简介:Theanalysisofthedataofmodeltestsoftwolargedeepwharvesandmonographicexperimentalstudiesshowthattwoaspectsaretobeimprovedsoastopredictthewaveupliftforcesonthebottomofacircularcylinder.Thefirstaspectistheupliftpressuredistributiononthebottom,andthesecondisthecorrectdeterminationofthephaseformaximumhorizontalwaveforces.Thesecondproblemhasbeensolved.Synthesizingtheresultsoftheoreticalanalysisandexperiments,wesuggestadiagramforthedeterminationofthephasewhenthemaximumhorizontalwaveforceappears.Onthebasis-efthediagramthesimultaneouswaveupliftforcescanbeobtainedforthestructuralstabilityanalysis.
简介:Basedonthe1stordercnoidalwavetheory,thenonlinearwavediffractionaroundacircularcylinderinshallowwaterisstudiedinthispaper.Theequationofthewavesurfacearoundthecylinderisformulatedandbyusingthisformulathewavesurfaceelevationonthecylindersurfacecanbeobtained.Inthispaper,theformulaforcalculatingthecnoidalwaveforceonacircularcylinderisalsoderived.Forthewaveconditionswhichareoftenencounteredinpracticalengineeringdesigns,theratiosofthenonlinearwaveforcestothelinearwaveforcesarecalculated,andtheresultsareplottedinthispaperfordesignpurposes.Inordertoverifythetheoreticalresults,modeltestsareconducted.Aftercomparingthetestresultswiththetheoreticalones,itisconcludedthat,inshallowwater,forthecaseofTg/d1/2>8-10andH/d>0.3,thecnoidalwavetheoryshouldbeusedtocalculatethewaveactiononacylindricalpier.
简介:Thelarge-diametercylinderstructure,whichismadeoflargesuccessivebottomlesscylindersplacedonfoundationbedorpartlydrivenintosoil,isarecentlydevelopedretainingstructureinChina.Itcanbeusedinport,coastalandoff-shoreworks.Themethodforstabilityanalysisofthelarge-diametercylinderstructure,especiallyforstabilityanalysisoftheembeddedlarge-diametercylinderstructure,isanimportantissue.Inthispaper,anideaispresentedthatis,em-beddedlarge-diametercylinderquayscanbedividedintotwotypes,i.e.thegravitywalltypeandthecylinderpilewalltype.Amethodforstabilityanalysisofthelarge-diametercylinderquayofthecylinderpilewalltypeisdevelopedandamethodforstabilityanalysisofthelarge-diametercylinderquayofthegravitywalltypeisalsoproposed.Theeffectofsig-nificantparametersonthestabilityofthelarge-dianetercylinderquayofthecylinderpilewalltypeisinvestigatedthroughnumericalcalculation.
简介:BothexperimentalandnumericalinvestigationsontheflowpastacylinderundertheinfluenceofLorentzforce(electromagneticforce)wereconductedinanelectricallylow-conductingfluid.TheLorentzforceisappliedbothlocally,whollyandperiodicallyonthesurfaceofthecylinder,andtheircontroleffectsforflowseparationwereinvestigatedBothexperimentalandnumericalresultsshowthatLorentzforcecansuppresstheflowseparationwithLorentzforceappliedonbothlocalandwholesurfaceofthecylinder.However,whentheperiodicandoppositeLorentzforceadopted,thecylinderwakecannotbestabilized.
简介:TheliftforcesonhorizontalcylindernearbottomisexperimentallyinvestigatdeatReynolds(Re)intherangelf2500~10000andKeulegan~CARPENTERNUMBERS(kc)intheintervalof5~20,andgapratio(e/D)isfrom(a0)areanalyzdebyusingtheFourieranalysesmethod.ItisfoundthatfoundthatbothCl&a0arethefunctionslftheKcnumber.
简介:由于胭脂波浪的物理机制的复杂性,rogue-wavestructure相互作用问题的理论学习仍然取得很少进步。为常规形状的结构,然而,给理论分析是可能的,如果流氓波浪的一个相对简单的模型被使用。波浪负担,由作为胭脂波浪的一个直觉的基本模型被知道的一个集中的波浪导致了,在沉没半的柱体之上被学习经分解。集中的波浪由高斯信封波浪是近似的,包含流氓波浪的大多数特征的一个理想的模型。衍射速度潜力通过水平力量的流动地,和公式的分离被导出,弯曲时刻被建议。导出的公式适当地被简化,并且对数字结果通过比较验证了。另外,参数的影响集中的沉没深度和波浪例如集中的度,放,彻底地被调查。
简介:Anumericalstudybasedonawakeoscillatormodelwasconductedtodeterminetheresponseperformanceofvortex-inducedvibration(VIV)onalongflexiblecylinderwithpinned-pinnedboundaryconditionssubjectedtolinearandexponentialshearflows.Thecouplingequationsofastructuralvibrationmodelandwakeoscillatormodelweresolvedusingastandardcentralfinitedifferencemethodofthesecondorder.TheVIVresponsecharacteristicsincludingthestructuraldisplacement,structuralfrequency,structuralwavenumber,standingwavebehavior,travellingwavebehavior,structuralvelocity,liftforcecoefficientandtransferredenergyfromthefluidtothestructurewithdifferentflowprofileswerecompared.ThenumericalresultsshowthattheVIVdisplacementisacombinationofstandingwavesandtravellingwaves.Forlinearshearflow,standingwavesandtravellingwavesdominatetheVIVresponsewithinthelow-velocityandhigh-velocityzones,respectively.Thenegativevaluesofthetransferredenergyonlyoccurwithinthelow-velocityzone.However,forexponentialshearflow,travellingwavesdominatetheVIVresponseandthenegativeenergyoccursalongtheentirelengthofthecylinder.
