简介：Anexperimentalmodelwassetuptoinvestigatetheformationandevolutionofthefreesurfacevortex.AParticleImageVelocimetry(PIV)wasusedtomeasurethefreesurfacevortexflowfieldatdifferentdevelopmentstages.Flowvisualizationwasusedtolocatethevortexpositionandfinditsstructure.Empiricalformulasaboutthecriticalsubmergenceandthewholefieldstructurewereobtained.ItisfoundthatthetangentialvelocitydistributionissimilartothatoftheRankinevortexandtheradialvelocitychangeslittleinthevortexfunctionalscope.Vortexstartsfromthefreesurfaceandgraduallyintensifiestoairentrainmentvortex.Thevortexcoremovesduringtheformationandevolutionofthefreesurfacevortex.Basedontheexperimentalmodel,thevortexpositionandstructurewerepredictedbynumericalsimulationcombinedwithavortexmodelandcomparedwiththatoftheexperiments,whichshowssatisfactoryagreement.

简介：Freesurfaceflowproblemsinvolvinglargefreemotionsareanalysedusingfiniteelementtechniques.InsolvingtheseproblemsanArbitraryLagrangian-Eulerian(ALE)kinematicaldescriptionofthefluiddomainisadopted,inwhichthenodalpointscanbedisplacedindependentlyofthefluidmotion.Anewmeshtracingmethodisproposedinthispaper.Toconfirmtheeffectivenessofthenewmethod,solitarywavepropagationisanalysedandthenumericalresultsarecomparedwiththeanalyticalresults.ThebehaviouroftheviscousfluidflowwithafreesurfaceisexpressedbytheunsteadyNavier-Stokesequation.Fornumericalintegrationintimethevelocitycorrectionfractionalstepmethodisused.

简介：

简介：垂直地在免费表面上侵犯的一口2D槽喷气的流动特征被大埃迪模拟(LES)数字地与一个动态Sub-GridScale(SGS)模型一起调查。σ-坐标转变被介绍印射深度变量物理领域到一件深度制服计算领域。裂口操作员计划，把答案过程切成移流，散开和压力繁殖步，被采用解决即时速度和压力地。一个充分非线性的Lagrange-Euler方法被用来计算免费表面举起。数字结果证明喷气在Eestablished流动(ZEF)的地区保留你方类似，当喷气的骚乱逐渐地变从时对各向同性在表面冲击(ZSI)的地区各向异性。当喷气接近免费表面时，中心线速度很快减少并且流动被免费表面偏斜。二口对称的表面喷气在水平喷气(ZHJ)的地区被形成。超高的AnapproximateGuassian分发也在免费表面上被形成。Thecomputed结果在对可得到的试验性的数据的好同意。

简介：Ageneralstochasticmodeloftheatmosphericpressureattheoceansurfacewasproposed,inwhichthepressurevariationwasrepresentedbyaspectraldecompositionthrougharandomprocessoforthogonalincrements.Fromthebasicequationsofidealandincompressiblefluidasetofperturbationequationsuptosecondorderhadbeenderivedandsolved.Thepressurevariationintheflowfieldhadbeencalculatedusingtheexplicitsolutionsobtained,andwhichdemonstratedaclearrelationbetweentheatmosphericpressureandtheoneatthebottomofdeepocean.Itcanbeseenthatthereisapartofthepressurevariationwhichisnotattenuatingwiththedepth.TheresulthadbeencomparedwiththoseofLonguet-HigginsandKadotaetal.andallpreviousresultsarecontainedinthesolutiongiveninthisartice.Therestrictiononthepreviousworkswithregardtotheprobabilitylawhasbeenremoved,andallconclusionsarededucedwithoutspecificassumptions.Theflexibilityoftheproposedmodelallowsforfurthergeneralizationandextensioninthephysicalaspectsandstatisticaltreatment.

