简介:NumericaltechniquesplayanimportantroleinCFD.Someofthemarereviewedinthispaper.ThenecessityofusinghighorderdifferenceschemeisdemonstratedforthestudyofhighReynoldsnumberviscousflow.Physicalguidelinesareprovidedfortheconstructionofthesehighorderschemes.Toavoidundulyadhoctreatmentintheboundaryregiontheuseofcompactschemeisrecommendedbecauseithasasmallstencilsizecomparedwiththetraditionalfinitedifferencescheme,BesidespreliminaryFourieranalysisshowsthecompactschemecanalsoyieldbetterspaceresolutionwhichmakesitmoresuitabletostudyflowwithmultiscalese.g.turbulence.Otherapproachessuchasperturbationmethodandfinitespectralmethodarealsoemphasized.Typicalnumericalsimulationswerecarriedout.ThefirstdealswithEulerequationstoshowitscapabilitiestocaptureflowdiscontinuity.TheseconddealswithNavier-Stokesequationsstudyingtheevolutionofamixinglayer,thepertinentstructuresatdifferenttimesareshown.Asymmetricbreakdownoccursandalsotheappearanceofsmallvortices.
简介:Thispaperdevelopsahypersonicaerothermalsimulationmethodformissileslotflow.ThefinitevolumemethodofstructuregridsolverisdevelopedforsolvingEulerandNavier-Stokesequations.ThesolverincludesPark'stwotemperaturemodelandtheairmulti-speciesreactionmodel.Thesecond-orderaccuracyTVDnumericalmethodwasdeducedtocomputethehypersonicaeroheatingwhichimprovesthecomputationalefficiency.Computationalresultsaregiventoshowthehighaccuracycomparingtotheexistingexperimentaldata.
简介:NowadaysComputationalFluidDynamics(CFD)softwareisadoptedasadesignandanalysistoolinagreatnumberofengineeringfields.Wecansaythatsingle-physicsCFDhasbeensufficientlymaturedinthepracticalpointofview.ThemaintargetofexistingCFDsoftwareissingle-phaseflowssuchaswaterandair.However,manymulti-physicsproblemsexistinengineering.Mostofthemconsistofflowandotherphysics,andtheinteractionsbetweendifferentphysicsareveryimportant.Obviously,multi-physicsphenomenaarecriticalindevelopingmachinesandprocesses.Amulti-physicsphenomenonseemstobeverycomplex,anditissodifficulttobepredictedbyaddingotherphysicstoflowphenomenon.Therefore,multi-physicsCFDtechniquesarestillunderresearchanddevelopment.Thiswouldbecausedfromthefactsthatprocessingspeedofcurrentcomputersisnotfastenoughforconductingamulti-physicssimulation,andfurthermorephysicalmodelsexceptforflowphysicshavenotbeensuitablyestablished.Therefore,innearfuture,wehavetodevelopvariousphysicalmodelsandefficientCFDtechniques,inordertosuccessmulti-physicssimulationsinengineering.Inthepresentpaper,Iwilldescribethepresentstatesofmulti-physicsCFDsimulations,andthenshowsomenumericalresultssuchasiceaccretionandelectro-chemicalmachiningprocessofathree-dimensionalcompressorbladewhichwereobtainedinmylaboratory.Multi-physicsCFDsimulationswouldbeakeytechnologyinnearfuture.
简介:Acombustionmodelofalarge-scalesupercriticalcirculatingfluidizedbed(CFB)boilerwasdevelopedforcomprehensivecomputational-fluid-dynamicsanalysis.Themodelincorporatesgas-solidhydrodynamics,coalcombustion,heattransferonheatexchangesurfacesinthefurnace,andheattransferbetweenfumaceandworkingmediumintheheattransfertubes.Insimulatingthedenseanddilutephasesinthefumace,thegas-solidhydrodynamicsisbasedontheEuler-Eulermodelandenergy-minimizationmultiscaledragmodel.Coalcombustionentailsevaporation,devolatilization,charcombustion,gashomogeneousreaction,andpollutantemission.Thecoefficientofheattransferbetweengas-solidandthewaterwallisestimatedusingtheclusterrenewalmodel,andforradiation,thediscreteordinatemodelisused.Moreover,thermohydraulicprocessesinthemembranewallarealsoineludedintheheattransferprocess.Themodelwassuccessfullyappliedinsimulationsofa350-MWsupercriticalCFBboiler.Detaileddistributionsofsolidsconcentration,oxygen,heatflux,andworkingmediumtemperatureintheboilerfurnacearepresented.
简介:摘 要:本文是对某TMF型(上冷冻、下冷藏式)风冷冰箱的冷冻风道进行CFD仿真,得到冷冻风道的流线图,压力云图,风道各出风口的出风量和占比数据。分析出,风扇与风道腔体边界距离偏小,空气撞击在边界上易形成局部涡流,增大风道局部阻力;风道左上,右上两出风口风量不均匀,右上出风口相对左上出风口流线密度有降低,出风口风速降低。并进行实验测试风道的各出风口风量,同仿真结果进行对比,测得各处风口风量趋势和仿真结果一致。
简介:InthisarticletheUDFscriptfileintheFluentsoftwarewasrewrittenasthe'connectingfile'fortheFluentandtheANSYS/ABAQUSinorderthatthejoinedfilecanbeusedtodoaero-elasticcomputations.InthiswaythefluidfieldiscomputedbysolvingtheNavier-Stokesequationsandthestructuremovementisintegratedbythedynamicsdirectly.Ananalysisofthecomputedresultsshowsthatthiscoupledmethoddesignedforsimulatingaero-elasticsystemsisworkableandcanbeusedfortheotherfluid-structureinteractionproblems.
