简介：Transversemixingcharacteristicsofsoluteintheopenchannelflowcanprovideusefulinformationforriverenvironmentalmanagement.Thelateralmixingcoefficientisacrucialparameterforreproducingthetransversemixingeitherbynumericalsimulationorbyanalyticalprediction.Sincethesolutemixingcanbegreatlyaffectedbythelateralvariationsinwaterdepth,mixingcoefficientshouldbedeterminedineachsub-section(i.e.,themainchannel,sideslopeandfloodplain)separately.Inthisarticle,thetransversemixinginasymmetrictrapezoidalcompoundchannelwasstudiedbasedonlaboratorymeasurementoflongitudinalandtransversevelocitycomponentsandlateraldistributionofsoluteconcentration.ThelateralmixingcoefficientwasestimatedbyadoptingdifferentSchmidtnumbersindifferentsub-sectionsdividedaccordingtothedevelopingtrendoftheeddyviscosity,andfinallyapiecewiselinearprofileofmixingcoefficientwasadoptedtoanalyticallypredictthetransversesoluteconcentration.Thecomparisonbetweentheanalyticallypredicteddataandthemeasuringsoluteconcentrationprovedthatthisisaneffectivewaytoestimatethelateralmixingintheopenchannelflowwithlateralvariationsinwaterdepth.

简介：Themechanicalenergyequationisafundamentalequationofa1-DmathematicalmodelinHydraulicsandEngineeringFluidMechanics.ThisequationforthetotalflowusedtobededucedbyextendingtheBernoulli’sequationfortheidealfluidinthestreamlinetoastreamtube,andthenrevisedbyconsideringtheviscouseffectandintegratedonthecrosssection.Thisderivationisnotrigorousandtheeffectofturbulenceisnotconsidered.Inthispaper,theenergyequationforthetotalflowisderivedbyusingtheNavier-StokesequationsinFluidMechanics,theresultsareasfollows:(1)Anewenergyequationforsteadychannelflowsofincompressiblehomogeneousliquidisobtained,whichincludesthevariationoftheturbulentkineticenergyalongthechannel,theformulaforthemechanicalenergylossofthetotalflowcanbedetermineddirectlyinthedeductionprocess.(2)Thetheoreticalsolutionofthevelocityfieldforlaminarflowsinarectangularopenchannelisobtainedandthemechanicalenergylossintheenergyequationiscalculated.ThevariationsofthecoefficientofthemechanicalenergylossagainsttheReynoldsnumberandthewidth-depthratioareobtained.(3)Theturbulentflowinarectangularopenchannelissimulatedusing3-DReynoldsaveragedequationsclosedbytheReynoldsstressmodel(RSM),andthevariationsofthecoefficientofthemechanicalenergylossagainsttheReynoldsnumberandthewidth-depthratioarediscussed.

简介：ＯＮＴＨＥＨＩＧＨＰＲＥＣＩＳＩＯＮＡＤＡＰＴＩＶＥＯＰＥＮＢＯＵＮＤＡＲＹＣＯＮＤＩＴＩＯＮＳＦＯＲＴＲＡＮＳＩＥＮＴＷＡＶＥＳ￥ＺｏｕＧｕａｎｇ－ｙｕａｎ（Ｄｅｐｔ．ｏｆＭｅｃｈａｎｉｃｓａｎｄＥｎｇｉｎｅｅｒｉｎｇＳｃｉｅｎｃｅｓ，Ｐｅｋｉｎｇ...

简介：ResultsofseveralLargeEddySimulations(LES)ofopenchannelflowswithnon-submergedvegetationarepresentedinthisarticle.Itisshownthatthevegetationcanmaketheflowstructureinthemainstreamdirectionuniformforbothsupercriticalandsubcriticalflows.Forsubcriticalflows,theLESresultsoftheensemble-averageoftime-averagedvelocitydistributionsatfourverticalsectionsaroundasingleplantareingoodagreementwithmeasurements.Thevelocityseesdoublepeaksattheupperandlowerpositionsofflows.Forsupercriticalflows,theensemble-averagevelocitiesseesomediscrepancybetweenLESandmeasurementresults.Somesecondaryfloweddiesappearnearthesingleplant,andtheyjustlocateinthepositionsofthedoublepeaksinstream-wisevelocityprofiles.ItisalsofoundthatthevegetationdragcoefficientdeceasesastheFroudenumberincreases.

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简介：Thispaperpresentsananalysisonthevelocitydistributionsofsteady,uniformsuspendedsediment-ladenflowsinopenchannels.Thesedimentparticle-particleinteractionsandthebuoyancyeffectsduetodensitystratificationaretakenintoaccountrespectivelythroughthewater-sedimentmixture’sconstitutiverelationshipandanadaptedMonin-Obukhovlengthscaletovalidatethetheoryforawiderspectrumofsedimentconcentrations.Thedevelopedmodel,withthesameyonKarmancoefficientasthatofasinglephaseflow,isshowntobeinexcellentagreementwithmeasurementsofcontrolledexperimentswithbothlowandheavysedimentconcentrations.

简介：Ageneralizedbendflowmodel,treatinga90°singlebendand60°continuousbends,wasdesignedtoquantitativelydescribe3-Dturbulencemechanismofcirculatingnot-fully-developedflowinopenchannelswithbends.The3-Dfluctuatingvelocitiesofturbulentflowweremeasuredandanalyzedwitha3-Dacoustic-Dopplervelocimeter.Formulafor3-Dturbulentintensitywasderivedusingthedimensionanalysisapproach.Expressionsofverticalturbulent-intensitydistributionswereobtainedwiththemultivariant-regressiontheory,whichagreewithexperimentdata.Distributionsofturbulentintensityandturbulentstresswerecharacterized,andtheirrelationshipswereconcluded.Inthebend-turbulent-flowcoreregion,longitudinalandlateralturbulent-intensitydistributionsarecoincidentwithlineardistribution,butinnear-wallregionarecoincidentwiththeGammadistribution.VerticalturbulentintensitydistributionsarecoincidentwiththeRayleighdistribution.Herein,itisconcludedthatthebendturbulenceisanisotropic.

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简介：Spatio-temporalcharacteristicsofthewall-boundedturbulentmixinglayerflowoveranopenstepandasquare-edgedribwereextensivelystudiedinalow-speedwindtunnel.Simultaneousmeasurementsofwall-pressurefluctuationsandvelocitymeasurementswereperformedbyusingmicrophonearrayandX-wire/splitfim,respectively.

简介：Channelconfluencesareuniversallypresentinnature.Theycanbedividedintotwotypes:asymmetricalriverconfluencesandsymmetricriverconfluences.ThelatterisalsocalledastheY-shapedconfluences.Mostofpreviousworkhaspaidmoreattentiontotheasymmetricalriverconfluences,butfewstudieshavebeenconductedontheY-shapedconfluences.Inthisarticle,theeffectsofbeddiscordanceontheflowpatternsat'Y'shapedopen-channelconfluenceswerestudiedbyusinga3-Dnumericalsimulation.Itisprovedthatthemodelcanundertakequantitativeassessmentoftheflowatconfluences.TheresultsindicatethattherearealotofdifferencesbetweentheY-shapedconfluenceandasymmetricalconfluence.ThediscordantbedheightplaysanimportantroleattheY-shapedjunction.