学科分类
/ 2
35 个结果
  • 简介:Thewave-seabedinteractionissueisofgreatimportanceforthedesignoffoundationaroundmarineinfrastructures.Mostpreviousinvestigationsforsuchaproblemhavebeenlimitedtouncoupledoronewaycoupledmethodsconnectingtwoseparatedwaveandseabedsubmodelswiththecontinuityofpressuresattheseabedsurface.Inthisstudy,astronglycoupledmodelwasproposedtorealizebothwaveandseabedprocessesinasameprogramandtocalculatethewavefieldsandseabedresponsesimultaneously.Theinformationbetweenwavefieldsandseabedfieldswerestronglysharedandthusresultsinamoreprofoundinvestigationofthemechanismofthewave-seabedinteraction.Inthisletter,thewaveandseabedmodelswerevalidatedwithpreviousexperimentaltests.Then,asetofapplicationofpresentmodelwerediscussedinpredictionofthewave-inducedseabedresponse.Numericalresultsshowthewave-inducedliquefactionareaofcoupledmodelissmallerthanthatofuncoupledmodel.

  • 标签: 耦合模型 海底 波传播 多孔 基础设施 相互作用
  • 简介:Inapreviouspaper,amethodhasbeendevelopedtostudythestabilitycharacteristicsoflaminarboundarylayersovercompliantwalls.Inthispaper,theeffectofdoublelayeredcompliantwallandKramertypecompliantwallondelayingthetransitionisinvestigated,anditisshownthattheredoesexistthepossibilitytode-laythetransitionbyapplyingsuchcompliantwalls.

  • 标签: TRANSITION compliant WALL STABILITY
  • 简介:Thestabilitycharacteristicsoflaminarboundarylayersovercompliantwallswasstudiedbythelineartheory.Unlikethepreviousauthors,thecoupledmotionofthefluidandsolidwasrequiredtosat-isfythecontinuityconditionsofboththevelocityandstressattheinterface.Resultsofcalculationsshowthatasthespeedratioordensityratioexceedsacertainthresholdvalue,thetwotypesofunstablewaveswillnolongerbedistinguishable,andthetangentialcomponentofthedisturbancestressisnolongernegligi-ble.Sotheneglectofit,asthepreviousauthorsdid,isunjustified.

  • 标签: STABILITY BOUNDARY LAYER compliant WALL
  • 简介:Oscillatoryturbulentflowoveraflatplateisstudiedusinglargeeddysimulation(LES)andReynolds-averageNavier-Stokes(RANS)methods.Adynamicsubgrid-scalemodelisemployedinLESandSaffman’sturbulencemodelisusedinRANS.Theflowbehaviorsarediscussedfortheacceleratinganddeceleratingphasesduringtheoscillatingcycle.ThefrictionforceonthewallanditsphaseshiftfromlaminartoturbulentregimearealsoinvestigatedfordifferentReynoldsnumbers.

  • 标签: turbulent FLOW large EDDY simulation(LES) Reynolds-average
  • 简介:Thisletterdescribesnumericalsimulationoftheunsteadyflowoveraslow-flyingbatbyusingtheimmersedboundarymethodbasedonthemeasuredbatwinggeometryandkinematics.Themainvorticalstructuresaroundthebatflappingwingsareidentified,illuminatingthelift-generatingroleoftheleadingedgevorticesgeneratedmainlyinthedownstroke.Furthermore,theliftdecompositionindicatesthatthevortexlifthasthedominantcontributiontothetime-averagedliftandtheliftassociatedwiththefluidaccelerationhastherelativelymoderateeffect.

