简介:竖轴固定偏角直叶片潮流水轮机的自启动能力较差。文章根据模型试验的观测分析,利用Fluent软件模拟计算在不同水流速度下叶片在圆周不同位置时的潮流水轮机自启动性能,并与加装叶柵附体的水轮机进行比较,得出加装叶柵附体可以提高水轮机的自启动性及水轮机的水动力性能。
简介:TheReynolds-averagedNavier-Stokes(RANS)method,alongwiththeFluentsoftwarepackage,wasusedtostudythesteadyandunsteadyinteractionofpropellersandrudderswithadditionalthrustfins.Theslidingmeshmodelwasemployedtosimulateunsteadyinteractionsbetweentheblades,therudderandthethrustfins.Basedonthenumericalresults,thepressuredistributiononthepropellerandtheefficiencyofthefinswerecalculatedasafunctionoftheattackangle.TheRANSresultswerecomparedwithresultscalculatedbythepotentialmethod.ItwasfoundthattheresultsforthepotentialmethodandtheRANSmethodhavegoodconsistency,buttheyyieldmaximumefficienciesforthefins,andthuscorrespondingattackangles,thatarenotidentical.
简介:Acomplianttowerismodeledasapartiallydry,partiallytapered,dampedTimoshenkobeamwiththesuperstructuremodeledasaneccentrictipmass,andanon-classicaldampedboundaryatthebase.Thefoundationismodeledasacombinationofalinearspringandatorsionalspring,alongwithparallellinearandtorsionaldampers(Kelvin-Voigtmodel).Thesuperstructureaddstothekineticenergyofthesystemwithoutaffectingthepotentialenergy,therebyreducingthenaturalfrequencies.Theweightofthesuperstructureactsasanaxialcompressiveloadonthebeam,reducingitsnaturalfrequenciesfurther.Theemptyspacefactorduetothetruss-typestructureofthetowerisincluded.Theeffectofsheardeformationandrotaryinertiaareincludedinthevibrationanalysis;withthenon-uniformbeammode-shapesbeingaweightedsumoftheuniformbeammode-shapessatisfyingtheendcondition.TheweightsareevaluatedbytheRayleigh-Ritz(RR)method,andverifiedusingfiniteelementmethod(FEM).Theweightofthesuperstructureactsasanaxialcompressiveloadonthebeam.Kelvin-Voigtmodelofstructuraldampingisincluded.Apartofthestructurebeingunderwater,thevirtualaddedinertiaisincludedtocalculatethewetnaturalfrequencies.Aparametricstudyisdoneforvariousmagnitudesoftipmassandvariouslevelsofsubmergence.ThecomputationalefficiencyandaccuracyoftheRayleigh-Ritzmethod,ascomparedtotheFEA,hasbeendemonstrated.Theadvantageofusingclosed-formtrialfunctionsisclearlyseenintheefficacyofcalculatingthevariousenergycomponentsintheRRmethod.