Compressible Flow Free Textbook

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Why the flow is choked?

Here, the explanation is based on the equations developed earlier and there is no known explanation that is based on the physics. First, it has to be recognized that the critical point is when

. It will be shown that a change in location relative to this point change the trend and it is singular point by itself. For example, $dP(@ M=1) = \infty$ and mathematically it is a singular point (see equation (9.24)). Observing from equation (9.24) that increase or decrease from subsonic just below one $M= (1 - \epsilon)$ to above just above one $M= (1+ \epsilon)$ requires a change in a sign pressure direction. However, the pressure has to be a monotonic function which means that flow cannot crosses over the point of

. This constrain means that because the flow cannot ``crossover''

the gas has to reach to this speed,

at the last point. This situation is called choked flow.

Next: The Trends Up: The Mechanics and Why Previous: The Mechanics and Why Index

Created by:Genick Bar-Meir, Ph.D.
On: 2007-11-21