简介:Amodelbasedonthedatafromforcedvibrationexperimentsisdevelopedforpredictingthevortex-inducedvibrations(VIV)ofelasticallymountedcircularcylindersinflow.Theassumptionsforfreeandforcedvibrationtestsareexploredbriefly.Energyequilibriumistakenintoaccounttosetuptherelationshipbetweenthedynamicresponseofself-excitedoscillationsandtheforcecoefficientsfromforcedvibrationexperiments.Thegapbetweenthesetwocasesisbridgedstraightforwardlywithcarefultreatmentofkeyparameters.Givenreducedmassmandmaterialdampingratioζofanelasticallymountedcircularcylinderinflow,theresponsecharacteristicssuchasamplitude,frequency,lock-inrange,addedmasscoefficient,cross-flowfluidforceandthecorrespondingphaseanglecanbepredictedallatonce.InstanceswithdifferentcombinationofreducedmassandmaterialdampingratioarecomparedtoinvestigatetheireffectsonVIV.Thehysteresisphenomenoncanbeinterpretedreasonably.ThepredictionsandtheresultsfromrecentexperimentscarriedoutbyWilliamson'sgroupareinrathergoodagreement.
简介:AmethodofcoupledBEM-FEManalysisfortheelasticspatialstructuresystemispresented.Itcanbeappliedtothecalculationofthestressanddeformationofthelarge-diamatercylinderstructuresystemanditissuitableforsymmetricornon-symmetricstructuresunderthedistributedorconcentratedload.NumericalexamplesshowthattheproposedmethodandcomputerprogramBEFEMarequiteefficientintheanalysisofthelarge-diametercylinderstructureproblemsinoceanengineering.
简介:Inthispaper,thefocusedwavegroupswithdifferentparametersandtheiractionsonaverticalcylinderareexperimentallystudied.Theharmonicwavecharacteristicsofthefocusingwavesareanalyzedbytheadditionandsubtractionofthecrestandtroughfocusingwaves.Theanalyzedresultsshowthathigherorderharmonicscanbegeneratedbecauseoftheinteractionofcomponentwaves.Nonlinearityincreaseswiththeinputtedwaveamplitudeandthefrequencywidthincrement.Further,thewaverun-uparoundtheverticalcircularcylinderisexperimentallystudied.Itincreaseswiththewavesteepnessandtherelativecylinderdiameterincrease.However,thevariationsofwaverun-uparoundthecircularcylinderaredifferent.Theresearchesprovideareferenceforfurthernumericalstudies.
简介:Inthispaper,theprincipleofmirrorimageisusedtotransformtheproblemofwavediffractionfromacircularcylinderinfrontoforthogonalverticalwallsintotheproblemofdiffractionoffoursymmetricincidentwavesfromfoursymmetricallyarrangedcircularcylinders,andthentheeigenfunctionexpansionofvelocitypotentialandGrafsadditiontheoremareusedtogivetheanalyticalsolutiontothewavediffractionproblem.Therelationofthetotalwaveforceoncylindertothedistancebetweenthecylinderandorthogonalverticalwallsandtheincidenceangleofwaveisalsostudiedbynumericalcomputation.
简介:Thispaperdiscussesnumericalresultsfromthree-dimensionallargeeddysimulationsofanoscillatingcylinderunderprescribedmovementsinuniformflow.Sixcases,namelypurein-line,purecross-flowandtwogroupsof'FigureofEight'oscillationpatternsareunderinvestigationatReynoldsnumberRe=24000.The'FigureofEight'patternineachgroupiswithidenticalshapebutoppositeorbitaldirections.Thenumericalresultsonhydrodynamicforces,higherorderforcecomponents,andvortexsheddingmodesareextensivelystudiedandcomparedwiththemeasuredexperimentaldata.Itisfoundthatthefluidforceinphasewiththevelocity,whichrepresentstheenergytransferbetweenthefluidandthecylinder,hasoppositesignanddifferentmagnitudeduetotheoppositeorbitaldirection.Higherorderforcecomponentsincross-flowdirectionarefoundtooccuratoddnumbertimesoftheoscillatingfrequency,whileevennumbersdominatethehigherorderforcecomponentsinin-linedirection.The2Cand2Tvortexsheddingmodesarewellreproducedduetotheoppositeorbitaldirectioneffect.Comparisonsbetweennumericalandexperimentalresultsindicatethatthepresentnumericalmodelcouldbearationaltoolfortheidentificationofhydrodynamiccoefficientswhicharenormallyappliedinempiricalmodelstopredictthevortex-inducedvibrationsofslendermarinestructures.