  • 标签: 数值模拟 非定常流 蝙蝠 飞行 几何形状 结构鉴定
  • 简介:Theflowstructuresinaseparatedshearlayeractuatedbyasyntheticjetactuatorwerestudiedusingexperimentalmethods.Whenforcedatafrequencymuchlowerthanthenaturalsheddingfrequency(fH/U=0.042orfX_r/U=0.24),theverticalflappingmotionoftheshearlayerdownstreamoftheseparationpointbecameprominent.Thesizeofthepeakinthepressurespectraattheforcingfrequency(St_A=f_AH/U)measuredneartheseparationpoint(x/H=1)increasedlinearlywiththeforcingamplitude(u′/U)suggestingalinearresponseofthepressurefluctuationstotheforcingbythesyntheticjet.ThelinearresponsedidnotholdforthepressurefluctuationsawayfromthejetexitasthemagnitudeofthepeakforSt_Ameasuredatx/H=3soonsaturatedwhentheforcingamplitudebecamelargerthan0.3.

  • 标签: 流动结构 周期性扰动 湍流脉动 线性响应 合成射流 脱落频率
  • 简介:Asawidelyusedfloodenergydissipator,thesteppedspillwaycansignificantlydissipatethekineticorhydraulicenergyduetotheair-entrainmentinskimmingflowoverthesteps.Thefree-surfaceaerationinvolvesthesharpdeformationofthefreesurfaceandthecomplexturbulentshearflows.Inthisstudy,thevolumeoffluid(VOF),mixture,andEulerianmethodsareutilizedtosimulatetheair-entrainmentbycouplingwiththeReynolds-averagedNavier–Stokes/largeeddysimulation(RANS/LES)turbulencemodels.Thefreesurfacedeformation,airvolumefraction,pressure,andvelocityarecomparedforthethreedifferentnumericalmethods.OnlytheEulerian+RANSmethodfailstocapturethefree-surfaceaeration.TheairvolumefractionpredictedbytheVOF+LESmethodbestmatchestheexperimentalmeasurement,whilethemixture+LESmethodpredictstheinceptionpointoftheairentrainmentmoreaccurately.

  • 标签:
  • 简介:Basedonthemultiplescatteringmethod,thispaperinvestigatesabenchmarkproblemofthepropagationofliquidsurfacewavesoverfinitegraphene(orhoneycomb)structuredarraysofcylinders.Comparingthegraphenestructuredarraywiththesquarestructuredandwithtrianglestructuredarrays,itfindsthatthefinitegraphenestructurecanproducemorecompletebandgapsthantheotherfinitestructures,andthefinitegraphenestructurehaslesslocalizedabilitythantheotherfinitestructures.

  • 标签:
  • 简介:这研究的目的是描绘元素的碳和器官的碳(EC和OC,分别地)喷雾器粒子(PM2.5)的内容在Tongliao收集了,在东北中国的HorqinSandland的一个地点。在春天2005期间,PM2.5集体集中是126±71μg·m?3,与更高的灰尘集中,在五期间,灰尘比在非尘封的天下暴雨(255±77对106±44μg·m?3)。在一个热/光的反射方法决定的PM2.5的平均OC和EC集中是15.7±7.3μg·m?3和3.3±1.7μg·m?3,分别地并且碳的喷雾器在正常的天与21.7%相比在灰尘暴风雨期间说明了9.9%PM2.5质量。到EC的OC的平均比率在灰尘暴风雨期间类似于在非尘封的天的那些,并且在OC和EC之间的关联系数高,0.86。高OC/EC比率,八碳部分的分布,和在有OC和EC的K之间的强壮的关系显示农村生物资源烧是到地区性的碳的喷雾器的主导的贡献者。

  • 标签: 东北地区 沙尘暴 有机碳 哈尔滨 沙地 2005年春季
  • 简介:Thisletterpresentsananalyticalsolutiontothehydrodynamiclubricationofacircularpointcontactslidingoveraflatsurfacewithcavitation.ThesolutionisfoundbysolvingtheReynoldsequationwithReynoldsboundaryconditionforcavitation.Thecavitationboundaryisshowntobestraightlinesdirected108.4°againsttheslidingdirection.Theresultisexperimentallyverifiedinthelimitoflargevaluesofviscosity,slidingvelocityandradiusofasphericalball.Thesolutionraisesquestionsaboutthecouplingbetweencavitationandfilmruptureandcanbeusedasanindependentcheckonthevalidityofnumericalsolutions.

