# fluid mechanics 1 (updated 2020-3-10).pdf - Chapter 1...

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Fluid Mechanics (Spring 2020) – Chapter 1 - U. Lei ( 李雨 ) Chapter 1: Introduction Definition of fluids The subject of fluid mechanics Applications of fluid mechanics Microscopic (molecular) versus macroscopic (continuum) approach Continuum approach Eulerian and Lagrangian description Reynolds transport theorem
Fluid Mechanics (Spring 2020) – Chapter 1 - U. Lei ( 李雨 ) Fluid: gas + liquid Three phases of substances: Solids, liquids and gases , depending on different values of pressure and temperature. The density of the solid and liquid are of the same order, and are in general of three order greater than that of the gas. The liquid and solid are group as condensed matters in Physics. The response of the liquid under the action of an applied shear stress is similar to that of the gas, and is fundamentally different from that of the solid. Therefore, the liquid and the gas are grouped together as a new category, the fluid .
Fluid Mechanics (Spring 2020) – Chapter 1 - U. Lei ( 李雨 ) Substance subject to a shear stress γ is fixed for a given τ . γ increases continuously as time increases for a given τ . Propose G τ γ = d dt γ τ μ = Elasticity : Some materials in between: viscoelastic materials / non-Newtonain fluids
Fluid Mechanics (Spring 2020) – Chapter 1 - U. Lei ( 李雨 ) Definition of fluid A fluid is defined as a substance that deforms continuously when subjected to a shear stress , no matter how small that shear stress may be.
Fluid Mechanics (Spring 2020) – Chapter 1 - U. Lei ( 李雨 ) Fluid Mechanics A discipline for the study of the response of the fluid under the action of applied forces
Fluid Mechanics (Spring 2020) – Chapter 1 - U. Lei ( 李雨 ) The response of the fluid includes its translation, rotation and deformation. The applied forces are generalized forces associated with all kinds of the driving mechanisms, including all kinds of forces such as that associated with the above shear stress , the pressure , the gravitational force , the surface tension , the buoyancy resulting from an applied temperature contrast, the electrical force if the fluid is a conductor, the magnetic force , and others.
Fluid Mechanics (Spring 2020) – Chapter 1 - U. Lei ( 李雨 ) Applications of fluid mechanics We live in air and cannot survive without water importance of fluid mechanics Two important topics in the last century : aeronautical and aerospace engineering geophysical fluid dynamics Recently, some interesting fluid mechanics problems in micro-scale appear in the microelectromechanical systems (MEMS).
Fluid Mechanics (Spring 2020) – Chapter 1 - U. Lei ( 李雨 ) Aerodynamics - examples (1) (McGraw Hill, 1982 )
Fluid Mechanics (Spring 2020) – Chapter 1 - U. Lei ( 李雨 ) Aerodynamics - examples (2) ____
Fluid Mechanics (Spring 2020) – Chapter 1 - U. Lei ( 李雨 ) Aerodynamics - examples (3)