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

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简介：Numericalinvestigationwasconductedonanairshipofhull-finconfigurationforaerodynamicandaeroelasticcharacteristicsinthree-dimensionalviscousflows.Themathematicalmodelwasbuiltandthecorrespondingnumericalcodewasdevelopedforthefluid-structureinteractionproblem.ThegoverningequationsoftheviscousflowwithLL-LowReynoldsmodifiedmodelweresolvedbythestandardSIMPLEalgorithmbasedonthefinitevolumemethod.Afluid-structurecoupledmethodwasemployedtosolvethenonlinearaeroelasticityproblemfortheairship.Thecomputationalresultsoftheviscousflowareingoodagreementwiththeexperimentalmeasurements.Thesimulationontheaeroelasticbehavioroftheairshipinatrimmedflightrevealstheeffectofstructureflexibilityontheaerodynamicperformance.

简介：Inthisarticle,theinfluenceofwettabilityonaliquidflowbetweentwoparallelplanewallswerestudiedbyusingNon-EquilibriumMolecularDynamics(NEMD)simulation.Thewettabilityofthesolidsurfacescanbedescribedasthecontactangle.Theliquidflowrate,theslipvelocityandthesliplengthwhichareaffectedbythecontactanglewereinvestigated.Theresultsshowthattheboundaryconditionatamicroscopiclevelisdifferentfroma'no-slip'conditionatamacroscopiclevel.Thereexitsaslippageofaliquidflowforthehydrophobicboundaryandanexternalforceisneededtoovercomethresholdpressureforthehydrophilicboundary.Andtheorderlylayereddistributionsoftheliquidparticlesnearthehydrophilicsurfacevaryfromaplacenearthehydrophobicsurface.Thestudyindicatesthatthesurfacewettabilityplaysasignificantroleonpossibilitiesofformingaviscouslayerandthedirectslipatthesolidsurface.Theresistanceofliquidflowcanbedecreasedbychangingthewettabilityofboundarysurface.

简介：Alongwiththeflourishingofthewindenergyindustry,floatingoffshorewindturbineshavearousedmuchinterestamongtheacademiaaswellasenterprises.Inthispaper,theeffectsofthesupportingplatformmotionontheaerodynamicsofafloatingwindturbinearestudiedusingtheopensourceCFDframeworkOpenFOAM.Theplatformmotionresponses,includingsurge,heaveandpitch,aresuperimposedontotherotationofthewindturbine.Thrustandtorqueonthewindturbinearecomparedandanalysedforthecasesofdifferentplatformmotionpatternstogetherwiththeflowfield.Itisshownthatthemovementofthesupportingplatformcanhavelargeinfluencesonafloatingoffshorewindturbineandthusneedstobeconsideredcarefullyduringthedesignprocess.

简介：Thefeaturesofunsteadyflowsuchaspressurevariationandfluctuationinalargehydraulicturbineusuallyleadtotheinstabilityofoperation.Thisarticlereportstherecentinsiteinvestigationconcerningthecharacteristicfrequenciesinpressurefluctuation,shafttorsionaloscillationandstructuralvibrationofaprototype700MWFrancisturbineunit.Theinvestigationwascarriedoutforawideloadrangeof200MW-700MWintheconditionofwaterhead57m-90m.Anextensiveanalysisofbothtime-historyandfrequencydataoftheseunsteadyhydraulicbehaviourswasconducted.Itwasobservedthatthepressurefluctuationinadrafttubeisstrongerthanthatinupstreamflowpassage.Thelowfrequencywithaboutonethirdofrotationfrequencyisdominativeforthepressurefluctuationinpartloadrange.Alsotheunsteadyfeaturesofvibrationofheadcoverandtorsionaloscillationofshaftexhibitedthesimilarfeatures.Numericalanalysisshowedthatthevibrationandoscillationarecausedbyvortexropeinthedrafttube.Inaddition,astrongvibrationwithspecialcharacteristicfrequencywasobservedfortheheadcoverinmiddleloadrange.Thepressurefluctuationinthedrafttubewiththesamefrequencywasalsorecorded.Becausethisspecialvibrationhasappearedinthedesignednormalrunningcondition,itshouldbeavoidedbycarefullyallocatingpowerloadinthefutureoperation.

