vortex nanoprecipitation reactor Turbulence

APPLIEDPHYSICSLETTERS94,204104͑2009͒Amicroscalemulti-inletvortexnanoprecipitationreactor:TurbulencemeasurementandsimulationJanineChungyinCheng,,2,a͒112DepartmentofChemicalandBiologicalEngineering,IowaStateUniversity,Arnes,Iowa50011,USADepartmentofMechanicalEngineering,IowaStateUniversity,Arnes,Iowa50011,USA͑Received16February2009;accepted27March2009;publishedonline21May2009͒MicroscalereactorscapableofgeneratingturbulentflowareusedinFlashNanoPrecipitation,anapproachtoproducefunctionalnanoparticleswithuniqueoptical,eactordesignandoptimizationcouldbegreatlyenhancedbydevscalemulti-inletvortexnanoprecipitationreactorwasinvestigatedusingmicroscopicparticleimagevelocimetryandcomputationalfltydatasuchasthemeanvelocityandturbulentkineticenergydisplayedgoodagreementbetweenexperimentandsimulationoverflowconditionsrangingfromfullylaminartoturbulent,demonstratingtheaccuracyofthesimulationmodelovertheentireturbulenttransitionrange.©2009AmericanInstituteofPhysics.͓DOI:10.1063/1.3125428͔Functionalnanoparticlesareincreasinglyimportantcosmetics,2indevelopingmaterialsfordyes,1pharmaceuticals,2–5andnumerousotherapplications,6–8re-sultingingreatinterestimple,colloidaldrugcarrierssuchasliposomalandmicellardispersionscon-sistingofparticles50–400nmindiameterhavepotentialuseinformulatinganticancertherapeuticsthatcanselectivelytargettumors.9FlashNanoPrecipitation10–12—anapproachtoproducefunctionalnanoparticlesstabilizedbyamphiphiliccopolymerself-assembly—tion,nanoparticlesenc-decoratedimmunoliposomescapableofevad-ingthereticuloendothelialsystemcanbedevelopedusinghydrophilicpolymer͑i.e.,polyethyleneglycol͒stabilizationtopreventadsorptionofcomponentsoftheimmunesystemandincreasethebindingandcirculationtime.13AsillustratedinFig.1,FlashNanoPrecipitationemploysrapidmixingofsolventandnonsolventtocreatehighsupersaturationtoini-tializeprecipitation;rapidmixinguncouplesthemixingpro-cessfromtheparticleaggregatocesshasbeendemonstratedinmicroscaledevicessuchascon-finedimpingingjetreactors͑CIJRs͒10,14,15andmulti-inletvortexreactors͑MIVRs͒.16MIVRsareofspecialinterestduetotheirflexibilityintheflconsistsofflowrates,tur-bulenceisnjectedstreamsformaswirl-ingvortexpatterninsteadofanimpingementzone͑asinaCIJR͒,,thechoicesofchemicalsaremoreflexibleanddifferentin-tensitiesofsupersaturationcanbeattainedbyinjoprecipitationishighlydependentonthea͒fl,inordertounder-standthemixingandnanoprecipitationmechanismswithintheMIVR,theflowwasinvestigatedusingmicroscopicpar-ticleimagevelocimetry͑microPIV͒,atechniqueformeasur-inginstantaneousvelocityfieldsinmicrofluidicdevices,17andcomputationalfluiddynamics͑CFDs͒.Thisworkrepre-sentsthefirststepindevelopingareliablecomputationalmodelfortheFlashNanoPrecipitationprocessinaMIVRcapableofpredictiscaleMIVRwasfabricatedwithanopticalwindowtoallowthelightfromafrequencydoubledneody-miumdopedyttriumaluminumgarnet͑Nd:YAG͒lasertoilluminate2␮mdiameterfluorescentseedparticlesandforimagestobecapturedwithachargecoupleddevice͑CCD͒cameraattachedtoaninvertedflctorandchannelheightwas1.53mm,theinletchannelwidthwas1.19mm,thereactordiameterwas6.26mm,flowwasimagedusinga4ϫ0.13numericalapertureobjectiveanda0.45ϫcou-Electronicmail:mgolsen@.1.