetengines,lowhulls,andauxiliaryplaningdevices.Thesemoderndesigns,therefore,havecompactsilhouetteswithcloselycoupledaerodynamicandhydrodynamiccomponents.Withaerodynamicsurfacesconstructedstrongertowithstandhigh-speedflightloads,considerableforcesmaybedevelopedontheBesurfacesbyimpinngsprayti
6、thoutnecessarilycausingdsmage.Theseimpinging-sprayforcesmaybelargeenoughtoaffecttske-offperform-ance,andhetherthereisa scaleeffectonthemwhenmodelperformancedataarescaledtofullsizebytheusualmethodsisthereforeoftiterest.Inthepresentstudytheliftanddragforcesonaflatcollectorplatecausedbysprayfromaflatpl
7、aningsurfacewereinvestigatedontwosizesofmodelsinLangleytankno.2. ComparisonsoftheresultsaregivenandanempcalmethdofcorrectingfortheapparentReynoldsnumbereffectobtainedissuggestedSYMEOI.SA wettedareaofspraycollector,sqftb beamofCD planingspraygenerator,ftdragcoefficient,Q-:$2CD,s spraydragcoefficient,
8、ED2CF PJAI skin-frictiondragcoefficient,CD-CLtanTCF,S .spray skin-frictionJJsdragcoefficient,:AV%ti2(a+ T). .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATTT3615 3CLCL,sDDEf3Lk2IsR.RssvaTplaningliftcoefficient,g L/5spraylfitcoefficient,$ s+pla
9、ningdragofspraygenerator,lbsprsydragofspraycollector,lbIRroudenumber,accelerationofplaningliftofsprayliftofwettedlengthwettedlengthhxatiW,32.2ft/sec2spraygenerator,lbsprsycollector,lbofspraygenerator,ftofspraycollector,ftReynoldsnumberofplaning-smfaceflow, vReynoldsnumberofsprayflow,V sim(a+T)Zqvwet
10、tedsreaofspraygenerator,sqftcarriage-speed,fpssprayanglemeasurdbetweenleadingedgeofsprayasitleaveschineofgeneratorandfreewatersurface,degldmmaticviscosity,ft2/secdensioftankwater,forsmallmodelsprayforcesP/2=0.9jlslug/cuft;forallothersp/2=O.* slug/cufttrimemglemeamuxdbetweenbottomofplan- swfaceandfre
11、ewatersurf=e,deg. . . _ . - - _ - -. .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4 NACATN3615lIeFARATusAm PROCEDUREDescriptionofModelsThemodelsconsistofa spraygeneratorandThespraygeneratorwasaflatrectangularplaninga spraycollector.plate.Thesprsy
12、collectorwasaflatrectangukrplatewhichwasmountedaboveandtotheresrofthegeneratorasshownh figme1. l%epertinentdtien-sionsofthetwomodelsarelistedh tableI.Thelsrgesprsygeneratorwasconstructedofmahoganylaminationsandwascoatedwithwhiteplastic.Thesmallspraygeneratorwascon-structedofonepieceofmahoganyandwasc
13、oatedonthebottanandsideswithwhiteplastic.Thefacesofthemdelsweremachinedtoa smoothsurfacesmdallcornerssadchinesweresharpandsqusre.Thebottomsofthegeneratorsweremsrkedoffwithgridstofacilitatereadingofwettedlengthsfrcmunderwaterphotographs.Thelargecollectorplatewasconstructedofmshoganylaminationscoatedw
14、ithwhiteplasticandwasreinforcedwithtwo3-inchsteelchannelsrunninglengthwisetomhimizedeflectionunderload.Thesmallcollectorplateconsistedofonepieceofclearplastic.Theloadsonthisplateweretoosmalltorequireexternalstiffening.TestMethcdsandEquipmentThetestsweremadewiththemaintotigcarriageinIangleytankno.2.
