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简介：Thenatureofthethree-dimensionaltransitionarisingintheflowpastacylinderisinvestigatedbyapplyingtheLifschitz-HameiritheoryalongspecialLagrangiantrajectoriesexistinginitswake.ResultsshowthatthevonKarmanstreetisunstablewithregardtoshort-wavelengthperturbations.Theasymptoticanalysispredictsthepossibleexistenceofbothsynchronous(asmodesAandB)andasynchronous(asmodeC)instabilities,eachassociatedtospecificLagrangianorbits.Theproposedstudyprovidesusefulqualitativeinformationontheoriginofthedifferentmodesbutnoquantitativeagreementbetweenthegrowthratespredictedbytheasymptoticanalysisandbyaglobalstabilityanalysisisobserved.Thereasonsforsuchmismatcharebrieflydiscussedandpossibleimprovementstothepresentanalysisaresuggested.

简介：把在一般计算液体动力学代码FLUENT6.3.26嵌入的二阶段的模型基于液体的体积，粘滞有在一艘可伸缩模型的KRISO容器轮船(KCS)附近的免费表面的流动数字地首先被模仿。然后与一个rigid-lid-free-surface方法，在水下流动地基于混合被计算模仿的多相的模型冒泡在KCS壳附近醒来。二方程的骚乱模型和雷纳兹应力建模的可实现的k-被用来在轮船上分析骚乱模型的效果冒泡醒来。空气乘火车模型，它相对免费表面的正常速度坡度，和解决的方法被品质上验证合理计算结果。

简介：Thephysicalmechanismforgenerationofstreamwisevortices(orribvortices)inthecylinderwakeisnumericallyinvestigatedwithafinite-differencescheme.Rayleigh’stheoryofcentrifugalinstabilityforinviscidaxisymmetricflowisextendedtoanalyzethe2-Dprimaryflows.Accordingly,ananalyticaldimensionlessgroupRay=-(r/vθ)■vθ/■r-1isderived,wherevθrepresentsthevelocityofafluidelementrelativetotheoncomingflow,risthelocalcurvatureradiusoftheelementpathline.CentrifugalinstabilityoccurswhenRay>0.StabilityanalysesarecarriedoutwiththisdiscriminantforprimaryflowsatdifferenttimelevelsinahalfsheddingperiodofthevonKarman(orvK)vortices.UnstableareasareidentifiedandthelocationsofribvorticesarecoincidentwellwiththeunstableareaswithinthefirstwavelengthofvKvorticesbehindthecylinder.Thenumericalresultsalsoshowthatribvorticesexperienceamplificationinthisregion.Itisapparentthatcentrifugalinstabilityplaysanimportantroleinthegenerationofribvorticesinthecylinderwake.

简介：Alargeamountofexperimentalworkhasbeencarriedoutinthepasttounderstandmeanandfluctuatingforcesonasinglecircularcylinderincrossflows.Incomparisonsubstantiallylessworkcanbefoundontheinterferencebetweenmultiplecylindersandthenumberofpublicationsavailablebecomesdrasticallysmallerasthenumberofcylindersinvolvedincreases.Thecurrentexperimentalworksystematicallyexaminesthewakeshieldingeffectsofthreecylindersinatowingtank.Thoughstaggered,thethreecylindersarearrangedmainlyalongtheflowdirectionwiththedownstreamcylinderssituatinginthewakesoftheupstreamcylinders.Thetestsaremainlycarriedoutinthesub-criticalReynoldsnumberregimewiththeupperendclosetothecriticalReynoldsnumberregime.Significantdragreductionondownstreamcylindersisidentified.

简介：俗说说春困秋乏．在这个忽冷忽热的季节．我们的身体会因为适应不良而出现反应，皮肤也是如此，一到这个季节就会出现过敏、起皮、发黑等一些现象，就像总也睡不醒一样．但本应生机勃勃的春季怎么可以被“困”打败呢．这回就让Nancy老师带美眉们一起来一次扫“重”大行动吧！

简介：Thepresentworkusesdynamicmodedecomposition(DMD)toanalyzewakeflowofNACA0015airfoilwithGurneyflap.ThephysicsofDMDisfirstintroduced.ThenthePIV-measuredwakeflowvelocityfieldisdecomposedintodynamicalmodes.Thevortexsheddingpatternbehindthetrailingedgeanditshigh-orderharmonicshavebeencapturedwithabundantinformationsuchasfrequency,wavelengthandconvectionspeed.Itisobservedthathigh-orderdynamicmodesconvectfasterthanlow-ordermodes;moreoverthewavel...

