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May 14, 2013, 03:23 |
CFX Solver manager runs for a long time!!
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#1 |
New Member
Candy
Join Date: May 2013
Posts: 12
Rep Power: 13 |
Hello Guys,
I cannot understand why the solver takes a long time (more than 2 hours) in the running process and how I can know whether the running is converging or diverging PS: I am using an SST model with a steady state solution. Thank you |
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May 14, 2013, 04:23 |
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#2 |
Senior Member
Matthias Voß
Join Date: Mar 2009
Location: Berlin, Germany
Posts: 449
Rep Power: 20 |
you can look at the convergence history by looking at the graphs in the solver monitor. (right click on Solution in WB2.0 or opening the CFX-Launcher-->Solver--> Monitor Run in Progress)
since you state 2h is a long time to run i assume you´re fairly new to this field. for the future: please provide just a little bit more info. |
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May 14, 2013, 04:35 |
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#3 |
New Member
Candy
Join Date: May 2013
Posts: 12
Rep Power: 13 |
Thanks,
Absolutely! I´m new to ANSYS For more info: I am working on a cooling technique using staggered Pin fins within a rectangular duct. I have to simulate the flow field. Then, I should calculate the friction factor (from the pressure drop) and the heat transfer coefficient. PS: I am using CFX in stand-alone mode not the WB Last edited by Amoul; May 14, 2013 at 09:02. |
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May 14, 2013, 04:39 |
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#4 |
Senior Member
Matthias Voß
Join Date: Mar 2009
Location: Berlin, Germany
Posts: 449
Rep Power: 20 |
you should definitely do some of the basic tutorials before starting your simulation. Check your convergence settings. If the simulations runs for several hours WITHOUT reaching the BASIC convergence settings, then there´s smth. wrong. Mesh, TimeStep, BC.
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May 14, 2013, 04:49 |
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#5 |
New Member
Candy
Join Date: May 2013
Posts: 12
Rep Power: 13 |
it is actually my question: How can I check the convergence settings?
I have already done basic tutorials: they do not explain how to check this. They directly move on to the CFX post without explaining the results of CFX solver manager :/ |
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May 14, 2013, 06:20 |
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#6 |
Senior Member
Mr CFD
Join Date: Jun 2012
Location: Britain
Posts: 361
Rep Power: 15 |
2 hours?
I've heard of people who run simulations for 3 weeks on 24 cores! |
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May 14, 2013, 06:41 |
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#7 |
Senior Member
Matthias Voß
Join Date: Mar 2009
Location: Berlin, Germany
Posts: 449
Rep Power: 20 |
please post a pic of your solver monitors. this will make it way easier.
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May 14, 2013, 08:20 |
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#8 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,830
Rep Power: 144 |
Yes, 2 hours is a bit laughable - I have run simulations which went for 6 weeks.
But you always approach big simulations with care. Do all your homework first to make sure you are not wasting your time. Run a small simulation to check things are working. Do all the necessary sensitivity checks so you know you will get it right the first time. And do lots of practise on smaller simulations before you commit to the big simulations. |
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May 14, 2013, 08:42 |
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#9 |
New Member
Candy
Join Date: May 2013
Posts: 12
Rep Power: 13 |
Please find here attached my solver window.
It is the simulation of the flow within a rectangular duct containing staggered pin fins. *Model: SST *Steady state solution *5% turbulence intensity Would you please tell me how could I check the sensitivity and the convergence settings of my solver knowing that i am using CFX stand-alone mode? Thank you! PS: Actually, it takes much more than 2 hours (maybe days, who knows ´cause I have not waited till the solver stops because I don t know how I can be sure that it is running correctly (it s converging) ) Last edited by Amoul; May 14, 2013 at 08:58. |
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May 14, 2013, 12:01 |
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#10 |
Senior Member
hamed
Join Date: Apr 2009
Posts: 148
Rep Power: 17 |
it is converged for basic tasks like getting rough results and initial conditions fo furture runs .10e-4 is enough for this purpuse but to have accurate results you whould let solver goes for RMS bellow 10e-5 or10e-6
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May 14, 2013, 20:10 |
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#11 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,830
Rep Power: 144 |
As Hamed has said, your simulation has converged a little bit but then stalled. This FAQ discusses what to consider next: http://www.cfd-online.com/Wiki/Ansys...gence_criteria
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May 15, 2013, 04:05 |
Thank you!
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#12 |
New Member
Candy
Join Date: May 2013
Posts: 12
Rep Power: 13 |
I would like to thank all of you for your help! I appreciate this
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