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Amoul May 14, 2013 03:23

CFX Solver manager runs for a long time!!
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 :confused:
PS: I am using an SST model with a steady state solution.
Thank you :)

mvoss May 14, 2013 04:23

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. ;)

Amoul May 14, 2013 04:35

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 :)

mvoss May 14, 2013 04:39

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.

Amoul May 14, 2013 04:49

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 :/

JuPa May 14, 2013 06:20

2 hours?

I've heard of people who run simulations for 3 weeks on 24 cores!

mvoss May 14, 2013 06:41

please post a pic of your solver monitors. this will make it way easier.

ghorrocks May 14, 2013 08:20

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.

Amoul May 14, 2013 08:42

1 Attachment(s)
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 :p ´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) )

hmasenger May 14, 2013 12:01

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

ghorrocks May 14, 2013 20:10

As Hamed has said, your simulation has converged a little bit but then stalled. This FAQ discusses what to consider next:

Amoul May 15, 2013 04:05

Thank you!
I would like to thank all of you for your help! I appreciate this :)

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