Actran_Shipbuilding-2012船舶噪声模拟案例

CopyrightFreeFieldTechnologiesACTRANforShipbuildingExamplesofShipbuildingApplications2CopyrightFreeFieldTechnologiesNoiseonaShipLow-frequencyNoiseDiscretion(exteriornoise):•Propellernoise•Hullradiation•Mufflernoise•Etc.Crewcomfort(interiornoise):•Dieselenginenoise•Turbulencenoise•Room-to-roominsulation•Etc.High-frequencyNoiseSonar:•Tonpilztransducer•SonararrayCopyrightFreeFieldTechnologiesCaseStudy-AddedMassEffectApplicationReview4CopyrightFreeFieldTechnologiesKeyACTRANfeaturesFiniteelementsformulationfortheacousticfluidandthestructureallowstoaccountfortheaddedmasseffectInfiniteacousticelementsallowstocomputeforthefarfieldradiationIncompatiblemeshesprojectionallowstousedifferentmeshrefinementsforthestructureandthefluidManytypesofexcitationsandBC+couplingwithotherCAEvendorsallowstoaccountforreallifeconditionsAcousticmeshStructuremesh5CopyrightFreeFieldTechnologiesACTRANModelDescriptionInfiniteelementsforthe«free-field»radiationSealevel:pressuresettoatmosphericalpressure(p=0)Actranmodelstheheavyfluidandthestructureinoneuniquemodel.TheaddedmasseffectofthefluidtothestructureisthenconsideredStructureandfluidisperfectlycoupledActransupportsincompatiblemesheswherevernecessary:Structureandfluidmeshescanbemeshedusingdifferentelementstopolgies(forexample:TETforfluid,HEXforstructure)Differentkindofexcitationscanbeapplied(structureoracoustic)6CopyrightFreeFieldTechnologiesResultsComparisonWaterloading:bothresultsareatthesamefrequency(70Hz).Deformationsaredifferent…Stronginfluenceofthesurroundingwateronthedynamicbehaviorofthestructure!FullycoupledsystemDynamicofthestructurewithoutfluidaround7CopyrightFreeFieldTechnologiesPlateDemonstrationPurpose:toevaluatetheimpactoftheaddedmasseffectoffluidonthestructureTwomodelsarecompared:1,fluidisair2,fluidiswater(heavyfluid)•Dimensions:•1mby1m•10cmthick•Aluminum•ExcitedbyapointforcePlatemodelAcousticmedium(freefield)AutomaticActrancouplingprocessinbothdirection:fluidstructure8CopyrightFreeFieldTechnologiesResponseofacousticpressureinthefarfield48Hz120.5Hz86.5Hz46.5Hz13.5HzPlateDemonstration–ResultsComparisonBluecurve:fluidisairGreencurve:fluidiswaterObservation:withwaterbeingaddedTheresonantfrequencyofstructureisshiftedtolowerfrequenciesCopyrightFreeFieldTechnologiesCaseStudy–RealisticShipEngineRoomProblemPresentedatISMA2010,Leuven,BelgiumBernardVanAntwerpen,Diegod’Udekem1,ChristofWeißenborn21FreeFieldTechnologiesSA,Belgium2GermanischerLloyd,GermanySimulationofthevibro-acousticcouplingbetweenstructuresandheavyfluids10CopyrightFreeFieldTechnologiesRealisticvibro-acousticmodel-StructureEngineroomsectionofashipVarioussteelpanelsVariousstiffenersSymmetricapproachselectedExcitationcomesfromenginevibrationEngineroomShellsBeamsShip11CopyrightFreeFieldTechnologiesRealisticvibro-acousticmodel-FluidCombinationoffinite/infiniteelements(freefieldradiation)Diffractionaccountedthroughfullshipgeometry(hardwallcondition)Symmetricapproachselected(hardwallcondition)Pressurereleaseconditionatair/waterinterfaceInfiniteelements12CopyrightFreeFieldTechnologiesResults–InfluenceoftheheavyfluidTheinfluenceofsurroundingairisnegligiblecomparedtotheaddedinertiaofthewaterAthigherfrequencies,weclearlysee:thefrequencyshiftthedecreaseofvibrationamplitude13CopyrightFreeFieldTechnologiesCouplingwithmultiplefluidsThestructureshelliscoupledwithmultiplefluids:InnerfluidisairExteriorfluidiswaterCopyrightFreeFieldTechnologiesCaseStudy-PropellerFairingApplicationReview15CopyrightFreeFieldTechnologiesPropellerFairingwithACTRANThiscasestudyshowspropellernoiseradiationinseawaterandtheacoustictreatmenteffectsontheruddersLafayetteClassFrigatefromFrenchArmyThevicinityofthepropellerismodeled50m30m15m130m16m16CopyrightFreeFieldTechnologiesAnadmittanceboundaryconditionTomodelacoustictreatmentontheruddersIncidentspinningductmodesToaccountfortherealpropellernoisesourceazeropressureBContheinterfacetheair/waterinterfaceInfiniteacousticelementsallowstocomputeforthefarfieldradiationKeyACTRANfeaturesComputationstatisticsNodes100,000Elements650,000Dofs150,000RAM3.5GBCPU/freq2minComputerLinux64bit(intel)PropellerexcitationAcoustictreatmentontheruddersInfiniteelement(noreflection+farfieldpropagation)Air/Waterinterface:ZeroPressurecondition17CopyrightFreeFieldTechnologiesVirtualmicrophoneareplacedonanarc40mfarfromthehull(ininfiniteelementdomain)Results–PressurefieldNotreatmentontheRuddersWithatreatmentontheRuddersDirectivityinthefarfieldThemaximumnoiseisreducedby3dBThetreatmentmodifiesthedirectivityCopyrightFreeFieldTechnologiesCaseStudy-EngineNoiseRadiationApplicationReview19CopyrightFreeFieldTechnologies3mLargeDieselEngineNoiseThiscasestudypresentstheradiationofalargeshipengineThismarinedieselenginehasthefollowingcharacteristics:16Vcylindersmaximumregime:1800RPMMaxPower4320KW(or5900CV)ThestructuraldynamicanalysiscanbeperformedinanexternalFEAsolver(NASTRAN,ANSYSorABAQUS)TheacousticradiationfromitsvibrationiscalculatedusingACTRANTheacousticmodelisdesignedtoreach1000Hz(order33ofRPM