简介：Thisarticlepresentsamathematicalmodeloftheplaneevolutionofalluvialmeanderingstreams,throughdownstreammigrationandlateralexpansionofmeanderloops.Undertheconditionsprevailinginnaturalstreams,thechannelcenterlinesfollowsine-generatedcurves,withanassumedsteady-stateturbulentandsubcriticalflow,oflargewidth-to-depthratio(≥15,forexample)andsmallFroudenumber(Fr).Theplanedeformationofthechanneliscausedbytheactiononthebanksoftheconvectivevertically-averagedmeanderingflow.Thegrowth(migrationandexpansion)ofmeanderloopsisattributedtotheregime-trend.Thecomputationalresultsofthemodelshowthattheobtainedmigrationandexpansionpatternsofthemeanderloopsareingoodagreementwiththoseofobservationsandmeasurementsinsimilarmeanderingstreams.

简介：Inthepresentresearch,abubbledynamicsbasedmodelforcavitatingflowsimulationsisextendedtohighervoidfractionregionforwiderrangeofapplications.Thepresentbubblemodelisbasedontheso-calledRayleigh-Plessetequationthatcalculatesatemporalbubbleradiuswiththesurroundingliquidpressureandisconsideredtobevalidinanareabelowacertainvoidfraction.ThesolutionalgorithmismodifiedsothattheRayleigh-Plessetequationisnomoresolvedoncethebubbleradius(orvoidfraction)reachesatacertainvaluetilltheliquidpressurerecoversabovethevaporpressureinordertoovercomethisproblem.Thisprocedureisexpectedtostabilizethenumericalcalculation.Theresultsofsimpletwo-dimensionalflowfieldarepresentedcomparedwiththeexistingbubblemodel.

简介：AnewtypeBoussinesqmodelisproposedandappliedforwavepropagationinawaveflumeofuniformdepthandoverasubmergedbarwithcurrentpresentorabsent,respectively.Firstly,forthepropagationofmonochromaticincidentwavewithcurrentabsent,theBoussinesqmodelistestedinitscompleteform,andinaformwithouttheintroductionofutilityvelocityvariables.Itisvalidatedthattheintroductionofutilityvelocityvariablescanimprovethecharacteristicsofvelocityfield,dispersionandnonlinearity.BothversionsoftheBoussinesqmodelsareofhigheraccuracythanthefully-nonlinearfourth-ordermodel,whichisoneofthebestformsamongtheexistingtraditionalBoussinesqmodelsthatdonotincorporatebreakingmechanisminonedimension.Secondly,theBoussinesqmodelinitscompleteformisappliedtosimulatingthepropagationofbichromaticincidentwaveswithcurrentpresentorabsent,respectively,andthemodeledresultsarecomparedtotheanalyticalonesortheexperimentalones.Themodeledresultsarereasonableinthecaseofinputtingbichromaticincidentwaveswiththestrongopposingcurrentpresent.

简介：Thispapergivesemphasisontheresearchoftheproblemoflocalheadlossofcrossfractureflowbyalotofmodelexperiments,andatheoreticalmodeloflocalheadlossofcrossfractureflowisfoundedbyuseofthemomentumlawofwaterflow.Throughthecorrelationanalysisbetweenmodelexperimentalresultsandtheoreticalmodel,thecorrectioncoefficientoftheoreticalmodelisdefinite.Theproposedcalculationformulaoflocalheadlossofcrossfractureflowcanbeusedtoanalyzetheproblemofnetworkfractureseepage.

简介：Inthisarticle,anewacoustictesttechniqueusingtowedmodelwasintroducedtostudyflownoisecausedbyasurfaceship.Theprojectofmodeltestwasbeproperlydesignedforacousticsignalcollectingandwiththehelpofappropriatedataprocessingmethoddifferentkindsofacousticsourcescouldbesuccessfullyidentified.Alotofworkaboutfuidnoisecouldbecarriedonwiththetowedmodel,andthenoisecorrespondingtolowfrequencywhichisespeciallyinterestedforitslongdistanceradiatingwithsmallattenuationcouldalsobestudiedinthisway.

