简介：TheFiniteAnalyticMethod(FAM)isanewnumericalmethodforsolvingNavier-Stokesequations.However,oncomplexgeometricdomainsthismethodmustemploytheboundary-fittedcoordinatetransformation,whichbecomesverydifficultforsomeflowregions.Inthispaper,theIsoparametricElement,whichhasbeenwidelyusedintheFiniteElementMethod,isincorporatedintotheFAM.Theflowregionissubdividedintoanumberofsmallar-bitaryquadrilaterals,andeachelementistransformedintoasquareelementbytheshapefunc-tionsofIsoparametricElement.ThenthepartialdifferentialequationsonthesquareelementcanbesolvedbytheFAM.Asanexample,theflowintubebundleshasbeencalculatedbythismethod.

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

简介：ＮＯＴＥＳ　ＯＮ　ＦＩＮＩＴＥ　ＥＬＥＭＥＮＴ　ＭＥＴＨＯＤ　ＡＮＤ　ＩＴＳ　ＧＥＮＥＲＡＬＩＺＡＴＩＯＮＮＯＴＥＳＯＮＦＩＮＩＴＥＥＬＥＭＥＮＴＭＥＴＨＯＤＡＮＤＩＴＳＧＥＮＥＲＡＬＩＺＡＴＩＯＮ￥Ｌ．Ｔａｏ（ＩｎｓｔｉｔｕｔｅｏｆＭｅｃｈａｎｉｃ...

简介：Inthispaperthefiniteelementmethodisusedtosolvethetwo-dimensionalgradi-entcurrentproblem,Thesolutionisobtainedbytwo-stepexplicitmethod.ItisverifiedwithgoodagreementbythefielddataofferedbyXiamenE.P.A.,Fujian,P.R.C.Theauthorsrec-ommendthattheproposedmethodissuitablefortheanalysisandcomputationoflongwavesofepeiricseaattheseawardfirth.

简介：NumericalsimulationsofextremewavegenerationarecarriedoutbyusingtheVolumeOfFluid(VOF)method.Extremewavesaregeneratedbasedonwavefocusingina2-Dnumericalmodel.TovalidatethecapabilityoftheVOF-basedmodeldescribedinthisarticle,thepropagationofregularwavesiscomputedandcomparedwiththetheoreticalresults.Byadjustingthephasesofwavecomponents,extremewavesareformedatgiventimeandgivenpositioninthecomputation.Thenumericalresultsarecomparedwiththeoreticalsolutionsandexperimentaldata.ItisconcludedthatthepresentmodelbasedontheVOFtechniquecanprovideacceptablyaccuratenumericalresultstoservepracticalpurposes.

简介：Thedynamicsindexes,playinganimportantroleinthecerebralcirculation,willbechangedsignificantlycomparedwiththeirnormalrangeinmanycerebrovasculardisease.ThegeometricalparametersofcerebrovascularmaybedetectedbyDSAorMRAscan,butthehemodynamicparameters,suchas,bloodflow,arteryresistanceandcompliancemustbecalculatedbybuildinghemodynamicsmodel.Thecerebralcircularsystemthathasfourentrancesforbloodflow(twocarotidandtwovertebralarteries)andthreecommunicatingarteriesismuchdifferentfromthesystematicststemwhichhasonlyoneentrance,ic.,theaortic.Thepurposeofthisstudyistosetupahemodynamicsmodelwithlumpedparameterstodescribethecerebralcirculation.Fromthismodel,wegetitsgoverningequationsandpresentanewmethodtocalculatethehemodynamicsindexesinclinicalapplication.

