[Svensen]

I run a steady-state simulation using simpleFoam. During first 200 iterations a solution converges quite well but suddenly after about 200 iterations a solution explodes... I've tried to play with relaxation coefficients but with no success.

Config files, log file and plot of residuals are attached in a zip file.

Maybe someone knows how to overcome this issue ??

[sheaker]

Hello.
It looks like You got 1000 iterations for pressure. Maybe You need to change Initial residual?

[Svensen]

Do you know how to do this ?

[sheaker]

Unfortunately I'm noob.

Maybe in file 0/p You can change internalField uniform to value that is close to Your calculation?

[RodriguezFatz]

You have really strange numerical settings. nNonOrthogonalCorrectors 15 ... why did you do that?

Can you post "checkMesh" output?

In fvSolution:

solvers
{
    p
    {
       
    solver           GAMG;
        tolerance        1e-12;
        relTol           0.001;
        smoother         DICGaussSeidel;
        nPreSweeps       0;
        nPostSweeps      1;
    nFinestSweeps    2;
    scaleCorrection  true;
    directSolveCoarsestLevel false;
        cacheAgglomeration on;
        agglomerator     faceAreaPair;
        nCellsInCoarsestLevel 500;
        mergeLevels      1;
        maxIter         100;
    }

    U
    {
        solver           smoothSolver;
        smoother         GaussSeidel;
        tolerance        1e-12;
        relTol           0.1;
        nSweeps          1;
        maxIter         100;
    }
}

Set nNonOrthogonalCorrectors to 1;
Set relaxation for pressure to 0.3 and for velocity to 0.7.

In fvSolution:
Set gradScheme default to "Gauss linear".

[betakv]

Try to change outlet boundary condition for velocity from
{
type zeroGradient;
}

to
{
type inletOutlet;
inletValue uniform (0 0 0);
value $internalField;
}