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large number of iteration within time step

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Old   October 19, 2017, 17:37
Default large number of iteration within time step
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Dear Foamers,

i am working with porousSimpleFoam, in my case solver is taking about 32 iterations in one time step to solve velocity, but about 300 iterations to solve pressure. the time of one time step is about 130 seconds. the solver reaches steady state after 13,000 steps, so it takes too long time on my machine.

my question is: is there is any thing i can do to decrease number of iterations per time step and overall time steps. in other words, is this high number of iterations and steps because of my case physics, or may i have something wrong?

thanks in advance,
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Old   October 23, 2017, 04:44
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Hi Ahmed,
Did you try the solution suggested in your earlier post (relaxing your relative convergence tolerances)?

I would also suggest using PBiCGStab as the solver for U, it is quite a bit faster than GaussSeidel, at least on my system.

Regards,
Karl
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Old   October 23, 2017, 13:07
Default high aspecct ratio of cell dimensions
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Hi All,

i have got a clue for my problem, although my mesh has no problems with orthogonality or skewness, there is a high aspect ratio between cell dimensions. that length of cell boundary in x and y direction was much greater that is in z direction.

running same solver on a finer mesh but with cells that has same length in all direction showed much faster convergence rate.

thanks,
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