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June 4, 2017, 09:57 |
UDF for Real gas model
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#1 |
Member
Kirill Borodin
Join Date: Mar 2016
Posts: 60
Rep Power: 10 |
Hello!
I'm trying to load my real gas model to Fluent, but I cannot even make the ideal gas equation of state work, even though I had taken the UDF for it from the User Guide (7.16.5 in the User Guide). For my problem I have P=15000 Pa, T=120 K at the inlet. The proper value of density for this model must be rho~0.436 kg/m3, but Fluent intializes it with value of rho=2.35E-5 kg/m3 in almost all cells and with value of rho~5E+7 kg/m3 in one cell. The process of calculation lasts for 0 iterations with Courant number CN=0.001, then I have: Divergence detected - temporarily reducing Courant number to 1e-08 and trying again... Error: Internal error at line 1596 in file '..\..\src\rp_mstage.c'. Divergence detected in AMG solver Error: Internal error at line 1596 in file '..\..\src\rp_mstage.c'. Divergence detected in AMG solver Error Object: #f I loaded and compiled the library as it was written in the Guide. Could you please help me with this problem? Regards, Kirill |
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June 5, 2017, 03:36 |
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#2 |
Senior Member
Kal-El
Join Date: Apr 2017
Location: Finland
Posts: 150
Rep Power: 9 |
Did you study the limitations of that code?
Are you using mass-flow inlet? |
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June 5, 2017, 05:07 |
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#3 | |
Member
Kirill Borodin
Join Date: Mar 2016
Posts: 60
Rep Power: 10 |
Quote:
For my problem the total pressure value is 6E7 Pa and total temperature is 1200 K. This corresponds to hypersonic flow with Mach number M~7. Could this problem type somehow influence the solution process with Pressure-based solver? Regards Sent from my C6903 using CFD Online Forum mobile app |
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June 6, 2017, 20:01 |
Try a pipe first
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#4 |
Senior Member
Svetlana Tkachenko
Join Date: Oct 2013
Location: Australia, Sydney
Posts: 415
Rep Power: 15 |
Perhaps you could try the real gas model on a simplified simulation first? For example, create a straight rectangular pipe and try the real gas model in that.
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June 7, 2017, 17:11 |
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#5 | |
Member
Kirill Borodin
Join Date: Mar 2016
Posts: 60
Rep Power: 10 |
Quote:
I also tried to run the calculation for a small number of iterations (for example 10) with the built-in ideal gas EOS and after that I turned on the real gas model (that was supposed to model the same gas with the same EOS). I monitored the evolution of static pressure, density, temperature and velocity fields. The temperature field started crashing after the very first iteration. I guess there's something wrong with energy equation? The other fields started crashing some more iterations later (I guess the crashing temperature field influenced them). Looking forward to your response! Regards Update: I tried this EOS on three different computers with three different versions of Fluent. There were the same problems Sent from my C6903 using CFD Online Forum mobile app |
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June 8, 2017, 15:55 |
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#6 |
Member
Kirill Borodin
Join Date: Mar 2016
Posts: 60
Rep Power: 10 |
Thanks to all - I used a code for real gas model for a too early version of Fluent. The code for 15th version differs from it a bit. Now the example model works
Sent from my C6903 using CFD Online Forum mobile app |
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June 9, 2017, 03:24 |
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#7 |
Senior Member
Svetlana Tkachenko
Join Date: Oct 2013
Location: Australia, Sydney
Posts: 415
Rep Power: 15 |
Congratulations, that was easy
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July 12, 2018, 13:37 |
pls help me
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#8 | |
New Member
Songyuan Liu
Join Date: Jul 2018
Posts: 1
Rep Power: 0 |
hallo, i have the same Problem , can u tell me , where can i find the new code for 15th Version ?
thanks Quote:
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September 7, 2018, 08:16 |
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#9 |
Member
Kirill Borodin
Join Date: Mar 2016
Posts: 60
Rep Power: 10 |
Hello! You may find the code in the User Guide in chapter 7.6.15. The chapter name is User Defined Real Gas Model.
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