简介:Thispaperpresentsreal-timemonitoringdataandanalysisresultsofthenon-stationaryvibrationsofanoperationalwindturbine.Theadvancedtime-frequencyspectrumanalysisrevealsvariednon-stationaryvibrationswithtimevaryingfrequencies,whicharecorrelatedwithcertainsystemnaturalmodescharacterizedbyfiniteelementanalysis.Undertheeffectsofstrongwindload,thewindturbinesystemexhibitscertainresonancesduetobladepassingexcitations.Thesystemalsoexhibitscertaininstabilitiesduetothecouplingofthetowerbendingmodesandbladeflapwisemodewithbladepassingexcitationsunderthevariationofwindspeed.Ananalyticalmodelisusedtoelaboratethenon-stationaryandinstabilityphenomenaobservedinexperimentalresults.ThepropertiesofthenonlinearinstabilitiesareevaluatedbyusingLyapunovexponentestimation.
简介:Windshearreflectsthatthewindfieldisnotuniform,whichisoneoftheprimaryfactorswhichmaketheretrievalofthewindfielddifficult.Basedonvolumevelocityprocess(VVP)windfieldretrievaltechnique,theintensityofwindshearisidentifiedinthispaper.Afteranalyzingthetraditionaltechniquesthatrelyonthedifferenceofradialvelocitytoidentifywindshear,afixeddifferenceamongradialvelocitiesthatmaycausefalseidentificationinauniformwindfieldwasfound.Becauseofthenon-uniformityinwindshearareas,thedifferenceofretrievedresultsbetweensurroundinganalysisvolumescanbeusedasameasurementtoshowhowstrongthewindshearis.AccordingtotheanalysisofasevereconvectiveweatherprocessthatoccurredinGuangzhou,itcanbefoundthattheareasofwindshearappearedwiththestrengthsignificantlylargerthaninotherregionsandthemagnitudegenerallylargerthan4.5m/(s·km).Besides,bycomparingthevariationofwindshearstrengthduringtheconvection,itcanbefoundthatnewcellswillbemorelikelytogeneratewhenthestrengthisabove3.0m/(s·km).Therefore,theanalysisofstrongwindshear'smovementanddevelopmentishelpfultoforecastingsevereconvections.
简介:Thegeophysicalmodelfunction(GMF)describestherelationshipbetweenabackscatteringandaseasurfacewind,andenablesawindvectorretrievalfrombackscatteringmeasurements.ItisclearthattheGMFplaysanimportantroleinanoceanwindvectorretrieval.TheperformanceoftheexistingKu-bandmodelfunctionQSCAT-1isconsideredtobeeffectiveatlowandmoderatewindspeedranges.However,intheconditionsofhigherwindspeeds,theexistingalgorithmsdivergealarmingly.owingtothelackofinsitudatarequiredfordevelopingtheGMFforthehighwindconditions,theQSCAT-1appearstooverestimatethes0,whichresultsinunderestimatingthewindspeeds.Severalmatch-upQuikSCATandspecialsensormicrowave/imager(SSM/I)windspeedmeasurementsofthetyphoonsoccurringinthewestPacificOceanareanalyzed.TheresultsshowthattheSSM/Iwindexhibitsbetteragreementwiththe'besttrack'analysiswindspeedthantheQuikSCATwindretrievedusingQSCAT-1.Onthebasisofthisevaluation,acorrectionoftheQSCAT-1modelfunctionforwindspeedabove16m/sisproposed,whichusesthecollocatedSSM/IandQuikSCATmeasurementsasatrainingset,andaneuralnetworkapproachasamultiplenonlinearregressiontechnologytechnology.InordertovalidatetherevisedGMFforhighwinds,themodifiedGMFwasappliedtotheQuikSCATobservationsofHurricaneIOKE.ThewindestimatedbytheQuikSCATforTyphoonIOKEin2006wasimprovedwiththemaximumwindspeedreaching55m/s.AnerroranalysiswasperformedusingthewindfieldsfromtheHollandmodelasthesurfacetruth.TheresultsshowanimprovedagreementwiththeHollandmodelwindwhencomparedwiththewindestimatedusingtheQSCAT-1.However,largebiasstillexisted,indicatingthattheeffectsofrainmustbeconsideredforfurtherimprovement.
