简介：Theformulaeusedtocalculatethefrictioninthenon-uniformflowchutewereexaminedwiththeexperimentaldata,andtheresultsshowthattheaccuracyoftheformulaisenoughforengineeringapplications.Acomparisonbetweentheresultsoffrictionrespectivelyfromtheuniformflowassumptionandthenon-uniformflowapproximationindicatesthattheformerisanorderofmagnitudelargerthanthelatterinthecaseofsteepchute.Thehydraulicdragonasteepchutewithaeratorswasmeasuredonthehydraulicmodeldirectlyandthecoefficientoftheaeratoreffectonthedragwasobtained.Thevariationpatternsofthewallshearjustdownstreamoftheaeratorswereinvestigatedandthemechanismoftheincreaseinthedragbyaeratorwereanalyzedqualitativelywiththemeasuredwater-depthsjustdownstreamtheaerators.

简介：Theinceptionoftipvortexcavitationisverysensitivetowaterquality.Inordertoquantifytheeffectofwaterqualityontheinceptionoftipvortexcavitation,wedevelopamotionmodeltodescribethemigrationandgrowthofnucleiinwater.Ananalyticalsolutionofmigrationofnucleiinavortexflowisobtainedsothatthecapturetimesofvariousnucleicanbegivenoutdirectly.Acriterionisbuilttodeterminethecriticalnucleusinacertainnucleispectradistribution.Tensilestrengthofthecriticalnucleusisusedtoquantifytheeffectofwaterqualityandcorrectthetipvortexcavitationinceptionnumber.Finallythischangeofcavitationinceptionnumberiscomparedwithexperimentalresultstovalidateourmodel.

简介：ThenumericalsolutionofBoussinesqequationsisworkedoutasaninitial-valueproblemtostudytheeffectoftheinstabilitiesofflowontheinitialerrorgrowthandmesoscalepredictability.Thedevelopmentofweathersystemsdependsondifferentdynamicinstabilitymechanismsaccordingtothespatialscalesofthesystemandthedevelopmentofmesoscalesystemsisdeterminedbysymmetricinstability.Sincesymmetricinstabilitydominatesamongthethreetypesofdynamicinstability,itmakesthepredictionoftheassociatedmesoscalesystemsmoresensitivetoinitialuncertainties.Thisindicatesthatthestrongerinstabilityleadstofasterinitialerrorgrowthandthuslimitsthemesoscalepredictability.Besidesdynamicinstability,theimpactofthermodynamicinstabilityisalsoexplored.Theevolvementofconvectiveinstabilitymanifestsasdramaticvariationinsmallspatialscaleandshorttemporalscale,andfurthermore,itexhibitstheupscalegrowth.Sincethesefeaturesdeterminetheinitialerrorgrowth,themesoscalesystemsarisingfromconvectiveinstabilityarelesspredictableandtheupscaleerrorgrowthlimitsthepredictabilityoflargerscales.Thelatentheatingisresponsibleforchangingthestabilityofflowandsubsequentlyinfluencingtheerrorgrowthandthepredictability.

简介：Inthiswork,westudiedthedimensionsofstreamtubeintheverticalaswellasinclinedbankconditions.Datawerecollectedfrombothaphysicalmodelanda3-Dnumericalmodel(SSIIM2).Equationsforpredictingstreamtubedimensionswerepresentedandcomparedwithexistingformulae.Incomparisonwithverticalbank,itisfoundthatincliningbankcausesthebottomstreamtubewidthtobegreaterthanatthesurface.Thestrengthofsecondarycurrentformedattheentranceofbranchchannelisreduced.Thesechangesinflowpatterncanreducetheamountofsedimentdeliveryintotheintake.

简介：Particleimpactdrillingisanefficientdrillingtechnologyfordeep-wellhardformation,Withthistechnology,therockiscutmainlybyhigh-speedsphericalparticleimpactunderhydraulicaction.Inthisarticle,theinfluenceofjetflowfactors,hydraulicfactorsandabrasivefactorsonrockbreakingisstudiedthroughindoorexperimentsofimpactbysteelparticles.Theresultsindicatethattheparticlewaterjethasanoptimalstandoffdistanceandparticleconcentration;therockbreakingeffectdeclineswiththeincreaseoftheconfiningpressureandthedecreaseofthepumppressureandparticlediameter.Thisstudywillprovidesomefoodofthoughtforthedevelopmentofparticleimpactdrillingtechnology.

