简介：Anewprocedurewasdevelopedforestimatingtheeffectivecollisiondiameterofanaggregatecomposedofprimaryparticlesofanysize.ThecoagulationcoefficientoftwooppositelychargedparticleswasmeasuredexperimentallyandcomparedwithclassicFuchstheory,includinganewmethodtoaccountforparticlenon-sphericity.Asecondsetofexperimentswereperformedonwell-definednanoparticleaggregatesatdifferentstagesofsintering,i.e.fromtheaggregatetothefullysinteredstage.Here,electricalmobilitywasusedtocharacterizetheparticledrag.Theaggregatesarebeingbuiltfromtwodifferentsize-fractionatednanoparticleaerosols,thenon-aggregatedparticlesarediscardedbyanelectrofilterandthentheyarepassedthroughafurnaceatconcentrationslowenoughnottoinducecoagulation.

简介：Thespectralpropertiesofnonlineardragforcesofrandomwavesonverticalcircularcylindersareanalyzedinthispaperbymeansofnonlinearspectralanalysis.Theanalysisprovidesbasicparametersforestimationofthecharacteristicdragforces.Numericalcomputationisalsoperformedfortheinvestigationoftheeffectsofnonlinearityofthedragforces.TheresultsindicatethatthewavedragforcescalculatedbylinearwavetheoryarelargerthanthosecalculatedbythethirdorderStokeswavetheoryforgivenwaves.Thedifferencebetweenthemincreaseswithwaveheight.Thewavedragforcescalculatedbyuseoflinearapproximationareabout5％smallerthantheiractualvalueswhenmeasuredinthepeakvaluesofspectraldensities.Thiswillresultinasafetyproblemforthedesignofoffshorestructures.Therefore,thenonlineareffectofwavedragforcesshouldbetakenintoconsiderationindesignandapplicationofimportantoffshorestructures.

简介：Windspeedscalinginsimilaritylawinwind-generatedwavesandthedragcoefficientarestudied.Inanalyzingthedatainthewindwavechannel,itisfoundthattheu.scalinggreatlyreducesthescatterintheU10scaling.Theu.scalinghasmuchlessscatterthanthescalingusingotherwindspeeds.Thefrictionvelocityseemstoplayadistinctiveroleinwavegrowth.Theresultisimportantintheapplicationsofthesimilaritylawandinwavemodeling.Intheoryitgivesaninsightintothemechanismofwindwaveinteraction.Itisfoundthatwavesteepnessisimportantininfluencingthedragcoefficient.Thevariabilityofthecoefficientsinthecurrentlywidelyuseddragformcanbeexplainedbythedifferencesinwavesteepnessintheobservations.Adragcoefficientmodelwithwindspeedandwavesteepnessasparametersisproposed.AnexplanationforKahma'sresultthattheu.scalingdoesnotreducethescatterintheU10scalingisgiven.

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

简介：Thedragreductionofcompliantsurfaceisstudiedinashipmodeltank.There-sultsofthemeasureddragofaflatplatemodelshowthatthecompliantsurfaceiscapableofre-ducingdraginacertainrangeofspeeds,Themaximumdragreductionis15.7%whenthecom-pliantsurfaceismerelyontheonesideoftheplate.Theseresultshaveconfirmedthepredictedcharacteristicsofcompliantsurfaces.

简介：Windsontheeartharecommonlystrongenoughtoerodetransportanddepositsediment.Themodesofsandtransportbythewindaregreatlydifferentfromthosebywaterflow.Ontheotherhandwind-blownsandsareofamaterialcirculationprocessoftheearthsurface.Theyaffectwind-sandtransportfluxandsandejectionofaflux,thedamageofgrainsformedcannotbeneglectedinengineering.Becauseofthecomplexityofwindblownsandfluxsystem,theunderstandingofitsbasicmechanicsisnotyetclear.Thekeyforcesinsandsalutationmainlyincludes:thevalidgravity,airdragforce'Magnusforce'Saffmanforce'Bassetforce'additionalqualityforceandscatterforceamonggrains.Themostimportantforceinsandsalutationistheairdragforce.Computationofthesinglespheredragcoefficientanddoublespheresdragcoefficientispresentedforthedistancebetweentwospheresbeingsmallerthantwelvetimesofthespherediameterandthespheresbeingatdifferentangularpositions.Theflowinterferenceoftwosphereswasinvestigatedforthedistances=0.08dto12d,angularpositionθ=0to360andReynoldsnumber1≤Re≤1000.