简介：Wake-upLight在距离你设定的时间还剩30分钟时，就会启动，模拟出黎明日出的效果，一点一点地驱走你卧室里的黑暗。有了它，你每天早上就不会再被刺耳的闹铃声吵醒．取而代之的是在温暖明媚的阳光中慢慢醒来。

简介：Wecomputethewakeofatwo-dimensionalandthree-dimensionalflexiblefininanunsteadyflowfieldwithheavingandpitchingmotionsusingFLUENT.Deflexionmodeisusedforanon-uniformcantileverbeamwithnon-uniformlydistributedload.Theeffectofchordwisedeflexionlengthonthecharacteristicsofpropulsionisdiscussedfortwo-dimensionalflexiblefin.Thethrustcoefficientdecreases,propulsiveefficiencyincreasesandtheintensityofturbulenceattenuatesgraduallyasthedeflexionlengthincreases.Forathree-dimensionalflexiblefin,theintensityofthevortexintheplaneofsymmetryishigherthanthatintheplaneat3/4spanlengthofthecaudalfin.Butthepropulsiveperformanceachievedisnotwhatweexpectedwiththegivendeflexionmode.

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简介：Thepresentpaperderivedtemperaturedistributionsinpowerseriesinasteadylaminarwakebehindaslenderstreamilinedheatedbodyofrevolution.Thetemperaturedistributionofthewakebehindthebodyfromx/d=2to70werefullyexploredusingarecirculatingwaterchannel.ThethermalwakepatternsbehingthebodywerevisualizedwiththeaidofinfraredpicturesandH2bubbles.

简介：SyntheticApertureRadar(SAR)imagingofoceansurfacefeaturesisstudied.ThesimulationoftheturbulentandvorticalfeaturesgeneratedbyamovingshipandSARimagingofthesewakesiscarriedout.Theturbulentwakedampingtheoceansurfacecapillarywavesmaybepartiallyresponsibleforthesuppressionofsurfacewavesneartheshiptrack.Thevortexpairgeneratingachangeinthelateralflowfieldbehindtheshipmaybepartiallyresponsibleforanenhancementofthewavesneartheedgesofthesmootharea.Thesehydrodynamicphenomenaaswellasthechangesofradarbackscattergeneratedbyturbulenceandvortexaresimulated.AnSARimagingmodelisthenusedonsuchoceansurfacefeaturestoprovideSARimages.Comparisonoftwoships'simulatedSARimagesshowsthatthewakefeaturesaredifferentforvariousshipparameters.

简介：Intensiveturbulenceexistsinthewakesofhighspeedtrains,andtheaerodynamicperformanceofthetrailingcarcoulddeterioraterapidlyduetocomplicatedfeaturesofthevorticesinthewakezone.Asaresult,thesafetyandamenityofhighspeedtrainswouldfaceagreatchallenge.Thispaperconsidersmainlythemechanismofvortexformationandevolutioninthetrainflowfield.ArealCRH2modelisstudied,withaleadingcar,amiddlecarandatrailingcarincluded.Di?erentrunningspeedsandcrosswindconditionsareconsidered,andtheapproachesofunsteadyReynold-averagedNavier–Stokes(URANS)anddetachededdysimulation(DES)areutilized,respectively.ResultsrevealthatDEShasbettercapabilityofcapturingsmalleddiescomparedtoURANS.However,forlargeeddies,thee?ectsoftwoapproachesarealmostthesame.Inconditionswithoutcrosswinds,twolargevortexstreetsstretchfromthetrainnoseandinteractstronglywitheachotherinthewakezone.Withthereinforcementoftheground,acomplicatedwakevortexsystemgeneratesandbecomesstrengthenedastherunningspeedincreases.However,thelocationsofflowseparationsonthetrainsurfaceandtheseparationmechanismkeepunchanged.Inconditionswithcrosswinds,threelargevorticesdevelopalongtheleewardsideofthetrain,amongwhichtheweakestonehasnoobviousinfluenceonthewakeflowwhiletheothertwostretchtothetailofthetrainandcombinewiththehelicalvorticesinthetrainwake.Thus,optimizationoftheaerodynamicperformanceofthetrailingcarshouldbeaimingatreducingtheintensityofthewakevortexsystem.