简介：Forventilatedcavitatingflowsinaclosedwatertunnel,thewalleffectmayexertanimportantinfluenceoncavityshapeandhydrodynamics.AnisotropicmixturemultiphasemodelwasestablishedtostudythewalleffectbasedontheRANSequations,coupledwithanaturalcavitationmodelandtheRNGk-εturbulentmodel.ThegoverningequationswerediscretizedusingthefinitevolumemethodandsolvedbytheGauss-Seidellinearequationsolveronthebasisofasegregationalgorithm.Thealgebraicmultigridapproachwascarriedthroughtoacceleratetheconvergenceofsolution.Thesteadyventilatedcavitatingflowsinwatertunnelsofdifferentdiameterweresimulatedforaconceptualunderwatervehiclemodelwhichhadadiskcavitator.Itisfoundthatthechokedcavitationnumberderivedisclosetotheapproximatesolutionofnaturalcavitatingflowfora3-Ddisk.Thecriticalventilationratefallswithdecreasingdiameterofthewatertunnel.However,thecavitysizeanddragcoefficientarerisingwiththedecreaseintunneldiameterforthesameventilationrate,andthecavitysizewillbemuchdifferentinwatertunnelsofdifferentdiameterevenforthesameventilatedcavitationnumber.

简介：Theflowthroughabreastwallspillwayisgreatlyaffectedbythecentripetalforceduetoadownstreamcurvedprofile.Therefore,themeanverticalpressuredistributionattheoutletsectionisnotconsistentwiththehydrostaticpressurelaw.Thisdistributioninturnaffectsthedischargecapacityofthebreastwallspillway.Thispaperexperimentallystudiestheeffectofaconvexdownstreamprofileonthemeanpressurevariationandthedischargeofabreastwallspillwaywithoutgates.Itisindicatedthattheeffectofthecurvilinearstreamlineonthemeanverticalpressurevariationissignificant.TheregressionanalysismethodisusedtodeterminethewaterheadeffectZooftheorificeopeningthroughthemeanpressurevariation.Adischargepredictionformulaofthebreastwallspillwayisobtainedunderthelimitedconditionsofalaboratoryflume.Thepredicteddischargeiscomparedtothemeasureddischarge.Agoodagreementisevidencedforthefreeorificeflowwitherrorswithin?5%,whileabigerror(20%orevenmore)isobtainedifthehydrostaticpressurelawisusedforthedeterminationofZo.

简介：Theeffectofvegetationontheflowstructureandthedispersionina180ocurvedopenchannelisstudied.TheMicroADVisusedtomeasuretheflowvelocitiesbothinthevegetationcasesandthenon-vegetationcase.Itisshownthatthevelocitiesinthevegetationareaaremuchsmallerthanthoseinthenon-vegetationareaandalargevelocitygradientisgeneratedbetweenthevegetationareaandthenon-vegetationarea.ThetransverseandlongitudinaldispersioncoefficientsareanalyzedbasedontheexperimentaldatabyusingthemodifiedN-zonemodels.Itisshownthattheeffectofthevegetationonthetransversedispersioncoefficientissmall,involvingonlychangesofasmallmagnitude,however,sincetheprimaryvelocitiesbecomemuchmoreinhomogeneouswiththepresenceofthevegetation,thelongitudinaldispersioncoefficientsaremuchlargerthanthoseinthenon-vegetationcase.

简介：Amulti-bubbledynamicscodeaccountingforgasdiffusionintheliquidandthroughthebubblewallwasdevelopedandusedtostudythemodificationofabubblenucleipopulationdynamicsbyapropeller.ThepropellerflowfieldwasobtainedusingaReynolds-AveragedNavier-Stokes(RANS)solverandbubblenucleipopulationswerepropagatedinthisfield.Thenumericalpro-cedureenabledestablishmentofthepossibilityofproductionbehindthepropellerofrelativelylargevisiblebubblesstartingfromtypicaloceannucleisizedistributions.Theresultinglargerbubblesareseentoclusterinthebladewakesandtipvortices.Parametricinvestigationsoftheinitialnucleisizedistribution,thedissolvedgasconcentration,andthecavitationnumberwereconductedtoide-ntifytheireffectsonbubbleentrainmentandtheresultantvoidfractionsandbubbledistributionmodificationsdownstreamfromthepropeller.Imposedsyntheticturbulence-likefluctuationsuntotheaverageRANSflowfieldwerealsousedtostudytheeffectavera-gingintheRANSprocedurehasontheresults.

简介：Toanalyzethemechanismofdragreducingeffectbycouplingflexibletubeswithturbulentflow,basedonexperimentalexaminationofmoreobviousturbulentdragreductioneffectinflexibletubesthaninrigidtubes,experimentalinvestigationwasperformedontheeffectofturbulentdragreduction,fluctuatingvibrationcharacteristicsofflexibletubeandthecorrelationsbyusingadouble-tubesystemandlaserdisplacementsensor.Theresultsareasfollows:withthedecreaseofthethicknessoftheflexibletubes,therootmeansquareoffluctuatingamplitudeoftheouterwallofthetubesincreases,andthenon-dimensionalburstperiodincreases,resultingintheincreaseofthereductionrateofdragcoefficientbycouplingflexibletubeswithturbulentflow.Atappliedpressure-balancedairontheouterwallandtheReynoldsnumberofabout1.75×104,thenon-dimensionalburstperiodsoftheflexibletubeswiththethicknessof2mm,3mm,4mmare141,126,105,respectively.

