简介：TheunsteadycavitationevolutionaroundtheClark-Yhydrofoilisinvestigatedinthispaper,byusinganimprovedfilter-basemodel(FBM)withthedensitycorrectionmethod(DCM).Toimprovethepredictionaccuracy,thefilterscaleisadjustedbasedonthegridsize.Thenumericalresultsshowthatasmallfilterscaleiscrucialfortheunsteadysimulationsofthecavitysheddingflow.ThehybridmethodthatcombinestheFBMandtheDCMcouldhelptolimittheoverpredictionoftheturbulentviscosityinthecavitationregiononthewallofthehydrofoilandinthewake.Thelargevalueofthemaximumdensityratio?l/?v,clippromotesthemasstransferratebetweentheliquidphaseandthevaporphase,whichresultsinalargesheetcavitylengthandthevaporfractionriseinsidethecavity.Thecavitypatternspredictedbytheimprovedmethodareverifiedbytheexperimentalvisualizations.Thetime-averagelift,thedragcoefficientandtheprimaryoscillatingfrequencyStforthecavitationnumber?=0.8,theangleofattack,?=8o,ataReynoldsnumberRe=7?105are0.735,0.115and0.183,respectively,andthepredictederrorsare3.29%,3.36%and8.93%.Thetypicalthreestagesinonerevolutionarewell-captured,includingtheinitiationofthesheet/attachedcavity,thegrowthtowardthetrailingedge(TE)withthedevelopmentofthere-entrantjetflow,andthelargescalecloudcavityshedding.ItisobservedthatthecloudcavitysheddingflowinducesthevortexpairsoftheTEvorticesinthewakeandthesheddingvortices.Thepositivevorticityvortexofthere-entrantjetandtheTEvorticesinteractsandmergeswiththenegativevorticityvortexoftheleadingedge(LE)cavitytoproducethesheddingflow.

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简介：ＵＮＳＴＥＡＤＹＰＲＯＰＥＬＬＥＲＳＵＲＦＡＣＥＰＲＥＤＩＣＴＩＯＮＷＩＴＨＡＰＯＴＥＮＴＩＡＬＢＡＳＥＤＰＡＮＥＬＭＥＴＨＯＤ￥ＣｈｅｎＪｉａ－ｄｏｎｇ（ＣｈｉｎａＳｈｉｐＳｃｉｅｎｔｉｆｉｃＲｅｓｅａｒｃｈＣｅｎｔｅｒ，Ｂｏｘ１１６，Ｗｕｘｉ２１...

简介：Anewmethodforsloshingsimulationinaswaytankispresent,inwhichthetwophaseinterfaceistreatedasaphysicaldiscontinuity,whichcanbecapturedbyawell-designedhighorderscheme.BasedonNormalizedVariableDiagram(NVD),ahighorderdiscretizationschemewithunstructuredgridsisrealized,togetherwithanumericalmethodforfreesurfaceflowwithafixedgrid.Thismethodisimplementedinanin-housecodeGeneralTransportEquationAnalyzer(GTEA)whichisanunstructuredgridsfinitevolumesolver.Thepresentmethodisfirstvalidatedbyavailableanalyticalsolutions.Asimulationfora2-Drectangulartankatdifferentexcitationfrequenciesoftheswayiscarriedout.AcomparisonwithexperimentaldatainliteratureandresultsobtainedbycommercialsoftwareCFXshowsthatthesloshingloadonthemonitorpointsagreeswellwiththeexperimentaldata,withthesamegrids,andthepresentmethodgivesbetterresultsonthesecondarypeak.Itisshownthatthepresentmethodcansimulatethefreesurfaceoverturningandbreakupphenomena.

简介：Theshiphullsurfaceoptimizationbasedonthewaveresistanceisanimportantissueintheshipengineeringindustry.Thewaveletmethodmayprovideaconvenienttoolforthesurfacehulloptimization.Asapreliminarystudy,weusethewaveletmethodtooptimizethehullsurfacebasedontheMichelwaveresistanceforaWigleymodelinthispaper.Firstly,weexpressthemodel’ssurfacebythewaveletdecompositionexpressionsandobtainareconstructedsurfaceandthenvalidateitsaccuracy.Secondly,werewritetheMichelwaveresistanceformulainthewaveletbases,resultinginasimpleformulacontainingonlytheshiphullsurface’swaveletcoefficients.Thirdly,wetakethesewaveletcoefficientsasoptimizationvariables,andanalyzethemainwaveresistancedistributionintermsofscalesandlocations,toreducethenumberofoptimizationvariables.Finally,weobtaintheoptimalhullsurfaceoftheWigleymodelthroughgeneticalgorithms,reducingthewaveresistancealmostbyahalf.Itisshownthatthewaveletmethodmayprovideanewapproachforthehulloptimization.

