run form mapField

andrea.pasquali · October 1, 2009, 10:40

Hi everybody,

I got a solution with a coarse mesh. I mapped it on a finest mesh with mapFields command, and it's ok.
Then I want to run with the finest mesh from the mapped solution, but at the beginning I obtain "floating point exception" and the run dies.
What's my problem?

Thanks for any reply,

Andrea

harishg · October 1, 2009, 18:19

Floating point exception usually points to a divide by zero. Do you change the BC between the coarse and fine mesh? Did it show the exception on the first timestep? What model and BC are you exactly using to study your problem?

andrea.pasquali · October 5, 2009, 06:41

Hi Harishg,
Thank you. At the beginning, when I start the run whit fine mesh, the solver read in file T a "nan" term. I changed it with zero value and maybe it's this that give me the problem. I'm using the same condition between coarse and fine mesh.
What means "nan" value? Can I try to change it with 0.000001 (small but no zero value)?

Thanks

Andrea

lord_kossity · October 5, 2009, 07:35

Hi Andrea,

nan means "not a number". This term usually stands for infinity. So replacing it with a small number won't help you out!

Regards,
Andreas

harishg · October 5, 2009, 09:59

My guess is that the coarse mesh run itself did not converge and produced Nan term. Hence the mapping transfers it to the fine mesh too. Check the files in the coarse mesh for the Nan term.

andrea.pasquali · October 5, 2009, 10:47

Thank Andreas and Harishg,
I saw my mapped files and I got "nan" value in epsilon, k, rho and T. I got also many "0" values; like this:

0
0
0
0
0
0
0
0
2.07259e-315
2.122e-314
99967.2
99967.2
6.2051e-315
nan
99934.6
6.2051e-315
0

In coarse mesh run I don't got "nan" or "0" value. It's a good solution and I reached small residuals. But I didn't say you that I obtained this solution with Openfoam1.5.x; instead I mapped it with last Openfoam1.6.x.
Can this be a problem, mapping OF15x solution on OF16x?

Thanks

Andrea

October 1, 2009, 10:40	run form mapField	#1
andrea.pasquali Senior Member Andrea Pasquali Join Date: Sep 2009 Location: Germany Posts: 142 Rep Power: 16	Hi everybody, I got a solution with a coarse mesh. I mapped it on a finest mesh with mapFields command, and it's ok. Then I want to run with the finest mesh from the mapped solution, but at the beginning I obtain "floating point exception" and the run dies. What's my problem? Thanks for any reply, Andrea

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October 1, 2009, 18:19		#2
harishg Senior Member N/A Join Date: Mar 2009 Posts: 189 Rep Power: 17	Floating point exception usually points to a divide by zero. Do you change the BC between the coarse and fine mesh? Did it show the exception on the first timestep? What model and BC are you exactly using to study your problem?

October 5, 2009, 06:41		#3
andrea.pasquali Senior Member Andrea Pasquali Join Date: Sep 2009 Location: Germany Posts: 142 Rep Power: 16	Hi Harishg, Thank you. At the beginning, when I start the run whit fine mesh, the solver read in file T a "nan" term. I changed it with zero value and maybe it's this that give me the problem. I'm using the same condition between coarse and fine mesh. What means "nan" value? Can I try to change it with 0.000001 (small but no zero value)? Thanks Andrea

October 5, 2009, 07:35		#4
lord_kossity Member Andreas Dietz Join Date: Mar 2009 Location: Munich Posts: 79 Rep Power: 17	Hi Andrea, nan means "not a number". This term usually stands for infinity. So replacing it with a small number won't help you out! Regards, Andreas

October 5, 2009, 09:59		#5
harishg Senior Member N/A Join Date: Mar 2009 Posts: 189 Rep Power: 17	My guess is that the coarse mesh run itself did not converge and produced Nan term. Hence the mapping transfers it to the fine mesh too. Check the files in the coarse mesh for the Nan term.

October 5, 2009, 10:47		#6
andrea.pasquali Senior Member Andrea Pasquali Join Date: Sep 2009 Location: Germany Posts: 142 Rep Power: 16	Thank Andreas and Harishg, I saw my mapped files and I got "nan" value in epsilon, k, rho and T. I got also many "0" values; like this: 0 0 0 0 0 0 0 0 2.07259e-315 2.122e-314 99967.2 99967.2 6.2051e-315 nan 99934.6 6.2051e-315 0 In coarse mesh run I don't got "nan" or "0" value. It's a good solution and I reached small residuals. But I didn't say you that I obtained this solution with Openfoam1.5.x; instead I mapped it with last Openfoam1.6.x. Can this be a problem, mapping OF15x solution on OF16x? Thanks Andrea