简介：DragreductionexperimentofthetravelingwavywallathighReynoldsnumberisconducted.Asuitoftravelingwavywalldeviceisdeveloped.Thedragforcesofthetravelingwavywallwithvariouswavespeeds(c)aremeasuredunderdifferentwaterspeeds(U)intheK15cavitationwatertunnelandarecomparedwiththatoftheflatplate.Theresultsshowthatthemeandragforceofthetravelingwavywallhavedecreasedandthenincreasedwithoscillationfrequencyincreasingatthesameflowspeed.Underdifferentflowspeeds,whentravelingwavewallreachedtotheminimumofdragforce,thecorrespondingtheratioofthewallmotionphasespeedctoflowspeedU,c/Uisslightlydifferent.Withintheparametersoftheexperiment,whenc/Ureachesacertainvalue,thedragforceofthetravelingwavywallcanbelessthanthatoftheflatplate.Thedragreductioncanbeupto42%.Furthermore,asthevalueofc/Uincreases,thetravelingwavywallcanrestraintheseparationandimprovethequalityofflowfield.

简介：Thispaperaddressestheproblemoftherenormalizationgroupkturbulencemodelingofavegetatedmulti-stagecompoundchannel.ResultsfromMicroacousticDopplervelocimeter(ADV)testsareusedwithtimeandspatialaveraging(doubleaveragingmethod)intheanalysisoftheflowfieldandthecharacterization.Comparisonsofthemeanvelocity,theReynoldsstress,andtheturbulentenergydistributionshowthevalidityofthecomputationalmethod.Themeanvelocityprofileseesanobviousdecelerationintheterracesbecauseofvegetation.Secondaryflowexistsmainlyatthejunctionofthemainchannelandthevegetationregiononthefirstterrace.Thebedshearstressinthemainchannelismuchgreaterthanthatintheterraces.Thedifferenceofthebedshearstressbetweentwoterracesisinsignificant,andthepresenceofvegetationcaneffectivelyreducethebedshearstress.

简介：ByusingtheReynoldsStressClosureModel(RSM),turbulentCounter-Gradient-Transport(CGT)phenomenonwasnumericallyinvestigatedinasymmetricflowwithajet,andthecomputationalresultswerecomparedwithexperimentaldata.ThecomputationalresultsshowthatthenegativeturbulentenergyproductiononlyappearsatsomecertainstationsinCGTregion,thisfactindicatesthattheCGTphenomenonexistsmorewidelythanthenegativeturbulentenergyproduction;whiletheCGTregionexistsallalong,itgraduallyshrinksinthefavorablepressuregradientzoneuntilthepositionofthewingcentralpartisreached,whereitvanishes,butitappearsintheadversepressuregradientregion;inaddition,thelocationintheflowwhereuv=0switchedsides,relativetowhere()U/()y=0,fromfavorablepressuregradienttoadversepressuregradient.ThepressuregradienttakesanimportanteffectontheregionofnegativeturbulentenergyproductionandCGT.

简介：Theaccuratemodelingandpredictionoftherotatingstallinacentrifugalpumpisasignificantchallenge.Oneofthemodelingtechniquesthatcanimprovetheaccuracyoftheflowpredictionsisthelargeeddysimulation(LES).ThequalityoftheLESpredictionsdependsonthesub-grid-scale(SGS)modelimplementedintheLES.ThispaperassessestheinfluenceofvariousSGSmodelsthataresuitableforpredictingrotatingstallinalow-specificspeedcentrifugalpumpimpeller.TheSGSmodelsconsideredinthepresentworkincludetheSmagorinskymodel(SM),thedynamicSmagorinskymodel(DSM),thedynamicnon-linearmodel(DNM),thedynamicmixedmodel(DMM)andthedynamicmixednon-linearmodel(DMNM).TheresultsobtainedfromthesemodelsarecomparedwiththePIVandLDVexperimentaldata.TheanalysisoftheresultsshowsthattheSGSmodelshavesignificantinfluencesontheflowfield.Amongthemodels,theDSM,theDMMandtheDMNMcansuccessfullypredictthe'two-channel'stallphenomenon,butnottheSMandtheDNM.Accordingtothesimulations,theDMNMgivesthebestpredictiononthemeanvelocityflowfieldandalsoindicatesimprovementsforthesimulationoftheturbulentflow.Moreover,thehighturbulentkineticenergypredictedbytheDMNMisinthebestagreementwiththeexperimentdata.

