高分子等效粘性对壁面湍流结构影响的数值模拟分析

江苏大学硕士学位论文
ABSTRACT
异丙基丙烯酰胺
Avarietyofdifferentpointsofviewaboutthemechanismofturbulencedragreductioninducedbythepolymerwereproposed,therepresentativetheoriesofwhichareviscositymechanismandelasticmechanismetc.Inthepresenttheviscositydragreductionandelasticdragreductionarestilloneofthethemesunderdebate.In
recentstudiesofpolymerdragreductioninwallturbulence,theeffectiveviscositytheorywasproposedbyL’VOVetaI(PRL,2004).Inthispaper,throughtheoreticalderivationalineareffectiveviscositymodelwasestablishedbasedonthistheoryanddescribepolymerdragreductionflowviathecouplingoft
hismodelandNavier—Stokesequation,researchofpolymerdragreductionisdonefromthepointofviewofviscosityeffects.
Usingeffectiveviscositymodel,numericalcalculationwasdonewithReynoldsStress
equationModeland
LargeEddySimulation,respectively.Inwhichtheeffectoftheboundary
layeronpolymerdragreductionWasstudiedbytheribstripsettingtodamagetheboundarylayer.First,thefurthervalidationofeffectiveviscositymodelwasundertakenbycomparingwithdirectnumericalsimulationresultsusingtheFENE·Pmodelunderthesameflowcondition.Byanalysisofthe
如来神掌之宇宙争雄
新型工业化道路
calculationresults,themainconclusionsaregivenasfollowing:(1)Thelineareffectiveviscositychangesthedistributionofmeanvelocityinthechannel,givesathickerelasticbufferlayerandreducestheReynoldsshear
stress.ThemeanvelocityprofileareclosetoVirk’Smaximumdragreductionasymptote,andtendsto
离婚冷静期细则
laminarflowvelocityprofilewhenreachhilghdragreduction(ormaximumdragreduction).(2)Throughtheanalysisofstressesitisfoundthatthelineareffectiveviscositychangestressbalancingintheturbulenceflows,whichreducetheReynoldsstressaccountsfortheproportionofthetotal
shearstress,increasetheviscousshearstress.Althoughviscousdissipationincreases,butincreasetheflowstabilityatthesametime.
(3)Throughtheanalysisofturbulenceintensityitisfoundthatthelineareffectiveviscositycanreflectthe
characteristicsoflowdragreductionflow,andelasticeffectsshouldbeconsideredinhighdragreduction,buttheviscouseffectsshouldplaytheleadingroleinthedragreduction.TheY-direction(verticalwalldirection)turbulenceintensitydirectlyinfluencethedragreduction,anditiscloselyrelatedtoY-directionelongationofpolymer,勘,whichsuggests勘directlyaffectthedragreduction,andwhichisconsistentwiththetheoreticalbasisoftheeffectiveviscosity.
(4)Thelineareffectiveviscositycanreduceturbulentburstsfrequency,andturbulent
Ill
血尿素
羟氨苄青霉素胶囊

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