用COMSOL设计新型管道消音器PPT格式课件下载.ppt

用COMSOL设计新型管道消音器PPT格式课件下载.ppt

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Effectivefromlowtointermediate.Disadvantage:

Bulky;

Passband;

Backpressure.ExpansionchamberMechanism:

Impedancemismatchatthejunction.（e.g.VehicleMuffler）3TheNovelDrum/PlateSilencerTensionedMembrane/plateMovingairinsidetheductpi:

IncidentSoundWave;

pr:

Reflectionduetosoundinducedstructuralvibration;

pt:

Transmittedsoundwavetothedownstream.4AdvantagesoftheNewSilencerEnvironmentally-friendly.（noairpollution,betterthanSAM）.Broadbandnoisereductionatlowfrequencies（comparedwiththeexpansionchamberofthesamegeometry）.（Huang,2002.Figure3（a）ExpansionchamberDrum/PlatesilencerMinimumbackpressure（pressureloss）.uTheflowcanpasssmoothly;

uNoextranoisebytheturbulentflowduetoflowseparation5SeveralPrototypesLeft:

2DPlatesilencer（Balsawood）TopRight:

Circularchamber+rectangularductBot.Right:

Fourcavities.6NumericalDesign:

OverviewKeyIssueintheNumericalModelingKeyIssueintheNumericalModelingFEMVSAnalyticalMethodFEMVSAnalyticalMethodTheUseofCOMSOLMultiphysicsTheUseofCOMSOLMultiphysicstosolvethefullsound-structurecoupling,includingthetosolvethefullsound-structurecoupling,includingtheeffectofflowinthemainduct.effectofflowinthemainduct.FEM:

FEM:

Easytouse;

versatileEasytouse;

versatileComplexgeometry;

Complexgeometry;

ComplexBCs.ComplexBCs.AccuracytobetestedAccuracytobetested.AnalyticalMethodAnalyticalMethodAcademicallyappreciated.Academicallyappreciated.Accurate;

Simplygeometry/Accurate;

Simplygeometry/BCsonly.BCsonly.Aneffectivedesigntool.Aneffectivedesigntool.7OutlineIntroductionontheductsilencerdesignFEMModelingof2DSilencerNumericalresultsfor2DConfigurationExtensionto3DDesignSummary82DDrumSilencer:

FEMModelingMulti-physicsDomainsMulti-physicsDomainsVibro-AcousticCouplingVibro-AcousticCouplingBackingCavityBackingCavity（HelmholtzEquation）（HelmholtzEquation）MainDuctMainDuct（ConvectiveWaveEq.）（ConvectiveWaveEq.）MembraneMembrane（StringVibration）（StringVibration）Membrane:

drivingforceMembrane:

drivingforceDuct+Cavity:

InterfaceBoundaryConditions.Duct+Cavity:

InterfaceBoundaryConditions.9SelectionofApplicationModesGeom1:

Geom1:

Duct+CavityDuct+CavityF:

VelocityPotentialF:

VelocityPotentialGeom2:

Geom2:

1DString1DStringeta:

displacementeta:

displacement10Sub-Domainsinthe2GeometriesGeom1:

Duct+CavityDuct+CavityInletInletoutletoutletcavitycavityHalfductHalfductInterfacesInterfacesGeom2:

Membrane（string）Membrane（string）11BoundaryConditions:

AcousticDomainNeumannBCInletInletoutletoutletcavitycavityInterfacesInterfacesTheacousticdomain12Vibro-AcousticCouplingAcousticpressureinthegoverningEq.formembranevibration:

AcousticpressureinthegoverningEq.formembranevibration:

Boundaryconditionsattheinterfacesoftheductandcavity:

Coupledvia“ExtrusionCouplingVariables”.Coupledvia“ExtrusionCouplingVariables”.13OutlineIntroductionontheductsilencerdesignFEMModelingof2DSilencerNumericalresultsfor2DConfigurationExtensionto3DDesignSummary14PrimaryResultsforSingleFrequencyTop:

Velocitypotential（F）atf=0.14Bottom:

AmplitudeoftheAcousticPressurealongthecrosssection.FPressure15PerformanceIndicator:

TransmissionLossDefinition:

Definition:

ThelogarithmicratiobetweenthesoundpowerThelogarithmicratiobetweenthesoundpowerincidenttothesilencerandthetransmittedsoundpowerfortheincidenttothesilencerandthetransmittedsoundpowerforthecasethereisano-reflectionterminationonthedownstreamside.casethereisano-reflectionterminationonthedownstreamside.CalculationCalculationinCOMSOLMultiphysicsinCOMSOLMultiphysics:

.16Performanceofa2DDrumSilencerPP11PP22PP33L:

L:

TLcomparisonbetweentheFEMTLcomparisonbetweentheFEMsimulationandtheexactsolution.simulationandtheexactsolution.R:

R:

MembranevibrationatthethreeMembranevibrationatthethreespectralpeaks.spectralpeaks.（Note:

configurationsarespecifiedinHuang,2002）（Note:

configurationsarespecifiedinHuang,2002）TL=0.02dBTL=0.02dB17EffectofMeanFlowL:

TLcompariso