王洪伟学习教程.pptx
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1、1Textbook:气体动力学基础王新月,陆利蓬 等 Fluid MechanicsFrank M.WhiteReferences:气体动力学基础潘锦珊等Grades:Homework:20%In class discuss&quiz:10%Midterm exam:30%(Open books)Final exam:40%(Close books)第1页/共35页2 Schedulel Chapter 1Introduction(6 hours)l Chapter 2Fluid Statics(4 hours)l Chapter 3Integral Relations(12 hours)l
2、Midterm Exam(2 hours)l Chapter 4Differential Relations(12 hours)l Chapter 5Boundary Layer(6 hours)lSummary(2 hours)lFinal Exam第2页/共35页3 Chapter 1 Chapter 1 Introduction 1.1 Preliminary Remarks When you think about it,almost everything on this planet either is a fluid or moves within or near a fluid.
3、-Frank M.White第3页/共35页4Curved shoot(Banana shoot)Force on a rotating cylinderSome examplesKarman VortexTacoma Bridge第4页/共35页5JupiterHuman plumeWing tip vortexTornadoSome other examples第5页/共35页6How can an airplane fly?Airplanes第6页/共35页7A turbofan(涡扇)jet engine第7页/共35页8What is Fluid Mechanics?Fluid Me
4、chanics is the study of fluid either in motion(Fluid Dynamics 流体动力学)or at rest(Fluid Statics 流体静力学)and subsequent effects of the fluid upon the boundaries,which may be either solid surfaces or interfaces with other fluids.What is a fluid?第8页/共35页9The concept of a fluidA solid can resist a shear stre
5、ss(剪切应力)by a static deformation.A fluid can not resist a shear stress by a static deformation.Any shear stress applied to a fluid,no matter how small,will result in motion of that fluid.The fluid moves and deforms continuously as long as the shear is applied.第9页/共35页10History and Scope of Fluid Mech
6、anicsPre-history:Sailing ships with oars(橹桨)and irrigation system were both known in prehistory第10页/共35页11Archimedes(285-212 BC)lParallelogram law for addition of vectorslLaw of buoyancy曹冲(196-208)第11页/共35页12Leonardo da Vinci(1452-1519)lEquation of conservation of mass in one-dimensional steady flow
7、lExperimentalistlTurbulence第12页/共35页13Isaac Newton(1642-1727)lLaws of motionlLaws of viscosity of newtonian fluid第13页/共35页1418th centuryMathematicians:Euler(欧拉):Euler equationBernoulli(伯努利):Bernoulli equationIdeal flow solutionsDAlembert(达朗贝尔):DAlembert paradox(佯谬,疑题)Engineers:Hydraulics(水力学),relayi
8、ng on experimentChannels,Ship resistance,Pipe flowsPitot Venturi Torricelli Poiseuille第14页/共35页1519th centuryNavier(1785-1836)&Stokes(1819-1905)N-S equationReynolds(1842-1912)TurbulenceFamous experiment on transition Reynolds Number第15页/共35页1620th centuryLudwig Prandtl(1875-1953)钱学森(1911-2009)陆士嘉(19
9、11-1986)Boundary layer theory(1904)The father of modern fluid mechanicsVon Karman(1881-1963)第16页/共35页171.2 Some Properties of fluids(1)Viscosity(粘性)When a fluid is sheared(剪切),it begins to move.Subsequently,a pair of forces appear on the shear surface,which resists the shear motion of the fluid.This
10、 is called viscosity.The nature of viscosityFor liquid it is cohesion(结合力)(oil_00100.mov)For gas it is the transport of momentum(动量输运)(Particle_flow.mov)第17页/共35页18Velocity gradientNewtonian law of viscosity(牛顿粘性定律,牛顿内摩擦定律)UUu(y)xyShear stressThe velocity gradient is comparable to deformation.This k
11、ind of linear fluid is called Newtonian fluid.(牛顿流体)m:Coefficient of viscosity Dynamic coefficient of viscosity(动力粘性系数)N s/m2Invisid flow,Ideal flow第18页/共35页19(2)Compressibility(压压缩性缩性)Incompressible(不可压):r=const Most liquid flows are treated as incompressible.(Only 1%increase if pressure increase b
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