15、Thelsrgemdel isshownattachedtothetowingcarriageinfigurel(a).Thespraygeneratorwasattachbymeansofarigidstruttoatwo-componentstrati-gagebalsncecapableofmeasuring3,500pousofliftand1,500poundsofdrag.Thecollectorplatewasattachedtoa s two-componentbalancecapableofmeasuring1, pOUIldSOfliftaIld250poundsOfdra
16、g.Eachbalmcewasprovidedwitha shieldtokeepthesprayfromwettingthestraingages.Eachbalancefedintoa separatetwo-chmnelstrip-chartrecorderThesmallmodelisshownattachedtothetowtngcarriagehfigurel(b).Thespraygeneratorwasattachdtothesmall-modeltowinggearh Iangleytankno.2. Liftsaddragweremeasuredby-electricals
17、train-gagebesmsandthedeflectionswerereadvisusllyongalvsmometers.Thecollectorplatewasattachedtoa specialbslancesho%mcoveredbya spray-shieldboxh figurel(b).A thinrubberdiaphrawasusedasa sealbetweentheplateandboxsndofferednoappreciablerestrainttothedeflectionofthestraingages.Figurel(c)isaphotographofth
18、isbalamcewiththesprsyshieldremoved.Theliftanddragonthespraycellscollectorweremeasu+dmountedatrightanglesbytwosingle-componentstrain-gageloadtoeachother.TheliftloadcellwasProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN361s 5capableofmeasuring5p
19、oundsandthedragcell3pounds.Theloadcellsfedintoatwo-channelstrip-chartrecorder.Underwaterphotoaphsweremadewitha 70-milltietercsmeramountedinawaterproofboxlocatedonthebottomofthetank.Thecameraandhigh-speedflashlampsweresetoffbytheactionofthecsxriagefiter-ruptingaphotoelectricbean.Photographsofthespray
20、weremade.asimilarcameramountedonaboomattachedtothetowingcarriage.Theaccuracyofthevariousbalsmcesandrecordimgdeviceswasconsideredtobeasfollows:Iargegeneratorlift,lb . . . . . . . . . . .Iargegeneratordrag,lb . . . . . . .kgecollectorlt,lb . . . . . . . . .Iargecollectordrag,lb . . . . . . . . . . .“S
21、mallgeneratorlift,lb . . . . . . . . . . . . .%allgeneratordragjlb . . . . . . . . . . .SmallcoIlectorlift,lb . . . . . . . . . . .SmaUcoll.ectordrag,lb . . . . . . . . . . .Tnbn,deg . . . . . . . . . . . . . .Speed,fps. do . . . . . . . . . . .Large-mdelwettedarea,sqft . . . . . . . .SmaU-modelwett
22、edsrea,sqft . . . . . . . . . . . .4.o*2. Otl.5to.3toa71080to.0203-0.010io.oo6*oelo.1to.02to.002Testsweremadeatgeneratortrtisof, 15,and20atwetted-length-besmratiosof1.0,”1.5,2.0,and2.5. Thecollectorplatewastestedat0trimintwoverticallocations,l.Oand1.5generator.besmsabovethefreewatersurface.Constant-
23、speedrunsweremadefrom10to80feetpersecondwithbothmodels.Small-mcdelspray-collectorforces,however,weremeasmedonlyupto35feetpersecondsincethisspeedcompsresonal?roudebasiswithabout80feetpersecondonthelargemodel.Themeasurementsweremadewithoutawindscreen.AerodynamictaresweremeasuredsmdsubtractedfromaU the
24、datapresented.DataReductionThewettedareaofthespraygeneratorwasmeasmedfromtheunder-waterphotographs.Eecauseofstructmaldeflectionscausedbytheforcesonthemodels,thewettedlengthsandtrimscouldnotbepresetasaccuratelyasdesired;therefore,a certainamountofcross-plottingwasrequired.Theplaningliftanddraginpound
25、swereplottedagainstthemeasuredwettedsreas,withspeedanddesiredtrimasparameters.Fromtheseplots,dataatthedesiredlength-beamratioswerereadandcross-plotteiagainsttruetrim.Thetruetrimwascomputedfromthemeasuredforcesandthecorrespondingtrimchsagesobtainedduringthebalancecalibrations.Wornthecrossplotstheplan
