简介：Anumericalanalysisofnon-Newtonianfluidflowinnon-planararterywithbifurcationwasperformedbyusingafiniteelementmethodtosolvethethree-dimensionalNavier-Stokesequationscoupledwiththenon-Newtonianconstitutivemodels,includingCarreau,CrossandBinghammodels.Theobjectiveofthisstudyistoinvestigatetheeffectsofthenon-Newtonianpropertiesofbloodaswellascurvatureandout-of-planegeometryinthenon-planardaughtervesselsonthevelocitydistributionandwallshearstress.Theresultsofthisstudysupporttheviewthatthenon-planarityofbloodvesselsandthenon-Newtonianpropertiesofbloodareofimportantinhemodynamicsandplayasignificantroleinvascularbiologyandpathophysiology.

简介：A2-DdepthaveragedRNGk-εmodelisdevelopedtosimulatetheflowinatypicalreachoftheUpperYellowRiverwithnon-monotonicbanks.Inordertotakeaccountoftheeffectofthesecondaryflowinabend,themomentumequationsaremodifiedbyaddinganadditionalsourceterm.Acomparisonbetweenthenumericalsimulationandthefieldmeasurementsindicatesthattheimproved2-DdepthaveragedRNGk-εmodelcanimprovetheaccuracyofthenumericalsimulation.Anarcsplineinterpolationmethodisdevelopedtointerpolatethenon-monotonicriverbanks.Themethodcanalsobereasonablyappliedforthe2-Dinterpolationoftheriverbedlevel.Throughacomparisonofthewatersurfacegradientssimulatedinthesevenbendsofthestudiedreach,someanalyticalformulaeareimprovedtoreasonablycalculatethelongitudinalandtransversegradientsinmeanderingriverreaches.Furthermore,thepositionsofthemaximumwaterdepthandthemaximumvelocityinatypicalbendarediscussed.

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简介：Athree-dimensionalmathematicalmodelforcalculatingthesteadyflowofcircularnon-buoyantturbulentsurfaceinacoflowingchannelispresentedinthispaper.Forclosingthecontrolequations,theκ-εturbulencemodelisusedinthemathematicalmodel.Thewall-functionmethodisemployedtotreatthewallboundaryconditionatthebottomplane.TheclosedcontrolequationsarediscretizedbyusingHybridFiniteAnalyticMethod(HFAM)onanon-uniformstaggeredgridsystem.Thenumericalresultsareobtainedfordifferentratioofthejetvelocitytothecoflowingvelocity.Thecomparisonwithexperimentaldatashowsgoodagreement.

简介：Theboundaryintegralmethod(BIM)isusedtosimulatethe3-Dgasbubble,generatedwithinthetwobubblepulsationperiodsinproximitytoafreesurfaceinaninviscid,incompressibleandirrotationalflow.ThepresentmethodiswellvalidatedbycomparingthecalculatedshapesofthebubbleandthefreesurfacewithboththeexperimentalresultsandthenumericalonesobtainedbytheAxisymmetricBIMcode.Theexpansion,thecollapseofthegasbubbleandthefurtherevolutionofthereboundingnon-sphericalbubblearesimulated.Thevariousvariationpatternsofthefreesurfacespikeandthebubblecentroidfordifferentstandoffdistances,thebuoyancyparametersandthestrengthparametersareobtainedtorevealthenonlinearinteractionbetweenthebubbleandthefreesurface.Theamplitudeofthesecondmaximumbubblevolumeandthefourtypicalpatternsofthebubblejetandthefreesurfacespikeareexaminedinthecontextofthestandoffdistance.Thelargebuoyancyisusedtoelevatethespraydomeratherthanthefreesurfacespike.

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简介：Basedonaseriesofexperimentsunderbothice-coveredandfreesurfaceconditions,thepresentarticlediscussestheroleofflowvelocityandcriticalshearReynoldsnumberforincipientmotionofbedmaterial.Theinfluenceoftheresistancecoefficientsofboththeundersideoftheicecoverandthechannelbedonthelocationofthemaximumvelocityhasbeendiscussed.Inaddition,theimpactsoficeandcompositeresistancecoefficientsonflowvelocityforincipientmotionofbedmaterialhavebeenassessed.ThediagramdescribingthecriticalshearReynoldsnumberandthedimensionlessshearstressfortheincipientmotionofsedimentundericecoveredconditionswithdifferentundercoverresistancecoefficienthasbeenestablished.TheeffectsofgrainsizeondensimetricFroudenumberforincipientmotionofbedmaterialhavebeeninvestigated.ArelationshipbetweenthedensimetricFroudenumberforincipientmotionofbedmaterialandthemediangrainsizeofbedmaterialaswellastheroughnesscoefficientofchannelbedandroughnesscoefficientoficecoverhasbeenestablished.

简介：Thethree-dimensionalNavier-Stokesequationsweresolvedwiththefractionalstepmethodwherethehydrostaticpressurecomponentwasdeterminedfirst,whilethenon-hydrostaticcomponentofthepressurewascomputedfromthepressurePoissonequationinwhichthecoefficientmatrixispositivedefiniteandsymmetric.Theeddyviscositywascalculatedfromtheefficientk-εturbulencemodel.TheresultingmodeliscomputationallyefficientandunrestrictedtotheCFLcondition.Computationswithandwithouthydrostaticapproximationwerecomparedforthesamecasestotestthevalidityoftheconventionalhydrostaticpressureassumption.Themodelwasverifiedagainstanalyticalsolutionsandexperimentaldata,withexcellentagreement.

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简介：A3-DnumericalformulationisproposedonthehorizontalCartesian,verticalsigma-coordinategridformodelingnon-hydrostaticpressurefree-surfaceflows.Thepressuredecompositiontechniqueandθsemi-implicitmethodareused,withthesolutionprocedurebeingsplitintotwosteps.First,withtheimplicitpartsofnon-hydrostaticpressuresexcluded,theprovisionalvelocityfieldandfreesurfaceareobtainedbysolvinga2-DPoissonequation.Second,thetheoryofthedifferentialoperatorisemployedtoderivethe3-DPoissonequationfornon-hydrostaticpressures,whichissolvedtoobtainthenon-hydrostaticpressuresandtoupdatetheprovisionalvelocityfield.Whenthenon-orthogonalsigma-coordinatetransformationisintroduced,additionaltermscomeintobeing,resultingina15-diagonal,diagonallydominantbutunsymmetriclinearsysteminthe3-DPoissonequationfornon-hydrostaticpressures.TheBiconjugateGradientStabilized(BiCGstab)methodisusedtosolvetheresulting3-Dunsymmetriclinearsysteminsteadoftheconjugategradientmethod,whichcanonlybeusedforsymmetric,positive-definitelinearsystems.Threetestcasesareusedforvalidations.Thesuccessfulsimulationsofthesmall-amplitudewave,asupercriticalflowoverarampandaturbulentflowintheopenchannelindicatethatthenewmodelcansimulatewellnon-hydrostaticflows,supercriticalflowsandturbulentflows.