  • 标签: 流体动力润滑 滑动接触 圆形 表面 平坦 空蚀
  • 简介:Environmentalpollutionanddecliningresourcesoffossilfuelsinrecentyears,haveincreaseddemandforbetterfueleconomyandlesspollutionforgroundtransportation.Amongthealternativesolutionsprovidedbyresearchersinrecentdecades,hybridelectricvehiclesconsistedofaninternalcombustionengineandanelectricmotorhavebeenconsideredasapromisingsolutionintheshort-term.Inthepresentstudy,fueleconomycharacteristicsofaparallelhybridelectricvehicleareinvestigatedbyusing...

  • 标签:
  • 简介:Thisstudyaimsatthemechanismofdragreductioninturbulentboundarylayer(TBL)withsuperhydrophobicsurface.Comparingthetime-resolvedparticleimagevelocimetry(TRPIV)measurementresultswiththatofhydrophilicsurface,thedragreductionrateoverasuperhydrophobicsurfaceisapproximately10%.Toinvestigatethecharacteristicsofcoherentstructureinadrag-reducedTBLwithsuperhydrophobicsurface,amodifiedmulti-scalespatiallocally-averagedstructurefunctionisproposedfordetectingcoherentstructure.Theconditionalsamplingandspatialphase-lockaveragemethodsareemployedtoobtainthetopologyofphysicalquantitieslikethevelocityfluctuation,spanwisevorticity,andReynoldsstressduringejectandsweepprocess.Theresultsindicatethatthesuppressionofcoherentstructureburstinthenear-wallregionisthekeymechanisminreducingtheskinfrictiondragforTBLoversuperhydrophobicsurface.

  • 标签: 疏水表面 减阻率 PIV实验 湍流边界层 超疏水性表面 粒子图像测速
  • 简介:Themechanicalbackgroundofthebivariatesplinespaceofdegree2andsmoothness1onrectangularpartitionispresentedconstructively.Makinguseofmechan-icalanalysismethod,byactingcouplesalongtheinterioredgeswithsuitableevaluations,thedeflectionsurfaceisdividedintopiecewiseform,therefore,therelationbetweenaclassofbivariatesplinesonrectangularpartitionandthepurebendingofthinplateisestablished.Inaddition,theinterpretationofsmoothingcofactorandconformalitycon-ditionfromthemechanicalpointofviewisgiven.Furthermore,byintroducingtwistingmoments,themechanicalbackgroundofanysplinebelongtotheabovespaceissetup.

  • 标签: 矩形 余因子 二变量 极限
  • 简介:Non-equilibriumturbulencephenomenahaveraisedgreatinterestsinrecentyears.Significanteffortshavebeendevotedtonon-equilibriumturbulencepropertiesincanonicalflows,e.g.,gridturbulence,turbulentwakes,andhomogeneousisotropicturbulence(HIT).Thenon-equilibriumturbulenceinnon-canonicalflows,however,hasrarelybeenstudiedduetothecomplexityoftheflows.Inthepresentcontribution,adirectnumericalsimulation(DNS)databaseofaturbulentflowisanalyzedoverabackwardfacingramp,theflowneartheboundaryisdemonstrated,andthenon-equilibriumturbulentpropertiesoftheflowinthewakeoftheramparepresentedbyusingthecharacteristicparameterssuchasthedissipationcoefficientCεandtheskewnessoflongitudinalvelocitygradientSk,butwithoppositeunderlyingturbulentenergytransferproperties.TheequationofLagrangianvelocitygradientcorrelationisexamined,andtheresultsshowthatnon-equilibriumturbulenceistheresultofphasede-coherencephenomena,whichisnottakenintoaccountinthemodelingofnon-equilibriumturbulence.Thesefindingsareexpectedtoinspiredeeperinvestigationofdifferentnon-equilibriumturbulencephenomenaindifferentflowconditionsandtheimprovementofturbulencemodeling.

