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-   -   Turning supersonic flow into subsonic (http://www.cfd-online.com/Forums/fluent/106673-turning-supersonic-flow-into-subsonic.html)

Salexv September 5, 2012 04:58

Turning supersonic flow into subsonic
 
Hello,
I have a supersonic converging-diverging inlet system using external and internal compression system.
My initial flow is Mach 3 and therefore, of course the flow throwout the whole inlet is supersonic.
I am trying to achieve a subsonic outlet of the inlet by increasing the pressure outlet. But it doesn't work because in supersonic flows, Fluent doesn't consider outlet pressure.
So how can I force the flow to become subsonic even though I can't change the pressure outlet?
Thanks

eng_s_sadeghi September 5, 2012 07:51

You can not force the outlet to achieve a pressure. Flow regime defines what should happen at the outlet

Salexv September 5, 2012 08:08

Thank you for your response.

So what you are saying is that there is no way to receive a supersonic inlet with a subsonic outlet (having a normal shock in the diverging part of the system)? In any way possible?

eng_s_sadeghi September 5, 2012 08:34

It depends just on boundary condition (not outlet) and geometry.

Salexv September 5, 2012 08:42

What condition do you think should I enter on the outlet? Tried changing it into "pressure inlet" and it didn't help.

flotus1 September 5, 2012 11:17

The problem is that in a supersonic flow, the flow field is not affected by the conditions downstream. Thus, the flow field in a given geometry is independent of the values you try to specify at the outlet.

Your only chance (if the upstream values are fixed) is to change the geometry.

Salexv September 23, 2012 09:35

Can someone help me please with this problem?
I've seen few works that managed to apply a high pressure outlet in a supersonic inlet, but couldn't reach the authors.
Does anyone know how to enforce it in FLUENT?
Thanks

syavash September 23, 2012 20:10

1 Attachment(s)
Quote:

Originally Posted by Salexv (Post 383198)
Can someone help me please with this problem?
I've seen few works that managed to apply a high pressure outlet in a supersonic inlet, but couldn't reach the authors.
Does anyone know how to enforce it in FLUENT?
Thanks

Hi Alexander,

I have a similar problem and I couldn't manage to find a solution.
There is an image of the geometry and Mach contours that I upload here.
How is it possible to get this solution?! Anyone knows it?


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