简介：ＴＨＲＥＥ－ＤＩＭＥＮＳＩＯＮＡＬＭＯＤＥＬＬＩＮＧＦＯＲＬＵＢＲＩＣＡＴＩＯＮＷＩＴＨＲＥＦＥＲＥＮＣＥＴＯＨＵＭＡＮＪＯＩＮＴＳＺｈａｎＪｉｅ－ｍｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＭｅｃｈａｎｉｃｓａｎｄＥｎｇｉｎｅｅｒｉｎｇ，Ｚｈｏｎ...

简介：ATime-domainHigher-OrderBoundaryElementMethod(THOBEM)isdevelopedforsimulatingwave-currentinteractionswith3-Dfloatingbodies.ThroughaTaylorseriesexpansionandaperturbationprocedure,themodelisformulatedtothefirst-orderinthewavesteepnessandinthecurrentvelocity,respectively.Theboundaryvalueproblemisdecomposedintoasteadydouble-bodyflowproblemandanunsteadywaveproblem.Higher-orderboundaryintegralequationmethodsarethenusedtosolvetheproposedproblemswithafourth-orderRunge-Kuttamethodforthetimemarching.Anartificialdampinglayerisadoptedtodissipatethescatteringwaves.Differentfromtheothertime-domainnumericalmodels,whichareoftenfocusedonthewave-currentinteractionwithrestrainedbodies,thepresentmodeldealswithafloatinghemisphere.Thenumericalresultsofwaveforces,waverun-upandbodyresponseareallinacloseagreementwiththoseobtainedbyfrequency-domainmethods.Theproposednumericalmodelisfurtherappliedtoinvestigatewave-currentinteractionswithafloatingbodyofcomplicatedgeometry.Inthiswork,theregularandfocusedwavecombinedwithcurrentinteractingwithatruss-sparplatformisinvestigated.

简介：Theproblemofpenetrativeconvectionwiththecubicandfifth-orderequationsofstateproposedbyMerker,WaasandGrigullisstudied.Bothlinearinstabilityandnonlinearstabilityanalysesareperformedtoassessthesuitabilityoflineartheorytopredictdestabilisationoftheconvection.Thevalidityofboththelinearinstabilityandglobalnonlinearenergystabilitythresholdsaretestedusingthree-dimensionalsimulation.Theresultsshowthatthelinearthresholdaccuratelypredictstheonsetofinstabilityinthebasicsteadystatesolution.

简介：Athree-dimensional(3-D)numericalmodelisestablishedtoinvestigatethetidalcurrentmotioncharacteristicsaroundtheharborentrance.Computationalapproachesconsistofthefinitedifferencemethod,time-splittingtechnique,C-grid,andahigh-orderturbulenceclosuremodel.TheOceanGeneralCirculationModel(OGCM)inundationschemeisincorporatedinthemodel.Anengineeringapplication,LianyungangHarbor,China,isusedasareal-lifecase.Themodelisvalidatedbyshowingthatthesimulatedresultsagreewellwiththefielddata.Intheapproachchannel,thetidalcurrentshowsadeflectioneffectespeciallyinthebottomlayer.AsforLianyungangHarbor,ajetflowformsatthetipofthenorthernbreakwater,whichdrivesacirculationflowattheinnersideoftheharborentrance.Inthevertical,theflowissignificantlystratifiedattheentrancesectionwithinthechannel,wheretheflowdirectionvariesbetweenlayersandthespeeddistributionisquiteuniform.These3-Dfeaturesbecomelessevidenttotheoffshore.Additionally,thesensitivityanalysisshowsthattheflowdeflectionisrelatedtothechanneldepth.Simulationresultsalsoimplythatthesiltationrateattheentrancesectionoftheapproachchanneltendstobemoreuniformbythe3-Dflowmotionfeature,andcouldbemoresignificantwiththeincreaseofthechanneldepth.