͑Coloronline͒dpolymersaredissolvedinsolventandinjectedtomixwithnonsotednanoparticlesareobtainedafterthestabilizationbycopolymerself-assembly.©2009AmericanInstituteofPhysics0003-6951/2009/94͑20͒/204104/3/$25.0094,204104-1Downloaded 08 Dec 2010 to 211.66.116.232. Redistribution subject to AIP license or copyright; see /about/rights_and_permissions

204104-2Cheng,Olsen,andFox0TangentialVelocity(m/s)(a)−0.02−0.04−0.06−0.08−0.1−40.01(b)RadialVelocity(m/s)0−0.01−0.02−0.03−0.04−4−2−.94,204104͑2009͒0X(mm)24FIG.2.͑Coloronline͒ctorwasilluminatedbyadualpulseNd:geswasdividedintosmallinterrogationwindowsandvectorswerecalculatedbycorrelatingtwoim-agestakenatdifferenttimes.0X(mm)24pling,resultinginameasurementdepth͑i.e.,depthofcorrelation͒18,19of86␮mandanin-planevectorspacingof57.6␮flhflowconditionandlocationinvestigated,anensembleof1200velocityfirdetailsofthemicroPIVsystemandtheexperimentalmethodologycanbefoundintheliterature.20,21ThemicroPIVdatawereusedtoevaluatetheaccuracyofusingexistingCFDmodelsinsimulatingtheflrsimulationswereperformedforlowRey-noldsnumbercases,andlargeeddysimulations͑LESs͒usingtheSmagorinsky–Lillysubgridmodel22,chosendu-dimensionalsimulationswereper-roPIVdataconsistedofplanesofinstantaneousvelocityvectorfieldsatthreedifferentheightsinthereactor:themid-heightofthereactor,andonequarterofareactorheightfromthetopandfromthebottom,asillustratedinFig.2ThreesetsofmicroPIVdatawerecollectedateachmea-surementplanecorrespondingtothreedifferentinletstreamReynoldsnumbers:Rej=53,Rej=93,andRej=aweretransformedinrisonbetweenex-perimentandsimulationwasaccomplishedbyextractingtwo-dimensional͑2D͒planesofdatafromtheCFDsiultsarepresentedhereasvelocityprofiRej=53case,theflowislaminarandtheflowpa.3,thetangentialvelocityprofileindi-catesthatthevortexflowswirlsfasteratthelocationclosesttothereactortop,suggestingthattheflowismainlyinflu-encedbythegeometryofthereactor,creaseintangentialve-locityistobeexpected,asvortexlinesarestretchedastheflialvelocitiesshowninFig.3remainnegative,indicatingaFIG.3.͑Coloronline͒VelocityprofilecomparisonofmicroPIVandCFDatRej=tractedfrommid-heightofthereactorarerepresentedby᭝,quarter-topplane:ᮀ,quarter-bottomplane:छ;simulationdataatcorre-spondinglocationsarerepresentedbyasolidline͑mid-plane͒,dashedline͑quarter-top͒,anddottedline͑quarter-bottom͒.simpleflowpatternwheretheinjectedflowisdirectedtotheoutletwithoutmuchcollisionandredirection͑notethatnega-tiveradialvelocityindicatesflowtowardthecenterofthereactor͒.Thetangentialandradialvelocitycomponentsarealsoroughlyofthesameorderofmagnitude,suggestingapoorlydevelopedvortexflscase,goodagreementbetweenexperimentandsimulationwasonlyachievedwhentheturbulencesubgridmodelwasturnedoff͑i.e.,whenalaminarsimulationwasperformed͒.AtRej=93,thehigherobservedratiooftangentialtoradialvelocityindicatesamoredevelopedvortexflgentialvelocityprofilesatdifferentheightsshowninFig.4areveryclosetooneanother,ertangentialvelocityat0TangentialVelocity(m/s)(a)−0.1−0.2−0.3−0.4−40.1(b)RadialVelocity(m/s)0.050−0.05−0.1−4−20X(mm)24−20X(mm)24FIG.4.͑Coloronline͒VelocityprofilecomparisonofmicroPIVandCFDatRej=aded 08 Dec 2010 to 211.66.116.232. Redistribution subject to AIP license or copyright; see /about/rights_and_permissions