简介:针对有关毒气急性中毒研究只能根据经验公式和接触限值划定危险区域进行定性评估的现状,提出结合毒气泄漏CFD数值模拟与中毒剂量反应模型进行中毒定量评估的方法。通过CFD计算泄漏毒气的实时浓度场,根据浓度场和暴露时间确定人员暴露剂量,最后根据剂量反应模型确定人员死亡百分比。以某硫黄回收装置的硫化氢泄漏为例,建立CFD模型。设置距地面高1.5m,与泄漏源水平距离分别为100m、200m、300m、400m、500m的5个监测点作为工作人员的急性中毒地点,模拟分为构建初始风场、硫化氢泄漏及随风场扩散3个阶段,根据CFD求解得出的监测点的硫化氢实时浓度场并结合中毒剂量反应模型对监测点人员中毒死亡风险进行定量评估。研究表明,基于CFD的毒气泄漏中毒定量评估技术能对泄漏区域任意位置、任意时刻的人员中毒风险进行定量评估,弥补了目前大多定性评价方法的不足。
简介:摘要:以某办公房间为例,利用计算流体力学( CFD)技术,对办公房间通风方案进行模拟。本文重点分析了通风过程中工作区的空气速度矢量、温度和空气年龄分布特性,以此为依据评价了室内的空气质量,并以此对送回风口的位置进行了调整,找到了较好的通风方式。对计算过程及结果的分析表明,送回风口的位置不同,不仅对室内的空气环境质量有影响,而且还会影响网格的划分与计算收敛的情况。
简介:AnumericalcasestudyonidentifyingtheoptimumnumberofbucketsforaPeltonturbineispresented.Threeparameters:numberofbuckets,bucketradialpositionandbucketangularpositionaregroupedsincetheyarefoundtobeinterrelated.Byidentifyingthebestcombinationoftheradialandangularpositionforeachnumberofbucketsitisshownthatreductioninthenumberofbucketsbeyondthelimitsuggestedbytheavailableliteraturecanimprovetheefficiencyandbebeneficialwithregardtothemanufacturingcomplexityandcostperspective.Theeffectofthisreductioninthenumberofbucketswasconfirmedexperimentally.
简介:Theresearchpurposeofthispaperistoestimatetheimpactsoftheparametersoftheguideplateontheverticalmotioncharacteristicsofthemoonpoolfluid.Withthevolumeoffluid(VOF)method,three-dimensionalmodelsofthemoonpoolfluidmotionsofthetrusssparplatformareestablished.Simulationresultsarethenpresentedforthemoonpoolforcedoscillationbyemployingthedynamicmeshmethodanduser-definedfunctionsinFLUENT.Themotionsofthemoonpoolfluidandtheloadsontheguideplatesareobtainedforbothcasesofsquare-ringandcrisscross.Theresultsshowthattheshapeandareaoftheguideplateatthebottomofthemoonpoolhaveasignificantimpactonthephysicalparametersofthemoonpool,includingtheloadonthemoonpoolguideplate,motionformofthemoonpoolfluidandthemassflowrate.
简介:Gas-solidtwo-phaseflowinacirculatingfluidizedbed(CFB)isaffectedbyoperatingconditions(e.g.,superficialgasvelocity,solidsinventory),materialpropertiesandgeometricfactors,suchastheentryandexitconfiguration.Inparticular,thesuspensionsection,whichislocatedbetweentheriserbottomandthesolidsrecycleinlet,affectsthehydrodynamicsintherisersignificantly.However,thesuspensionsectionhasreceivedlessattentioncomparedwithothergeometricfactors.Mostcomputationalfluiddynamics(CFD)simulations,especiallytwo-dimensionalsimulationsdonottakethisfactorintoaccount.Weperformedthree-dimensional,full-loopCFDsimulationswithadragcoefficientthatwasdeterminedbytheenergy-minimizationmulti-scalemodel,andinvestigatedtheflowbehavioroftwoCFBswithdifferentsuspension-sectionlengths.ThesimulationresuitsrevealedthattheaxialprofilesofvoidageintheriserwithalongersuspensionsectionaremorelikelyS-shaped,whereasthosewithshortersuspensionsectionsdecayexponentially.ThedependencesofsolidsfluxonsolidsinventorydifferinthetwoCFBs.Ashortersuspensionsectionmayresultinasmoothtransitionfromdilutetodensetransportwithoutintermediateaccumulativechoki-ng,whereasaIongersuspensionsectionmayleadtoachokingtransition.Thesesimulationresultsarequalitativelyconsistentwiththeflowbehaviorsdescribedinliterature.