iteration no. explodes, solution diverges

adamsinan · September 26, 2012, 10:19

Hi everyone,

after few steps from run begin, the No. of iterations for Ux, Uy, Uz, k and epsilon begin to explode then Co No. also explodes & the solution diverges.

I'm using OF2.1, k-epsilon model, pisoFoam, 8-nodes.
Thanks in advance for help.
(please, tell me if you need more infos)

treima · September 26, 2012, 10:43

Hi,

some more information would be useful, i.e.
- timesteps
- geometry
- size of cells
- boundary conditions
and so on

.

Without you just cam guess, why it doesn´t work!

adamsinan · September 26, 2012, 11:11

Hi Treima,

I have a flow around a cylinder (inlet, outlet, no-slip wall bed),
cells no. is 4.5 million,
time-step: I tried different values (from 1e-5 to 0.01 ) (the same happened with all, except sometimes more working iterations).

I tried the same case (finer mesh) in OF1.6.x & it worked...I switched to OF2.1 because I have problem with parallel run in the older version.

Please, tell me if you need more info.

treima · September 27, 2012, 03:45

At the first moment i thought your timestep ist to large or your boundary conditions are wrong. But if the case worked in an older version of OpenFOAM, this is a little bit confusing. I don´t know, if there are any changes in OpenFOAM or in your case, which cause the mistake. I´m not so familiar with the older versions...

And always give as much informations as possible!

September 26, 2012, 10:19	iteration no. explodes, solution diverges	#1
adamsinan New Member sinan Join Date: Sep 2012 Posts: 4 Rep Power: 14	Hi everyone, after few steps from run begin, the No. of iterations for Ux, Uy, Uz, k and epsilon begin to explode then Co No. also explodes & the solution diverges. I'm using OF2.1, k-epsilon model, pisoFoam, 8-nodes. Thanks in advance for help. (please, tell me if you need more infos)

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September 26, 2012, 10:43		#2
treima Member Join Date: Mar 2012 Location: Munich, Germany Posts: 67 Rep Power: 14	Hi, some more information would be useful, i.e. - timesteps - geometry - size of cells - boundary conditions and so on . Without you just cam guess, why it doesn´t work!

September 26, 2012, 11:11		#3
adamsinan New Member sinan Join Date: Sep 2012 Posts: 4 Rep Power: 14	Hi Treima, I have a flow around a cylinder (inlet, outlet, no-slip wall bed), cells no. is 4.5 million, time-step: I tried different values (from 1e-5 to 0.01 ) (the same happened with all, except sometimes more working iterations). I tried the same case (finer mesh) in OF1.6.x & it worked...I switched to OF2.1 because I have problem with parallel run in the older version. Please, tell me if you need more info.

September 27, 2012, 03:45		#4
treima Member Join Date: Mar 2012 Location: Munich, Germany Posts: 67 Rep Power: 14	At the first moment i thought your timestep ist to large or your boundary conditions are wrong. But if the case worked in an older version of OpenFOAM, this is a little bit confusing. I don´t know, if there are any changes in OpenFOAM or in your case, which cause the mistake. I´m not so familiar with the older versions... And always give as much informations as possible!