简介：Lawofthepropagationoferrorscausedbytheinconsistencyoftheboundaryscalesimilitudeinrivermodelexperimentispresentedinthispaper.Thefluctuationofscaletransfersalongthecharacteristicline,ifthedischargeandsedimentatentranceandthewaterlevelatthetailgatedrift.Thefluctuationofscalepropagateswiththederivedscalefunctionduetotopographicdeviation.Allerrorswillaccumulatetothefinalmeasureddata

简介：AnewReynolds-averagedNavier-Stokes(RANS)turbulencemodelisdevelopedinordertocorrectlypredictthemeanflowfieldinadrafttubeoperatingunderpartialloadusing2-Daxisymmetricsimulations.Itisshownthatalthough2-Daxisymmetricsimulationscannotmodelthe3-Dunsteadyfeaturesofthevortexrope,theycangivetheaveragelocationofthevortexropeinthedrafttube.Nevertheless,RANSsimulationsunderpredicttheturbulentkineticenergy(TKE)productionanddiffusionnearthecenterofthedrafttubewherethevortexropeforms,resultinginincorrectcalculationofTKEprofilesand,hence,poorpredictionoftheaxialvelocity.Basedonthisobservation,anewk-εturbulenceRANSmodeltakingintoaccounttheextraproductionanddiffusionofTKEduetocoherentstructuresassociatedwiththevortexropeformationisdeveloped.Thenewmodelcansuccessfullypredictthemeanflowvelocitywithsignificantimprovementsincomparisonwiththerealizablek-εmodel.ThisisattributedtobetterpredictionofTKEproductionanddiffusionbythenewmodelinthedrafttubeunderpartialload.Specifically,thenewmodelcalculates31%moreproductionand46%morediffusionrightattheshearlayerwhencomparedtothek-εmodel.

简介：Aninvestigationoftheventilatedsupercavitationforasupercavitatingvehiclepitchingupanddowninthesupercavitywascarriedoutinahigh-speedwatertunnel.Theemphasisislaidontheunderstandingoftheinteractionofthevehicleaftbodywiththecavityboundary.Theflowcharacteristicsweremeasuredandthestabilityofsupercavitingflowwithdifferentpitchingfrequenciesandamplitudeswasanalyzed.Inparticular,theobjectivesofthisstudyaretounderstandtheeffectoftheimpactuponthecavitydistortion,andtoquantifytheimpactprocessbyinvestigatingtheevolutionofthepressureinsidethecavityandthentheloadsonthevehicleduringthepitchingmotion.Itisalsoshownthattheevolutionofthepressuredetectedindifferent,asinsidethesupercavity,iscoherentanduniformduringtheperiodsofthepitchingmotion.Thisstudyisofdirectrelevancetoreliableandaccuratepredictionofhydrodynamicloadsassociatedwiththeslammingandimpactonsupercavitatingvehicles.

简介：Inthisstudy,amulti-relaxationtimelatticeBoltzmannmodelforshallowwaterinacurvilinearcoordinategridisdevelopedusingthegeneralizedformoftheinterpolationsupplementedlatticeBoltzmannmethod.TheTaylor-Coletteflowtestsshowthattheproposedmodelenjoysasecondorderaccuracyinspace.Theproposedmodelisappliedtothreetypesofmeanderingchannelswith180°,90°and60°consecutivebends.Thenumericalresultsdemonstratethatthesimulatedresultsagreewellwithpreviouscomputationalandexperimentaldata.Inaddition,themodelcanachievetheacceptableaccuracyintermsofthewaterdepthandthedepth-averagedvelocitiesforshallowwaterflowsincurvedandmeanderingchannelsoverawiderangeofbendangles.

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简介：Thehydraulicandsedimentdepositionproblemsinthewaterintakesystemofapumpinghousewerestudiedbyphysicalmodel.Theexperimentalresultsofdifferentworkingcasesindicatethatthesedimentdepositionsatthegates,stillingbasinandculvertsareveryfewwhenthesystemwasnormallyoperated,butintheforebayofpumpinghouse,especiallyinthepumpinghouseforlivingwater,theamountofsedimentdepositionsometimesisconsiderablylarge.Atthefrontoftheentryofpumpinghouseforlivingwater,installingasetofobliquepipescanpreventthecoarsegrainstoenterit,thedepositionamountwillobviouslydecrease.

简介：Inthisarticle,theunifiedmathematicalmodelforsplashdropletsandsuspendedmistofatomizedflowwasestablished,whichclassifiestheatomizedsourcesintothesplashsourceandthesuspendedsource.Forthesplashsource,theLagrangianmethodwasusedtosimulatetherandommotionofsplashwaterdroplets,andforthesuspendedsourcethetheoryofair-watertwo-phaseflowwasusedtosimulatethemistflowmovinginparticleclouds.Therainfallintensityoftheatomizedflowwasobtainedbysummarizingtherainfallintensitiesrelativetotheabovetwotypesofatomizedsources.Bothexperimentaldataandprototypeobservationdatawereusedfortheverificationofthemathematicalmodel.Forboththedistributionofrainfallintensity,andtheouteredgeoftheatomizedflow,thesimulationresultsareinagreementwiththeexperimentaldataorprototypeobservationdata.