简介：Inthisstudy,theeffectofthefreesurfaceonthecloudcavitatingflowaroundabluntbodyisinvestigatedbasedonthewatertankexperimentandtheCFDmethod.Numericalresultsareingoodagreementwithexperimentaldata,andthemeshindependenceofthemethodsisverified.Thecavityevolutionprocessincludesthecavitygrowth,there-entrantjet,thecavityshedding,andthecollapse,whichcanallbeobservedfromthewatertankexperiment.Theeffectsofthefreesurfaceonthecavitylength,thethickness,andthecavityevolutionperiodareanalyzedbycomparingthedifferencebetweenthecavitatingflowsontheupperandlowersidesofthebody.Thisstudyalsoexaminestheeffectofthedistancebetweenthefreesurfaceandthemodelthroughaseriesofwatertankexperimentsandnumericalsimulations.Thecavitystabilityandasymmetry,aswellasthethicknessandthevelocityofthere-entrantjetinsidethecavity,whichvarieswiththesubmergeddepth,arediscussedwithconsiderationoftheeffectofthefreesurface.Theeffectofthefreesurfaceonthecavitatingflowaroundthebluntbodyisenhancedwiththedecreaseofthesubmergeddepth.

简介：AnumericalsimulationmodelbasedonanopensourceComputationalFluidDynamics(CFD)package-OpenFieldOperationandManipulation(OpenFOAM)hasbeendevelopedtostudyhighlynonlinearsteadyandunsteadyfreesurfaceflows.Atwo-fluidformulationisusedinthismodelandthefreesurfaceiscapturedusingtheclassicalVolumeOfFluid(VOF)method.TheincompressibleEuler/Navier-Stokesequationsaresolvedusingafinitevolumemethodonunstructuredpolyhedralcells.Bothsteadyandunsteadyfreesurfaceflowsaresimulated,whichinclude:(1)asubmergedNACA00122-Dhydrofoilmovingataconstantspeed,(2)theWigleyhullmovingataconstantspeed,(3)numericalwavetank,(4)greenwaterovertoppingafixed2-Ddeck,(5)greenwaterimpactonafixed3-Dbodywithoutorwithaverticalwallonthedeck.ThenumericalresultsobtainedhavebeencomparedwiththeexperimentalmeasurementsandotherCFDresults,andtheagreementsaresatisfactory.Thepresentnumericalmodelcanthusbeusedtosimulatehighlynonlinearsteadyandunsteadyfreesurfaceflows.

简介：ＷＡＶＥ　ＥＱＵＡＴＩＯＮ　ＭＯＤＥＬ　ＦＯＲ　ＮＵＭＥＲＩＣＡＬ　ＳＯＬＵＴＩＯＮＳ　ＯＦ　ＡＤＶＥＣＴＩＯＮ－ＤＯＭＩＮＡＮＴ　ＨＥＡＴ　ＴＲＡＮＳＦＥＲＷＡＶＥＥＱＵＡＴＩＯＮＭＯＤＥＬＦＯＲＮＵＭＥＲＩＣＡＬＳＯＬＵＴＩＯＮＳＯＦＡＤＶＥＣＴ...

简介：Numericalsimulationsareperformedforlaminarnaturalconvectionheattransferfromacenteredconductingbodyenclosedinasquarecavity.Ahighaccuracyunsteadynumericalmethodisused,combiningtheuniqueconditionofthepressure,theconvergentsolutionsandthestream-functionvalueoftheinsideheat-conductingbodyaregivensimultaneously.Twoexamplesaresimulatedwiththisnumericalmethodandcomparedwiththeexperimentalresults.Theresultsofthenumericalsolutionsareconsistentwiththeexperimentalresults.Itshowsthatthenumericalmethodisvalidandfeasible.

简介：Fluidflowandheattransfercharacteristicsoutsideavibratingtubewerenumericallysimulatedbythedynamicmeshmethod.Themechanismofheattransferenhancementviaperiodicvibrationofthetubewasexploredbyusingthefieldsynergyprinciple.Itisfoundthatthefieldsynergyanglebetweenfluidvelocityvectorandtemperaturegradientvectorforaperiodicallyvibratingtubeissignificantlysmallerthanthatforastationarytube,anditchangesapproximatelyaccordingtothesinusoidallawinavibrationperiod.Theeffectoftimephaseofthevibrationonthefieldsynergyangleandconvectiveheattransfercoefficientwerealsodiscussed.Resultsindicatethatthevibrationcanenhanceheattransferandthiseffectismoreremarkablewhentimephaseanglerangesbetween50oand140oinahalfperiod.Especiallywhenthetimephaseangleis90o,theaveragefieldsynergyangleoutsidethetubereachestheminimum,whichleadstothebestheattransferperformance.

