汽车空气动力学仿真概要.docx

汽车空气动力学仿真概要.docx

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汽车空气动力学仿真概要

汽车空气动力学仿真VehicleAerodynamicsSimulation张扬军ZhangYang-Jun清华大学汽车工程系应用空气动力学组汽车安全与节能国家重点实验室AppliedAerodynamicsGroup,DeptofAutoEng.,TsinghuaUniv.StateKeyLabofAutomotiveSafetyandEnergy

VehicleAerodynamicsSimulation汽车空气动力学仿真123456汽车空气动力学概述汽车空气动力学仿真特点汽车空气动力学仿真难点汽车空气动力学仿真平台仿真平台（VASS应用总结与展望123456IntroductiontoRoadVehicleAerodynamicsSomeSalientFeaturesofRoadVehicleFlowSimulationMainDifficultiesofRoadVehicleFlowSimulationVehicleAerodynamicsSimulationSystem（VASSVASSApplicationsConclusionsandOpenFeatures

1汽车空气动力学概述1.1空气动力学对汽车性能的影响1.2汽车空气动力学性能1.3汽车空气动力学特点1.4空气动力学研究方法IntroductiontoVehicleAerodynamics1.11.21.31.4VehicleAttributesAffectedbyAerodynamicsVehicleAerodynamicsCharacteristicsPeculiaritiesofRoadVehicleAerodynamicsMethodsforVehicleAerodynamic

1.1空气动力学对汽车性能的影响VehicleAttributesAffectedbyAerodynamics动力性经济性舒适性安全性美观性Maximumspeed&AccelerationFuelEconomyComfortSafetyVisibility

1.2汽车空气动力学性能VehicleAerodynamicsCharacteristics气动力气动力矩油耗、操纵稳定性流场结构流动机理、气动噪声、雨水流动、尘土堆积aerodynamicforceandmomentcoefficientsfueleconomy,handlingstabilityflowstructureflowmechanism,aerodynamicnoise,rainwater,dustaccumulating

1.2汽车空气动力学性能VehicleAerodynamicsCharacteristics冷却散热器、发动机、制动器和差速器冷却通风与换气进出风口位置、风量、风速及风路，除结雾性能coolingradiator,engine,brake,anddifferentialcoolingventilation&air-exchangeproperlylocateopeningsforairinletsandoutlets,airflowrate,velocity,airflowpath,defrosting,etc.

1.2汽车空气动力学性能VehicleAerodynamicsCharacteristics空气动力分量阻力升力侧向力侧倾力矩横摆力矩纵倾力矩相关的动力性能油耗、最高车速、加速行驶稳定性抗侧风能力（侧移抗侧风能力（侧移抗侧风稳定性行驶稳定性力力矩airforcecomponentsairdragairforcesliftsideforcerollingmomentyawingmomentpitchingmomentperformancefueleconomy,topspeed,accelerationdirectionstabilitycrosswindcrosswindcrosswinddirectionstabilitymoment

1.3汽车空气动力学特点VehicleAerodynamicspeculiarities研究空间有限目标多元化无法量化比较流动复杂manydetailsprimarilydeterminedby“otherthanaerodynamic”argumentstheobjectivesofaerodynamicsdifferingwidelydifficulttobequantifiedforweighingtherelativeimportancecomplexflow

1.3汽车空气动力学特点VehicleAerodynamicspeculiarities研究空间有限车身设计主要由机械工程学、人体工程学和美学等决定，外形和车内空气动力学设计优化的研究与应用均仅能在有限的机动空间中进行manydetailsprimarilydeterminedby“otherthanaerodynamic”argumentsWiththeracecarbeingtheonlyexception,theshapeofaroadvehicleisnotprimarilydeterminedbytheneedtogeneratespecificaerodynamiceffects--as,forinstance,anairplaneisdesignedtoproducelift

1.3汽车空气动力学特点VehicleAerodynamicspeculiarities无法量化比较汽车空气动力学优化设计与控制研究需考虑艺术、时尚和喜好。

而艺术、时尚和喜好与气动性能的重要性是无法具体量化比较的。

difficulttobequantifiedforweighingtherelativeimportanceWhiletheprocessofweighingtherelativeimportanceofasetofneedsfromvariousdisciplinesisgenerallycomparabletothatinotherbranchesofappliedfluidmechanics,thesituationinvehicleaerodynamicsisuniqueinthatanadditionalcategoryofargumentshastobetakenintoaccount:

art,fashion,andtaste.Incontrasttotechnicalandeconomicfactors,theseadditionalargumentsaresubjectiveinnatureandcannotbequantified.

