0112-湍流模型介绍.pdf

《0112-湍流模型介绍.pdf》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、TURBULENCEMODELSANDTHEIRAPPLICATIONSPresentedby:T.S.D.KarthikDepartmentofMechanicalEngineeringIITMadrasGuide:Prof.FranzDurst10thIndoGermanWinterAcademy20112Outline3TurbulencemodelsintroductionBoussinesqhypothesisEddyviscosityconceptZeroequationmodelOneequationmodelTwoequationmodelsAlgebraicst

2、ressmodelReyoldsstressmodelComparisonApplicationsDevelopmentsConclusionTurbulenceModelsandTheirApplicationsTurbulencemodels4Aturbulencemodelisaproceduretoclosethesystemofmeanflowequations.Formostengineeringapplicationsitisunnecessarytoresolvethedetailsoftheturbulentfluctuations.Turbulencemod

3、elsallowthecalculationofthemeanflowwithoutfirstcalculatingthefulltime-dependentflowfield.Weonlyneedtoknowhowturbulenceaffectedthemeanflow.InparticularweneedexpressionsfortheReynoldsstresses.Foraturbulencemodeltobeusefulit:musthavewideapplicability,beaccurate,simple,andeconomicaltorun.Turbulen

4、ceModelsandTheirApplicationsCommonturbulencemodels5Classicalmodels.BasedonReynoldsAveragedNavier-Stokes(RANS)equations(timeaveraged):Zeroequationmodel:mixinglengthmodel.OneequationmodelTwoequationmodels:k-stylemodels(standard,RNG,realizable),k-model,andASM.Sevenequationmodel:Reynoldsstressmod

5、el.ThenumberofequationsdenotesthenumberofadditionalPDEsthatarebeingsolved.Largeeddysimulation.Basedonspace-filteredequations.Timedependentcalculationsareperformed.Largeeddiesareexplicitlycalculated.Forsmalleddies,theireffectontheflowpatternistakenintoaccountwitha“sub-gridmodel”ofwhichmanystylesare

6、available.DNSTurbulenceModelsandTheirApplicationsClassification6TurbulenceModelsandTheirApplicationsPredictionMethods7TurbulenceModelsandTheirApplicationsBoussinesqhypothesis8ManyturbulencemodelsarebasedupontheBoussinesqhypothesis.Itwasexperimentallyobservedthatturbulencedecaysunlessthereissheari

7、nisothermalincompressibleflows.Turbulencewasfoundtoincreaseasthemeanrateofdeformationincreases.Boussinesqproposedin1877thattheReynoldsstressescouldbelinkedtothemeanrateofdeformation.Usingthesuffixn