简介:Whethertheconceptofeffectivestressandstraininelastic-plastictheoryisstillvalidundertheconditionoffinitedeformationwasmainlydiscussed.Theuni-axialcompressionexperimentsinplanestressandplanestrainstateswerechosenforstudy.Inthetwokindsofstressstates,thestress-straincurvedescribedbylogarithmstrainandrotatedKirchhoffstressmatchestheexperimentsdatabetterthanthecurvesdefinedbyotherstressstraindescription.
简介:Twodimensionalequationsofsteadymotionforthirdorderfluidsareexpressedinaspecialcoordinatesystemgeneratedbythepotentialflowcorrespondingtoaninviscidfluid.Fortheinviscidflowaroundanarbitraryobject,thestreamlinesarethephicoordinatesandvelocitypotentiallinesarepsi-coordinateswhichformanorthogonalcurvilinearsetofcoordinates.Theoutcome,boundarylayerequations,isthenshowntobeindependentofthebodyshapeimmersedintotheflow.Asafirstapproximation,assumptionthatsecondgradetermsarenegligiblecomparedtoviscousandthirdgradeterms.Secondgradetermsspoilscalingtransformationwhichisonlytransformationleadingtosimilaritysolutionsforthirdgradefluid.ByusingLiegroupmethods,infinitesimalgeneratorsofboundarylayerequationsarecalculated.Theequationsaretransformedintoanordinarydifferentialsystem.NumericalsolutionsofoutcomingnonlineardifferentialequationsarefoundbyusingcombinationofaRunge-Kuttaalgorithmandshootingtechnique.
简介:Thestructuraldynamicsproblems,suchasstructuraldesign,parameteridentificationandmodelcorrection,areconsideredasakindoftheinversegeneralizedeigenvalueproblemsmathematically.Theinverseeigenvalueproblemsarenonlinear.Ingeneral,theycouldbetransformedintononlinearequationstosolve.Thestructuraldynamicsinverseproblemsweretreatedasquasimultiplicativeinverseeigenalueproblemswhichweresolvedbyhomotopymethodfornonlinearequations.Thismethodhadnorequirementsforinitialvalueessentiallybecauseofthehomotopypathtosolution.Numericalexampleswerepresentedtoillustratethehomotopymethod.
简介:AfastadaptivesymplecticalgorithmnamedMultiresolutionSymplecticScheme(MSS)wasfirstpresentedtosolvetheproblemofthewavepropagation(WP)incomplexmedia,usingthesymplecticschemeandDaubechies'compactlysupportedorthogonalwavelettransformtorespectivelydiscretisethetimeandspacedimensionofwaveequation.TheproblemwassolvedinmultiresolutionsymplecticgeometryspaceundertheconservativeHamiltoniansystemratherthanthetraditionalLagrangesystem.Duetothefascinatingpropertiesofthewaveletsandsymplecticscheme,MSSisapromisingmethodbecauseoflittlecomputationalburden,robustnessandrealityoflong-timesimulation.
简介:Fromsuchactualconditionsastheeffectsofcharacteristicsofmiltilayerpetroleumgeologyandpermeationfluidmechanics,anewnumericalmodelisputforwardandcouplingsplitting-upimplicitinteractiveschemeisformed.FortheactualsituationofDongyinghollow(four-layer)andTanhairegion(three-layer)ofShengliPetroleumField,thenumericalsimulationtestresultsandtheactualconditionsarecoincident.
简介:Adirectnumericalsimulationisperformedon2563gridsfordecayingisotropicturbulence.Thetotalkinematicenergy,Taylormicro-scale,Taylormicro-scaleReynoldsnumberandthevelocityderivativeskewnessarecalculated.Thesnapshotsofenergyspectraandenergytransferspectraareplotted.ThesemeasurementsverifytheDIApredictions:decayingisotropicturbulencehastheenergypropagationandoccupiesthefinaldecayperiods.Theskewnessremainstosomelevelwithsmallvariationeveninthefinaldecayperiod.
简介:Inthispaper,wecarryoutananalysisofthestructuralpropertiesofthesolutionstothespeedgradient(SG)trafficflowmodel.Undertheconditionthattherelaxationeffectcanbeneglected,itisshownthata1-shockora1-rarefactionisassociatedwiththefirstcharacteristic,butontheotherhand,acontactdiscontinuityratherthana2-shockora2-rarefactionisassociatedwiththesecondcharacteristic.Sincetheexistenceofa2-shockor2-rarefactionviolatesthephysicalmechanismofthetrafficflow,theSGmodelismorereasonable.Iftherelaxationeffectcannotbeneglected,itissomewhatdifficulttocarryouttheanalyticalanalysisandthenumericalsimulationresultsshouldbeobtained.
简介:Inordertoinvestigatetheinfluenceoftheverticalvibrationloadingontheliquefactionofsaturatedsand,onedimensionalmodelforthesaturatedsandwithaverticalvibrationispresentedbasedonthetwophasecontinuousmediatheory.Thedevelopmentoftheliquefactionandtheliquefactionregionareanalyzed.Itisshownthattheverticalvibrationloadingcouldinduceliquefaction.Therateoftheliquefactionincreaseswiththeincreaseoftheinitiallimitstrainorinitialporosityoramplitudeandfrequencyofloading,andincreaseswiththedecreaseofthepermeabilityorinitialmodulus.Itisshownalsothatthereisaphaselaginthesandcolumn.Whenthesandpermeabilitydistributionisnon-uniform,theporepressureandthestrainwillrisesharplywherethepermeabilityisthesmallest,andfracturemightbeinduced.Withthedevelopmentofliquefaction,thestrengthofthesoilfoundationbecomessmallerandsmaller.Inthelimitingcase,landslidesordebrisflowscouldoccur.