1.3汽车空气动力学特点VehicleAerodynamicspeculiarities目标多元化共同目标不同目标低阻力负升力通风与空调气动噪声侧风敏感性赛车、高速车轿车、公共汽车轿车、公共汽车轿车、厢式车theobjectivesofaerodynamicsdifferingwidelydesirableforallroadvehicle:

lowdragdifferentrequirements:

negativeliftracecars,highspeedcarsventilation&aircond.cars,busescrosswindsensitivitycars,vanslowwindnoisecars,buses

1.3汽车空气动力学特点VehicleAerodynamicspeculiarities几何结构复杂流动复杂粘性湍流强三维性非定常旋涡分离内外流相互作用热交换地面效应complexgeometryexternalflowandinternalflowinteractionheatexchangegroundeffectViscosityturbulencestrong3Deffectsunsteadyvortex&flowseparation

1.4空气动力学研究方法MethodsforVehicleAerodynamics风洞试验堵塞效应地面效应投资大周期长内部流动困难数值仿真发展迅速应用广泛新途径wind-tunneltesting:

blockagegroundproximityeffecthighcostcosttimedifficultiesforinternalflowCFD,numericalsimulationdevelopedquicklywidelyusednewdesigntool

FeaturesofVehicleAerodynamicsSimulation2汽车空气动力学仿真特点可预先研究不受条件限制信息丰富成本低周期短usedinearlydesignstagenearlynolimitationsmoreinformationlowcostsavingtime

FeaturesofVehicleAerodynamicsSimulation2汽车空气动力学仿真特点可预先研究性能研究设计优化提供依据usedinearlydesignstageperformanceresearchduringtheearlydesignperiod,itcangenerateinformationbeforeatestablemodelevenexists.design&optimizeaerodynamicdesignandperformancestudymaybestudiediterativellywiderangeofdesignoptionsCFDsimulationiswellsuitedtotheanalysisofawiderangeofshapeoptions,etc.设计初期：

空气动力学性能预测、分析与气动设计交叉进行，得最佳气动设计为汽车造型、空调和通风系统的设计与布置提供依据。

FeaturesofVehicleAerodynamicsSimulation2汽车空气动力学仿真特点不受条件限制流动参数范围广泛无干扰效应等影响不受湍流、风速风向、气温气压以及Re数等限制，能给出流场参数定量结果。

无洞壁干扰、风洞试验段堵塞效应，可避免风洞试验的支架干扰、模型弹性变形等技术问题以及道路试验条件和交通状况的影响Withoutthelimitationsofturbulence,windvelocity,pressure,temperatureandReynoldsnumbersetc.numericalmethodsarenotnecessarilyburdenedwiththelimitationsofthewindtunnel.Forexample,computationalspacecanbemadelargeenoughtoeliminateblockageeffects.

FeaturesofVehicleAerodynamicsSimulation2汽车空气动力学仿真特点信息丰富各种行驶状况瞬态气动特性各种行驶状况，获得比风洞试验更丰富的信息，包括试验难以测量和解释的信息侧风时瞬态气动特性影响操纵稳定性的研究，数值仿真比风洞试验方法更具优势非定常气动干扰同向及对开时非定常气动干扰等试验难于研究，仿真更有其独特优点muchmoreinformationavailablethanfromaroutineexperimentsometimesaCFDsimulationpermitstheinvestigationofsituationsthatcannoteberealisticallyduplicatedinawindtunnel,suchastransientcrosswindsensitivity.theaerodynamicsoftwovehiclesinthepassingorovertakingmode,forexample,posesadifficultproblemforwindtunneltests.

FeaturesofVehicleAerodynamicsSimulation2汽车空气动力学仿真特点70’s风洞试验数值仿真100h成本低周期短90’s1800h成本降低了近100倍lowcostsavingtimeCFDisbecomingmarkedlymoreeconomicalastimegoesduetotherevolutionaryadvancesincomputertechnology

DifficultiesofVehicleAerodynamicsSimulation3汽车空气动力学仿真难点1、几何结构复杂，网格建模困难complexgeometry,gridgenerationdifficult

DifficultiesofVehicleAerodynamicsSimulation3汽车空气动力学仿真难点2、为充分发展湍流，不能按层流计算流动fulldevelopedturbulentflow

DifficultiesofVehicleAerodynamicsSimulation3汽车空气动力学仿真难点3、流动强三维性，难于简化分析strongthree-dimensionaleffects,2Dsolutionisnotsuitable

DifficultiesofVehicleAerodynamicsSimulation3汽车空气动力学仿真难点4、各种尺度旋涡，闭式、开式分离流动；机理还不很清除，物理数学模型问题vortexflow,closedoropenregionsofseparatedflow

DifficultiesofVehicleAerodynamicsSimulation3汽车空气动力学仿真难点5、地面效应，航空成果难于直接应用groundproximityeffect,aircraftindustrymethodsarenotalwaysdirectlyapplicableorsuitabletotreatproblemsofvehicleaerodynamics.

