简介：Dropshaftsareverticalstructureswidelyusedinurbandrainagesystemsandbuildingsforwatertransportation.Inthispaper,aphysicalmodelstudywasconductedtoinvestigatetheairentrainmentinthedropshaftundervariousflowregimeswithandwithoutairventilation.Observedfromtheexperiments,theairentrainmentmechanismsvariedwiththewaterflowregimesinthedropshaft.Whentherewasnowaterplugformedinthedropshaft,aircouldbesupplieddirectlyfromdownstream.Oncethewaterplugwasformed,whilewithoutventing,theairwasreplenishedonlyfromdownstreamintermittentlyandthenintheformoflargeairbubbletravelingupwardstotheairspaceatthetop;whilewithventing,airwasmainlyreplenishedfromthedropshafttopandnolargeairbubblewasobserved.Theexperimentalresultsalsoshowedthattheamountofentrainedairinthedropshaftwithventingwasgreaterthanthatwithoutventing.

简介：Anewflowtheoryisestablishedthroughtheobjectivityrequirementonthefluiddynamics.Itwasknownthatinhomogeneousfluidmotiongaverisetoviscousforcewhiletheselectionofobserversondifferentspace-timepointswouldchangesuchaninhomogeneouscharacter.Therefore,whentheviscousforcewasconsideredasanobjectiveexistenceforeigntotheselectionofobservers,theforminvariancesofviscousforceandmomentumequationunderlocalrotationtransformationrequiredanewdynamicfield,namelythevortexfieldtobeintroduced.ThenthedynamicalequationsofallflowfieldswereobtainedthroughconstructingtheLagrangiandensityoffluidsystemandusingthevariationalapproachofenergy.

简介：WithoutsimplifyingtheN-SequationsofGermano’s,westudytheflowinahelicalcircularpipeemployingperturbationmethod.Athirdperturbationsolutionisfullypresented.Thefirst-second-andthird-ordereffectsofcurvatureкandtorsionтonthesecondaryflowandaxialvelocityarediscussedindetail.Thefirst-ordereffectofcurvatureistoformtwocounter-rotatingcellsofthesecondaryflowandtopushthemaximurnaxialvelocitytotheouterbend.Thetwocellsarepushedtotheouterbendbythepuresecond-ordereffectofcurvature.Thecombinedhigher-order(second-,third-)effectsofcurvatureandtorsion,arefoundtobeanenlargementofthelowervortexofthesecondaryflowatexpenseoftheupperoneandaclockwiseshiftofthecentersofthesecondaryvorticesandthelocationofmaximumaxialvelocity.Whentheaxialpressuregradientissmallenoughorthetorsionissufficientlylargerthanthecurvature,thelocationofthemaximalaxialvelocityisneartheinnerbend.Theequationofthevolumefluxisobtainedfromintegratingtheperturbationsolutionsofaxialvelocity.Fromtheequationthevalidityrangeoftheperturbationsolutionsinthispapercanbeobtainedandtheconclusionthatthethreetermsoftorsionhavenoeffectonthevolumefluxcaneasilybedrawn.Whentheaxialpressuregradientislessthan22.67,thevolumefluxinahelicalpipeislargerthanthatinastraightpipe.

简介：Theflowcharacteristicsinaspouted-fluidbeddifferfromthoseinspoutedorfluidizedbedsbecauseoftheinjectionofthespoutinggasandtheintroductionofafluidizinggas.Theflowbehaviorofgas-solidphaseswaspredictedusingtheEulerian-Euleriantwo-fluidmodel(TFM)approachwithkinetictheoryforgranularflowtoobtaintheflowpatternsinspouted-fluidbeds.Thegasfluxandgasincidentanglehaveasignificantinfluenceontheporosityandparticleconcentrationingas-solidspouted-fluidbeds.Thefluidizinggasfluxaffectstheflowbehaviorofparticlesinthefountain.Inthespouted-fluidbed,thesolidsvolumefractionislowinthespoutandhighintheannulus.However,thesolidsvolumefractionisreducednearthewall.

