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Old   December 9, 2004, 09:44
Default supersonic flow
  #1
Steffen
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Hi everyone

I am about to simulate a supersonic flow in a safety valve.Actually in the flow near the smallest diameter is expexted to appear normal shocks, oblique shocks and also expansion fans.The problem right now is that a supersonic flow is appearing all across the smallest diameter but I don't see any shocks when teh flow decelerates afterwards.Perhaps you could help me somehow especially with the settings I have to adjust.Moreover I am not sure which solver to use.I started with the segerated one although it is a high-compressible flow.But if I use the coupled one the program always shows me a divergence.Maybe you could give me some hints about that because I am quite sure that the problem has nothing to do with the grid because I only have quadrates in there.

Thanx
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Old   December 9, 2004, 18:31
Default Re: supersonic flow
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Jason
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Did you turn on ideal gas law? (it's under the material properties)

Even with a quad mesh, you need enough refinement to capture shocks and expansion.

You can try turning of the turbulence model when solving with the coupled solver. Also, the coupled solver has problems dealing with large separation regions. I talked to a tech support today who won't use the coupled solver until you get above Mach 1.5. He swears by the segregated solver, and he has good results to back it up. It might be the way to go for your situation. Just remember your mesh has to be a little finer if you use the segregated solver than the coupled solver.

Hope this helps.

Goodluck, Jason
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Old   December 10, 2004, 03:57
Default Re: supersonic flow
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nabeel mohsin
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hi, if you use segregated solver than start simulation with reduced underrelaxtion factor of momentum nabeel
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Old   January 3, 2005, 11:58
Default what are the boudary
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ravi
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I am solving the supersonic flow through a rectangular duct. I am giving stagnation pressure and temparature at inlet. I know static pressure at outlet. what are the conditons that are to be given at outlet for supersonic flow

ravi
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Old   January 3, 2005, 17:54
Default Re: what are the boudary
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Jason
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If you know the pressure at the exit, then use a pressure outlet boundary condition.

Jason
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