  • 标签: NON-EQUILIBRIUM TURBULENCE BACKWARD RAMP direct numerical
  • 简介:在最后20年里,因为他们的低biodegradability,从塑料生产的废物正在成为一个环境问题,变得明显。尽管几个方法为再循环浪费塑料被建议了,材料恢复不是现在的问题的一个长期的答案,这通常被接受,并且那个精力或化学恢复是一种更吸引人的选择,包括裂开进单体成分,生产精力的燃烧,并且生产有用中间的化学药品的热或催化的变换。这篇论文是在为精力恢复的最后选择的区域的贡献。有很多份出版物,为裂开聚合物进烃的一个范围报导分子的筛和非结晶的硅石氧化铝催化剂的使用。这里报导的研究工作表明我的能力在击碎聚乙烯进汽油的酣睡的催化剂变化产品。它为我被发现那酣睡的MCM-41催化剂,它有它的crystallinity的裂开的活动增加,与更小的毛孔直径显示更高的活动。烃产品分发强烈显示击碎机制的一个carbenium离子。产品分发也与从热裂开的测试获得的那些相比。

  • 标签: 废塑料 聚乙烯破裂 MCM-41 环境问题
  • 简介:Inthispaper,wederivetheanalyticalsolutionsinathree-dimensionalanisotropicmagnetoelectroelasticbimaterialspacesubjecttouniformextendeddislocationsandtractionswithinahorizontalcirculararea.ByvirtueoftheStrohformalismandFouriertransformation,thefinalexpressionofsolutionsinthephysicaldomaincontainsonlylineintegralsover[0,2π]ratherthaninfiniteintegrals.Asthereducedcases,thehalf-spaceandhomogeneousfull-spacesolutionscanbedirectlyderivedfromthepresentsolutions.Also,intermsofmaterialdomains,thepresentsolutionscanbereducedtothepiezoelectric,piezomagnetic,purelyelasticmaterialswithdifferentsymmetriesofmaterialproperty.Tocarryoutnumericalcalculations,Gaussquadratureisadopted.Inthenumericalexamples,theeffectofdifferentloadinglocationsontheresponseattheinterfaceisanalyzed.Itisshownthat,whenthemagnetictractionorelectricdislocationisapplied,thephysicalquantitiesontheinterfacemaynotdecreasemonotonicallyastheloadingareamovesawayfromtheinterface.Thedistributionsofdifferentin-planephysicalquantitiesontheupperandlowerinterfacesundervariousextendedhorizontalloadingsarecomparedandthedifferencesarediscussed.Theworkpresentedinthispapercanserveasbenchmarksforfuturenumericalstudiesinrelatedresearchfields.

  • 标签: 扩展位错 各向异性 圆形区域 牵引 均匀 磁电
  • 简介:Ananalysisisperformedtostudytransientfreeconvectiveboundarylayerflowofacouplestressfluidoveraverticalcylinder,intheabsenceofbodycouples.Thesolutionofthetime-dependentnon-linearandcoupledgoverningequationsiscarriedoutwiththeaidofanunconditionallystableCrank–Nicolsontypeofnumericalscheme.Numericalresultsforthesteady-statevelocity,temperatureaswellasthetimehistoriesoftheskin-frictioncoefcientandNusseltnumberarepresentedgraphicallyanddiscussed.Itisseenthatforallflowvariablesasthecouplestresscontrolparameter,Co,isamplified,thetimerequiredforreachingthetemporalmaximumincreasesbutthesteady-statedecreases.

  • 标签: 直圆柱 自然对流 普朗特数 应力参数 瞬态 时间变化