简介：Thepaperstudiestheproblemoffluidflowandfluidshearstressincanaliculiwhentheosteonissubjecttoexternalmechanicalloadingandbloodpressureoscillation.Thesingleosteonismodeledasasaturatedporoelasticcylinder.Solidskeletonisregardedasaporoelastictransverselyisotropicmaterial.Togetnear-realisticresults,boththeinterstitialfluidandthesolidmatrixareregardedascompressible.BloodpressureoscillationintheHaveriancanalisconsidered.Usingtheporoelasticitytheory,ananalyticalsolutionoftheporefluidpressureisobtained.Assumingthefluidincanaliculiisincompressible,analyticalsolutionsoffluidflowvelocityandfluidshearstresswiththeNavier-Stokesequationsofincompressiblefluidareobtained.Theeffectofvariousparametersonthefluidflowvelocityandfluidshearstressisstudied.更多还原

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简介：所有液体动态方程在他们的当模特儿的规模下面是有效的，意味着免费路径例如粒子并且意味着Boltzmann方程的碰撞时间规模和NavierStokes(NS)方程的水动力学规模。当前的计算液体动力学(CFD)集中于部分微分方程(PDE)的数字答案，并且它的目的是得到这些管理方程的精确答案。在如此的一个CFD惯例下面，它是难的开发盖住流动物理从的一个统一计划对水动力学运动因为没有能用Boltzmann做光滑的转变到当模特儿的NS的如此的管理方程，连续地可伸缩。液体动力学的学习需要超出传统的数字部分微分方程。出现设计应用程序，例如为近空间的飞行和流动和热转移在的空气车辆设计微设备，确实要求煤气的动力学的概念的进一步的扩大到物理现实，而非传统的可区分的管理方程的更大的域。在当前的阶段，非平衡流动物理很好还没由于适当工具的缺乏被探索了或清楚地理解。不幸地在当前的数字PDE途径下面，它是难的由于有效PDE的缺席开发如此的一个有意义的工具。以便多尺度的构造和类似于构造管理方程的Boltzmann或NS的当模特儿的过程的multiphysics模拟方法，一个数字算法的发展应该基于物理建模的第一个原则。在这份报纸，而不是跟随传统的数字PDE路径，我们介绍为CFD算法开发的作为一个原则的直接建模。因为所有计算与有限房间分辨率在一个discretized空格被进行，要当模特儿的流动物理不得不在网孔尺寸和时间步骤规模被做。这里，CFD是差不多分离数字进化方程的直接构造，在网孔尺寸和时间步骤将玩的地方，在建模的动态角色处理。与在网孔之间的比率的变化，尺寸和本地粒子意味着免费路径，从到水动力学波浪繁殖的运动粒子运输和碰撞的计划愿望俘获流动物理。基于直接建模，流动运动的连续动力学�

简介：Thispaperconsiderstheunsteadyunidirectionalflowofamicropolarfluid,producedbythesuddenapplicationofanarbitrarytimedependentpressuregradient,betweentwoparallelplates.Theno-slipandtheno-spinboundaryconditionsareused.ExactsolutionsforthevelocityandmicrorotationdistributionsareobtainedbasedontheuseofthecomplexinversionformulaofLaplacetransform.Thesolutionoftheproblemisalsoconsiderediftheupperboundaryoftheflowisafreesurface.Theparticula...

简介：Thispaperisconcernedwiththedispersionofparticlesonthefluid-liquidinterface.Inapreviousstudywehaveshownthatwhensmallparticles,e.g.,flour,pollen,glassbeads,etc.,contactanair-liquidinterface,theydisperserapidlyasiftheywereinanexplosion.Therapiddispersionisduetothefactthatthecapillaryforcepullsparticlesintotheinterfacecausingthemtoacceleratetoalargevelocity.Inthispaperweshowthatmotionofparticlesnormaltotheinterfaceisinertiadominated;theyoscillateverticallyabouttheirequilibriumpositionbeforecomingtorestunderviscousdrag.Thisverticalmotionofaparticlecausesaradially-outwardlateral(secondary)flowontheinterfacethatcausesnearbyparticlestomoveaway.Thedispersiononaliquid-liquidinterface,whichistheprimaryfocusofthisstudy,wasrelativelyweakerthanonanair-liquidinterface,andoccurredoveralongerperiodoftime.Whenfallingthroughanupperliquidtheparticleshaveaslowervelocitythanwhenfallingthroughairbecausetheliquidhasagreaterviscosity.Anotherdifferencefortheliquid-liquidinterfaceisthattheseparationofparticlesbeginsintheupperliquidbeforetheparticlesreachtheinterface.Therateofdispersiondependedonthesizeoftheparticles,thedensitiesoftheparticleandliquids,theviscositiesoftheliquidsinvolved,andthecontactangle.Forsmallparticles,partialpinningandhysteresisofthethree-phasecontactlineonthesurfaceoftheparticleduringadsorptiononliquid-liquidinterfaceswasalsoimportant.Thefrequencyofoscillationofparticlesabouttheirfloatingequilibriumincreasedwithdecreasingparticlesizeonbothair-waterandliquid-liquidinterfaces,andthetimetoreachequilibriumdecreasedwithdecreasingparticlesize.Theseresultsareinagreementwithouranalysis.