简介：TheturbulenceflowFreeSurfacehasimportantapplicationsinhydraulicspillwaysstructure,suchasthehydraulicjump,energydissipationflowetc.Thisisbeingconsideredasverycomplicatedflow,andhasnotyetbeensolvedquitewellbynumericalmethod.Inthispaper,aLarge-scalecomputationalsoftwarepackagearedevelopedfornumericallaboratoryofhydraulicspillwaystructure.Somemethods,suchasturbulencemodel,freesurfaceandirregularboundarytreatingtechniques,scientificcomputervisualizationareputforwardandperformed.

简介：ＣＯＭＰＵＴＡＴＩＯＮＯＦＴＵＲＢＵＬＥＮＴＦＬＯＷＡＮＤＨＥＡＴＴＲＡＮＳＦＥＲＩＮＬＡＲＧＥＲＡＤＩＵＳ９０－ＤＥＧＲＥＥＣＩＲＣＵＬＡＲＢＥＮＤＳＭ．Ｊ．Ｗａｎｇ（ＴｅｃｈｎｉｓｃｈｅＵｎｉｖｅｒｓｉｔａｔＭｕｎｃｈｅｎ，ＢＲＤ）ＳｕＭｉｎｇ－...

简介：AraisedpanelmethodbasedonNURBS(Non-UniformRationalB-Splines)forfree-surfaceflowswithforwardspeedispresented.Inthisgeneralizedpanelmethod,NURBSareemployedtorepresentthebodygeometry,disturbedfreesurface,andtoexpresstheunknownsourcestrengthdistribution,onthebodysurfaceandabovethefreesurface.Comparedwithcommonhigher-orderpanelmethods,ithasnoneedofadoptinglocalcoordinates.NURBSmakethegeometryrepresentationofthebodyshapeandthewavepatternmoreprecise.Raisedpanelsabovethefreesurfaceproducelessnumericaldispersionerror,needlessCPUconsumptionandarehelpfulandcombinedwithcollocation-pointshiftingup-stream,cansatisfytheradiationconditionnumerically.ByusingcontinuousanddiscreteFourieranalysis,numericalerrorsofthismethodarediscussedandageneralexpressionfortheerrorsofnumericaldampinganddispersion,includingtheeffectsoftheverticaldistanceofsingularitiestothefreesurface,theorderofsingularitydistributionrepresentedbyB-splinesinpanels,andcollocation-pointshiftingisderived.

简介：Anumericalsimulationisperformedforthermalinstabilityandheattransferofviscoelasticfluidsinboundedporousmediaunderthebottomconstantheatfluxboundarycondition.Theresultsforsixdifferentcombinationsofrelaxationandretardationtimesdemonstratetheexistenceofthethermalinstabilityinducedflowbifurcation.Itisfoundthattheincreaseoftherelaxationtimecanenhancetheheattransferefficiencybydisturbingthefluidflowandfacilitatingthebifurcation.Theincreaseoftheretardationtimecanstabilizetheflowandpostponethebifurcation,leadingtosimplerflowpatternandlowerheattransferrate.

简介：Thecut-offnegativepressuremethodisoneofeffectiveapproachestosolvetheseepageflowwithfreesurface.Accordingtothecharacteristicsofthismethod,however,ithasbeenfoundoutthatthedeficiencyofthealgorithmsistoeasilycauseinaccuratesimulationinthevicinityoffreesurfaceowingtothepenaltyfunctionwithonlyonecontrollingpenaltyparameter.Therefore,animprovedcut-offpressuremethodwaspresentedbyconstructingpenaltyfunctionwithtwocontrollingpenaltyparameters.Theimprovedalgorithmswereillustratedtobeabletoimprovethesimulationaccuracyandraisetheconvergencespeedthroughconsideringtheeffectsofthepartiallysaturatedorunsaturatedelementsmorereasonablyandcalculatingthenodalexternalforcesmoreaccurately.Finally,theimprovedcut-offnegativepressuremethodwasappliedtothesimulationofunsteadyseepageflowwithfreesurface,andthecorrespondingprogramcodesweredevelopedwithvalidationofsomecases.