DifficultiesofVehicleAerodynamicsSimulation3汽车空气动力学仿真难点6、流场与温度场耦合,热源难于确定flowfieldcouplingtemperaturefield,enginecooling,etc.

DifficultiesofVehicleAerodynamicsSimulation3汽车空气动力学仿真难点7、流场相互作用问题，存在内外流耦合问题internalandexternalflowfieldsarecloselyrelated.Bothflowfieldsmustbeconsideredtogether

DifficultiesofVehicleAerodynamicsSimulation3汽车空气动力学仿真难点8、流动非定常，定常体系难于考虑flowisunsteady,however,theaerodynamicdesignsystemisasteadyone.

4汽车空气动力学数值仿真平台VehicleAerodynamicsSimulationSystem（VASS4.1开发背景4.2技术方案4.3系统组成4.4仿真环境4.5技术水平4.6主要特色backgroundtechnicalblueprintsystemintroductionsimulationenvironmenttechnicallevelmainfeatures

4.1仿真平台开发背景BackgroundofVASSDevelopment国外国际上各有关厂、所和学校在80年代初就开始了相关研究并建立了仿真系统国内我国还处于起步阶段,还没有相应仿真系统backgroundoverseas:

CFDisadevelopmenttooldomestic:

noCFDsystemforvehicleaerodynamicssimulation

4.1仿真平台开发背景BackgroundofVASSDevelopment清华大学985项目轿车车身车型总体设计关键技术和轿车数字化工程均将汽车空气动力学仿真平台作为主要研究内容，希为汽车车型车身设计能力的提高提供技术支持vehicleaerodynamicssimulationsystem（VASSdevelopmentisoneofthemainresearchsubjectsatTsinghuaUniversity

4.2仿真平台技术方案TechnicalBluePrintforVASS网格系统流场控制方程方程求解方法湍流模型分区生成结构/非结构杂交化网格雷诺平均N－S方程RANS有限体积法FVM二方程湍流模型/低Re数修正ThecapabilityofanunstructuredhybridgridmethodtocomputetheNavier-Stokesequationsisdiscussedforcomplexflowsaroundautomobileconfigurations.Theunstructuredhybridgrid,whichiscomposedofastructuredorasemistructuredgridforthenear-wallviscousregion,aprismaticgridfortheexteriorregularcomputationaldomain,andanunstructuredgridfortheremainderofthecomputationaldomain,isusedtotreatsuchviscousflows.TheNavier-Stokesequationsaresolvedonthehybridgridbyacell-vertex,upwindfinitevolumemethod.

4.3仿真平台系统组成VASSIntroduction主要模块非结构网格生成模块结构网格生成模块数学物理模型选择模块初始条件设定模块边界条件设定模块计算控制条件设定模块数值计算模块气动力及气动力矩计算模块mainmodulesunstructuredgridgenerationprismaticgridgenerationtheoreticalmodelselectioninitialconditiondeterminationboundaryconditiondeterminationcalculationcontroldeterminationnumericalcomputationaerodynamicforceandmomentcal.

4.3仿真平台系统组成VASSIntroduction系统窗口systemwindows

4.3仿真平台系统组成VASSIntroduction系统窗口systemwindows

4.3仿真平台系统组成VASSIntroduction系统窗口systemwindows几何数据引入、网格生成、网格检查、边界条件生成、边界条件检查、流体热物性质、工况条件、计算控制参数、仿真计算、后处理、结果输出

Hardware,software&OperatingSystem4.4仿真平台仿真环境硬件环境：

操作系统：

软件环境:

内存>256MB硬盘空间>3GWindowsNT或UNIXICEM-CFD4.0STAR-CD3.1simulationenvironmenthardwareoperatingsystemsoftwarememory>256MBharddisk>3GWindowsNTorUNIXICEM-CFD4.0STAR-CD3.1

4.5仿真平台技术水平VASSEvaluation专业性：

能够有效模拟复杂的三维汽车流场的粘性湍流流动。

通用性：

能对于不同车型生成自适应网格，并可模拟多种工况条件，参数设置方便平台具有良好的操作性和可扩容性specializedinvehicleaerodynamicssimulation,automaticadaptivegridsystemgeneration,suitabletoextensivesituations,easytooperate

4.5仿真平台技术水平VASSEvaluation核心软件可靠，仿真精度高ICEM－CFD，STAR－CD国际汽车界广泛实用系统验证考核国际通用考核汽车流场计算准确性的Ahmed模型，气动阻力试验值0.184,计算值0.181,误差1.63%ThenumericalaccuracyofVASShasbeendiscussedbycomparingwith