简介：由于山论的阻塞，弱风醒来在华南海发生在夏天离开东北越南。在风下面醒来，温暖的水从两个高分辨率的卫星数据和水道学的观察被观察。温暖的水的wake在6月形成，继续在7月和8月成熟，开始在9月腐烂，并且消失在10月。温暖的水也弄醒表演柔韧日报它在日子期间加强并且在夜里变弱的变化。温暖的水醒来能通过导致风的混合被产生并且热(潜伏的热流动)过程。在这份报纸，一个混合的层模型被用来分别地在季节、日报的timescales上评估二个过程的相对重要性。结果比导致风的混合在季节的timescale上处理的证明热过程做更大的贡献到wake，当时温暖的水醒来被导致风的混合统治过程在上一日报timescale。

简介：TheintrinsicphysicalrelationshipofvorticitybetweenmodesAandBinthethree-dimensionalwaketransitionisinvestigated.Directnumericalsimulationsfortheflowpastasquare-sectioncylinderarecarriedoutatReynoldsnumbersof180and250,associatedwithmodesAandB,respectively.Basedontheanalysisofspacialdistributionsofvorticityinthenearwake,characteristicsoftheverticalvorticityinmodesAandBareidentified.Moreover,therelationshipofthreevorticitycomponentswithspecificsignsissummarizedintotwosignlaws,asintrinsicphysicalrelationshipsbetweentwoinstabilitymodes.Bythetheoryofvortex-inducedvortex,suchtwosignlawsconfirmthattherearetwoandonlytwokindsofvortex-sheddingpatternsinthenearwake,justcorrespondingtomodesAandB.Inbrief,alongthefreestreamdirection,modeAcanbedescribedbytheparallelsheddingverticalvorticeswiththesamesign,whilemodeBisdescribedbytheparallelsheddingstreamwisevorticeswiththesamesign.Finally,itisfoundoutthatthe-typevortexisabasickindofvortexstructureinbothmodesAandB.

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简介：Movingshipsproduceasetofwavesof"V'patternontheocean.ThesewavescanoftenbeseenbySyntheticApertureRadar(SAR).Thedetectionofthesewakescanprovideimportantinformationforsurveillanceofshipping,suchasshiptravelingdirectionandspeed.AnovelapproachtothedetectionofshipwakesinSARimagesbasedonfrequencydomainisprovidedinthisletter.ComparedwithtraditionalRadon-basedapproaches,computationisreducedby20%-40%withoutlosingnearlyanyofdetectionperformance.ThetestingresultsusingrealdataandsimulationofsyntheticSARimagestestthealgorithm'sfeasibilityandrobustness.

简介：TheresultsofplaneturbulentwakegivenbyChouPeiyuanareconsideredasthefirstorderap-proximationandputintotheequationsofturbulentfluctuation.Theequationsaresolvednumericallywithintherangeofmicro-scalebymeansofspectrummethod.Thedouble,tripleandquadruplefluctuatingvelocitycorrelationsareobtainedbycomputation.Theyareingoodagreementwithexperimentalresults.

简介：Theflowbehindathree-dimensionalrotationallyoscillatingcircularcylinderwasstudiedbyanumericalmethod.ThecomputationswereperformedataReynoldsnumberof260,whichisatalevelthattheflowwakehasdevelopedintoathree-dimensionalstatecalledMode-B.Thepurposeofthispaperistoexaminetheinfluenceofvariousrotationalamplitudes(0.1-0.7)onthewakeinstabilityoftheflow,whiletheoscillationfrequencyisfixedtothevalueofthatmeasuredinthewakeofastationarycylinder.Theresultsshowthattherotationwithsufficientlyhighamplitudebringstheflowbacktoitsnominaltwo-dimensionalstate.Moreover,itisfoundthatthevalueofthetime-averageddragandtheRMSvalueoftheliftarelargerthanthoseofastationarycircularcylinder.