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August 12, 2014, 10:03 |
Supersonic flow over flate plate
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#1 |
New Member
Sazid Zamzl Hoque
Join Date: Aug 2014
Posts: 6
Rep Power: 11 |
Hi everyone,
I am trying to model supersonic flow over flat plate in ansys fluent. I am using fluent for last two months only. I am finding difficult to give the outlet boundary condition in fluent. I applied the outflow boundary condition to outlet. but, it gives an error as I am using ideal gas as fluid. |
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August 12, 2014, 10:25 |
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#2 | |
Senior Member
Amin
Join Date: Oct 2013
Location: Germany
Posts: 397
Rep Power: 14 |
Quote:
Outflow boundary condition is a special model! It can not be used for compressible flow and you know every supersonic flow is compressible! It can not be used with pressure inlet boundary condition! You can find more details in ansys fluent user guide! Good luck! |
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August 12, 2014, 11:12 |
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#3 |
New Member
Sazid Zamzl Hoque
Join Date: Aug 2014
Posts: 6
Rep Power: 11 |
Thanks Mr. amin.z,
yeah I just got the information about outflow boundary condition. But I cannot figure out what are the actual boundary conditions that should be used in compressible flow over flat plate. The boundary conditions I have used are: inlet : pressure inlet outlet : pressure outlet free stream : pressure far field flat plate : wall But the solution is not converging, are these boundary conditions correct? |
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August 12, 2014, 11:34 |
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#4 | |
Senior Member
Amin
Join Date: Oct 2013
Location: Germany
Posts: 397
Rep Power: 14 |
Quote:
When you using "pressure far field", the outlet face must be far enough! The convergence for supersonic flows usually need great iterations! If divergence happens for your model, you must change the under relaxation factors (in pressure based solver) or Courant number (in density based solver) for stabling the solution! Last edited by amin.z; August 12, 2014 at 13:22. |
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August 12, 2014, 14:11 |
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#5 |
New Member
Sazid Zamzl Hoque
Join Date: Aug 2014
Posts: 6
Rep Power: 11 |
I tried changing the courant number and under ralaxation factor, but still the solution is diverging. If you give me a fluent file of the flow upto convergent it will be very helpfull for me.
Thank you |
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August 12, 2014, 14:46 |
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#6 |
Senior Member
Amin
Join Date: Oct 2013
Location: Germany
Posts: 397
Rep Power: 14 |
I don't understand your meaning dear!
Are your sure quality of your grid is ok and it's enough fine...!? It can be reason of divergence! Also you must ensure that your initalization be close to your final results! It's very important for converging! For 1 year, I worked on supersonic flow and convergent-divergent nozzles! I'm suggesting you: "For supersonic flow analysis you must be very patient! Because somitimes a small change in solution setup and B.Cs can diverge the solution!" |
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August 12, 2014, 14:56 |
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#7 |
New Member
Sazid Zamzl Hoque
Join Date: Aug 2014
Posts: 6
Rep Power: 11 |
I used instructions to mesh the flow region from "Computational fluid dynamics: a practical approach" and I think the quality is fine. Anyway thanks a lot for your help.
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August 17, 2014, 04:40 |
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#8 | |
New Member
Sazid Zamzl Hoque
Join Date: Aug 2014
Posts: 6
Rep Power: 11 |
Quote:
the solution is converged for the supersonic flow. But the solution is not correct. what will be the temperature for the plate? I know the Tinf (288.16 K). And should I have to give back flow temperature in pressure outlet boundary condition? |
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August 17, 2014, 04:54 |
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#9 | |
Senior Member
Amin
Join Date: Oct 2013
Location: Germany
Posts: 397
Rep Power: 14 |
Quote:
What is the solution residuals? Supersonic flows usually need at least 1e-7 for convergence! And do you increase courant number and under relaxation factors after solution convergence with small values of their!?? And if it's ok,check and ensure that BCs been ok! Be careful about "total" input values! , If you have backflow in outlet, of course it's better to set a logical value for its! |
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August 17, 2014, 14:09 |
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#10 | |
New Member
Sazid Zamzl Hoque
Join Date: Aug 2014
Posts: 6
Rep Power: 11 |
Quote:
Thanks a lot amin.z . |
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