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,anddenoi

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

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

4、utionsandLESturbulentmodelswerediscussedwithoutmicro-jetcontrol.Thenwecomparedthenumericalresultswiththeexperimentalresultsinordertovalidatethemathematicalmodel.Tofurtheranalyzingthemechanismofmixingenhancement,theeffectofactuationfrequencyandmassflow

5、ratioofthemicro-jetonthemixingcharacteristicswereinvestigated.Ithasbeennumericallyfoundoutthat:thedecayrateofthemeanvelocityfirstincreasethendecreasesastheactuationfrequencyincreasingwhentwomicro-jetcontrolwasused.Whentheactuationfrequencyequalstothev

6、ortexsheddingfrequencyoftheturbulentjet,thedecayratereachesthemaximum,whichindicatesthemixingisgreatlyenhanced.Alsowefoundthatwhenthemassflowratiois0.66%,thedecayratehasmaximumvalue.ByanalyzingthevorticalstructurerecognizedbasedonQriterion,ithasbeenfo

7、undthatwhenC<0.25%themicro-jetswereassimilatedintotheshearmlayerofthemainjet;AsCincreasesto0.33%,theshearlayerwaspenetratedbymthemicro-jets,andthemicro-jetsinteractwiththeringvorticesattheoutletofmainjet,resultinginenhancedmixing;WhenCincreasesto4.1%,

8、twomicro-jetscollidemandevolveintooppositelystructures,whichinteractwithringvorticesatthedownstream.Thisworkgainedanimprovedunderstandingoftheenhancedmixingmechanismwithunsteadymicro-jetcontrol,whichprovidesabasisforpromotingtheapplicationandd