简介:AnFEanalysisprocedurewaspresentedtopredictthebehaviorofsoilogeogridinterctionunderautomobileloading.Thedynamicinteractionsbetweenthetransversebars,thelongitudinalribsandthesoilweresimulatedbyasystemconsistingofnonlinearsprings,dashpotsandmasses,tostudythedeformationpropertiesofthereinforcedsoil.Theequivalentstiffnessanddampingratioscouldbedeterminedwiththeshakingtable.Thedynamicresponsesofareinforcedsubgradewereanalyzedwiththe3Dfiniteelementapproach.Thisapproachisprogrammedandappliedtoanalyzethesoilogeogridinteractionunderdynamicloading.Thecomparativeanalysisoftheresponseofthereinforcedsubgradeandthatofthesubgradewithoutreinforcementshowsthatthegeogridplacedatthebottomofthebaselayermayeffectivelyreducetheaccumulativeplasticdeformationduetothecyclicautomobileloading.
简介:AconstitutiveequationtheoryofOldroydfluidBtype,i.e.theco-rotationalderivativetype,isdevelopedfortheanisotropic-viscoelasticfluidofliquidcrystalline(LC)polymer.Analyzingtheinfluenceoftheorientationalmotiononthematerialbehaviorandneglectingtheinfluence,theconstitutiveequationisappliedtoasimplecaseforthehydrodynamicmotionwhentheorientationalcontributionisneglectedinitandtheanisotropicrelaxation,retardationtimesandanisotropicviscositiesareintroducedtodescribethemacroscopicbehavioroftheanisotropicLCpolymerfluid.UsingtheequationfortheshearflowofLCpolymerfluid,theanalyticalexpressionsoftheapparentviscosityandthenormalstressdifferencesaregivenwhichareinagoodagreementwiththeexperimentalresultsofBaeketal.Forthefiberspinningflowofthefluid,theanalyticalexpressionoftheextensionalviscosityisgiven.
简介:ThesedimentationsoftwocylindricalparticlesinthreedifferentinitialrelativepositionsarenumericallysimulatedusingthelatticeBoltzmannmethod.Themovementcharacteristicsandparticleinteractionsduringtheirsedimentationarepresentedanddiscussedindetail.Theresultsshowthat,(i)ifthetwoparticlesarereleasedparallelbutseparatedhorizontally,theypushawayeachother,rotateinwardsandseparatehorizontallyastheyfall;(ii)ifthetwoparticlesarereleasedparallelbutseparatedvertically,thesedimentationbehaviorcanbeclassifiedintothreestages:trailing,tumblingandseparating;(iii)ifthetwoparticlesarereleasedperpendicularbutseparatedvertically,thesedimentationbehaviorcanbecharacterizedas:trailingandrotating,touchingandsliding.Inordertovalidateoursimulation,experimentswerealsoconductedandtheresultsagreewellwiththenumericalones.
简介:TheaerodynamicforcesandflowstructureofamodelinsectwingisstudiedbysolvingtheNavier-Stokesequationsnumerically.Afteraninitialstartfromrest,thewingismadetoexecuteanazimuthalrotation(sweeping)atalargeangleofattackandconstantangularvelocity.TheReynoldsnumber(Re)consideredinthepresentnoteis480(Reisbasedonthemeanchordlengthofthewingandthespeedat60%winglengthfromthewingroot).Duringtheconstant-speedsweepingmotion,thestallisabsentandlargeandapproximatelyconstantliftanddragcoefficientscanbemaintained.Themechanismfortheabsenceofthestallorthemaintenanceoflargeaerodynamicforcecoefficientsisasfollows.Soonaftertheinitialstart,avortexring,whichconsistsoftheleading-edgevortex(LEV),thestartingvortex,andthetwowing-tipvortices,isformedinthewakeofthewing.Duringthesubsequentmotionofthewing,abase-to-tipspanwiseflowconvertsthevorticityintheLEVtothewingtipandtheLEVkeepsanapproximatelyconstantstrength.ThispreventstheLEVfromshedding.Asaresult,thesizeofthevortexringincreasesapproximatelylinearlywithtime,resultinginanapproximatelyconstanttimerateofthefirstmomentofvorticity,orapproximatelyconstantliftanddragcoefficients.Thevariationoftherelativevelocityalongthewingspancausesapressuregradientalongthewingspan.Thebase-to-tipspanwiseflowismainlymaintainedbythepressure-gradientforce.
简介:针对无阻尼惯导系统的误差特点,设计了适合航空应用的惯性(INS)/天文(CNS)/Doppler组合导航系统,建立了该组合导航系统卡尔曼滤波模型.仿真试验表明,该组合导航系统能为飞行体提供精确的导航信息.
简介:TheChineseSocietyofParticuologyisavoluntaryorganizationofworkersinresearch,developmentandapplicationofthescienceandtechnologyofparticles.TheSocietyisdedicatedtofostedngliaisonandexchangeamongitsmembersthroughscientificandtechnicalsymposiaandseminarsofbothanationalandinternationalnatureandtodisseminatingknowledgeonparticlesthroughcontinuingeducationandpublicationintheformofscientifictransactionsandofjournalsonnewsandotheritemsofcurrentinterest.Itsultimateobjectiveistoservethecountry'sneedsformodernization.
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