简介：Thewatertemperaturestratificationinlargereservoirsmighthaveseriousecologicalandenvironmentalconsequences.Themodelingofthetemperaturedistributionanditshistoryisofgreatimportancebothforstudyingtheunderlyingmechanismsandforcontrollingtheadverseeffects.Todevelopaneffectiveandefficientmethodforsimulationoftemporalandspatialtemperaturevariations,alatticeBoltzmannmethod(LBM)modelfor3-Dthermalbuoyancyflowsisproposedandvalidatedbythetemperaturedatameasuredinamodelreservoir.ThispaperdiscussesimportantaspectsoftheLBManditsturbulencemodel,analyzesthegravitysinkingmechanismofcoldcurrents,anddemonstratesthecomplexityofthetemperatureredistributionprocess.Goodagreementbetweenthesimulatedandmeasuredresultsshowsthatthenewlydevelopedmethodisfeasibleandpowerful,anditwillbeusedforthewatertemperaturepredictioninactualreservoirsinanearfuture.

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

简介：Airentrainmentisknowntobeoneofefficientandinexpensivemethodstopreventcavitationdamagesinhydropowerprojects.Theshapeofsuddenexpansion-fallisusedasacommondeviceformitigatingcavitationerosions.Thecomplexflowpatternswithcavitationarenumericallysimulatedbyusingtherealizablek-εturbulencemodelandtheair-watermixturemodel.Thecalculatedresultsarecomparedwellwiththeexperimentalresultsaswellasthoseobtainedwiththek-εturbulencemodelwiththeVolumeOfFluid(VOF)Model.Thecalculatedresultsagreewellwiththeexperimentaldatafortheaerationcavityandwallpressure.Moreover,theairconcentrationnearsidewallissimulatedbyamixturemodel.ItisfoundthatthemixtureturbulencemodelissuperiortotheVOFturbulencemodel.

简介：Channelconfluencesareuniversallypresentinnature.Theycanbedividedintotwotypes:asymmetricalriverconfluencesandsymmetricriverconfluences.ThelatterisalsocalledastheY-shapedconfluences.Mostofpreviousworkhaspaidmoreattentiontotheasymmetricalriverconfluences,butfewstudieshavebeenconductedontheY-shapedconfluences.Inthisarticle,theeffectsofbeddiscordanceontheflowpatternsat'Y'shapedopen-channelconfluenceswerestudiedbyusinga3-Dnumericalsimulation.Itisprovedthatthemodelcanundertakequantitativeassessmentoftheflowatconfluences.TheresultsindicatethattherearealotofdifferencesbetweentheY-shapedconfluenceandasymmetricalconfluence.ThediscordantbedheightplaysanimportantroleattheY-shapedjunction.

简介：ＡＳＥＰＡＲＡＴＥＤ－ＬＡＹＥＲＦＩＮＩＴＥＡＮＡＬＹＴＩＣＭＥＴＨＯＤＦＯＲＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＡＴＨＲＥＥ－ＤＩＭＥＮＳＩＯＮＡＬＶＩＳＣＯＵＳＦＬＯＷＦＩＥＬＤＡＲＯＵＮＤＡＳＨＩＰＳＴＥＲＮＬｉＴｉｎｇ－ｑｉｕ；Ｍｉａｏ...

简介：Duetotheintricatestructureofporousmedia,themacroscopicpetrophysicaltransportpropertiessuchasthepermeabilityandthesaturationusedforthereservoirpredictionalsoshowaverycomplexnatureandaredifficulttoobtain.Thus,abetterunderstandingoftheinfluenceoftherockstructureonthepetrophysicaltransportpropertiesisimportant.Inthispaper,wepresentauniversalfinitevolumeelementmodelingapproachtoreconstructthethreedimensionalporemodelsfromthemicro-CTimagesbasedonthecommercialsoftwareMimicsandICEM,priortotheporenetworkmodelbasedonsomebasicassumptions.Moreover,tetrafinitevolumeelementsarepileduptorealizethegeometryreconstructionandthemeshingprocess.Comparedwiththeformermethods,thisprocessavoidsthetremendouslylargestoragerequirementforthereconstructedporousgeometryandthefailuresofmeshingthesecomplexpolygongeometries,andatthesametimeimprovesthepredictionsofpetrophysicaltransportbehaviors.ThemodelistestedontwoBereasandstones,foursandstonesamples,twocarbonatesamples,andoneSyntheticSilica.Single-andtwophaseflowsimulationsareconductedbasedontheNavier-StokesequationsintheFluentsoftware.Goodagreementsareobtainedonboththenetworkstructuresandpredictedsingle-andtwo-phasetransportpropertiesagainstbenchmarkexperimentaldata.