简介:ThisstudyinvestigatedtheflowcharacteristicsalteredbyJangBogoAntarcticResearchStationusingcomputationalfluiddynamics(CFD)modeling.ThetopographyandbuildingsaroundJangBogoStationwereconstructedwithcomputeraided-designdataintheCFDmodeldomain.Wesimulated16caseswithdifferentinflowdirections,andcomparedtheflowcharacteristicswithandwithoutJangBogoStationforeachinflowdirection.Thewinddatarecordedbythesite’sautomaticweatherstation(AWS)wereusedforcomparison.WindroseanalysisshowedthatthewindspeedanddirectionaftertheconstructionofJangBogoStationwerequitedifferentfromthosebeforeconstruction.Wealsoinvestigatedhowvirtualwindfenceswouldmodifytheflowpatterns,changingthedistanceofthefencefromthestationaswellastheporosityofthefence.Forwesterlyinflows,whentheAWSwasdownwindofJangBogoStation,thedecreaseinwindspeedwasmaximized(-81%forwest-northwesterly).ThewindspeedreductionwasalsogreaterasthedistanceofthefencewasclosertoJangBogoStation.Withthesamedistance,thefencewithmediumporosity(25%–33%)maximizedthewindspeedreduction.Theseresultssuggestthatthelocationandmaterialofthewindfenceshouldbeselectedcarefully,orAWSdatashouldbeinterpretedcautiously,forparticularprevailingwinddirections.
简介:Withtheadvancesof数字天气模拟和更新的减少的数据吸收骑车,表面观察数据吸收在数据吸收系统变得越来越重要。一个更好的数据吸收系统应该在表面层包含热力学的进程的限制,这广泛地被接受。在这份报纸,因此,一个新表面风观察操作员在全球、地区性的吸收预言System_3D变化(GRAPES_3D-Var)被利用,与在行星的边界层(PBL)的热力学的过程的限制。为了研究这新表面的能力,在吸收弯屈观察操作员并且预报,一系列实验被使用GRAPES模型操作。主要结果显示表面风观察操作员的这个新方法与GRAPES模型一起在预报上有积极影响。
简介:Windspeedscalinginsimilaritylawinwind-generatedwavesandthedragcoefficientarestudied.Inanalyzingthedatainthewindwavechannel,itisfoundthattheu.scalinggreatlyreducesthescatterintheU10scaling.Theu.scalinghasmuchlessscatterthanthescalingusingotherwindspeeds.Thefrictionvelocityseemstoplayadistinctiveroleinwavegrowth.Theresultisimportantintheapplicationsofthesimilaritylawandinwavemodeling.Intheoryitgivesaninsightintothemechanismofwindwaveinteraction.Itisfoundthatwavesteepnessisimportantininfluencingthedragcoefficient.Thevariabilityofthecoefficientsinthecurrentlywidelyuseddragformcanbeexplainedbythedifferencesinwavesteepnessintheobservations.Adragcoefficientmodelwithwindspeedandwavesteepnessasparametersisproposed.AnexplanationforKahma'sresultthattheu.scalingdoesnotreducethescatterintheU10scalingisgiven.
简介:AnellipticalwindfieldmodeloftyphoonsisputforwardbasedonthecharacteristicsofthetyphoonwindfieldsoccurringintheYellowSeaandBohaiSea.Bycontrastingitwiththecirculartyphoonwindfieldmodel,itisfoundthattheellipticalmodelcanadequatelyrepresenttherealwindfieldandtracetheprocessofatyphoonstormsurge.Thenumericallysimulatedresultsofstormsurgesbyusingtheellipticalmodelareingoodagreementwiththeobservationsandmarkedlybetterthanthosebyusingthecircularmodel.
