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Supersonic and subconic outlet

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Old   March 29, 2007, 03:58
Default Supersonic and subconic outlet
  #1
Dmitry
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I have a problem in modelling a Laval nozzle. I can choose only subsonic or supersonic outlet boundary condition in CFX. But really there are subsonic regions near wall and supersonic region dar from walls. So, what should I do?
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Old   March 29, 2007, 22:43
Default Re: Supersonic and subconic outlet
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HekLeR
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If it's mostly supersonic just run supersonic.
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Old   March 30, 2007, 09:59
Default Re: Supersonic and subconic outlet
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Dmitry
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Thank you, HekLeR. I tried, but when I applied supersonic condition, I didn't get any solution (fatal overflow solver error). When I applied subsonic condition, I got M<<1 at exit.
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Old   April 2, 2007, 17:04
Default Re: Supersonic and subconic outlet
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HekLer
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Probably you still need to run supersonic, but you might have to play with the timestep, eg: smaller maybe....

The problem may be that part of the outlet is subsonic, temporarily, and then there is no way for the system to physically feel the specified pressure.

You might play with stopping the solver just before it blows to see what the solution is looking like. i.e. why is it going bad?

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