简介:ItiswellknownthattheReynoldsnumberhasasignificanteffectonthevortex-inducedvibrations(VIV)ofcylinders.Inthispaper,anovelin-line(IL)andcross-flow(CF)couplingVIVpredictionmodelforcircularcylindershasbeenproposed,inwhichtheinfluenceoftheReynoldsnumberwascomprehensivelyconsidered.TheStrouhalnumberlinkedwiththevortexsheddingfrequencywascalculatedthroughafunctionoftheReynoldsnumber.ThecoefficientofthemeandragforcewasfittedasanewpiecewisefunctionoftheReynoldsnumber,anditsamplificationresultedfromtheCFVIVwasalsotakenintoaccount.TheoscillatingdragandliftforcesweremodelledwithclassicalvanderPolwakeoscillatorsandtheirempiricalparametersweredeterminedbasedonthelock-inboundariesandthepeak-amplitudeformulas.Anewpeak-amplitudeformulafortheILVIVwasdevelopedundertheresonanceconditionwithrespecttothemass-dampingratioandtheReynoldsnumber.Whencomparedwiththeresultsfromtheexperimentsandsomeotherpredictionmodels,thepresentmodelcouldgivegoodestimationsonthevibrationamplitudesandfrequenciesoftheVIVbothforelastically-mountedrigidandlongflexiblecylinders.ThepresentmodelconsideringtheinfluenceoftheReynoldsnumbercouldgenerallyprovidebetterresultsthanthatneglectingtheeffectoftheReynoldsnumber.
简介:Anexperimentalstudyonabareflexiblecylinderaswellascylindersfittedwithtwotypesofcross-sectionedhelicalstrakeswascarriedoutinatowingtank.Themainpurposeofthispaperistoinvestigatetheeffectsofstrakes'crosssectiononthevortex-inducedvibrations(VIV)suppressionofaflexiblecylinder.Thesquare-sectionedandroundsectionedhelicalstrakeswereselectedintheexperimentaltests.Theuniformcurrentwasgeneratedbytowingthecylindermodelsalongthetankusingatowingcarriage.TheReynoldsnumberwasintherangeof800–16000.Thestrainresponsesweremeasuredbythestraingagesincross-flow(CF)andin-line(IL)directions.Amodalanalysismethodwasadoptedtoobtainthedisplacementresponsesusingthestrainsignalsindifferentmeasurementpositions.Thecomparisonoftheexperimentalresultsamongthebarecylinder,square-sectionedstrakedcylinderandroundsectionedstrakedcylinderwasperformed.Thehelicalstrakescaneffectivelyreducethestrainamplitude,displacementamplitude,responsefrequenciesanddominantmodesofaflexiblecylinderexcitedbyVIV.Andthemeandragcoefficientsofstrakedcylinderswereapproximatelyconsistentwitheachother.Inaddition,thesquaresectionedandround-sectionedstrakesnearlysharethesimilarVIVreductionbehaviors.Sometimes,thestrakeswithround-sectionrepresentmoreexcellenteffectsontheVIVsuppressionofresponsefrequencythanthosewithsquaresection.
简介:柱体的垂直摆动与不同直径比率Dd/Dc和厚度比率td/Dc被3D学习(三维)在这份报纸开发的数字模型,并且通过2D与结果相比获得了(二维)数字模型。高顺序的迎风的计划被使用稳定计算,并且集中被多格子方法加速。2D和3D模拟结果之间的差别的质、量的分析与一个依附底部的磁盘在流动地特征和垂直地震荡的柱体的水动力学系数上揭示3D效果。液体领域上的3D效果主要在三个流旋涡的模式的意义被反映:x相对在2D模拟产生的旋涡在锋利的边附近在流动地上有更大的效果。在沿着轴的取向的片,沿着光线的轴的y比沿着环绕的方向的x,更在速度上显示光线的效果在磁盘的锋利的边附近比环绕的效果读了。旋转相互作用在水平飞机的液体的z在举运动期间是不足道的。基于2D和3D模拟结果,分开增加的集体系数和抑制比率的增加的政体的转弯的点被识别。直径比率Dd/Dc和厚度比率td/Dc详细被讨论。