用COMSOL设计新型管道消音器PPT格式课件下载.ppt

1、Effective from low to intermediate.Disadvantage:Bulky;Passband;Back pressure.Expansion chamber Mechanism:Impedance mismatch at the junction.（e.g.Vehicle Muffler）3The Novel Drum/Plate SilencerTensioned Membrane/plateMoving air inside the ductpi:Incident Sound Wave;pr:Reflection due to sound induced s

2、tructural vibration;pt:Transmitted sound wave to the downstream.4Advantages of the New SilencerEnvironmentally-friendly.（no air pollution,better than SAM）.Broadband noise reduction at low frequencies（compared with the expansion chamber of the same geometry）.（Huang,2002.Figure 3（a）Expansion chamberDr

3、um/Plate silencerMinimum back pressure（pressure loss）.u The flow can pass smoothly;u No extra noise by the turbulent flow due to flow separation5Several PrototypesLeft:2D Plate silencer（Balsa wood）Top Right:Circular chamber+rectangular ductBot.Right:Four cavities.6Numerical Design:Overview Key Issue

4、 in the Numerical Modeling Key Issue in the Numerical Modeling FEM VS Analytical Method FEM VS Analytical Method The Use of COMSOL MultiphysicsThe Use of COMSOL Multiphysics to solve the full sound-structure coupling,including the to solve the full sound-structure coupling,including the effect of fl

5、ow in the main duct.effect of flow in the main duct.FEM:FEM:Easy to use;versatileEasy to use;versatile Complex geometry;Complex geometry;Complex BCs.Complex BCs.Accuracy to be tested Accuracy to be tested.Analytical MethodAnalytical Method Academically appreciated.Academically appreciated.Accurate;S

6、imply geometry/Accurate;Simply geometry/BCs only.BCs only.An effective design tool.An effective design tool.7OutlineIntroduction on the duct silencer designFEM Modeling of 2D SilencerNumerical results for 2D ConfigurationExtension to 3D DesignSummary 82D Drum Silencer:FEM Modeling Multi-physics Doma

7、ins Multi-physics Domains Vibro-Acoustic Coupling Vibro-Acoustic Coupling Backing Cavity Backing Cavity（Helmholtz Equation）（Helmholtz Equation）Main Duct Main Duct（Convective Wave Eq.）（Convective Wave Eq.）Membrane Membrane （String Vibration）（String Vibration）Membrane:driving force Membrane:driving fo

8、rce Duct+Cavity:Interface Boundary Conditions.Duct+Cavity:Interface Boundary Conditions.9Selection of Application ModesGeom1:Geom1:Duct+Cavity Duct+Cavity F:Velocity PotentialF:Velocity PotentialGeom2:Geom2:1D String 1D String eta:displacementeta:displacement10Sub-Domains in the 2 Geometries Geom1:D

9、uct+Cavity Duct+Cavity InletInletoutletoutletcavitycavityHalf ductHalf ductInterfacesInterfacesGeom2:Membrane（string）Membrane（string）11Boundary Conditions:Acoustic DomainNeumann BCInletInlet outletoutletcavitycavityInterfacesInterfacesThe acoustic domain12Vibro-Acoustic Coupling Acoustic pressure in

10、 the governing Eq.for membrane vibration:Acoustic pressure in the governing Eq.for membrane vibration:Boundary conditions at the interfaces of the duct and cavity:Coupled via“Extrusion Coupling Variables”.Coupled via“Extrusion Coupling Variables”.13OutlineIntroduction on the duct silencer designFEM

11、Modeling of 2D SilencerNumerical results for 2D ConfigurationExtension to 3D DesignSummary 14Primary Results for Single FrequencyTop:Velocity potential（F）at f=0.14Bottom:Amplitude of the Acoustic Pressure along the cross section.FPressure15Performance Indicator:Transmission LossDefinition:Definition

12、:The logarithmic ratio between the sound power The logarithmic ratio between the sound power incident to the silencer and the transmitted sound power for the incident to the silencer and the transmitted sound power for the case there is a no-reflection termination on the downstream side.case there i

13、s a no-reflection termination on the downstream side.Calculation Calculation in COMSOL Multiphysicsin COMSOL Multiphysics:.16Performance of a 2D Drum SilencerP P1 1P P2 2P P3 3L:L:TL comparison between the FEM TL comparison between the FEM simulation and the exact solution.simulation and the exact solution.R:R:Membrane vibration at the three Membrane vibration at the three spectral peaks.spectral peaks.（Note:configurations are specified in Huang,2002）（Note:configurations are specified in Huang,2002）TL=0.02 dBTL=0.02 dB17Effect of Mean FlowL:TL compariso