基于ANSYS CFX 的噪音分析

OVERVIEWOFNOISECAPABILITIESINANSYSCFXThabetBelamriANSYSCanadaLtdOctober2006OutlineNoisemodelingbackgroundLighthillacousticanalogy FfowcsWilliamsandHawkingsmodelLowsonModelANSYSCFXnoisecapabilitiesAdvanceturbulencemodellingNearfieldapplications:automotive,turbomachineryFarfieldapplications:turbomachineryNoisesourcestrengthcalculationConclusionsNoisemodelingbackgroundJetNoiseinafreefieldatrestDensityPressureSpeedofsoundFarfromthejet,pressureperturbationWaveequationLighthillacousticanalogyNoisemodelingbackground

(1)Continuity(2)MomentumLighthillacousticanalogyNoisemodelingbackground

(4)LighthillacousticanalogyNoisemodelingbackground

LighthillTensorReynoldsTensorCompressivestressTensorViscousstressTensorLighthillacousticanalogyNoisemodelingbackgroundPhysicalmodelMathematicalmodelFfowcsWilliams&HawkingsmodelNoiseModelingBackgroundmonopolesourceSelfnoiseinteractionnoisedipolesourceSelfnoisequadrupolesource++FfowcsWilliams&HawkingsmodelNoiseModelingBackground-Lowspeedmachines:TipMachnumber<0.35HigherMachnumberLessaccuracy-Forceactingasapunctualforceonthegravitycentre-Smallbladespan-UsageofSemi-empiricalcoefficienttodefinetheloadingdecay (loadingcoefficient)LowsonmodelModelassumptionsNoiseModelingBackgroundh:Loadingcoefficient=(2.0-2.5)UnsteadyforcecomponentsM:Machnumberz:Bladenumber

:Rotationalspeed[rd/s]steadyforcecomponents:Fx0andFy0

:HarmonicmodeJn:BesselfunctionofnthorderLowsonmodelAcousticpressureforthemthharmonicNoiseModelingBackgroundSoundpowerforthemthharmonicAcousticpressureforthemthharmonicSoundpressurelevelsin[dB]:Soundpowerlevelsin[dB]:LowsonmodelFx0andFy0areobtainedfromasteadystatesolutionBladepassageanditsharmonicsANSYSCFXNoiseCapabilitiesCFDSteady/TransientsimulationsCFDPredictionsofAcousticsourcesNoiselevelsattheobserverpositionSysnoiseTurboNoiseFarfieldNearfieldANSYSCFXNoiseCapabilitiesNearfieldCalculation(Pseudosound)-AccurateTransientdatafromCFD-AdvanceturbulencemodellingFarfieldcalculation-TurboNoisemacro(Lowsonmodel) -InterfacetoFarfieldCodes(Sysnoise,inhousecode)Predictionofnoisesourcesfordesign comparison

ANSYSCFXNoiseCapabilitiesAccuracyofnoisepredictionsdependsonResolvedscalesModeledModeltypeAllNoneDNSLargeSmallLESNoneAllURANSHybrid-gridcontrolledDESHybrid-modelcontrolledSASAdvanceTurbulencemodelingANSYSCFXNoiseCapabilitiesDNSLengthscalevariation103UnrealisticcalculationtimesLESWallboundedflows

gridrequirementsBoundaryconditions:Inlet,walls,...URANSDampingofsmallstructuresSingle-modebehaviourModelchallengesAdvanceTurbulencemodelingANSYSCFXNoiseCapabilitiesURANSDetachedEddySimulation(DES)URANS&LESTurbulencelengthscalevs.gridwidthScale-AdaptiveSimulation(SAS)Model-inherenttransitionURANSmodeLESmodeLessgridsensitiveAdvanceTurbulencemodelingSASANSYSCFXNoiseCapabilitiesNewk-

tmodelRottaNaturallengthscalevonKarmanlengthscale

AdvanceTurbulencemodelingSAS:Scale-AdaptiveSimulationANSYSCFXNoiseCapabilitiesURANSLESAdvanceTurbulencemodelingSAS:Scale-AdaptiveSimulationANSYSCFXNoiseCapabilitiesApplicationtoautomotive:sideviewmirrorNearFieldPredictionEUprojectDESIDERTestcasePlatedimensionsL

W=2.4

1.6CylinderDiameter:D=0.2mRearFacelocation:0.9mFreestreamVelocity:140km/h

ReD:520000Mach:0.112.4m1.6m140km/h0.9mANSYSCFXNoiseCapabilitiesMesh:BoxaroundthePlate&CylinderHeightofdomain:10diameters(D=0.2m)wall-normaldistancearound1-3*10-4mobstacleedgesresolution:stepsizesaround0.02*D(height)-0.03*D(circumf.)10D7.5D4DApplicationtoautomotive:sideviewmirrorNearFieldPrediction3mnodesANSYSCFXNoiseCapabilitiesApplicationtoautomotive:sideviewmirrorNearFieldPredictionInflowNormalvelocity:140km/hTu=0.5%,=2tOutflowstaticpressureOpening,zerogradientturbulenceSASturbulencemodelTime-stepδt=210-5sDisturbance

representationT:T=D/Uinf=0.005[s]Statisticconvergence-Totalsamplingtime=160T-Timeusedforstatistics=last60T=0.3[s]Maximumresolvedfrequency-Fmax=1/(9-12)δt=4000-5000HzBoundaryconditionsTimescalesANSYSCFXNoiseCapabilities101-115

dynamicpressure1-34staticpressureTransientpressuremeasured@18locations(101-123)Applicationtoautomotive:sideviewmirrorNearFieldPredictionSoundPressureLevels(SPL)from:DataandSimulationsANSYSCFXNoiseCapabilitiesVorticityApplicationtoautomotive:sideviewmirrorNearFieldPredictionTurbulencestructuresANSYSCFXNoiseCapabilitiesApplicationtoautomotive:sideviewmirrorNearFieldPredictionSensor112ANSYSCFXNoiseCapabilitiesApplicationtoautomotive:sideviewmirrorNearFieldPredictionSensor119ANSYSCFXNoiseCapabilitiesApplicationtoturbomachines:cavityflowNearFieldPredictionLWD=511Depth=0.1mInflowNormalvelocityMa=0.85OutflowAveragestaticpressureWallsSymmetrySASturbulencemodelTime-stepδt=210-5sBoundaryconditionsCavitydimensionsANSYSCFXNoiseCapabilitiesTransientpressuremeasured@10floorlocations(K20-K29)PowerSpectrumDensity(PSD)obtainedfrom:DataSimulationsRossitermodesK20K29Applicationtoturbomachines:cavityflowNearFieldPredictionANSYSCFXNoiseCapabilitiesPressureamplitudePowerSpectrumDensityK29Applicationtoturbomachines:cavityflowNearFieldPredictionANSYSCFXNoiseCapabilitiesK29NearFieldPredictionApplicationtoturbomachines:cavityflowANSYSCFXNoiseCapabilitiesApplicationtoturbomachines:cavityflowNearFieldPredictionRossitermode:1Rossitermode:2Rossitermode:4Rossitermode:3ThefrequencyfortheRossitermodecanbecomparedwiththeEigenfrequencyofthecavity!ANSYSCFXNoiseCapabilities-CFX-POSTLoadtheresfile-CFX-POSTToolsMacroCalculator-Bladeselection:AutomaticS