204104-30−0.5−1−1.5−2−40.4RadialVelocity(m/s)0.20−0.2−0.4−40.40.30.20.10−4Cheng,Olsen,.94,204104͑2009͒TangentialVelocity(m/s)(a)−2(b)0X(mm)24−2(c)0X(mm)24−20X(mm)24kineticenergy͑TKE͒atsinceonlyplanarvelocityfieldscanbeobtainedusingmicroPIV,onlya2DTKEcanbecalcu-lated͓i.e.,k2D=1/2͑uЈ2+vЈ2͒,whereuЈandvЈarethermsvelocitycomponents͔.k2DwasalsocalculatedfromplanarvelocityfieldsextractedfromtheCFDsimulationsresultsforthesimulationsagreewellwiththeexperimentsexceptalongtheaxisofthereactor,etheradialandtangentialvelocitiesaresmallalongthereactoraxis,r,theobservedTKEattheaxisisduenotonlytoturbulentvelocityfluctua-tions,butalsoduetosmallunsteadymotionsofthevortexcoreresultingfromflthesimulations,whichcanhaveperfectlyconstantinletconditions,thereex-istsmallperturbationstotheexperimentalinletvelocitycon-ditionsduetothemechanicalnatureofthegearpumps,andtheseperturbationsresultingreatervortexmotion,andhence,kpresentedhererepresentsthefirstexperimen-talvalultsshowthatLESiscapableofaccuratelymodelingtheflowfifindingisanimportantfirststepinthedevelopmentofcomputermodelsofthenanoprecipitationprocesswithinamicroscaleMIVR,resultinginapowerfuldesigntoolforcustere,,,ra,a,NanoLett.5,1321͑2005͒.,,g,liveryRev.54,S131͑2002͒.nn,,r,rm.39,173͑1993͒.,.284,109͑2004͒.,.160,229͑1998͒.oehm,k,,ncapsul.17,195͑2000͒.s,,,,hies,,,.252,387͑2002͒.,,ry,.5,567͑2003͒.ng,r,,,ka,,rster,is,65,1513͑2002͒.’homme,.56,1021͑2003͒.’homme,.-.226,U487͑2003͒.’homme,.91,118302͑2003͒.,ma,,ru,.190,49͑1999͒.’homme,AIChEJ.49,2264͑2003͒.,,,LabChip9,1110͑2009͒.,,,’homme,,.63,2829͑2008͒.go,y,rt,,,25,316͑1998͒.,29,S166͑2000͒.n,,,l.15,318͑2004͒.,Eng.128,305͑2006͒.,uidFlow27,123͑2006͒.,Astrophys.J.428,729͑1994͒.,yn.8,131͑1996͒.1FIG.5.͑Coloronline͒Velocityprofileand2DTKEcomparisonofmi-croPIVandCFDatRej=r-bottomthantheothertwolocationssuggeststheflowisstillaffectedbythegeometry;ialvelocityprofileshowninFig.4differsfromtheRej=53͑laminar͒casewiththepresenceofnon-negativeradialvelocityatthemid-heightplane,indicatingacomplexflowpatternwheretheiiscasewasmodeledbyLES͑withthetur-bulencesubgridscalemodelturnedon͒,atsincethevortexflowismoredevelopedinthiscase,theradialvelocityisanorderofmagnitudesmallerthanthetangentialvelocity,makingtheradialcomponentmorediffi,thRej=240case,thetangentialvelocityprofilesshowninFig.5areclosetooneanother,attheprofileedifferentfromtheRej=93case,dicatesastrongvor-texflowwheretheinletstreamscolialvelocitiesshowninFig.5haveamagnitudeofonly5%ofthatofthetangentialvelocities,indicatingastrongvortexflowandalsocausingdiffishighReynoldsnumber,theturbulentDownloaded 08 Dec 2010 to 211.66.116.232. Redistribution subject to AIP license or copyright; see /about/rights_and_permissionsk(kg−m/s)22