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-   -   GAMG vs. PCG in fvSolution (

grandgo July 21, 2011 04:39

GAMG vs. PCG in fvSolution
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

Antony_Bosco November 13, 2015 09:58


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.


KateEisenhower March 7, 2017 08:38


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,


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