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

简介：Nano-literflowratemeasurementsinmicro-tubeswithdisplacementmethodwereperformedandtheeffectofcapillarityforceontheaccuracywasinvestigatedthroughlabexperimentsandtheoreticalanalysisinthisarticle.Theexperimentswereconductedunderthepressuredropsrangingfrom1kPato10kPainacircularpipewithadiameterof50μm,togivethepressure-flowrate(P-Q)relationandverifytheapplicabilityoftheclassicalHagen-Poiseuille(HP)formula.TheexperimentalresultsshowedthatthereexistedadiscrepancybetweentheexperimentaldataandthetheoreticalvaluespredictedbytheHPformulaifthecapillaryeffectwasnotconsidered,whichexceededobviouslythelimitofthesystemerror.Andhenceamodifiedformulafortherelation,takingthecapillaryeffectintoaccount,waspresentedthroughtheoreticaldeduction,andaftertheHPformulahadbeenmodifiedtheerrorwasprovedtobelessthan3%,whichwaspermittedincomparisonwiththesystemerror.ItwasalsoconcludedthatonlybyeliminatingtheeffectofthecapillaryforceinexperimentscouldtheoriginalHPformulabeemployedtopredictthepressure-flowraterelationintheHagen-Poiseuilleflowinthemicro-tube.

简介：Thispaperhaspredictedtherangeandvolumeofunsteadysheetcavitationofapropellerbyusingthesurfacepanelmethod.Thelinearizationincavitythicknessisadoptedtoreducethecomputingtimeandstoragespace.Theiterationschemebetweenchordwisestripshasbeenusedbecausetherangeandvolumeofcavitationarebothunknown.Thepropellercavitationrangedeterminedbythecalculationmethodpresentedinthispaperagreeswiththeobservationresultsofcavityimageatcavitationtunnelverywell,andthisprovesthepracticabilityofthemethod.

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

简介：Theunsteadysheetcavitationofpoddedpropellerwaspredictedbyusingasurfacepanelmethod.Theinteractionbetweenpropellerandpodwastreatedwiththeiterativecalculationofinducedvelocitypotential,andthemethodofinducedvelocitypotentialcansaveagreatdealofstorageandcomputationtimecomparedtothemethodofinducedvelocity.Theinducedvelocitypotentialofunitsingularityoneverypodpaneltoeverykeybladepanelandofunitsingularityoneverykeybladepanelanditswakepaneltoeverypodpanelwerecalculatedwhenthekeybladeisateveryangleposition.Basedonthewakemodeloftheconventionalsinglepropeller,anewwakemodelofpoddedpropellerwasconstructed.Thepropellerisanalyzedonlyonthekeybladeinordertosavecomputationtimeandmemoryspace.Themethodcanbeusedtocalculatethehydrodynamicsperformanceandcavitationofpropellerinuniformandnon-uniforminflows.Itcangivetheunsteadyforceandcavitationshapeofpropeller.Thepropellercavitationrangedeterminedbythepresentmethodagreeswiththeobservationresultsofcavityimagegivenincavitationtunnelwell,andthisprovesthepracticabilityofthemethod.

简介：Thispaperdealswiththeproblemofdeterminingtwounknownparametersofsomenonlinearreaction-diffusionmodels.Thesereaction-diffusionmodelsarederivedfromapplicationsinthegroundwaterflowtransport,environmentalsciences,gasdynamics,heatandmasstransfer,industrialautomatizationandsomeotherengineeringtechnologicalfields.Theadjointmethodbasedonthevariationalprincipleisarelativelynewoptimalcontrolmethod.Itisusedintheidentificationoftheunknowndiffusioncoefficient,andsomecoefficientsofthenonlinearsinkorsourcetermsinthesesystems.Atfirst,theproblemistransferredintoanoptimizationproblemofminimizingafunctional,andtheadjointequationsofthegoverningequationsarederivedfromtheadjointmethod.Then,theformulasaregiventocalculatethegradientoftheobjectivefunctionwithrespecttothecoupleofunknownparameters.Atlast,aniterativegradient-basedoptimizationalgorithmispresentedforsolvingtheoptimizationproblem.Anumericalexampleisofferedintheend.Itshowstheeffectivenessoftheproposedapproach.

