王洪伟PPT课件.ppt

王洪伟PPT课件.ppt

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,SchoolofJetPropulsion,ENGINEERINGFLUIDMECHANICS,Textbook:

气体动力学基础王新月，陆利蓬等References:

FluidMechanicsFrankM.White气体动力学基础潘锦珊等Teachers:

陆利蓬王洪伟邹正平（4-5班）李秋实景晓东李志平（1-3班）Grades:

30%homework+70%finalexam,ContentsChapter1Introduction（6hours）Chapter2FluidStatics（4hours）Chapter3IntegralRelations（12hours）Chapter4DifferentialRelations（8hours）Chapter5BoundaryLayer（6hours）Chapter6FlowCompressibility（2hours）Chapter7Vorticity（4hours）Summary（2hours）,Chapter1Introduction,1.1PreliminaryRemarksWhenyouthinkaboutit,almosteverythingonthisplaneteitherisafluidormoveswithinornearafluid.-FrankM.White,Someexamples,Jupiter,Humanplume,Wingtipvortex,Tornado,A3807379.824.2（m）,An-2258488.418.1（m）,Aturbofan（涡扇）jetengine,；,CFM56inMTU,WhatisFluidMechanics?

FluidMechanicsisthestudyoffluideitherinmotion（FluidDynamics流体动力学）oratrest（FluidStatics流体静力学）andsubsequenteffectsofthefluidupontheboundaries,whichmaybeeithersolidsurfacesorinterfaceswithotherfluids.,Whatisafluid?

Theconceptofafluid,Asolidcanresistashearstress（剪切应力）byastaticdeformation.Afluidcannotresistashearstressbyastaticdeformation.Anyshearstressappliedtoafluid,nomatterhowsmall,willresultinmotionofthatfluid.Thefluidmovesanddeformscontinuouslyaslongastheshearisapplied.,HistoryandScopeofFluidMechanics,Pre-history:

Sailingshipswithoars（橹桨）andirrigationsystemwerebothknowninprehistory,Archimedes（285-212BC）,ParallelogramlawforadditionofvectorsLawofbuoyancy,曹冲（196-208）,LeonardodaVinci（1452-1519）,Equationofconservationofmassinone-dimensionalsteadyflowExperimentalistTurbulence,IsaacNewton（1642-1727）,LawsofmotionLawsofviscosityofNewtonianfluid,18thcentury,Mathematicians：

Euler（欧拉）：

EulerequationBernoulli（伯努利）：

Bernoulliequation,Idealflowsolutions,DAlembert（达朗贝尔）：

DAlembertparadox（佯谬，疑题）,Engineers：

Hydraulics（水力学）relayingonexperiment,Channels，Shipresistance，Pipeflows,PitotVenturiTorricelliPoiseuille,19thcentury,Navier（1785-1836）&Stokes（1819-1905）N-Sequation,Reynolds（1842-1912）TurbulenceFamousexperimentontransitionReynoldsNumber,20thcentury,LudwigPrandtl（1875-1953）,钱学森（1911-2009）,陆士嘉（1911-1986）,Boundarylayertheory（1904）Tobethesinglemostimportanttoolinmodernflowanalysis.,Thefatherofmodernfluidmechanics,VonKarman（1881-1963）,1.2SomePropertiesoffluids,

（1）.viscosity（粘性）*Definition：

Whenafluidissheared（剪切）,itbeginstomove.Subsequently,apairofforcesappearontheshearsurface,whichresiststheshearmotionofthefluid.Thisiscalledviscosity.,*Thenatureofviscosity：

Forliquiditiscohesion（结合）（oil_00100.mov）,Forgasitisthetransportofmomentum（动量输运）（Particle_flow.mov）,Velocitygradient,*Newtonianlawofviscosity（牛顿粘性定律，牛顿内摩擦定律）,Shearstress,Thevelocitygradientiscomparabletodeformation.,ThiskindoflinearfluidiscalledNewtonianfluid.（牛顿流体）,Realfluid（Viscous）,Idealfluid（Inviscid&Frictionless）,Forcertainfluid,misfunctionoftemperature.（liquids,gases）,m:

CoefficientofviscosityDynamiccoefficientofviscosity（动力粘性系数）Ns/m2,n=m/r:

Kinematiccoefficientofviscosity（运动粘性系数）m2/s,

（2）.Compressibility（压缩性）,Incompressible（不可压）:

r=constMostliquidflowsaretreatedasincompressible.Only1%increaseifpressureincreaseby220,Compressible（可压缩）:

r=r（P,T）Gasescanalsobetreatedasincompressiblewhentheirvelocityislessthan0.3Manumbers,（3）.StateRelationsforGasesPerfect-gasLaw（理想气体状态方程）,ErnstMach,R=287.06forair,（4）.ThermalConductivity（热传导）,:

heatfluxinndirectionperunitareak:

coefficientofthermalconductivityT:

temperaturen:

directionofheattransfer,Fourierslawofheatconduction,1.3TheFluidasaContinuum（连续介质）,Density（密度）,Elementalvolume（流体微团、流体质点）Largeenoughinmicroscope（微观）10-9mm3ofairatstandardconditionscontainsapproximately3107molecules.,Mostengineeringproblemsareconcernedwithphysicaldimensionsmuchlargerthanthislimitingvolume.,Suchafluidiscalledacontinuum,whichsimplymeansthatitsvariationinpropertiesissosmooththatthedifferentialcalculuscanbeusedtoanalyzethesubstance.,*Smallenoughinmacroscope（宏观）.,微观无穷大宏观无穷小,Sodensityisessentiallyapointfunctionandfluidpropertiescanbethoughtofasvaryingcontinuallyinspace.,1.4Surfaceforce（表面力）andbodyforce（质量力，体积力）,Surfaceforcesactcontinuouslyonthesidesurfacesoffluidelements.Pressure,friction.Contactsurfaceforceperunitarea（单位面积）（应力）,Bodyforcesactontheentiremassoftheelement.Gravity,electromagnetic.NocotactPerunitmass（单位质量）g,1.5Twodifferentpointsofviewinanalyzingproblemsinmechanics,*TheEulerianview（欧拉观点）andtheLagrangianview（拉格朗日观点）TheEulerianviewisconcernedwiththefieldofflow,appropriatetofluidmechanics.,TheLagrangianviewfollowsanindividualparticlemovingthroughtheflow,appropriatetosolidmechanics.,Thecontrastoftwoframes,*Flowclassification（流动分类）,Ac