第一章-2012-王洪伟.ppt

1 ENGINEERINGFLUIDMECHANICS SchoolofJetPropulsion2012 2 Textbook 气体动力学基础 王新月 陆利蓬等 FluidMechanics FrankM WhiteReferences 气体动力学基础 潘锦珊等Grades Homework 20 Inclassdiscuss quiz 10 Midtermexam 30 Openbooks Finalexam 40 Closebooks 3 ScheduleChapter1 Introduction 6hours Chapter2 FluidStatics 4hours Chapter3 IntegralRelations 12hours MidtermExam 2hours Chapter4 DifferentialRelations 12hours Chapter5 BoundaryLayer 6hours Summary 2hours FinalExam 4 Chapter1Introduction 1 1PreliminaryRemarksWhenyouthinkaboutit almosteverythingonthisplaneteitherisafluidormoveswithinornearafluid FrankM White 5 Someexamples 6 Jupiter Humanplume Wingtipvortex Tornado Someotherexamples 7 Howcananairplanefly Airplanes 8 Aturbofan 涡扇 jetengine 9 WhatisFluidMechanics FluidMechanicsisthestudyoffluideitherinmotion FluidDynamics流体动力学 oratrest FluidStatics流体静力学 andsubsequenteffectsofthefluidupontheboundaries whichmaybeeithersolidsurfacesorinterfaceswithotherfluids Whatisafluid 10 Theconceptofafluid Asolidcanresistashearstress 剪切应力 byastaticdeformation Afluidcannotresistashearstressbyastaticdeformation Anyshearstressappliedtoafluid nomatterhowsmall willresultinmotionofthatfluid Thefluidmovesanddeformscontinuouslyaslongastheshearisapplied 11 HistoryandScopeofFluidMechanics Pre history Sailingshipswithoars 橹桨 andirrigationsystemwerebothknowninprehistory 12 Archimedes 285 212BC ParallelogramlawforadditionofvectorsLawofbuoyancy 曹冲 196 208 13 LeonardodaVinci 1452 1519 Equationofconservationofmassinone dimensionalsteadyflowExperimentalistTurbulence 14 IsaacNewton 1642 1727 LawsofmotionLawsofviscosityofnewtonianfluid 15 18thcentury Mathematicians Euler 欧拉 EulerequationBernoulli 伯努利 Bernoulliequation Idealflowsolutions D Alembert 达朗贝尔 D Alembertparadox 佯谬 疑题 Engineers Hydraulics 水力学 relayingonexperiment Channels Shipresistance Pipeflows PitotVenturiTorricelliPoiseuille 16 19thcentury Navier 1785 1836 Stokes 1819 1905 N Sequation Reynolds 1842 1912 TurbulenceFamousexperimentontransitionReynoldsNumber 17 20thcentury LudwigPrandtl 1875 1953 钱学森 1911 2009 陆士嘉 1911 1986 Boundarylayertheory 1904 Thefatherofmodernfluidmechanics VonKarman 1881 1963 18 1 2SomePropertiesoffluids 1 Viscosity 粘性 Whenafluidissheared 剪切 itbeginstomove Subsequently apairofforcesappearontheshearsurface whichresiststheshearmotionofthefluid Thisiscalledviscosity Thenatureofviscosity Forliquiditiscohesion 结合力 oil 00100 mov Forgasitisthetransportofmomentum 动量输运 Particle flow mov 19 Velocitygradient Newtonianlawofviscosity 牛顿粘性定律 牛顿内摩擦定律 Shearstress Thevelocitygradientiscomparabletodeformation ThiskindoflinearfluidiscalledNewtonianfluid 牛顿流体 m CoefficientofviscosityDynamiccoefficientofviscosity 动力粘性系数 N s m2 Invisidflow Idealflow 20 2 Compressibility 压缩性 Incompressible 不可压 r constMostliquidflowsaretreatedasincompressible Only1 increaseifpressureincreaseby220 Compressible 可压缩 r r p T Gasescanalsobetreatedasincompressiblewhentheirvelocityislessthan0 3Manumbers ErnstMach 21 4 ThermalConductivity 热传导 Fourier slawofheatconduction 3 StateRelationsforGases R 287 06forair Perfect gasLaw 理想气体状态方程 22 1 3TheFluidasaContinuum 连续介质 Density 密度 Elementalvolume 流体微团 质点 Largeenoughinmicroscope 微观 10 9mm3ofairatstandardconditionscontainsapproximately3 107molecules Mostengineeringproblemsareconcernedwithphysicaldimensionsmuchlargerthanthislimitingvolume 23 Suchafluidiscalledacontinuum Whichsimplymeansthedifferentialcalculuscanbeusedtoanalyzethesubstance Smallenoughinmacroscope 宏观 微观足够大 宏观足够小 24 1 4Surfaceforce 表面力 andbodyforce 质量力 体积力 Surfaceforcesactcontinuouslyonthesidesurfacesoffluidelements Pressure Friction ContactPerunitarea 单位面积 应力 Bodyforcesactontheentiremassoftheelement Gravity Electromagnetic NocontactPerunitmass 单位质量 g 25 1 5Twodifferentpointsofviewinanalyzingproblemsinmechanics TheLagrangianview 拉格朗日法 TheLagrangianviewfollowsanindividualparticlemovingthroughtheflow appropriatetosolidmechanics Thecontrastoftwoframes TheEulerianviewisconcernedwiththefieldofflow appropriatetofluidmechanics TheEulerianview 欧拉法 26 Flowclassification 流动分类 AccordingtoEulerianview anypropertyfisfunctionofcoordinates space andtime InCartesiansystem 直角坐标系 itcanbeexpressedas f x y z t x y z t Eulerianvariablecomponent 欧拉变数 f Functionoftime unsteady 非定常 steady 定常 f Functionofspace one dimensional 1 D 一维 two dimensional 2 D 二维 three dimensional 3 D 三维 27 OneTwodimensionalThree SteadyUnsteady CompressibleIncompressible ViscousInviscid Threedimensionalunsteadycompressibleviscousflow Onedimensionalsteadyincompressibleinvisidflow 28 Apathlineistheactualpathtraversedbyagivenfluidparticles 1 6Pathline 迹线 Streamline 流线 Flowfield 流场 Pathlinesinsteadyflow Pathlinesinunsteadyflow 29 Astreamlineisthelineeverywheretangenttothevelocityvectoratagiveninstant Forsteadyflow Streamline Pathline Streamlinesinsteadyflow Streamlinesinunsteadyflow 30 Streamsurface 流面 Streamtube 流管 Flowpattern 流型 Streamsurface Acollectionofallthestreamlinespassingthroughalinewhichisnotastreamline Streamtube Aclosedcollectionofstreamlines Flowpattern asetofstreamlines 31 Flowfield 流场 Inagivenflowsituation thepropertiesofthefluidarefunctionsofpositionandtime namelyspace timedistributionsofthefluidproperties Streamlinecannotintersect 相交 exceptforsingularitypoint 奇点 32 Streamlineequation 流线方程 ds Infinitesimal 无穷小 33 Example Giventhesteadytwo dimensionalvelocitydistributionu kx v ky w 0 wherekisapositiveconstant Computeandplotthestreamlinesoftheflow includingdirection Solution Sincew 0 themotionistwo dimensional Integrating Hyperbolas 双曲线 34 Direction u kx v kyQuadrantI 第一象限 x 0 y 0 u 0 v 0 Atthepoi