简介:AtestrigisbuilttomodelthedynamicresponseofsubmarinepipelineswithanunderwatershakingtableintheStateKeyLaboratoryofCoastalandOffshoreEngineering,DalianUniversityofTechnology,China.Modeltestsarecarriedouttoconsidertheeffectsofexcitingwavedirectionsandtypes.Basedontheexperimentalresults,twohydrodynamicforcemodelsderivedfromMorisonequationandWakemodelarepresentedrespectively.Byuseofhydrodynamicforcemodelssuitableforfreespanningsubmarinepipelinesunderearthquakes,discretizedequationsofmotionareobtainedandfiniteelementmodelsareestablishedtoanalyzedynamicresponseoffreespanningsubmarinepipelinesubjectedtomulti-supportseismicexcitations.ThecomparisonofnumericalresultswithexperimentalresultsshowsthattheimprovedMorisonandWakehydrodynamicforcemodelscouldsatisfactorilypredictdynamicresponseonthefreespanningsubmarinepipelinessubjectedtoearthquakes.
简介:Ahigher-efficientthree-dimensionalnon-hydrostaticmodelisdevelopedtosimulatesmallamplitudefreesurfaceflowsbasedonastaggeredunstructuredgrid.Inthismodel,afractionalstepalgorithmisadoptedtosolvetheNavier-Stokesequationsintwomajorsteps.Atop-layerpressuremethodisproposedtominimizethenumberofverticallayersandsubsequentlythecomputationalcost.Threeclassicalexamplesofsmallamplitudefreesurfaceflowsareusedtodemonstratethecapabilityandefficiencyofthemodel.Thesatisfactoryresultsdemonstratedthecapabilityandefficiencyofmodellingarangeofsmallamplitudefreesurfaceflowswithonlyasmallnumberofverticallayers.
简介:Theproblemofconstructingamodelreferenceadaptivecontrollawforanuncertain1-dimensionalparabolicsystemisconsideredinthisarticle.Thecontrollerdesignedhereinvolvesonlytheplantstatebutnoitsderivatives.Aprioriboundsontheplant'suncertainparametersareusedtoproposeswitchinglawswhichserveasanadaptivemechanism.Theexponentialdecaytozeroofthestateerrorwithanyprescribedrateisguaranteedbychoosingacontrollerparametercorrespondingly.Numericalstudiesarealsopresentedtoillustratetheapplicabilityofthecontrollaw.
简介:Thethree-dimensionalNavier-Stokesequationsweresolvedwiththefractionalstepmethodwherethehydrostaticpressurecomponentwasdeterminedfirst,whilethenon-hydrostaticcomponentofthepressurewascomputedfromthepressurePoissonequationinwhichthecoefficientmatrixispositivedefiniteandsymmetric.Theeddyviscositywascalculatedfromtheefficientk-εturbulencemodel.TheresultingmodeliscomputationallyefficientandunrestrictedtotheCFLcondition.Computationswithandwithouthydrostaticapproximationwerecomparedforthesamecasestotestthevalidityoftheconventionalhydrostaticpressureassumption.Themodelwasverifiedagainstanalyticalsolutionsandexperimentaldata,withexcellentagreement.
简介:Asemi-implicit3-Dnumericalformulationforsolvingnon-hydrostaticpressurefree-surfaceflowsonanunstructured,sigmagridisproposed.Pressure-splittingand9semi-implicitmethodsareinheritedandreformedfromCasulli'sz-coordinateformulation.Thenon-orthogonalsigma-coordinatetransformationleadstoadditionalterms.Theresultinglinearsystemforthenon-hydrostaticcorrectionisdiagonallydominantbutunsymmetric,anditissolvedbytheBiCGstabmethod.Incontrastwithz-coordinatenon-hydrostaticmodels,thenewmodelfitsverticalboundariesmuchbetter,whichisimportantforthelong-timesimulationofsedimenttransportandriverbeddeformation.Alock-exchangedensityflowiscomputedtodeterminewhetherthenewschemeisabletosimulatenon-hydrostaticfree-surfaceflows.ThenewmodelisfurtherverifiedusingthefielddataofanaturalriverbendofthelowerYangtzeRiver.Goodagreementbetweensimulationsandearlierresearchresults,fielddataisobtained,indicatingthatthenewmodelisapplicabletohydraulicprojectsinrealrivers.
简介:A3-DnumericalformulationisproposedonthehorizontalCartesian,verticalsigma-coordinategridformodelingnon-hydrostaticpressurefree-surfaceflows.Thepressuredecompositiontechniqueandθsemi-implicitmethodareused,withthesolutionprocedurebeingsplitintotwosteps.First,withtheimplicitpartsofnon-hydrostaticpressuresexcluded,theprovisionalvelocityfieldandfreesurfaceareobtainedbysolvinga2-DPoissonequation.Second,thetheoryofthedifferentialoperatorisemployedtoderivethe3-DPoissonequationfornon-hydrostaticpressures,whichissolvedtoobtainthenon-hydrostaticpressuresandtoupdatetheprovisionalvelocityfield.Whenthenon-orthogonalsigma-coordinatetransformationisintroduced,additionaltermscomeintobeing,resultingina15-diagonal,diagonallydominantbutunsymmetriclinearsysteminthe3-DPoissonequationfornon-hydrostaticpressures.TheBiconjugateGradientStabilized(BiCGstab)methodisusedtosolvetheresulting3-Dunsymmetriclinearsysteminsteadoftheconjugategradientmethod,whichcanonlybeusedforsymmetric,positive-definitelinearsystems.Threetestcasesareusedforvalidations.Thesuccessfulsimulationsofthesmall-amplitudewave,asupercriticalflowoverarampandaturbulentflowintheopenchannelindicatethatthenewmodelcansimulatewellnon-hydrostaticflows,supercriticalflowsandturbulentflows.
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