Large Eddy Simulations of Compressible Mixing Layers

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1、LargeEddySimulationsofCompressibleMixingLayersAThesissubmittedforthedegreeofMasterofScience(Engg.)intheFacultyofEngineeringbyKowsikVRBodiDepartmentofAerospaceEngineeringIndianInstituteofScienceBangalore-560012,IndiaApril2005AbstractThisthesisisconcernedwithinvestigatingtheapplicabili

2、tyoflargeeddysimulations(LES)forsimulatingcompressiblemixinglayers,withtheultimateaimofutilizingLESasatooltoinvestigatethee®ectsofcompressibilityandcon¯nementontheevolutionofmixinglayers.Inviewoftheinabilityoftemporalsimulationstocaptureallthefeaturesinvolvedinmixinglayersasencounter

3、edinpractice,spatiallydevelopingmixinglayersasobservedinexperimentsaresimulatedinthepresentwork.Hence,thecomputationaldomainstartsfromthetrailingedgeofthesplitterplatedividingtheincomingstreams,andincludesboththetransitionalwakeandthemixinglayerregions.TheperformanceofReynolds-Averag

4、edmethods,derivedfromthecompressible°uid{°owequations,inpre-dictingcompressiblemixinglayershasbeenevaluated.Two-equationmodelslikek¡"andSSTmodelshavebeenfoundtohavecompletelyfailedinreproducingthee®ectofcom-pressibilityonmixinglayerevolution.LargeEddySimulationswithDynamic-Smagorinsk

5、ymodelingofsubgrid-scalee®ects,usingasecond-orderaccurateschemeasimplementedintheCFDsoftwareCFX,ofhighspeedmixinglayerswithlowandmoderatecompressibil-itye®ectsareperformed.Simulationsinthepresentworkareofquasi-twodimensionalnature,asmuchofthespan-wisemotionsarenotresolved,thoughtheir

6、e®ectsaremod-elledthroughthesubgrid-scalemodel.Thesimulationswerecheckedforthedependenceofthemean°owpredictionsontheaveragingduration,computationalgridre¯nementandinitialconditions.Predictionofthe¯rstorderstatisticslikemixinglayergrowthrate,andthemeanvelocitypro¯leshasbeenfoundtobeve

7、rygood.Predictionofsecondorderstatisticshasbeenfoundtobeinagreementwiththe¯ndingsofexperimentalandDirectNumericalStudies.Thelow-speedstreamhasbeenfoundtobemorereceptivetothe°uctuationsinducedbythemixinglayer,therebyleadingtohigherlevelsof°uctuationin-tensitiesonthelow-speedsideofmixi

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