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：Aquaticvegetationhasasignificantimpactonwatercurrents.Toevaluatetheeffectsofchangesintheaquaticvegetationonwatercurrentsofdifferentvelocity,a3-Dhydrodynamicmodelwasthendevelopedbytakingintoconsiderationoftheadditionalhydraulicresistanceoftheaquaticplants.TheNavier-StokesequationswerethensolvedusingtheSIMPLEmethodandthek-εturbulencemodel.CalculationsusingtheestablishedmodelswereusedtoforecasttheverticaldistributionofthehorizontalvelocityandhorizontalflowunderthetransmissionconditionsoftheSouth-NorthWaterDiversionintheNansiLake.Andcomparativecalculationfortheflowvelocitywasalsoperformedusingthesimplifiedmethodofassigningahighroughnesscoefficienttothelakebedinthesamearea.Resultssuggestthataddingadditionalhydraulicresistanceoftheaquaticplantsisfeasible.Thecalculationerrorsbetweensimulationresultandthefieldobserveddataaresmallerthan15%,while,thoseerrorsareupto35%iftheinfluenceofaquaticvegetationisdealtwiththesimplifiedmethod.

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

简介：TheasymmetricinletvelocityprofilehasbeenobservedinphantommodelusingLDAandinhealthsubjectsusingMagnetResonance(MR).TheeffectsofasymmetricinletaxialvelocityprofileontheflowfieldandtheWallShearStress(WSS)ofcarotidbifurcationwerenumericallystudiedhereinwiththeTF-AHCBmodel.TheresultsshowthattheWallShearStressGradient(WSSG)inthefrontpartofthesinusforinward-tiltinginletaxialvelocityprofileisnearly2timesofthatforthesymmetriconeinthebeginningofsystole,theendofsystole,anddiastole,respectively.TheareaofWSSbelow5×10-3Paattheouterwallofthesinusforoutward-tiltinginletaxialvelocityprofileis1.5timesofthatfortheinward-tiltingoneduringdiastoleofthecardiaccycle.Theasymmetricinletvelocityprofilescanreducetheflowvelocityneartheinnerwallofthesinus,whichhasbeennormallyconsideredahighvelocityregion.Itisconcludedthatbesidesbifurcationgeometryandflowwaveform,theasymmetryofinletvelocityprofileisprobablyafactorinfluencingatherosclerosis.

简介：Inthepresenceofbottomwater,adropinthereservoirpressureduetofluidproductioncausestheaquiferwatertoexpandandtoflowintothereservoir.Therefore,hydrocarbonproductionfromawellislimitedbythecriticalflowrate.Themainpurposeofthisstudyistoinvestigatethebreakthroughtimeandthecriticalratebyusinganovel3-Dhorizontalwellmodel.Basedonthehypothesisthatthehorizontalwellislocatedinanypositionofacircularreservoirwithno-flowboundaryonthetopofthereservoirandconstantpressureboundaryatthebottom,thehorizontalwellhasbeenregardedasaninfiniteconductivitylinesinkandthena3-Dsteady-stateflowmodelofthehorizontalwellissetup.ApointsinkpressuresolutioncanbeobtainedwiththeFouriertransform.Theresultofthepressuredistributionoftheuniformfluxhorizontalwellcanbepresentedbymeansoftheprincipleofsuperposition.Accordingtothestablewatercrestingtheory,thisstudyconfirmsthestableheightofwatercrestingandthecriticalrate.Meanwhile,itcanre-confirmthebreakthroughtimeataspecificrate.Theoutputofacomparisonbetweenthis3-Dmodelandthereservoirnumericalsimulator(Eclipse)showsthemethodpresentedherecanbeappliedtoinvestigatethebehaviorofawatercrestingandtopredictthebreakthroughtimeatthebottomwaterdriverreservoir.

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简介：TheUSM-θmodelofpowerlawfluidfordensetwo-phaseturbulentflowwasdeveloped,whichcombinestheunifiedsecond-ordermomentmodelfortwo-phaseturbulencewiththeparticlekinetictheoryfortheinter-particlecollision.Thismodelwasusedtosimulatetheturbulentflowofpowerlawfluidsingle-phaseinpipe.ItisshownthattheUSM?θmodelhasbetterpredictionresultthanthekf?εf?kp?εp?θmodel.TheUSM?θmodelwasthenusedtosimulatethedensetwo-phaseturbulentupflowofpowerlawfluidwithparticles.Withtheincreaseoftheflowexponent,thevelocitiesofpowerlawfluidandparticlesincreasenearthepipecentre.Comparisonbetweenthetwo-phaseflowofpowerlawfluid-particleandofliquid-particleindicatesthattheaxialfluctuationvelocityoffluidphaseandparticlephaseinliquid-particletwo-phaseflowissmallerthanthatinthepowerlawfluidtwo-phaseflow,butthetwo-phasevelocitiesofpowerlawfluid-particleandliquid-particleareclosetoeachother.