基于非定常微射流控制的圆湍射流数值模拟研究

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1、哈尔滨工业大学工学硕士学位论文AbstractTurbulentroundjetiswidelyusedinenvironmentandindustry,andreceivesalotofattentioninthelastdecade.Togetabettercombustionmixingratiooffossilfuels,decreasingcarbondioxide,toxicgasesandPM2.5emissions,rapiddiffusionforcooling,anddenoisin

2、g,etc,mixingenhancementofturbulentjetispopularinthoseresearch,andfluidicinjectionisaneffectivechoiceamongthemeanstogetthis.Thispaperbuiltasimulationplatformofturbulentroundjetwithunsteadymicro-jetcontrolbasedontheopensourceC++librarywhichisOpenFOAM,andco

3、mparedwithCFDcommercialsoftwareAnsysFluent.Wenumericallysimulatedthemixingcharacteristicsoftheturbulentroundjet(R8000)underunsteadyemicro-jetcontrolbasedonandOpenFOAM.Firstly,differentgeometries(withnozzleandwithoutnozzle),fourmeshgenerationsolutionsand

4、LESturbulentmodelswerediscussedwithoutmicro-jetcontrol.Thenwecomparedthenumericalresultswiththeexperimentalresultsinordertovalidatethemathematicalmodel.Tofurtheranalyzingthemechanismofmixingenhancement,theeffectofactuationfrequencyandmassflowratioofthemi

5、cro-jetonthemixingcharacteristicswereinvestigated.Ithasbeennumericallyfoundoutthat:thedecayrateofthemeanvelocityfirstincreasethendecreasesastheactuationfrequencyincreasingwhentwomicro-jetcontrolwasused.Whentheactuationfrequencyequalstothevortexsheddingfr

6、equencyoftheturbulentjet,thedecayratereachesthemaximum,whichindicatesthemixingisgreatlyenhanced.Alsowefoundthatwhenthemassflowratiois0.66%,thedecayratehasmaximumvalue.ByanalyzingthevorticalstructurerecognizedbasedonQriterion,ithasbeenfoundthatwhenC<0.25%

7、themicro-jetswereassimilatedintotheshearmlayerofthemainjet;AsCincreasesto0.33%,theshearlayerwaspenetratedbymthemicro-jets,andthemicro-jetsinteractwiththeringvorticesattheoutletofmainjet,resultinginenhancedmixing;WhenCincreasesto4.1%,twomicro-jetscollidem

8、andevolveintooppositelystructures,whichinteractwithringvorticesatthedownstream.Thisworkgainedanimprovedunderstandingoftheenhancedmixingmechanismwithunsteadymicro-jetcontrol,whichprovidesabasisforpromotingtheapplicationandd