CFD Online Logo CFD Online URL
Home > Forums > OpenFOAM Running, Solving & CFD

GAMG vs. PCG in fvSolution

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   July 21, 2011, 04:39
Default GAMG vs. PCG in fvSolution
Join Date: Oct 2010
Location: Stuttgart
Posts: 35
Rep Power: 9
grandgo is on a distinguished road
hi foamers,

i'm working with two domains of exactly same geometry and case configurations. one domain has 150000 cells, the other about 6*10^6 cells.

in the coarse domain case the GAMG solver needs about 30 iterations for one timestep (nCellsInCoarsestLevel = 1000). on the other hand, if i choose PCG the calculation needs 230 iterations.

in the fine domain case it's the opposite: PCG needs about 1000 iterations but GAMG does need more (maxIter limitation at 1500, various nCellsInCoarsestLevel).

what's your experience with GAMG? any tips what i could try?

best regards
grandgo is offline   Reply With Quote

Old   November 13, 2015, 09:58
New Member
Antony Ashley Raja B
Join Date: Jul 2015
Posts: 16
Rep Power: 4
Antony_Bosco is on a distinguished road

Did you find any answer?

I am solving a external flow simulation. When i increase the number of layers and decrease the min thickness close to 9.6e-06,in a GAMG solver the iterations reach close to 1000 and crashes but on the other hand PCG works very well.

Is there any reason behind.

Antony_Bosco is offline   Reply With Quote

Old   March 7, 2017, 08:38
Senior Member
Join Date: Mar 2015
Posts: 250
Rep Power: 5
KateEisenhower is on a distinguished road

Thanks for opening this topic. I have two suggestions:

1) Some people here on the forum say nCellsInCoarsestLevel shouldn't be above 50. On my cases I always make sure to make a "nCellsInCoarsestLevel-study".

2) I think your post would be even more meaningful if you would tell us the calculation time/iteration or per timestep. The number of iterations alone is not so meaningful from my point of view.

Best regards,

KateEisenhower is offline   Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Velocity blows up suddenly after 30,000+ iterations lordvon OpenFOAM Running, Solving & CFD 15 October 19, 2015 13:52
GAMG solver causes troubles colinB OpenFOAM Running, Solving & CFD 5 June 13, 2013 07:48
Floating point exception error Alan OpenFOAM Running, Solving & CFD 10 April 6, 2012 14:02
Problems with simulating TurbFOAM barath.ezhilan OpenFOAM 13 July 16, 2009 05:55
Differences between serial and parallel runs carsten OpenFOAM Bugs 11 September 12, 2008 11:16

All times are GMT -4. The time now is 22:25.