文档介绍：Chapter 6
Compressible flow
Introduction
1
When is a pressible?
Pressure
Fluid element
Pathline
pressible flow differs from an pressible one in that significant change happens in the density.
2
Density of a fluid element increases or decreases as the pressure does pressible flow
3
When pressibility important?
When a fluid moves at high speed, density changes e significant
- flow speed
- sound speed
Ma< pressible
Ma>
4
Examples of high speed flow
Ma=
Ma=
Ma=4
Ma=25
5
Flow speed in a typical aeroengine
6
History
Untill the late 1930s, engineers could ignore pressibility of air
Aerodynamics, a subject pressible gas and air flow,makes possible the remarkable progress in modern aeronautics and astronautics
Ernst Mach
Prandtl
von Karman
7
Distinctive features pressible flow
Shock wave
Supersonic nozzle
Laval Nozzle
Ma<1
Ma>1
8
Assumptions pressible flow
Internal energy u and enthalpy h:
Adiabatic flow with negligible heat transfer
Reversible process with fluid friction being neglected
isentropic flow
Perfect gas
Specific heat ration:
9
For isentropic flow:
10