简介：Hydrodynamicoptimizationofthehullformscanberealizedthroughtheimplementationandintegrationofcomputationaltoolsthatconsistofahydrodynamicmodule,ahullsurfacerepresentationandmodificationmodule,andanoptimizationmodule.Inthepresentpaper,anewbulbousbowgenerationandmodificationtechniquehasbeendevelopedandintegratedintothehullsurfacerepresentationandmodificationmodule.Aradialbasisfunctionbasedsurrogatemodelisdevelopedtoapproximatetheobjectivefunctionsandreducethecomputingcost.Amulti-objectiveartificialbeecolonyoptimizationalgorithmisimplementedandintegratedintotheoptimizationmodule.Toillustratetheintegratedhydrodynamicoptimizationtools,acargoshipisoptimizedforreduceddrag.Theoptimalhullformsobtainedarethenvalidatedcomputationallyandexperimentally.Validationresultsshowthatthepresenttoolscanbeusedefficientlyandeffectivelyinthesimulationbaseddesignofthehullformsforreduceddrag.

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简介：Experimentally,theelectrondrageffectoncarbonnanotubesurfaceinflowingliquidswasinvestigated.Itwasfoundthatelectriccurrentcouldbegeneratedinmetalliccarbonnanotubesimmersedintheliquids.CarbonnanotubesweresynthesizedonSisubstratebyhotfilamentchemicalvapordeposition.Theexperimentalresultsshowedthattheflow-inducedcurrentonthesurfaceofcarbonnanotubefilmswascloselydependedontheflowrate,concentration,propertiesandtemperatureofliquids.Theflow-inducedcurrentwasincreasedwiththeincreasingofflowrate,concentrationandtemperatureofliquids.Theobtainedresultswerediscussedindetail.

简介：EffectsoftheorientationandapexangleonthesettlingvelocityofconicalparticlesinBinghamplas-ticfluidsarenumericallyinvestigatedoveraReynoldsnumberrangeof1≤Re≤100,Binghamnumberrangeof0≤Bn≤100,andconeanglerangeof20≤α≤150°.Governingequations(ofcontinuityandmomentum)aresolvednumericallyusingthefiniteelementmethodtoobtainvelocityandpressurefieldsthatarepostprocessedtoobtainvaluesofthedragcoefficien.Futthermore,theeffectofconeori-entationontheflowfieldisvisualizedandexploredintermsofstreamlinecontoursandthemorphologyofyielded/unyieldedregions.Finally,theobtainedvaluesofdragarecorrelatedviaasimplepredictiveexpressionintermsofthemodifiedReynoldsnumber.Theeffectoftheconeangleondragisfoundtobemoderatebecausethedragforceactingonthelateralsurfaceisasmallfractionoftheoveralldrag.

简介：ThesupersonicductflowwithfixedbackpressuretostagnationpressureratioPb/P0underheatingisinvestigatedanalytically.A“FlowPatternDiagram”Whichconsistsofsixpatternzonesisdeveloped.BythisdiagramtheactualflowstateinsupersonicductflowsystemcanbedeterminedconvenientlywhenPb/Poandheatingintensityareknows.Itisimpossibleforflowwithheavyheatingtobecomesupersonic,eventhoughthepressureratioismuchsmallerthanthecriticalpressureratio,Basedontheanalogybetweenviscouseffectandheatingeffectathermaldragfactorhaseendefined.whichcanpredicttheflowpropertyvariationduetoheatingandtherelaiveimportanceofviscouseffectandheatingeffect.

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：一个维的Bose气体是不平常的超流体。与更高空间的尺寸相对照，非古典的旋转惯性的存在直接没被连接到无穷小的杂质的无驱散的运动。最近，有原子开始了的ultracold的试验性的测试和为drag力量的量的预言由动人的障碍经历了变得可得到。这热门评论讨论在与superfluidity的四轮马车标准的关系从线性反应理论获得的drag力量。基于在之上改进了动态结构因素的分析、数字的理解，不同障碍潜力的结果被获得包括单个杂质，光格子和随机的潜力从点缀模式产生了。在随机的潜力的superfluidity的动态故障在这些系统在与安德森本地化和预言的超流体绝缘体转变的关系被讨论。

