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Dept.ofMech.EngineeringUniversityofKentucky1AcousticBEMME599/699Vibro-AcousticDesignTHEBOUNDARYELEMENTMETHODDept.ofMech.EngineeringUniversityofKentucky2AcousticBEMME599/699Vibro-AcousticDesignTheBoundaryElementMethodüConceptualdescriptionoftheBEMüPreprocessingvMeshvBoundaryConditionsüSolutionüPost-ProcessingDept.ofMech.EngineeringUniversityofKentucky3AcousticBEMME599/699Vibro-AcousticDesignFEMBEMDomainmethodBoundarymethodDiscretizationvolume(3-D)surface(2-D)CalculationofmodeseasyexpensiveSoundradiationonlywithI-FEMeasyInteriorproblemseasyeasyComparisonofFeatures:AcousticFEM/BEMDept.ofMech.EngineeringUniversityofKentucky4AcousticBEMME599/699Vibro-AcousticDesignOverviewofNumericalMethods:DefinitionsInteriorNoiseAnalysisRadiationAnalysisAcousticboundaryelements(theseare2-Dsurfaceelementsonly)InteriorNoiseAnalysisRadiationAnalysisAcousticboundaryelements(theseare2-Dsurfaceelementsonly)Dept.ofMech.EngineeringUniversityofKentucky5AcousticBEMME599/699Vibro-AcousticDesignThePointMonopoleSource–KeytotheBEMrSoundpressureadistancerfromthepointsourcerp(r)PhaseQ=sourcestrengthjkrerQrp-=)(Dept.ofMech.EngineeringUniversityofKentucky6AcousticBEMME599/699Vibro-AcousticDesignMathematicalFormulationoftheDirectBEM**BoundaryElementAcoustics,T.W.Wu,WITPress,2000v,psrpqUsingGreen’sSecondIdentityHelmholtzIntegralEquationpperikriverdSsikroikrS=+-⎡⎣⎢⎤⎦⎥--∫414pqrwp()cosDept.ofMech.EngineeringUniversityofKentucky7AcousticBEMME599/699Vibro-AcousticDesignüDirectBEMüIndirectBEMüFEMOverviewofSolutionOptionsDept.ofMech.EngineeringUniversityofKentucky8AcousticBEMME599/699Vibro-AcousticDesignDirectBEM(DBEM)-TwoTypesofProblemsExterior(radiation)vspecifiedBoundarymesh(2-Dsurfacemesh)punknownInterior(cavity)vzpDept.ofMech.EngineeringUniversityofKentucky9AcousticBEMME599/699Vibro-AcousticDesignDisadvantagesoftheDBEM•boundarymustbeclosed-can’tmodelopensystemssuchaspartialenclosures•matrixisnon-symmetric-couplingtoFEMnotefficient-inefficientforlargemeshes•non-uniquenessproblem(radiationonly)-mustaddinteriorpointsODP’sDept.ofMech.EngineeringUniversityofKentucky10AcousticBEMME599/699Vibro-AcousticDesignIndirectBoundaryElementMethod(IBEM)vzpNoisesourcevpOpeningsDept.ofMech.EngineeringUniversityofKentucky11AcousticBEMME599/699Vibro-AcousticDesignFeaturesoftheIBEM•moregeneralthanDBEM•moredifficulttouseandtointerpretresults•symmetricmatrix-efficientforlargemeshes-efficientcouplingwithFEM•non-existenceproblem(radiationfromclosedbodies)-mustaddabsorbingelementsDept.ofMech.EngineeringUniversityofKentucky12AcousticBEMME599/699Vibro-AcousticDesignStartingSYSNOISE•TypeSYSNOISE•CreateaNewModel•InputaName•FilenameExtension.sdbDept.ofMech.EngineeringUniversityofKentucky13AcousticBEMME599/699Vibro-AcousticDesignSYSNOISESolutionOptionsModelOptionDept.ofMech.EngineeringUniversityofKentucky14AcousticBEMME599/699Vibro-AcousticDesignSYSNOISESolutionOptionsDept.ofMech.EngineeringUniversityofKentucky15AcousticBEMME599/699Vibro-AcousticDesignInputtheMesh•FileImportInANSYSFileArchiveWriteFileFormatDept.ofMech.EngineeringUniversityofKentucky16AcousticBEMME599/699Vibro-AcousticDesignViewingtheMesh•FromthetoolbarDept.ofMech.EngineeringUniversityofKentucky17AcousticBEMME599/699Vibro-AcousticDesignViewingtheMesh•FromthemenusDept.ofMech.EngineeringUniversityofKentucky18AcousticBEMME599/699Vibro-AcousticDesignChecktheNormals•DirectüPointtowardstheacousticdomain•IndirectüDefineboundaryconditionside•ViewingnormalsDept.ofMech.EngineeringUniversityofKentucky19AcousticBEMME599/699Vibro-AcousticDesignCorrectingtheNormals•GeometryReverseElementsSelectAllDept.ofMech.EngineeringUniversityofKentucky20AcousticBEMME599/699Vibro-AcousticDesignAutomaticNormalCorrection•GeometryCheckMeshDept.ofMech.EngineeringUniversityofKentucky21AcousticBEMME599/699Vibro-AcousticDesignViewingtheReversedNormals•ToggledisplaytoseeinsideDept.ofMech.EngineeringUniversityofKentucky22AcousticBEMME599/699Vibro-AcousticDesignApplyingFluidProperties•ModelFluidPropertiesDept.ofMech.EngineeringUniversityofKentucky23AcousticBEMME599/699Vibro-AcousticDesignIstheBEMMeshFineEnough?vLinearElements–atleast6elements/wavelengthvParabolicElements–atleast2elements/wavelengthvAcousticwavelengthisafunctionoffrequencyBEMsolutiontime:(Nodes)3fc=lDept.ofMech.EngineeringUniversityofKentucky24AcousticBEMME599/699Vibro-AcousticDesignCheckingtheMaximumFrequency•Inquirefmaximum…Dept.ofMech.EngineeringUniversityofKentucky25AcousticBEMME599/699Vibro-AcousticDesignSelectingSetsforBoundaryCondtions•FromthetoolbarSelectElementsDept.ofMech.EngineeringUniversityofKentucky26AcousticBEMME599/699Vibro-AcousticDesignViewingSets•ViewSetsDept.ofMech.EngineeringUniversityofKentucky27AcousticBEMME599/699Vibro-AcousticDesignViewingSetsDept.ofMech.EngineeringUniversityofKentucky28AcousticBEMME599/699Vibro-AcousticDesignBoundaryConditionsforBEM•ParticleVelocity-Defaultisvn=0•Pressure•Impedancenvpz=Dept.ofMech.EngineeringUniversityofKentucky29AcousticBEMME599/699Vibro-AcousticDesignApplyingVelocityBoundaryConditions•ModelVibratingPanelsManual…Dept