[shaileshbg]

Hello Foamers,

I am working on multi-region heat conduction using chtMultiRegionSimpleFoam.

1) the h residual has decreased below the specified tolerance of 1e-06, see the attached residual plot.
2) the temperature values no longer change with subsequent iterations, see attached temperatures plot.
3) the number of iterations also reduce to zero, see attached iterations image.
4) have tried increasing the nNonOrthogonalCorrectors to 3 to increase the number of iterations per time step, and increased the under-relaxation factor of h to 1

solvers
{
    h
    {
        solver           PCG;
        preconditioner   DIC;
        tolerance        1e-06;
        relTol           0.01;
    }
}

SIMPLE
{
    nNonOrthogonalCorrectors 3;
}

relaxationFactors
{
    equations
    {
        h              1;
    }
}

but the log file says regions are not converged.

DICPCG:  Solving for h, Initial residual = 5.284098e-07, Final residual = 5.284098e-07, No Iterations 0
- selecting cells using cellZone tumor
- selected 20643 cell(s) with volume 4.159077e-06
- selecting cells using cellZone tumor
- selected 20643 cell(s) with volume 4.159077e-06
- selecting cells using cellZone tumor
- selected 20643 cell(s) with volume 4.159077e-06
DICPCG:  Solving for h, Initial residual = 5.284098e-07, Final residual = 5.284098e-07, No Iterations 0
- selecting cells using cellZone tumor
- selected 20643 cell(s) with volume 4.159077e-06
Min/max T:301.8466 304.3565

Regions not converged after 300 iterations
ExecutionTime = 56.99 s  ClockTime = 73 s

End

Could anyone please let me know why it is not converging.
Many thanks in advance,
Shailesh

[tomf]

Hi Shailesh,

Happy New Year!

I would say your result is converged. All the metrics you showed indicate that it is converged. I do not recall ever seeing the remark in the log about convergence with any SIMPLE solver, only with the PIMPLE solvers.

Some questions that may help you get conclusions:
Did you check the results visually?

Did you use some particular functionObject that could cause this remark?

Regards,
Tom

[shaileshbg]

Hi Tom,

Thank you for your reply and a very happy new year to you.

I managed to get the solver to converge by using residualControls, here is a snippet of my fvSolution

SIMPLE
{
    nNonOrthogonalCorrectors 3;
    
   residualControl
    {
        h
        {
            tolerance 1e-6;
            relTol 0.1;
        }
    }   
}

Now I get converged solutions.

Warm Regards,
Shailesh