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简介：平均深度的流动污染物质联合了的A2D模型基于空铅树网孔被建立精确地在这篇论文与不规则的自然边界在水区域模仿流动。格子被递归的分关于播种点产生。一个发现newneighbor算法被介绍。管理方程是在由越过在房间之间的接口使用有限的卷方法，和质量，动量和污染物质的正常流动的并置的保守变量的discretized被一个Godunov类型流动DifferenceSplitting(FDS)计划计算。模型被使用在一条腹股沟附近模仿流动地。计算的值与观察数据一致。结果显示空铅树网孔有好本地分辨率，高效率和容易的本地精炼。当适用于复杂流动领域时，空铅树格子模型能在效率提供获得，是清楚的或强壮砍流动。最后，模型在江苏HaizhouBay被用于流动地和集中地模拟。模仿的弄脏的区域与观察被匹配很好。因此，这个模型能被用来与不规则的自然土地边界预言实际的水区域的流动和集中地。

简介：Channelfrictionisanimportantparameterinhydraulicanalysis.AchannelfrictionparameterinversionmethodbasedonKalmanFilterwithunknownparametervectorisproposed.Numericalsimulationsindicatethatwhenthenumberofmonitoringstationsexceedsacriticalvalue,thesolutionishardlyaffected.Inaddition,KalmanFilterwithunknownparametervectoriseffectiveonlyatunsteadystate.Forthenonlinearequations,computationsofsensitivitymatricesaretime-costly.Twosimplifiedmeasurescanreducecomputingtime,butnotinfluencetheresults.Oneistoreducesensitivitymatrixanalysistime,theotheristosubstituteforsensitivitymatrix.

简介：Thecontrolofturbulencebydimples/pimpleshasdrawnmoreandmoreattention.Theobjectiveofthispaperistoinvestigatetheeffectivenessoftheactivedimples/pimplesforthedragreductionintheincompressibleturbulentflow.Firstly,thedragreductionbytheoppositioncontrolbasedonactivedimples/pimplesatthelowerwallisstudiedviathedirectnumericalsimulationoftheturbulentchannelflow.Itisfoundthatlargeactivedimples/pimplescannotsuppressthestreamwisevorticessignificantlyandthusalmostnodragreductionisachieved.Smallactivedimplesandpimpleswiththediameterofonefourthofthestreakwidthcanbothreducethefrictiondrag,butpimpleswillinducealargerpressuredragthandimples.Thenthesuboptimalcontrolschemeisexaminedbasedonsmallactivedimplesusingthespanwisewallshearinformationonly.Itisshownthatthefrictiondragdecreasesbyabout4.5%butthetotaldragisonlyreducedbyabout2.7%abatedbythepressuredrag.Comparedwiththeactuationoftheall-pointblowing/suctionortheall-pointwallmovement,theeffectivenessoftheturbulentdragreductionbasedonactiveshallowdimplesismuchsmaller.

简介：Acomputercode,ELANEX,includingseveralHomogenous-Equilibrium-Model(HEM)typecavitationmodels,weredeveloped,tonumericallysimulatenaturalcavitationphenomena.Theeffectivenessofthecodewascheckedbycavitationflowsaroundthediskandcylinderbodyforawiderangeofdifferentcavitationnumbers.Cavityprofileswerecomparedwiththeanalyticsolutionofdiskandempiricalformulaefittedfromtheexperimentdata,andcontrastbetweendifferentcavitationmodelswerefulfilledaswell.Thecavitylengthandmaximalcavitydiameterwerefoundtoagreewellwiththeanalyticsolutions,anddetailedcavityprofileswereinaccordancewiththeexperimentalformula.Comparisonwiththehemisphereheadedcylinderbodypresentedagoodagreementofthepressurecoefficientwiththeexperimentdata.Reasonabledrag-forcecoefficientvariationanddrag-forcereductioneffectwereobtained.

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.

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简介：FlowsaroundacircularcylinderdisplayinganunsteadyvortexsheddingprocessattheReynoldsnumbersof1000,3900and1×104arestudiedusingafinite-volumeTotalVariationDiminishing(TVD)schemeforsolvingtheUnsteadyReynolds-AveragedNavier-Stokes(URANS)equations.AnElementalVelocityVectorTransformation(EVVT)approachisproposedforthelocalnormalandtangentialvelocitytransformationattheinterfacesofmainandsatelliteelements.Thepresentedmethodisvalidatedbycomparingwiththeavailableexperimentaldataandnumericalresults.Itisshownthatthetwo-dimensionalTVDfinitevolumemethodwiththeRenormalizationGroup(RNG)turbulencemodelcanbeusedtodeterminehydrodynamicforcesandcapturesvortexsheddingcharacteristicsverywell.

简介：Themeasurementaccuracyofanultrasonicheatmeterdependsontherelationshipoftheprofile-linearaveragevelocity.Therearevariousmethodsforthecalculationofthelaminarandturbulenceflowregions,butfewmethodsforthetransitionregion.Atpresent,thetraditionalmethodtodealwiththetransitionregionistoadopttherelationshipfortheturbulentflowregion.Inthisarticle,asimplifiedmodelofthepipeisusedtostudythecharacteristicsofthetransitionflowwithspecificReynoldsnumber.Thek-εmodelandtheLargeEddySimulation(LES)modelare,respectively,usedtocalculatetheflowfieldofthetransitionregion,andacomparisonwiththeexperimentresultsshowsthattheLESmodelismoreeffectivethanthek-εmodel,itisalsoshownthattherewillbealargeerroriftherelationshipbasedontheturbulenceflowisusedtocalculatetheprofile-linearaveragevelocityrelationshipofthetransitionflow.Theprofile-linearaveragevelocityfortheReynoldsnumberrangingfrom5300to10000arecalculated,andtherelationshipcurveisobtained.Theresultsofthisarticlecanbeusedtoimprovethemeasurementaccuracyofultrasonicheatmeterandprovideatheoreticalbasisfortheresearchofthewholetransitionflow.