简介：Theflowbetweentwocoaxialconicalcylindersisnumericallystudiedfortwodifferentconfigurations,withtheinnerconerotatingandtheouteroneatrest.Itisfoundthat,inoneconfiguration,atleastatasmallReynoldsnumber(Re),thepressureisadecreasingfunctionofzwhileintheotherconfiguration,itisanincreasingfunctionofz.Inthefirstconfiguration,thepressurecurvesfordifferentRehaveintersections,whileinthesecondconfigurationtheydonot.ThegapbetweentwoconicalcylindersisfilledwithsixpairsofTaylorvorticesataboutthesameReynoldsnumberandineachpairofvorticesinthefirstconfiguration,theuppervortexislargerthanthebottomonewhileinthesecondconfiguration,thebottomvortexislargerthantheupperone.

简介：Thispaperstudiesthewall-boundedflowaroundacylindricalatahighReynoldsnumbersbodyinadeterminedcomputationaldomain,withsimulationsofthe3-D,turbulentconcentricannulusflowinastraightpipe.Numericalresultsshowthatareversingzone,appearingasatonguezonewithnestedvelocitieshigherthanthesurroundingarea,existsbehindthecylindricalbody.Theannulusspaceisaregionofhighvelocityandlowpressure.Thezerovelocity,ofcombinedtheX-velocityandtheY-velocity,existsinthecrosssectionsandnovortexsheddingisformedbehindtheattachingcylinders.Amongallinvestigatedeffectingfactors,thediametersoftheattachingandthemaincylindersaffectthewakefeaturebehindthecylindricalbodywhilethemaincylinderlengthdoesnotaffectthedistributiontendencyoftheflowfield.Thediametersofthemaincylinderandthepipeaffectthepressurevaluesandthedistributiontendenciesonthemaincylindersurface.Obviously,theincreaseofthepipediameterreducesthedragcoefficientofthecylindricalbodyandtheincreaseofthediameterofthemaincylinderincreasesthedragcoefficientgreatly.Thenumericalinvestigationoftheconcentricannulusflowprovidesfoundationsforfurtherimprovementsoftheintricateflowstudies.

简介：A3-Dtimedomainmethodisdevelopedtoinvestigatethegapinfluenceonthewaveforcesfor3-Dmultiplefloatingstructures.Specialhydrodynamicresonanceduetosmallgapsbetweenmultiplefloatingstructuresonwaveforcesisexamined.Strongandcomplicatehydrodynamicinteractionsbetweenthefloatingbodiesareobservedandthenumericalcomputationshaveprovedtheexistenceofthesharppeakforceresponseoneachfloatingbodyatsomespecialresonantwavenumbers.Bycomparisonwiththeresultsfromthefrequencydomaintechnique,theresultsobtainedfromthetimedomainmethodrevealthesimilarresonantphenomenaandhydrodynamicinteraction.TheresonantwavenumbersarealsoprovedaroundkL=nπ(n=1,2,…,∞)withacorrespondingfrequencyshift.Thestronghydrodynamicinteractionfeatureispracticallysignificantforthedesignofmodulestructuresandthelinks(connection)inwholethefloatingbodysystem.