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简介：Astochasticsimulationoffluidflowinporousmediausingacomplexvariableexpressionmethod(SFCM)ispresentedinthispaper.Hydraulicconductivityisconsideredasarandomvariableandisthenexpressedincomplexvariableform,therealpartofwhichisadeterministicvalueandtheimaginarypartisavariablevalue.ThestochasticseepageflowissimulatedwiththeSFCMandiscomparedwiththeresultscalculatedwiththeMonteCarlostochasticfiniteelementmethod.InusingtheMonteCarlomethodtosimulatethestochasticseepageflowfield,thehydraulicconductivityisassumedinthreedifferentprobabilitydistributionsusingrandomsamplingmethod.Theobtainedseepageflowfieldisexaminedthroughskewnessanalysis,andtheskeweddistributionprobabilitydensityfunctionisgiven.TheheadmodevalueandtheheadcomprehensivestandarddeviationareusedtorepresentthestatisticsofcalculationresultsobtainedbytheMonteCarlomethod.ThestochasticseepageflowfieldsimulatedbytheSFCMisconfirmedtobesimilartothatgivenbytheMonteCarlomethodfromnumericalaspects.TherangeofcoefficientofvariationofhydraulicconductivityinSFCMislargerthanusedpreviouslyinstochasticseepageflowfieldsimulations,andthecomputationtimeisshort.TheresultsprovedthattheSFCMisaconvenientcalculatingmethodforsolvingthecomplexproblems.

简介：Existingfarfieldexpressionsofsecondorderpotentialsarebynomeanscomplete.Hencetherehasbeennoexactfarfieldexpressionofsecondorderpotentials.InthispaperthefarfieldexpressionforΦd（2）ispurposelyavoidedindeducingtheformulaeofsecondorderforcesandaseriesoffunctionsΦdRnareused.Thefarfieldexpressionofisgiven,whichfor（x,U,z）∈Σ,φdRn（2）φd（2）.Usingthesepropertiesformulaeforcalculatingsecondorderdiffractionforcesareobtained.Tocalculatetheintegral∫∫1/gfΨdsitisdividedintotwoparts.Oneistheintegraloverafinitedomainandthefunctionundertheintegraliscontinuous,sotheusualapproximateintegrationformulaemaybeused.Theotheristheintegraloveraninfinitedomain.Usingthefarfieldexpressionoffirstorderpotentials,formulaeforcalculatingtheintegraltomeetgivenaccuraciesaregiven.Themooringforceinsurgedirectionisusedforcomparisonbetweennumericalpredictionsandexperimentalmeasurements.Thepredictedresultsarecheckedagainstthemeasuredvalueinaspeciallydesignedtest.Inthelowfrequencydomainofinterest,themooringforcesinsurge,forcalculatedandexperimentalspectraareingoodconsistencysolongasthedampingcoefficientsischoosenappropriately.

简介：Time-domainanalysisisusedtopredictwaveloadingandmotionresponsesforashiptravellingataconstantspeedinregularobliquewaves.Thecombineddiffractionandradiationperturbations,causedbythesteadyforwardspeedoftheshipandhermotions,areconsideredasadistributionofnormalvelocitiesonthewettedhullsurface.Theship-hullboundaryconditionisexactlyfulfilledbyexpressingthefluidnormalvelocitiesasafiniteseriesintermsofthebodygeometryandtheincidentwavepotential.Asfarastheauthorsareaware,nosimilarworkispublishedtodate.ThenewtheoryisappliedtopredictforcesandmotionsatforwardspeedforaWigleyship-hullinheadwavesandacatamaran-ferryinobliquewaves.PredictionsarecomparedwithpublishedtheoreticalandexperimentalresultsfortheWigleyship-hull,andthecomparisonisgood.Forthecatamaran,aself-propelledmodelisbuiltandtestedinthelargetowingtankandseakeepingbasinoftheChinaShipScientificResearchCentre,Wuxi

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

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