AERODYNAMIC EFFECTS

DOT/FAA/AR-07/16AirTrafficOrganizationOperationsPlanningOfficeofAviationResearchandDevelopmentWashington,DC20591CharacteristicsofRunbackIceAccretionsandTheirAerodynamicEffectsApril2007FinalReportThisdocumentisavailabletotheU.S.publicthroughtheNationalTechnicalInformationService(NTIS),Springfield,Virginia22161.U.S.DepartmentofTransportationFederalAviationAdministrationNOTICEThisdocumentisdisseminatedunderthesponsorshipoftheU.S.DepartmentofTransportationintheinterestofinformationexchange.TheUnitedStatesGovernmentassumesnoliabilityforthecontentsorusethereof.TheUnitedStatesGovernmentdoesnotendorseproductsormanufacturers.Tradeormanufacturer'snamesappearhereinsolelybecausetheyareconsideredessentialtotheobjectiveofthisreport.ThisdocumentdoesnotconstituteFAAcertificationpolicy.ConsultyourlocalFAAaircraftcertificationofficeastoitsuse.ThisreportisavailableattheFederalAviationAdministrationWilliamJ.HughesTechnicalCenter'sFull-TextTechnicalReportspage:actlibrary.tc.faa.govinAdobeAcrobatportabledocumentformat(PDF).TechnicalReportDocumentationPage1.ReportNo.DOT/FAA/AR-07/162.GovernmentAccessionNo.3.Recipient'sCatalogNo.5.ReportDateApril20074.TitleandSubtitleCHARACTERISTICSOFRUNBACKICEACCRETIONSANDTHEIRAERODYNAMICEFFECTS6.PerformingOrganizationCode7.Author(s)EdwardA.Whalen,AndyP.Broeren,andMichaelB.Bragg8.PerformingOrganizationReportNo.10.WorkUnitNo.(TRAIS)9.PerformingOrganizationNameandAddressUniversityofIllinoisAerospaceEngineeringDepartment306TalbotLaboratory,104S.WrightSt.Urbana,IL6180111.ContractorGrantNo.12.SponsoringAgencyNameandAddressU.S.DepartmentofTransportationFederalAviationAdministrationAirTrafficOrganizationOperationsPlanningOfficeofAviationResearchandDevelopmentWashington,DC2509113.TypeofReportandPeriodCoveredFinalReport14.SponsoringAgencyCodeAIR-10015.SupplementaryNotesTheFederalAviationAdministrationAirportandAircraftSafetyR&DDivisionCOTRwasJamesRiley.16.AbstractTheresultsofaresearchprogramtoinvestigaterunbackiceaccretionsduetohot-airiceprotectionsystems,scalingofexternalflowparametersfortestingthermalsystems,andtheresultingaerodynamiceffectsarepresented.IceaccretiontestingwasconductedattheNationalAeronauticsandSpaceAdministrationGlennIcingResearchTunneltoevaluatethermalscalingmethodsandproducerepresentativerunbackiceaccretionsusingabusinessjetwingsectionequippedwithahot-air,anti-icingsystem.Testconditionssimulatedanairplaneholdinginbothatambientstaticairtemperaturesnearfreezing(warmhold)andwellbelowfreezing(coldhold),aswellasdescendingthrough(descent)Title14CodeofFederalRegulationsPart25AppendixCicingconditions.Warm-holdiceaccretionswerecharacterizedonthesuctionsurfacebydensefrozenrivuletsthatformedaridgewhilethepressuresurfaceaccretionwascomposedofnodulesandchunksthatformedaridge.Inallcases,acleanairfoilregionofvaryingchordwiseextentwaslocatedupstreamoftherunbackiceaccretions.Therunbackridgeformationswereshowntobeverysensitivetototalairtemperatureinbothheightandchordwiselocation.Increasedhot-airtemperatureandmassflowratewerefound,ingeneral,tocorrespondtoshorterridgeslocatedfartheraftonthemodel.Thecold-holdaccretionshadthecharacterofrimeiceandexhibitedmorespanwisevariationduetotheproximityoftheridgetothehot-airjetimpingementzones.Descentaccretionsalsoexhibitedspanwisevariationinchordwiseposition,butweremoreuniforminheightthanthecold-holdaccretion.Resultsofthescalinganalysisshowedthatausefulandqualitativelyaccuratescalingmethodwasdevelopedforscalingthermalanti-icingsystemsforgroundtesting,butfurtherdevelopmentandinvestigationofthemethodsandgoverningequationsarerequired.Windtunneltestingwasalsoconductedtoevaluatetheaerodynamicperformanceeffectsofrunbackiceaccretions.SimulatediceshapeswerescaledfromthedocumentediceaccretionsfortestingintheIllinois3-by4-ftsubsonicwindtunnel.Simplegeometricscalingandboundary-layerscalingmethodswereused.TheNationalAdvisoryCommitteeforAeronautics(NACA)3415andtheNACA23102weretestedataReynoldsnumberof1.8x106andMachnumberof0.18,withandwithoutthesimulatediceshapesattached.Themaximumliftcoefficient(Clmax)oftheNACA3415wasreducedto1.16from1.35,andthestallingangleofattackwasreducedby1degreeduetothethree-dimensional(3-D)warmholdsimulation,whiletheNACA23012experiencedareductioninClmaxto1.16from1.46,andalossof2degreesinstallingangleofattack.The3-Dcold-holdsimulationreducedClmaxto0.9andcauseda3degreereductioninstallingangleofattackfortheNACA3415.ThesameiceshapereducedClmaxto0.73andcauseda4degreereductioninstallingangleofattackfortheNACA23012.Geometricallyscaledtwo-dimensional(2-D)simulationsofthewarm-holdaccretionswerefoundtoenhancetheliftperformanceoftheNACA3415andhadlittleeffectontheNACA23012.Theboundary-layer-scalediceshapeswereobservedtocausegreaterpenaltiesthanboththe2-Dand3-Dgeometricallyscalediceshapes.Therefore,geometricscalingmaynotbesufficientforscalingrunback-typeiceaccretionsovertherangeofscalesandReynoldsnumbertested.17.KeyWordsRunbackicing,Ridgeice,Thermaliceprotection,Anti-icing,Hot-air,Aerodynamicperformancedegradation,Simulatedridgeshapes,Spanwiseridgeice18.DistributionSt