26、ingliftand. . . -. . . . . . . _ -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 NACATN3615dragatthedesiredwetted-length-beamratio,trim,andspeedwereobtained.ThesedatawerereducedtocoefficientformbytherelationshipsCL=- CD. me -fritionoeffiient:s+ :s
27、+forthegenatorwascomputedbytherelationCF= -CLtanT.The sprayforcesonthelargemodelwerehandledinamannersimilartothatusedfortheplaningforces.Themeasuredsprayliftanddragforcesobtainedwiththecollectorplatewereplottedagainstthewettedsreaofthegenerator.Thencrossplotsagainsttruegeneratortrimweremade.TheSmall
28、-mdeltestequipmentwassuchthatthesprayforcescouldbeobtainedbysettingthedestredtrimandwettedlengthaccu-rately;thus,liftanddrageratorwettedFigure2fairingandforcesweresreabythecross-plottwerenotnecesssry.Thesprayreducedtocoefficientformbasedonthegen-followingrelationships:CL,S= k#DsCD,s; s+RESULTSANDDIS
29、CUSSION?AnalysisofPlaningDatashowstypicalunderwaterphotographsofthespraygenerator.Theplaningliftcoefficientsobtainedwithboththelsrgeandsmallgen-eratorsareshowninfigure3,alongwithcurvesbasedonthetheoryofShuford(ref.1). lhetestdataofthetwomcdelssreingoodagreementwitheachotherandareinreasonableagreemen
30、twiththetheory.Theskin-frictionportionofthetotaldragmeasuredat trimisplottedagainstReyaoIdsnumberalongwiththeBlasiuslsminm?lineandtheSchoenherrturbulentline(ref.2)infigure4. Thisplotindicatesthath thelow-spedrangethesmall-modelboundarylayerwaslsminar.Athigherspeedstheboundarylayerwastransitionalfrom
31、lsmtisrtoturbulent. AtthehighestReynoldsnumbersobtained,theboundarylsyer.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN3615becsmefullyturbulent.Thebound layerturbulentthroughouttheentirespeedrange7ofthelsrgemodelwasandverygoodagreementwiththe
32、Schoenherrfullytmbulentlinewasobtained.Attrhs ofl”and20theeffectofReynoldsnumberonthetotaldragwasnegligible,aswouldbeexpected.At10WtrimS,however,OPerconsiderationoftheReynoldsnuabereffectontheskinfrictionmust,ofcourse,bemadeinordertoscalethesmall-modeldatawiththebestaccuracypossible.AnalysisofSprayD
33、ataFigure5showsphotographsofthesmall-modelspray.Figure6showsphotographsofthelarge-modelspr.Thesprayanglea forrepresentativeconditionsmeasuredfromphotographssuchasshowninfigme isplottedinfigure7. Thesprayanglewasmeasmedbetweentheleadingedgeofthesprayasitleftthechineofthegeneratorandthefreewatersurfac
34、e.Itwasmeasuredfromthesmall-modelphotographsonlybutmustberepresentativeofthelargemodelalsosincethetwoflowsaresimilarasisshownsubsequently.Thetrimofthegeneratorwasfoundtobetheprimaryparametergoverningthesprsysingleandthemaximumverticalheightofthespray.Thesprayangleincreasdrapidlywithincreasingspeedan
35、dthenbecameconstsatatspeedsaboveabout22.5feetpersecond.Thespeedatwhichthesprsyanglebecomesconstantmaybetakenasanaddi-tional.parameterforestablishingthespeedatwhichtheplateisfullyplaning.Representativesprayliftamdspraydrag.coefficientswe plottedagainstl%oudenumberinfigures8 to12. Thebestvalueof L/D o
36、btainedonthecollectorplatewaslessthan2.5;hence,thesprayimpingingonanaerodynamicsurfacecanseriouslyreducethevalueof L/D ofawater-basedairplsae.Thesprayforcecoefficientsplottedinfigures8to1.2srebasedonthegeneratorwettedsreah ordertocomparethesprayforcecoef-ficientsforthetwomcdelsatlikeplaningcondition
37、s.Thesprayliftcoefficientsobtainedwiththesmamodelagreewiththoseofthelargemodel.Sincetheseliftcoefficientssreinagreement,thetwoflowsareassuredtobeslar; thatis,boththedynsmicpressureofthesprayV2 andthewetteduea ofthecollectorplatecanbescadefinedastheprckluctofthecollectorwidthandthewettedlenh Zs (actu