简介：Takingaccountofturbulenceintensity,non-uniformityofvelocitydistributionattheinitialandsequentsec-tionofhydraulicjumpandfrictionaldragonthefloorwithinjumprange,thispaperderivesnewformulasforcal-culatingtheratioofconjugatedepthsandtheefficiencyofenergydissipationinthetwo-dimensionalfreehydraulicjump.Ithasbeenverifiedbytestdatathatthenewformulasarenotonlyexactintheorybutalsostillbetterinconformitywithpractice.

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

简介：Makingfulluseoffunctionalvariationswithvariabledomainforhandlingboththefreesurfaceandunknownpartofthedamwall,afamilyofvariationalprinciples(VPs)forthehybrid(direct-inverse)problemoffreesurfacespillwayflowundergravityisformulatedintermsofthepotentialfunctionΦ.Thistheoryoffersnewrationalandversatilewaysfordamde-signandasoundtheoreticalbasisfornumericalsolution,e.g.bythefiniteelementmethod(FEM).

简介：Anexperimentalstudywascarriedouttoinvestigatetheinfluenceofdoubletwisted-tapeinserts(DTs)inmicro-fintubes(MFs)onheattransfer,frictionfactorandthermalperformancefactorcharacteristicsofthecompounddevicesinthefollowingconfigurations:(1)twistedtapesactedinthesamedirection(forco-swirl)whileMFandtwistedtapesactedinthesame(parallel)direction(MF-CoDTs:P),(2)twistedtapesactedinthesamedirection(forco-swirl)whilemicro-fintubeandtwistedtapesactedinoppositedirections(MF-CoDTs:O)and(3)twistedtapesactedinoppositedirectionsforcounterswirl(MF-CDTs).TheMFaloneandtheMFequippedwithasingletwistedtapeinparallel/oppositearrangementwerealsoconsideredforcomparison.TheexperimentswereconductedfortheflowswiththeReynoldsnumbersbetween5650and17000,underuniformheatfluxcondition.TheexperimentalresultsindicatethatMF-CDTsinducestrongerswirl/turbulenceflow,resultinginhigherheattransferrate,frictionfactorandthermalperformancefactorthanothercombineddevices.ThethermalperformancefactorsassociatedwiththeuseofMF-CDTswerefoundtobehigherthanthoseassociatedwiththeusesofMF-CoDTs:P,MF-CoDTs:OandMFaloneupto9.3%,6.5%and56.4%,respectively.TheempiricalcorrelationsdevelopedusingthepresentexperimentaldatafortheNusseltnumber,frictionfactorandthermalperformancefactorarealsoreported.

简介：Inthepresentpaper,two-andthree-dimensionalvelocitypotentialsgeneratedbypulsatingpressuredistributionsofinfiniteextentonthefreesurfaceofinfinite-depthwatersarestrictlyderivedbasedonspecialcasesofconcentratedpulsatingpressure.Thefar-fieldasymptoticbehaviourofthepotentialsandtheradiationconditionstobesatisfiedbythemarediscussed.Itisprovedinageneralsensethatthepotentialsshouldbecomposedofaforcedwavecomponent,afreewavecomponentandalocaldisturbancecomponent.Theradiationconditionoftheforcedwavecomponentshouldcorrespondtothefar-fieldasymptoticbehaviourofthepressuredistribution,Hence,theformulationofradiationconditionsforthesecond-orderdiffractionpotentialshastheoreticallybecomeclear,Theradiationconditionsfortwo-andthree-dimensionalproblemsareexplicitlygiveninthepaper.