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Turning supersonic flow into subsonic

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Old   September 5, 2012, 04:58
Default Turning supersonic flow into subsonic
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Alexander
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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
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Old   September 5, 2012, 07:51
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You can not force the outlet to achieve a pressure. Flow regime defines what should happen at the outlet
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Old   September 5, 2012, 08:08
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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?
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Old   September 5, 2012, 08:34
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It depends just on boundary condition (not outlet) and geometry.
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Old   September 5, 2012, 08:42
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What condition do you think should I enter on the outlet? Tried changing it into "pressure inlet" and it didn't help.
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Old   September 5, 2012, 11:17
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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.
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Old   September 23, 2012, 09:35
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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
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Old   September 23, 2012, 20:10
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Quote:
Originally Posted by Salexv View Post
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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File Type: gif Untitled.gif (26.2 KB, 9 views)
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