38、ally,theentirewidthOPthecollectorwasnotwettedatthelowesttrimangleandthelargestheightofthecollectorabovethewater.)Thesprayfrictiondragcoefficientsaccordingtotheseassumptions,as andReynoldsnumberswerecomputed,D8CF,S=;AVs2VszsRs=yProvided by IHSNot for ResaleNo reproduction or networking permitted with
39、out license from IHS-,-,-,NACATN3615 9TheexperimentalvariationofsprayfrictiondragcoefficientwithReynoldsnumberisshowninfigwes13to17alongwiththeSchoenherrturbulentskin-frictionline.ReasonableagreementwiththeSchoenherrlinewasobtained. somecasesthedatafallslightlyhigherorlowerthantheSchoenherrlinebti,i
40、ngeneral,arestillparsXleltothisline.Thisdiscrepancyisprobablyduetotheratherinaccuratemethodofdeterminingthewettedareaofthecollectorplate.Thissmalysisindicatesthat the scale effectonthetangentialforceduetosprsyisprimsril.ythatduetothevariationh skinfrictionwithReynoldsnumberandhencecanbeappreciable.l
41、Yitisdesirabletocorrectforthisscaleeffect,certainobservationsandmeaswementsarerequiredtoestablishtheeffectiveReynoldsnumberandfrictioncoefficientsassociatedwiththeareaswettedbythespray.ThemethoduEedinthispaper,althoughempirical,willresultina closerapprox-imationofthefull-scaledragthancouldbeobtained
42、byscalingthetotal.tiel dragbytheltrouderelations.AnymethcdwhichsatisfactorilyrelatesthesprsydragandReynoldsnumberwouldbesufficient.CONCLUSIONSAnexpertientalinvestigationwasmadetodeterminethescaleeffectsoftheforcesfromwatersprsygeneratedbyaflatrectangularplaningsurfaceandimpingingona collectorplatere
43、presentativeofsnaerodynamicsurfaceorotherpartofawater-basedairplane.Fromtheresultsofthisinvestigation,thefollowingconclusionsweredrawn:1.Itwasfoundthatimphng-sprayliftforcescouldbescaledbytheconventionalIthus,aReynoldsnumbereffectonthespraydragwasindicated.2. usinganemptiicalmethodforcorrectingthesp
44、rayfrictiondragcoefficientsonaReynoldsnumberbasis,reasonableagreementwiththeSchoenherrlinewasgenerallyobtained.LangleyAeronauticallaborato,NationalAdvisoryCommitteeforAeronauticsjey Field,Vs.,Cbtober31,1955. = _ . ._ .- . . - -Provided by IHSNot for ResaleNo reproduction or networking permitted with
45、out license from IHS-,-,-10 NACATN3615lmFmENcEs1.Shuford,CharlesL.,Jr.:AReviewofplaningTheoryandExperimentWithaTheoreticalStudyofPure-PlaningLiftofRectangularFlatPlates.NACATN3233,19.2.Davidson,KennethS.M.: ResistanceandPower. DetailedConsiderations- Skinl?riction.Vol.IIofParticiplesofNavalArchitect
46、me,ch.II,pt.2,sec.7,HenryE.RossellandIarenceB.pman, eik.,Sot.NavalArch.andkine g., 1939,pp.76-83.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN3615 ILWIPEWHNWPMODELareh inches.DIMENSIONSANDTESTPARMEWEMIargegeneratorbeam,10tithes;lsxgebeam,2 i
47、nches;smallco12ectorcollectordtiiona beem,53.3inches;smallgenerator10.67inchesb-l+cCollector- -1I 4A Watersurface.W%yw*T=151.8xgeDjmensionaT=910 2.0A 15 3.0B 80 16q- . 2(30IJ2.03.0161.630.250.52.03.04.05.0-t-10 2.015 3,080 16101580+10.35 2.07.1.25 0.25-+-l-=2.3 8.151.250.25+2.5 0.510 2.015 3.0E I 2.
48、5 0.5 2.5F_1015F202.0 10153.020 I 4.04.0 20I 25 I 5.0 25 I 5.0 25.- . . - . -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ia71II_ _ - .d,(a) Largemxlel, L-90540Fe l.-Photograph0s?tielaandtestequipmentinsbelledon towingcarriage.Provided by IHSNot for ResaleNo reproduction or networking permitted without license fr