简介：Thisstudypresentsthenumericalresultsforthethree-dimensionalnaturalgas-airmixinginarectangularsubsonicchannelunderthestandarddatumstate.ThelowerandupperdecompositionmethodwasemployedtoobtainthesolutionsofthefullNavier-Stokesequationscapableofdescribingcompressiblefluidmixing.Gridwasgeneratedbytheareaorthogonaltechnique.Theresultsindicatethatthree-dimensionalmixingbetweenNaturalGas(NG)andairhasmorecomplicatedcompressiblewavesaroundtheinjectionnozzle.Thepresenceofinjectionwithlargespeedcansuppresstheboundaryseparationhappenedoccurringatthetopwallduetothechannelexpansion,butmakesthenear-wakeflowmorecomplicated.Themixingregioncanbewidenedbyincreasingtheinjectionspeed.TherecurrenceofthevortexstructureandthecoherentstructurecanbefoundfromthefullNavier-Stokessimulation.ItcanbeconcludedthattheincreaseintheinjectionvelocitycanimprovetheeffectivenessofmixingofNGandairinthenearwakeoftheinjectors.

简介：Three-dimensionalnumericalmanifoldmethodforunconfinedseepageanalysisisproposedinthisarticle.Byconstructinghydraulicpotentialfunctionsofthemanifoldelement,theelementconductivitymatrixandtheglobalsimultaneousequationsforunconfinedseepageanalysisarederivedindetail.Thealgorithmoflocatingthefreesurfaceandtheformulaforseepageforcesarealsogiven.Three-dimensionalmanifoldmethodemploysthetetrahedralmathematicalmeshestocoverthewholematerialvolume.Intheiterativeprocessforlocatingthefreesurface,themanifoldmethodcanachieveanaccurateseepageanalysisofthesaturateddomainbelowthefreesurfacewithmathematicalmeshesunchanged.Sincetheshapeofmanifoldelementscanbearbitrary,thedisadvantageofchangingthepermeabilityoftransitionalelementscutbythefreesurfaceintheconventionalFiniteElementMethod(FEM)isremoved,andtheaccuracyoflocatingthefreesurfacecanbeensured.Furthermore,theseepageforceactingonthetransitionalelementscanbeaccuratelycalculatedbythesimplexintegration.Numericalresultsforatypicalexampledemonstratethevalidityoftheproposedmethod.

简介：Inthispaperthecomplexstructureandpatternofshipsternflowdrivenbymulti-propellersissimulatednumericallybyusingRANSequationswithK-εturbulencemodelandpropellerliftingsurfacetheoryasessentialresearchtoolandcouplingthecomputercodeofshipsternflowtothecomputercodeofpropellerperformancepredictionthroughthemediumofbodyforce.Ashipmodelwithfourpropellersisselectedasthenumericalexample.Detailedcomputationalresultsarepresentedgraphicallyandthequalitativeandquantitativeanalysisismade.Finally,thecomparisonbetweenthecalculatedresultandtheavailableexperimentaldataismade.Theagreementbetweenthemissatisfactory.