简介：ThevalidityofNavier'spartialslipconditionisinvestigatedbystudyingtheoscillatoryflowinacoatedchannel.Thetwo-fluidmodelisusedtosolvetheunsteadyviscousequationsexactly.Partialslipisexperiencedbythecorefluid.ItisfoundthatNaviersconditiondoesnotholdforanunsteadycorefluid.

简介：Vibrationofacircularmembraneincontactwithafluidhasextensiveapplicationsinindustry.Thenaturalvibrationfrequenciesfortheasymmetricfreevibrationofacircularmembraneincontactwithaboundedincompressiblefluidarederivedinthispaper.Consideringsmalloscillationsinducedbythemembranevibrationinanincompressibleandinviscidfluid,thevelocitypotentialfunctionisusedtodescribethefluidfield.Twoapproachesareusedtoderivethefreevibrationfrequenciesofthesystem,whichincludeavariationalformulationandanapproximatesolutionemployingtheRayleighquotientmethod.Agoodcorrelationisfoundbetweenfreevibrationfrequenciesevaluatedbythesemethods.Finally,theeffectsofthefluiddepth,themassdensity,andtheradialtensiononthefreevibrationfrequenciesofthecoupledsystemareinvestigated.

简介：Theuniquecharacteristicsofgas-solidstwo-phaseflowandfluidizationintermsoftheflowstructuresandtheapparentbehaviorofparticlesandfluid-particleinteractionsarecloselylinkedtophysicalpropertiesoftheparticles,operatingconditionsandbedconfigurations.Fluidizedbedsbehavequitedifferentlywhensolidproperties,gasvelocitiesorvesselgeometriesarevaded.Anunderstandingofhydrodynamicchangesandhowthey,inturn,influencethetransferandreactioncharacteristicsofchemicalandthermaloperationsbyvariationsingas-solidcontact,residencetime,solidcirculationandmixingandgasdistributionisveryimportantfortheproperdesignandscale-upoffluidizedbedreactors.Inthispaper,ratherthanattemptingacomprehensivesurvey,weconcentrateonexaminingsomeimportantpositiveandnegativeimpactsofparticlesizes,bubbles,clustersandcolumnwallsonthephysicalandchemicalaspectsofchemicalreactorperformancefromtheengineeringapplicationpointofviewwiththeaimofforminganadequateconceptforguidingthedesignofmultiphasefluidizedbedchemicalreactors.

简介：Thisworkinvestigatestheflowofathirdgradefluidinarotatingframeofreference.Thefluidisincompressibleandmagnetohydrodynamic(MHD).Theflowisboundedbetweentwoporousplates,thelowerofwhichisshrinkinglinearly.Mathematicalmodellingoftheconsideredflowleadstoanonlinearproblem.Thesolutionofthisnonlinearproblemiscomputedbythehomotopyanalysismethod(HAM).Graphsarepresentedtodemonstratetheeffectofseveralemergingparameters,whichclearlydescribetheflowcharacteristics.

简介：Anexactsolutionisdevelopedforthetimeperiodicelectroosmoticflowofanon-Newtonianfluidbetweenthemicro-parallelplates.TheconstitutiveequationsofageneralizedBurgersfluidareusedinthemathematicalformulation.TheresultingproblemissolvedbyaFouriertransformtechnique.Graphsareplottedanddiscussedforvariousemergingparametersofinterest.

简介：ThesedimentationsoftwocylindricalparticlesinthreedifferentinitialrelativepositionsarenumericallysimulatedusingthelatticeBoltzmannmethod.Themovementcharacteristicsandparticleinteractionsduringtheirsedimentationarepresentedanddiscussedindetail.Theresultsshowthat,(i)ifthetwoparticlesarereleasedparallelbutseparatedhorizontally,theypushawayeachother,rotateinwardsandseparatehorizontallyastheyfall;(ii)ifthetwoparticlesarereleasedparallelbutseparatedvertically,thesedimentationbehaviorcanbeclassifiedintothreestages:trailing,tumblingandseparating;(iii)ifthetwoparticlesarereleasedperpendicularbutseparatedvertically,thesedimentationbehaviorcanbecharacterizedas:trailingandrotating,touchingandsliding.Inordertovalidateoursimulation,experimentswerealsoconductedandtheresultsagreewellwiththenumericalones.

简介：Theinertiasofthefluidandtheinnercylinderincoaxialcylinderrheometer(CACR)havegreatinfluenceontheunsteadyflowofnon-Newtonianfluid.EvenfortheNewtonianfluidthereexistthesocalled'stressovershoot'phenomenon.Inthepresentarticlethisphenomenonwasstudiedindetailandamethodcorrectingthemeasuredresultsforanunsteadyflowintherheometerwasproposed.Itisfoundthattheinertiaeffectofthefluidcanbeignoredwhenthegapbetweencylindersissmall.

简介：ThispaperstudiesRayleigh-B'enardconvectionofmicropolarfluidlayerheatedfrombelowwithrealisticboundaryconditions.AspecificapproachforstabilityanalysisofaconvectiveproblembasedonvariationalprincipleisappliedtocharacterizetheRayleighnumberforquitegeneralnatureofboundingsurfaces.TheanalysisconsistsofreplacingthesetoffieldequationsbyavariationalprincipleandtheexpressionsforRayleighnumberarethenobtainedbyusingtrialfunctionsatisfyingtheessential...

简介：TheconstitutiveequationforasemiconcentratedfibresuspensionintheOldroyd-Bfluidhasbeenderivedfromastatisticalmodelofsuchasuspensionbyemployingthemoleculartheoryforpolymericliquids.Tocircumventtheoreticaldifficultiesinviscoelasticfluidmechanics,severalsimplifiedmodelsareusedtoaccountfortheinteractionsoffibresandpolymermolecules.Someofmaterialfunctionsarecalculatedintermsoftheconstitutiveequation.

简介：ResearcheffortsmadesofartosimulatefibresuspensionflowsarelimitedtofibresuspensionsinNewtonianfluids.Thoughshortfibrecompositesaremostlymadeofpolymers,lackofsuitableconstitutiveequationsforfibresuspensionsinviscoelasticfluidsfrustratesattemptstosimulateflowsofthesesuspensions.ApreliminaryworkdonebytheauthorledtoaconstitutiveequationforsemiconcentratedfibresuspensionsintheOldroyd-Bfluid.Thispaperdescribesthemathematicalformulationoftheflowproblemsforsuchasuspensionandthenumericalproceduretosolvethem.Somenumericalresultsofflowpastasphereinatubearealsopresented.

简介：EffectsoftheorientationandapexangleonthesettlingvelocityofconicalparticlesinBinghamplas-ticfluidsarenumericallyinvestigatedoveraReynoldsnumberrangeof1≤Re≤100,Binghamnumberrangeof0≤Bn≤100,andconeanglerangeof20≤α≤150°.Governingequations(ofcontinuityandmomentum)aresolvednumericallyusingthefiniteelementmethodtoobtainvelocityandpressurefieldsthatarepostprocessedtoobtainvaluesofthedragcoefficien.Futthermore,theeffectofconeori-entationontheflowfieldisvisualizedandexploredintermsofstreamlinecontoursandthemorphologyofyielded/unyieldedregions.Finally,theobtainedvaluesofdragarecorrelatedviaasimplepredictiveexpressionintermsofthemodifiedReynoldsnumber.Theeffectoftheconeangleondragisfoundtobemoderatebecausethedragforceactingonthelateralsurfaceisasmallfractionoftheoveralldrag.