Dynamics of microcapsulsRBC in time dependent shear flow.pdf

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1、DYNAMICSOFMICROCAPSULESANDREDBLOODCELLSINTIME-DEPENDENTSHEARFLOWBYMENGYEZHAOAthesissubmittedtotheGraduateSchool—NewBrunswickRutgers,TheStateUniversityofNewJerseyinpartialfulfillmentoftherequirementsforthedegreeofMasterofScienceGraduatePrograminMechanicalandAerospaceEngin

2、eeringWrittenunderthedirectionofProfessorProsenjitBagchiandapprovedbyNewBrunswick,NewJerseyOCTOBER,2011ABSTRACTOFTHETHESISDynamicsofMicrocapsulesandRedBloodCellsinTime-dependentShearFlowbyMengyeZhaoThesisDirector:ProfessorProsenjitBagchiThisthesispresentsathree-dimensio

3、nalnumericalstudyonthedynamicsofdeformablecapsulesinsinusoidallyoscillatingshearflow.Forthisstudy,weconsidercapsulesofsphericalandoblatespheroidrestingshapes.Forspheri-calrestingshapes,wefindidenticaldeformationresponseduringpositiveandnegativevorticity.However,thedeforma

4、tionresponsebecomesunequalandshowscomplexbehaviorfornonsphericalrestingshapes.Theaverageelonga-tionishigherintheretardingphaseoftheshearflowthanintheacceleratingphase.Primarilytwotypesofdynamicsareobservedfornonsphericalshapes:aclockwise/counter-clockwiseswingingmotionin

5、responsetothealteringflowiidirectionthatoccursatbothhighandlowvaluesofshearrateamplitudes,andacontinuous/unidirectionaltumblingmotionthatoccursatintermediatevalues.Theunidirectionaltumblingmotionoccursdespitethefactthatthetime-averagevorticityiszero.Suchatumblingmotionis

6、accompaniedbyacontinuoustank-treadingmotionofthemembraneintheoppositedirection.Weobtainphasediagramthatshowsexistenceoftwocriticalshearratesandtwooscillationfre-quencies.Theunidirectionaltumblingmotionoccursintheintermediaterange,andtheclockwise/counter-clockwiseswingin

7、gmotionoccursotherwise.Wealsofindthatthedynamicsishighlysensitivetotheinitialcondition.Aswingingisgenerallyobservedwhenthecapsuleisreleasedalignedwiththeextensionalorcompressionalaxisoftheshearflow,andatumblingisobservedotherwise.Theseresultssuggestthepossibilityofchaotic

8、behaviorofcellsintime-dependentflows.Weprovideexplanationsofsuchcomplexdynamicsbyanalyzingthecouplingbe-tweenth