简介:Thesubsystemsynthesismethodhasbeendevelopedinordertoimprovecomputationalefficiencyforamultibodyvehicledynamicsmodel.Usingthesubsystemsynthesismethod,equationsofmotionofthebasebodyandeachsubsystemcanbesolvedseparately.Inthesubsystemsynthesismethod,variouscoordinatesystemscanbeusedandvariousintegrationmethodscanbeappliedineachsubsystem,aslongastheeffectivemassmatrixandtheeffectiveforcevectorareproperlyproduced.Inthispaper,comparativestudyhasbeencarriedoutforthesubsystemsynthesismethodwithCartesiancoordinatesandwithjointrelativecoordinates.Twodifferentintegrationmethodssuchasanexplicitintegratorandanexplicitimplicitintegratorareemployed.Inordertoseetheaccuracyandcomputationalefficiencyfromthedifferentmodelsbasedonthedifferentcoordinatesystemsanddifferentintegrationmethods,aroughterrainrunsimulationshasbeencarriedoutwitha6×6off-roadmultibodyvehiclemodel.
简介:Forthethree-dimensionalconvection-dominatedproblemofdynamicsoffluidsinporousmedia,thesecondorderupwindfinitedifferencefractionalstepsschemesapplicabletoparallelarithmeticareputforward.Fractionalstepstechniquesareneededtoconvertamulti-dimensionalproblemintoaseriesofsuccessiveone-dimensionalproblems.Sometechniques,suchascalculusofvariations,energymethod,multiplicativecommutationruleofdifferenceoperators,decompositionofhighorderdifferenceoperators,andthetheoryofpriorestimatesareadopted.Optimalorderestimatesarederivedtodeterminetheerrorinthesecondorderapproximatesolution.Thesemethodshavealreadybeenappliedtothenumericalsimulationofmigration-accumulationofoilresourcesandpredictingtheconsequencesofseawaterintrusionandprotectionprojects.
简介:Densegas-particleflowsareencounteredinavarietyofindustriallyimportantprocessesforlargescaleproductionoffuels,fertilizersandbasechemicals.Thescale-upoftheseprocessesisoftenproblematicandisrelatedtotheintrinsiccomplexitiesoftheseflowswhichareunfortunatelynotyetfullyunderstooddespitesignificanteffortsmadeinbothacademicandindustrialresearchlaboratories.Indensegas-particleflowsboth(effective)fluid-particleand(dissipative)particle-particleinteractionsneedtobeaccountedforbecausethesephenomenatoalargeextentgoverntheprevailingflowphenomena,i.e.theformationandevolutionofheterogeneousstructures.Thesestructureshavesignificantimpactonthequalityofthegas-solidcontactandasadirectconsequencethereofstronglyaffecttheperformanceoftheprocess.Duetotheinherentcomplexityofdensegas-particlesflows,wehaveadoptedamulti-scalemodelingapproachinwhichbothfluid-particleandparticle-particleinteractionscanbeproperlyaccountedfor.Theideaisessentiallythatfundamentalmodels,takingintoaccounttherelevantdetailsoffluid-particle(latticeBoltzmannmodel)andparticle-particle(discreteparticlemodel)interactions,areusedtodevelopclosurelawstofeedcontinuummodelswhichcanbeusedtocomputetheflowstructuresonamuchlarger(industrial)scale.Ourmulti-scaleapproach(seeFig.1)involvesthelatticeBoltzmannmodel,thediscreteparticlemodel,thecontinuummodelbasedonthekinetictheoryofgranularflowandthediscretebubblemodel.Inthispaperwegiveanoverviewofthemulti-scalemodelingstrategy,accompaniedbyillustrativecomputationalresultsforbubbleformation.Inaddition,areaswhichneedsubstantialfurtherattentionwillbehighlighted.
简介:Thecalculationofsettlingspeedofcoarseparticlesisfirstlyaddressed,withacceleratedStokesiandynamicswithoutadjustableparameters,inwhichfarfieldforceactingontheparticleinsteadofparticlevelocityischosenasdependentvariablestoconsiderinter-particlehydrodynamicinteractions.Thesedimentationofasimplecubicarrayofsphericalparticlesissimulatedandcomparedtotheresultsavailabletoverifyandvalidatethenumericalcodeandcomputationalscheme.TheimprovedmethodkeepsthesamecomputationalcostoftheorderO(NlogN)asusualacceleratedStokesiandynamicsdoes.Then,morerealisticrandomsuspensionsedimentationisinvestigatedwiththehelpofMontCarlomethod.Thecomputationalresultsagreewellwithexperimentalfitting.Finally,thesedimentationoffinercohesiveparticle,whichisoftenobservedinestuaryenvironment,ispresentedasafurtherapplicationincoastalengineering.
简介:Globalbifurcationsandmulti-pulsechaoticdynamicsforasimplysupportedrectangularthinplatearestudiedbytheextendedMelnikovmethod.Therectangularthinplateissubjecttotransversalandin-planeexcitation.Atwo-degree-of-freedomnonlinearnonautonomoussystemgoverningequationsofmotionfortherectangularthinplateisderivedbythevonKarmantypeequationandtheGalerkinapproach.Aone-tooneinternalresonanceisconsidered.Anaveragedequationisobtainedwithamulti-scalemethod.Aftertransformingtheaveragedequationintoastandardform,theextendedMelnikovmethodisusedtoshowtheexistenceofmulti-pulsechaoticdynamics,whichcanbeusedtoexplainthemechanismofmodalinteractionsofthinplates.AmethodforcalculatingtheMelnikovfunctionisgivenwithoutanexplicitanalyticalexpressionofhomoclinicorbits.Furthermore,restrictionsonthedamping,excitation,anddetuningparametersareobtained,underwhichthemulti-pulsechaoticdynamicsisexpected.Theresultsofnumericalsimulationsarealsogiventoindicatetheexistenceofsmallamplitudemulti-pulsechaoticresponsesfortherectangularthinplate.