简介:Smoothedparticlehydrodynamics(SPH)isaLagrangianmeshlessparticlemethod.Itisoneofthebestmethodforsimulatingviolentfreesurfaceflowsinfluidsandsolvinglargefluiddeformations.Dambreakingisatypicalexampleoftheseproblems.ThebasisofSPHwasreviewed,includingsometechniquesforgoverningequationresolution,suchasthesteppingmethodandtheboundaryhandlingmethod.Thennumericalresultsofadambreakingsimulationwerediscussed,andthebenefitsofconceptslikeartificialviscosityandpositioncorrectionwereanalyzedindetail.Whencomparedwithdambreakingsimulatedbythevolumeoffluid(VOF)method,thewaveprofilegeneratedbySPHhadgoodagreement,butthepressurehadonlyreasonableagreement.Improvingpressureresultsisclearlyanimportantnextstepforresearch.
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.