Floating point exception

Breivik · May 2, 2012, 19:14

Hi,
I'm currently doing a simulation of a full skale ship following the instructions from the KRISO case giving some tweak on the mesh settings.
When I've run som iterations I get the following message: Floating point exception, and i see that the residuals are sky high. I've encountered this problem before once when I reduced the prism layer thickness down to 1.5%, so I just adjusted it to 2% and it worked (Why?), but this does not help now. The residuals are sky hight alredy at 17 iterations.

If anyone could help me with this I would be much obliged.

Best regards
Breivik.

ryancoe · May 3, 2012, 10:47

Sounds like your mesh may be the issue. In your example with the prism layer, you may have created very low aspect ratio cells (which are not desirable) with the overall thickness set at 1.5%. This may have been corrected by increasing the thickness.

Try using some of the mesh diagnostic tools, as well as looking at your volume mesh with some of the cell quality scalars.

Since this is an unsteady simulation, you may also need to check you time-step size.

Breivik · May 3, 2012, 11:00

Thank you for the answer. It helped when I increased my tim-step

esha · July 8, 2019, 10:29

Updating solution at time levels N and N-1.
iter continuity x-velocity y-velocity time/iter
done.
# Divergence detected in AMG solver: pressure coupled -> Decreasing coarsening group size!
# Divergence detected in AMG solver: pressure coupled -> Increasing relaxation sweeps!
# You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t)
what does that mean? please explain.

May 2, 2012, 19:14	Floating point exception	#1
Breivik New Member Breivik Join Date: Mar 2012 Location: Norway Posts: 10 Rep Power: 14	Hi, I'm currently doing a simulation of a full skale ship following the instructions from the KRISO case giving some tweak on the mesh settings. When I've run som iterations I get the following message: Floating point exception, and i see that the residuals are sky high. I've encountered this problem before once when I reduced the prism layer thickness down to 1.5%, so I just adjusted it to 2% and it worked (Why?), but this does not help now. The residuals are sky hight alredy at 17 iterations. If anyone could help me with this I would be much obliged. Best regards Breivik.

May 3, 2012, 10:47		#2
ryancoe Member Ryan Coe Join Date: Jun 2010 Location: Albuquerque, NM Posts: 98 Rep Power: 16	Sounds like your mesh may be the issue. In your example with the prism layer, you may have created very low aspect ratio cells (which are not desirable) with the overall thickness set at 1.5%. This may have been corrected by increasing the thickness. Try using some of the mesh diagnostic tools, as well as looking at your volume mesh with some of the cell quality scalars. Since this is an unsteady simulation, you may also need to check you time-step size. __________________ Ryan

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May 3, 2012, 11:00		#3
Breivik New Member Breivik Join Date: Mar 2012 Location: Norway Posts: 10 Rep Power: 14	Thank you for the answer. It helped when I increased my tim-step

July 8, 2019, 10:29		#4
esha Member Join Date: Aug 2018 Posts: 90 Rep Power: 8	Updating solution at time levels N and N-1. iter continuity x-velocity y-velocity time/iter done. # Divergence detected in AMG solver: pressure coupled -> Decreasing coarsening group size! # Divergence detected in AMG solver: pressure coupled -> Increasing relaxation sweeps! # You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t) what does that mean? please explain.