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

简介：Themovementofwaterflowinunsaturatedfracturedrockwasinvestigatedwiththesandstonesamplethroughexperimentalresearchandnumericalsimulation.Theexperimentalresultsshowthatthearrivingtimeofwettingfrontisdelayedbythefracture,resultingintheincreaseofwatersaturationinthedomainontheupstreamsideofthefracture,whichwilllocallyenhancewaterflowthroughthematrix.Thenumericalsimulationwiththefinitevolumemethodcaptureseffectivelythesecharacteristics.Thecomparisonbetweensimulatedandobservedtraveltimeandarrivingtimeofwettingfrontshowsthattheirdifferenceareverysmallandthesimulatedresultsareinagreementwiththeobservedresults,whichimpliescalibratedparametersarereliableandeffective.Thenaccordingtothecalibratedparameters,fracturedmodelswereestablishedtoexaminehowthechangeoflargefracturedaperturewouldaffectthearrivingtimeofwettingfronts,pressureheadsandwatersaturationontheupstreamanddownstreamsidesoffracture.

简介：

简介：Thecoldflowcharacteristicsareinvestigatedtoshowtheeffectofthestructuralparametersoftheflowguidevaneonthetrappedvortexcombustor(TVC).TheresultsshowthatthestructuralparametershavesignificanteffectsontheTVC.Asa/Hincreases,thetotalpressureloss,thewallshearstressatthebottomofthecavityandtheturbulentintensityinthemaincombustionzoneincrease.b/Bdoesnothaveasignificanteffectonthecavityflowstructureandthetotalpressureloss,andthewallshearstressatthebottomofthecavityincreasesasb/Bincreases.Thereisnosignificantincreaseoftheturbulentintensitywiththeincreaseofb/B.Theincreaseofc/Lhaslittleeffectonthetotalpressureloss,anditisnotconducivetoastablecombustion.Asc/Lincreases,thewallshearstressatthebottomofthecavitydecreases.Whena/H=0.4,b/B=0.4,c/L=0.1,adesirabledual-vortexstructureisformedwithanacceptablepressurelosstoachieveastablecombustion.Moreover,toascertainthattheflameisstablefordifferentvaluesofVmawiththeoptimalstructuralparameters,theeffectofVmaontheflowfieldisdiscussed.Resultssuggestthatthedual-vortexstructurehasnorelationshipwiththeincreaseofVma.Furthermore,anunsteadysimulationisconductedtoshowthegenerationandthedevelopmentofthedual-vortex.

简介：Failureofbridgesduetolocalscourinthevicinityofbridgeabutmentsisacommonoccurrence.Inthisstudy,experimentsundertwodifferentchannelconditionswereconductedtoassesstheimpactsofvegetationonchannelbanksonlocalscouraroundawing-wallabutmentwithcircularedges.Someexperimentswereconductedinchannelwithvegetationonchannelbanks,andotherexperimentsinchannelwithoutvegetationonchannelbank.TheflowvelocityandReynoldsstressdistributionsinscourholesaroundawing-wallabutmentwithcircularedgeswerecomparedunderthese2differentchannelconditions.Resultsrevealthatthevegetated-bankscanreducethetimeforachievingtheequilibriumconditionfrom17hto9h.Also,vegetated-bankchannelscanresultinasignificantdecreaseinthemaximumscourdepthfrom0.084m(forbarechannelbank)to0.00032m.Additionally,aroundtheabutment,vegetated-banksplayasignificantroleindiminishingtheReynoldsstress(RS)nearthebedandremovingnegativevaluesinRSdistributionbyweakeningunfavorablepressuregradientanddown-flowintheupstreamofabutment.

简介：Thispaperstudieswaterandsolutetransportinsoil.ItmainlydealswiththeadsorptionbehaviorofheavymetalCd++insoilatdifferentPHvaluesandthedynamiccharac-tersofadsorptionprocessinunsaturatedstate.Throughtheoreticalanalysisandexperimentalre-search,theadsorptionisothermandtheequationsofdynamicadsorptioninsaturatedandunsatu-ratedstatesareproposed.

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

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：Lid-drivenmixedconvectionhasbeengivenimmenseimportanceduetoitswiderangeofapplications.AT-shapedcavityisintroducedandpertinentparameterscontrollingmixedconvectionphenomenonareanalyzedinthispaper.Water-Al2O3nanofluidisconsideredinsidethecavitytoaugmentheattransferrate.Galerkinweightedresidualmethodoffiniteelementanalysisisappliedforthenumericalsimulations.Numericalsolutionisobtainedfordifferentsolidvolumefractionsofnanofluid(?=0-0.15),Grashofnumbers(Gr=0.1?5000)andReynoldsnumbers(Re=0.31?1000)inlaminarflowregime.Specialattentionisgivenontheanalysisofflowatthepuremixedconvectionregime.ItisfoundthatGrashof,ReynoldsandRichardsonnumbersalongwithsolidvolumefractionofnanofluidhavesignificanteffectonheattransfercharacteristicsinsidethecavity.ResultsarepresentedusingstreamlineandisothermcontoursalongwithrelatedvariationofaverageNusseltnumbersoftheheatedwallandaveragefluidtemperatureinsidethecavity.