简介：Thispaperpresentsastudyondragcoefficientsundertyphoonwindforcingbasedonobservationsandnumericalexperiments.ThefrictionvelocityandwindspeedaremeasuredatamarineobservationplatformintheSouthChinaSea.Threetyphoons:SOULIK(2013),TRAMI(2013)andFITOW(2013)areobservedatabuoystationinthenortheastseaareaofPingtanIsland.Anewparameterizationisformulatedforthewinddragcoefficientasafunctionofwindspeed.Itisfoundthatthedragcoefficient(Cd)increaseslinearlywiththeslopeof0.083?10?3forwindspeedlessthan24ms?1.Toinvestigatethedragcoefficientunderhigherwindconditions,threenumericalexperimentsareimplementedforthesethreetyphoonsusingSWANwavemodel.Thewindinputdataareobjectivereanalysisdatasets,whichareassimilatedwithmanysourcesandprovidedeverysixhourswiththeresolutionof0.125°×0.125°.Thenumericalsimulationresultsshowagoodagreementwithwaveobservationdataundertyphoonwindforcing.Theresultsindicatethatthedragcoefficientlevelsoffwiththelinearslopeof0.012?10?3forhigherwindspeeds(lessthan34ms?1)andthenewparameterizationimprovesethesimulationaccuracycomparedwiththeWu(1982)defaultusedinSWAN.

简介：WaterramjetsusingouterwaterasanoxidizerhavebeendemonstratedasapotentialpropulsionmodeforunderwaterHighSpeedSupercavitatingVehicles(HSSVs)becauseoftheirhigherenergydensity,powerdensity,andspecificimpulse,butwaterfluxchangestheshapesofsupercavity.TouncoverthecavitatordragcharacteristicsandthesupercavityshapeofHSSVswithwaterinflowforramjets,supercavitationflowsaroundadiskcavitatorwithinletholearestudiedusingthehomogenousmodel.Bychangingthewaterinflowintherangeof0-10L/sthroughcavitatorshavingdifferentwaterinletareas,aseriesofnumericalsimulationsofsupercavitationflowswasperformed.Thewaterinflowfluxoframjetssignificantlyinfluencesthedragfeaturesofdiskcavitatorsandthesupercavityshape,butithaslittleinfluenceontheslenderratioofsupercavitaty.Furthermore,asthewaterinletareaincreases,thedragcoefficientofthecavitators'frontfacedecreases,butthisincreasedoesnotinfluencethediameterofthesupercavity'smaximumcrosssectionandthedragcoefficientoftheentirecavitatorsignificantly.Inaddition,withincreasingwaterfluxoftheramjet,boththedragcoefficientofcavitatorsandthemaximumdiameterofsupercavitiesdecreasestably.ThisresearchwillbehelpfulforlayoutoptimizationandsupercavitatyschemedesignofHSSVswithwaterinflowforramjets.

简介：Inthenaturalworld,plantsandanimalshaveevolvedovertimetobestadapttotheenvironment.Theyinteractveryeffectivelywiththesurroundingenvironmentbyexchangingenergiesandmassflowacrosstheircuticlesofspecificmicrostructuresandfunctionstoachieveperfectenergybalance.Suchdifferentfunctionsmayincludethelimitationofuncontrolledlossofwater,protectionfromsolarradiation,microeffectofinducedturbulenceonflowdragreduction,defenceagainstpathogens,changingsurfacewettabilityandhydropho-

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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：DragforcesactingonSchlegel'sblackrockfishSebastesschlegeliwerestudied.AnewdragforcetransducerwasdesignedandusedtomeasurethewaterdragonSchlegel'sblackrockfishinaverticalrecirculatingflumetank.Fourteenindividualswereinvestigated,yieldingtwomeandragcoefficientsreferredtothecross-sectionalareaandvolume2/3respectivelyatwatervelocitiesrangingfrom0.3to1.0ms-1.ThedragcoefficientscanbeusedforestimatingthedragforcesactingonSebastesschlegeliinwater.

简介：NumericalsimulationsandexperimentalresearcharebothcarriedouttoinvestigatethecontrolledeffectofspanwiseoscillatingLorentzforceonaturbulentchannelflow.ThevariationsofthestreaksandtheskinfrictiondragareobtainedthroughthePIVsystemandthedragmeasurementsystem,respectively.Theflowfieldinthenear-wallregionisshownthroughdirectnumericalsimulationsutilizingspectralmethod.Theexperimentalresultsareconsistentwiththenumericalsimulationresultsqualitatively,andboththeresultsindicatethatthestreaksaretiltedintothespanwisedirectionandthedragreductionutilizingspanwiseoscillatingLorentzforcescanberealized.Thenumericalsimulationresultsrevealmoredetailofthedragreductionmechanismwhichcanbeexplained,sincethespanwisevorticitygeneratedfromtheinteractionbetweentheinducedStokeslayerandintrinsicturbulentflowinthenear-wallregioncanmakethelongitudinalvorticestiltandoscillate,andleadstoturbulencesuppressionanddragreduction.