简介：Toclarifytheinfluencesofthetipclearanceflowsontheunsteadycavitatingflow,thethree-dimensionalunsteadycavitatingflowsthroughboththetwo-dimensionalcascadesandthethree-dimensionalinducerwithandwithouttipclearanceareperformednumerically.ThegoverningequationsforthecompressiblefluidflowwiththeDESturbulencemodelareemployedwiththeassumptionoftheisentropicprocessofliquidphase.Theevolutionofcavitiesisrepresentedasthesource/sinkofvaporphase.Thebasicequationsinthecurvelinearcoordinatearesolvedbythefinitedifferencemethod.Astheresultsofthethree-dimensionalcavitatingflowsthroughthetwo-dimensionalcascades,thetipclearanceflowsfromthepressuresidetothesuctionsideofthebladeproducesthetipvortexcavitation,whichaffectsthesheetcavitationontheleadingedgeofthenextbladeandenhancestheblockageeffectnearthecasingthantheflowswithouttipclearance.Ontheotherhand,inthecaseofthethree-dimensionalinducer,thelargebackflowcavitationisobservedaroundtheinletoftheinducer,wherethecavitiesaredevelopedonthecasingbythetipclearanceflows.Thelargepressuregradientbetweenthenon-cavitatingpressuresideandthecavitatingsuctionsideenhancesthetipclearanceflows.Thecalculationconsideringthetipclearancereproducesthedevelopedcavitationregionsimilartothatofexperimentalvisualizations.Additionally,thebackflowcavitationrotateswiththespeedslowerthantherotationspeedoftheinducer.Then,therotationofbackflowcavitationcausestheperiodicfluctuationoftheoutletpressuregreaterthanthatoftheinletpressure.

简介：Alargeamountofexperimentalworkhasbeencarriedoutinthepasttounderstandmeanandfluctuatingforcesonasinglecircularcylinderincrossflows.Incomparisonsubstantiallylessworkcanbefoundontheinterferencebetweenmultiplecylindersandthenumberofpublicationsavailablebecomesdrasticallysmallerasthenumberofcylindersinvolvedincreases.Thecurrentexperimentalworksystematicallyexaminesthewakeshieldingeffectsofthreecylindersinatowingtank.Thoughstaggered,thethreecylindersarearrangedmainlyalongtheflowdirectionwiththedownstreamcylinderssituatinginthewakesoftheupstreamcylinders.Thetestsaremainlycarriedoutinthesub-criticalReynoldsnumberregimewiththeupperendclosetothecriticalReynoldsnumberregime.Significantdragreductionondownstreamcylindersisidentified.

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简介：Thequasi-2Dmodel,takingintoaccounttheaxialvelocityprofileinthecrosssectionandneglectingtheconvectiveterminthe2-Dequation,canmoreaccuratelysimulatethewaterhammerthanthe1-Dmodelusingthecross-sectionalmeanvelocity.However,ascomparedwiththe1-Dmodel,thequasi-2Dmodelbearsahighercomputationalburden.Inordertoimprovethecomputationalefficiency,the1-Dmethodisproposedtobeusedtosolvedirectlythepressureheadandthedischargeinthequasi-2Dmodelinthispaper,basedonthefactthatthepressureheadobtainedasthesolutionofthetwo-dimensionalcharacteristicequationisidenticaltothatsolvedbythe1-Dcharacteristicequations.Theproposedschemesolvesdirectlythe1-DcharacteristicequationsforthepressureheadandthedischargeusingtheMOCandsolvesthe2-Dcharacteristicequationfortheaxialvelocitiesinordertocalculatethewallshearstress.Iftheradialvelocityisneeded,itcanbeevaluatedeasilybyanexplicitequationderivedfromtheexplicit2-Dcharacteristicequation.Inthenumericaltest,theaccuracyandtheefficiencyoftheproposedschemearecomparedwithtwoexistingquasi-two-dimensionalmodelsusingtheMOC.Itisshownthattheproposedschemehasthesameaccuracyasthetwoquasi-2Dmodels,butrequireslesscomputationaltime.Therefore,itisefficienttousetheproposedschemetosimulatethe2-Dwaterhammerflows.

简介：为在调查的飘动的plateare附近的二维的流动的水动力学特征。在大雷纳兹数字近似下面，流动被假定是combinationof外部潜在的流动和薄旋涡层，它由边界层和shedfree组成砍层。为描述外部不稳定的potentialflow的非线性的数学明确的表达结合了一个不稳定的边界层方程为内部粘滞邻近thewaving板的流动被开发。有在thetrailing边强加的一个非线性的Kutta条件的一个半分析的方法被用来解决外部流动和进化的速度领域由一个大振幅的飘动盘子弄醒vortexinduced。不稳定的边界层方程是解决的byextendingPohlhausen“s方法到它的不稳定的对应物。戳并且粘滞拖系数，推进的效率，和模式醒来旋涡表被讨论。