简介：Thesheet/cloudcavitationisofagreatpracticalinterestsincethehighlyunsteadyfeatureinvolvessignificantfluctuationsaroundthebodywherethecavitationoccurs.Moreover,thecavitatingflowsarecomplicatedduetothethermaleffects.ThepresentpapernumericallystudiestheunsteadycavitatingflowsaroundaNACA0015hydrofoilinthefluoreketoneandtheliquidnitrogenwithparticularemphasisonthethermaleffectsandthedynamicevolution.Thenumericalresultsandtheexperimentalmeasurementsaregenerallyinagreement.Itisshownthatthetemperaturedistributionsarecloselyrelatedtothecavityevolution.Meanwhile,thetemperaturedropismoreevidentintheliquidnitrogenforthesamecavitationnumber,andthethermaleffectsuppressestheoccurrenceandthedevelopmentofthecavitatingflow,especiallyatalowtemperatureinthefluoroketone.Furthermore,thecavitatingflowsarecloselyrelatedtothecomplicatedvortexstructures.Thedistributionsofthepressurearoundthehydrofoilisamajorfactoroftriggeringtheunsteadysheet/cloudcavitation.Atlast,itisinterestingtofindthatoneseesasignificantthermaleffectonthecavitationtransition,asmallvalueofσ/2ɑisrequiredinthethermo-sensitivefluidstoachievethesimilarcavitationtransitionthatoccursinthewater.

简介：Inthispaper,thebuoyanttrajectoriesoflaminarfarthermalwakesbehindslenderstreamlinedheatedbodiesofrevolutioninstablestratifiedfluidhavebeeninvestigatedintheoryandexperiment.Ithasbeenfoundthatthebuoyanttrajectoriesofthermalwakesinstratifiedfluidaredifferentfromthatinhomogeneousfluid.Thebuoyanttrajectoriesofthermalwakesinstratifiedfluidarewavy.Thefactorsinfluencingthebuoyanttrajectoriesofaxisymmetriclami-narthermalwakesinstratifiedfluidareRichardsonnumber,Nusseltnumberandnumber.Thevalidityoftheoreticalanalysishasbeenprovedbytheresultsofmeasurementsandvisualiza-tions.Thebuoyanttrajectoriesofthermalwakesafterunderwaterbodiescanbeestimatedbyre-sultshereinpresented.

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简介：Thisarticleexperimentallyinvestigatedthepressureandcavitationcharacteristicsofhighvelocityflowoverasurfaceirregularitywithandwithoutaerationinanon-circulatingwatertunnelsystem.Thesurfaceirregularityisacylindricalprotrusionmadeofstainlesssteelof6mmdiameterand2mmheight.PressureswithandwithoutaerationweremeasuredwithMPX400Dpressuretransducersandreal-timelyacquiredbyaSINOCERAYE6263dataacquisitionsystem.Variationsinflowregimeswithandwithoutaerationwereobserved.Pressureprofilesandtheirvariationswithairconcentrationupperandlowercylindricalprotrusionontheinvertandobvertwallsweredetermined.Variationsofcavitationnumberwithairconcentrationlowercylindricalprotrusionwereanalyzed.Also,cavitationnumbersinthepresenceandabsenceofaerationwerecompared.

简介：Thisworkaimstoinvestigatetheeffectsofdosingregimentsondrugdeliveryinsolidtumorsandtovalidatethemwithexperimentsonrats.Thelumpedparametermodelsofpharmacokineticsandofdrugdeliveryintumorweredevelopedtosimulatetimecoursesofaveragedrugconcentration(Ct)oftumorinterstitiumintwotypesofdosingregiments(i.e.,single-shotandtriple-shotones).Thetworegimentswereperformedviaantitumordrug,hydroxycamptothecin(HCPT),onrats,tomeasurethedrugconcentrationinthetumor.Thesimulationsofthedrugconcentrationinthetumorofthetwodosingregimentswereconductedandcomparedwiththeexperimentaldataonrats.Thecoefficientsinthemodelswereinvestigated.Itisconcludedthatthetriple-shotmethodismoreeffectivethanthatofsingle-shotinjection.Thepresentlumped-parametermodelisquantitativelycompetentfordrugdeliveryinsolidtumor.