简介:Themainintentionofthepresentstudyistoreducewind,wave,andseismicinducedvibrationsofjackettypeoffshorewindturbines(JOWTs)throughanewlydevelopedvibrationabsorber,calledtunedliquidcolumngasdamper(TLCGD).UsingaSimulink-basedmodel,ananalyticalmodelisdevelopedtosimulateglobalbehaviorofJOWTsunderdifferentdynamicexcitations.ThestudyisfollowedbyaparametricstudytoexploreefficiencyoftheTLCGDintermsofnacelleaccelerationreductionunderwind,wave,andearthquakeloads.StudyresultsindicatethatoptimumfrequencyoftheTLCGDisratherinsensitivetoexcitationtype.Inaddition,whilethegaininvibrationcontrolfromTLCGDswithhighermassratiosisgenerallymorepronounced,heavyTLCGDsaremoresensitivetotheirtunedfrequencysuchthatill-regulatedTLCGDwithhighmassratiocanleadtodestructiveresults.ItisrevealedthatawellregulatedTLCGDhasnoticeablecontributiontothedynamicresponseoftheJOWTunderanyexcitation.
简介:Spectralcharacteristicsofwind-generatedwavesinlabortaoryarepresentedonthebasisofasystematicmeasurementinalarge-scalewind-wavechannelandcomparedwiththoseinthefield.Ama-rkedcharacteristicsofthemeasuredspetraistheexistenceofsecondaryspectrum-peak.Thedependenceofspectralpeak-frequency,peak-valueandzeroth-ordermomentonwindspeedandfetcharepresentedandfoundroughlysimilartothoseinthefieldrepresentedbytheJONSWAPspectrum,regardlessofthedifferencesincoefficient.Thespectralslopeβathigh-frequenciesarefoundsomewhatgreaterthanthoseoffieldwind-wavesinbothcasesofdeepandshallowwaters.Exceptforthelow-frequencypart,thespec-tralformsmeasuredindifferentwindconditionsaresimilarandfitfortheJONSWAPspectrumwithγ=6andβ=5.5.Somerelevantproblemsarediscussed.
简介:Bytheuseofthe3/2powerlawpresentedbyTobacombinedwiththesignificantwaveenergybalanceequationforwindwave,windwavegrowthatalimitedfetchisanalyticallyinvestigated.Thenewwindwavegrowthrelations(WWGRs)areanalyticallyderivedwithshelteringcoefficientandwinddragcoefficientasparameters.Thegeometricalaverageofobservationalvaluesofshelteringcoefficientandthearithmeticaverageofobservationalvaluesofwinddragco-efficientareappliedtodeterminethenewWWGRs.ComparisonswithexistingempiricalWWGRsaremade.
简介:由风和水的复杂侵蚀,是也叫的aeolian-fluvialinteractions,在干旱、半干旱的区域是一个重要侵蚀过程和风景。在风和水过程,空间环境转变和时间的环境变化之间的连接的Theeffectiveness是决定风神河的相互作用的geomorphologicsignificance的三个主要驱动力。作为互连的建筑群和内部联合系统,由风和水的复杂侵蚀有空间时间的变化特征。由风和水的复杂侵蚀的过程能被划分成palaeoenvironmental过程和当代的过程。在干燥陆地的早工作经常被归因于倡导an'aeolianist'或一个“河成论者”的二所学校之一观点,因此是直到1930年代关于由风和水的复杂侵蚀的研究被进行了。有二个障碍,由风和水限制复杂侵蚀的研究。第一,怎么在不同时间、空间的规模转变仍然是未解决的;并且第二,研究方法论仍然是不成熟的。以后,侵蚀,在风中的复域土壤侵蚀度和水蚀愿望的机制和控制是关于由风和水的复杂侵蚀的研究的焦点。
简介:-Driftcurrentinducedbywindandwavesisinvestigatedwithphase-averagedNavier-StokesequationinwhichtheReynoldsstressisclosedbyk-εmodel.Thegoverningequationsaresolvedbythefinitevolumemethodinasystemofnonorthogonalcoordinateswhichisfittedtothephase-averagedwavesurface.Thepredicteddriftcurrentisfairlyreasonableandthedragcoefficientofsea-surfacepredictedwiththenewlydevelopedinterfaceconditionsshowsgoodagreementwithpreviousmeasurementswhenbreakingwavesdonotexist.
