Copyright by Dr.Zheyan Jin Chapter 1 Introduction to Aerodynamics 1.2 Some Fundamental Aerodynamic Variables Pressure: The normal force per unit area exerted on a surface due to the time rate of change of momentum of the gas molecules impacting on that surface. Density: Mass per unit volume. The temperature of a gas is directly proportional to the average kinetic energy of the molecules of the Temperature: fluid.In fact,if KE is the mean molecular kinetic energy,then temperature is given by KE=3kT/2, where k is the Boltzmann constant. velocity is the rate of change of position.It is Velocity: a vector physical quantity;both speed and direction are required to define it
Copyright by Dr. Zheyan Jin Chapter 1 Introduction to Aerodynamics Chapter 1 Introduction to Aerodynamics 1.2 Some Fundamental Aerodynamic Variables Pressure: The normal force per unit area exerted on a surface due to the time rate of change of momentum of the gas molecules impacting on that surface. Density: Mass per unit volume. The temperature of a gas is directly proportional to the average kinetic energy of the molecules of the fluid. In fact, if KE is the mean molecular kinetic energy, then temperature is given by KE=3kT/2, where k is the Boltzmann constant. Temperature: velocity is the rate of change of position. It is a vector physical quantity; both speed and direction are required to define it. Velocity: The temperature of a gas is directly proportional to the average kinetic energy of the molecules of the fluid. In fact, if KE is the mean molecular kinetic energy, then temperature is given by KE=3kT/2, where k is the Boltzmann constant. Temperature:
Copyright by Dr.Zheyan Jin Chapter 1 Introduction to Aerodynamics 1.2 Some Fundamental Aerodynamic Variables ↑yd V+dV 之-- dy t=lim( dA 1 The limiting form of the magnitude of the frictional Shear Stress: force per unit area,where the area of interest is perpendicular to the y axis and has shrunk to nearly zero at point 1. dv T=μ μ，viscosity coefficient y dV/dy,velocity gradient In reality,u is a function of the temperature of the fluid
Copyright by Dr. Zheyan Jin Chapter 1 Introduction to Aerodynamics Chapter 1 Introduction to Aerodynamics 1.2 Some Fundamental Aerodynamic Variables a b dy y V+dV V f dF y V d d 1 2 lim ( ) dA dFf The limiting form of the magnitude of the frictional force per unit area, where the area of interest is perpendicular to the y axis and has shrunk to nearly zero at point 1. Shear Stress: μ,viscosity coefficient dV/dy, velocity gradient In reality, μis a function of the temperature of the fluid
Copyright by Dr.Zheyan Jin Chapter 1 Introduction to Aerodynamics 1.3 Aerodynamic Forces and Moments Pressure distribution over the body surface. Two sources: Shear stress distribution over the body surface. Illustration of pressure and shear stress on an aerodynamic surface
Copyright by Dr. Zheyan Jin Chapter 1 Introduction to Aerodynamics Chapter 1 Introduction to Aerodynamics 1.3 Aerodynamic Forces and Moments Pressure distribution over the body surface. Two sources: Shear stress distribution over the body surface. τ p s Illustration of pressure and shear stress on an aerodynamic surface