PART I FUNDAMENTAL PRINCIPLES (基本原理)
PART I FUNDAMENTAL PRINCIPLES （基本原理） In part I, we cover some of the basic principles that apply to aerodynamics in general. These are the pillars on which all of aerodynamics is based
Chapter 1 Aerodynamics Some Introductory Thoughts The term aerodynamics"is generally used for problems arising from flight and other topics involving the flow of air udwig Prandtl, 1949 Aerodynamics: The dynamics of gases, especially of atmospheric interactions with moving objects The American Heritage Dictionary of English Language, 1969
Chapter 1 Aerodynamics: Some Introductory Thoughts The term “aerodynamics” is generally used for problems arising from flight and other topics involving the flow of air. Ludwig Prandtl,1949 Aerodynamics:The dynamics of gases, especially of atmospheric interactions with moving objects . The American Heritage Dictionary of English Language,1969
1. 1 Importance of Aerodynamics Historical Examples o Sea battle between English fleet and Spanish fleet, English channel, 8-8-1588 (英国与西班牙海战,英吉利海峡) o First flight of Wright brothers, 12-27-1903 (怀特兄弟首次飞行) o Minimizing of aerodynamic heating of ICBMS (洲际弹道导弹气动热降低问题)
1.1 Importance of Aerodynamics: Historical Examples Sea battle between English fleet and Spanish fleet, English channel,8-8-1588 (英国与西班牙海战，英吉利海峡） First flight of Wright brothers,12-27-1903 (怀特兄弟首次飞行） Minimizing of aerodynamic heating of ICBMs (洲际弹道导弹气动热降低问题）
o Impetus to the study of fluidmechnics (流体力学研究的推动力) 1. Newtons sine-square law 2. Experiments carried out by D'Alembert 3. Euler's description of the flow model
Impetus to the study of fluidmechnics （流体力学研究的推动力） 1. Newton’s sine-square law 2. Experiments carried out by D’Alembert 3. Euler’s description of the flow model
1. Newtons sine-square law a)Newton considered a fluid flow as a uniform rectilinear stream of particles, much like a cloud of pellets from a shotgun blast Rectilinear stream of discrete particles Upon impacting the body, the particles give up the mentum normal travel downstream along the surface
1. Newton’s sine-square law a) Newton considered a fluid flow as a uniform, rectilinear stream of particles, much like a cloud of pellets from a shotgun blast
b)Newton assumed that upon striking a surface inclined at a angle 6 to the stream, the particles would transfer their normal momentum to the surface but their tangential momentum would be preserved. Hence, after collision with the surface, the particles would then move along the surface. This led to an expression for the hydrodynamics force on the surface which varies as sin 0
b) Newton assumed that upon striking a surface inclined at a angle to the stream, the particles would transfer their normal momentum to the surface but their tangential momentum would be preserved. Hence, after collision with the surface, the particles would then move along the surface. This led to an expression for the hydrodynamics force on the surface which varies as 2 sin
2. DAlembert The experiment results show: the rule that for oblique resistance varies with the sine square of the angle of the incidence holds good only for angle between 50 and 90 deg and must be abandoned for lesser angles
2. D’Alembert The experiment results show: the rule that for oblique resistance varies with the sine square of the angle of the incidence holds good only for angle between 50 and 90 deg and must be abandoned for lesser angles
3. Euler noted The fluid moving toward a body before reaching the latter, bends its direction and its velocity so that when it reaches the body it flows pass it along the surface, and exercise no other force on the body except the pressure corresponding to the single points of the contact
3. Euler noted The fluid moving toward a body “before reaching the latter, bends its direction and its velocity so that when it reaches the body it flows pass it along the surface, and exercise no other force on the body except the pressure corresponding to the single points of the contact
4. Real case for fluid approaching a body All the fluid particles are in random motion, and has a average velocity. During their motion, they collide with each other. The molecules strike on to the solid surface will be rebounded and these rebounded molecules will make collision to other molecules. This process transfers the message of the existence of the body and most of the particles will go other round After the collision between fluid particles and solid surface, the momentum change of the particles is in the perpendicular direction of the surface
4. Real case for fluid approaching a body All the fluid particles are in random motion, and has a average velocity. During their motion, they collide with each other. The molecules strike on to the solid surface will be rebounded, and these rebounded molecules will make collision to other molecules. This process transfers the message of the existence of the body, and most of the particles will go other round. After the collision between fluid particles and solid surface, the momentum change of the particles is in the perpendicular direction of the surface
o First flight of wright brothers DeC.17,1903
First flight of Wright brothers Dec. 17, 1903