简介:在这研究,越过从1956~2004的中国的最大的风速度(WSmax)变化基于观察车站数据被分析,并且为20462065和20802099的WSmax的变化用三个全球气候模型被投射(GFDL_CM2_0,CCCMA_CGCM3,并且MRI_CGCM2)那参予了IPCC第四份评价报告(AR4)。观察到年度、季节的WSmax和强风天的频率显示出明显的衰退趋势。年度WSmax每十年由约1.46ms1减少了,并且强风天的数字从1956~2004每十年到3.0天减少了。年度、季节的WSmax减少的振幅比年度、季节的平均的风速度(WSavg)的那些大。变弱东方亚洲冬季和夏天季风在整个中国上是为WSmax和WSavg的不同减少的原因。在东南的WSmax的减少中国的沿海的区域与在中国和减少的数字的冷波浪的减少的紧张有关(并且减少的紧张)land-falling,台风在西北太平洋发源。全球气候模型GFDL_CM2_0,MRI_CGCM2,和EBGCM(上面的整体提及三个全球气候模型)一致地建议年度、季节的WSmax价值将相对19812000在20462065和20802099期间减少。模型也建议在为整个中国的WSmax的减少在20462065和20802099期间与冷波浪的减少的紧张和冬季季风的减少的紧张有关,并且在在东南的WSmax的减少中国的沿海的区域在一样的时期期间相应于在在夏天的西北太平洋上的热带气旋的减少的数字。
简介:Athree-dimensionalnumericalmodel,EFDC(environmentalfluiddynamicscode)isappliedtothePamlicoRiverEstuary(PRE)ineasternNorthCarolinaoftheUnitedStatestoexaminethewindimpactonpollutantagedistributionsandresidencetime.Aseriesofmodelexperimentsrepresentingbasecase,remote-wind-inducedwaterlevelset-upandlocalwindscasesareconducted.ModelresultsindicatethatthepollutantmeanageandthesystemresidencetimearefunctionsofgravitationalcirculationinthePRE.Thesystemresponsestoremote-wind-inducedwaterlevelset-uparedifferentindifferentportionsofthePRE.Undersuchcondition,dissolvedsubstancesintheupstreamportionofthePREhaveayoungerageandshorterresidencetime(comparedwiththebasecase),bycontrast,theyhaveaolderageandlongerresidencetimeinthedownstreamportionofthePRE.Upriveranddownriverlocalwindsappeartohaveoppositeimpactsonpollutantagedistributions.ThesubstancesareretainedmuchlongerwithinthePREunderupriverwindthanthoseunderdownriverwind.Themodelresultsalsosuggestthatacross-riverwindsmayleadtolongerresidencetimethroughenhancedturbulencemixing,whichslowsdownthegravitationalcirculationinthePRE.
简介:CallaghanandWhite(2009)putforwardtheautomatedwhitecapextraction(AWE)techniquetodeterminethewhitecapcoverage(W).AnimprovedAWEwasusedtoanalyzeimagescollectedintheSouthChinaSeaduring2012and2013andinwesternPacificduring2015todetermineW.Theinfluencesofmeteorologicalandoceanographicfactorsonwhitecapcoveragewereinvestigatedinthisstudy.ItisfoundthatWincreaseswithwindspeed.ScalefactorandexponentofparameterizationforW(U10)varygreatlyindifferentmodels.Overall,thereisalargerscatterofWatlowwindspeedthanathighwindspeed.Wdecreaseswiththeincreasingofwaveage.Comparedwithwindspeed,thescatterofWissmallerwithwaveage,whichmeanstheimpactofwaveageonthewhitecapcoverageismorerobustundervariousenvironmentalconditions.ThereisnosignificantdependenceonSSTandwhitecapcoverageseemstoweaklydecreasewithSST.Wdecreaseswiththeatmosphericstability.RelationshipbetweenWandwindspeedchangewhenswellsaredominant.SwellcansuppresswavebreakinganddecreaseW.Theeffectisindependentofthedeflectionanglebetweenwindwaveandswell.
简介:MultivariateObjectiveAnalysisofWindandHeightFieldsintheTropicsS.K.Sinha,S.G.NarkhedkarandS.Rajamani(IndianinstituteofTropical...