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supersonic flow

Paul Sears wrote:
>        I've just been reading Rogers and Mayhew (Engineering Thermodynamics
> Work and Heat Transfer) about venturi devices.  The reason I have been 
> reading it had nothing to do the list, but the stuff I found is relevant.  Gas
> flow can indeed be supersonic in convergent-divergent nozzles.  It's
> described beginning at the bottom of p 380 in the ancient edition (1967)
> I borrowed.  I can't say I worry about it overmuch, but it is interesting
> stuff (and vital in some instances).

You prompted me to dig out my own Fluid Mechanics text (Streeter & Wylie
'75). The supersonic flow occurs in the divergent section of the
convergent-divergent nozzle (like a jet engine) but in the throat, the
flow is still fully choked, or sonic. There are also shock wave
boundaries separating the supersonic flow from the ambient fluid.

I think there could also be supersonic flow in a very small region of a
fully choked valve, right after the minimal aperture, if the shape of
the valve were right. I don't know. It would make for a noisy valve
wouldn't it?
Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!