[MichiB]

Hi everybody!

we are trying to calculate the transient turbulent flow through a pump, yet with little success. We where using turbDymFoam, with a uniform (p and U) initial calculation domain. The calculation somehow diverges, and we can't figure out why.
The fvSchemes we set look as follows:

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
ddtSchemes
{
default Euler;
}
gradSchemes
{
default Gauss linear;
grad(p) Gauss linear;
grad(U) Gauss linear;
}
divSchemes
{
default none;
div(phi,U) Gauss linearUpwind Gauss;
div(phi,k) Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,omega) Gauss upwind;
div(phi,R) Gauss upwind;
div(R) Gauss linear;
div(phi,nuTilda) Gauss upwind;
div((nuEff*dev(grad(U).T()))) Gauss linear;
}
laplacianSchemes
{
default none;
laplacian(nuEff,U) Gauss linear corrected;
laplacian((1|A(U)),p) Gauss linear corrected;
laplacian(DkEff,k) Gauss linear corrected;
laplacian(DepsilonEff,epsilon) Gauss linear corrected;
laplacian(DomegaEff,omega) Gauss linear corrected;
laplacian(DREff,R) Gauss linear corrected;
laplacian(DnuTildaEff,nuTilda) Gauss linear corrected;
laplacian(rAU,p) Gauss linear corrected;
laplacian(rAU,pcorr) Gauss linear corrected;
laplacian(nu,U) Gauss linear corrected;
}
interpolationSchemes
{
default linear;
interpolate(U) linear;
interpolate(HbyA) linear;
interpolate(1|A) linear;
}
snGradSchemes
{
default corrected;
}
fluxRequired
{
default no;
p;
pcorr;
}

// ************************************************** *********************** //

We now wanted to initialize the field with a steady state solution using MRFSimpleFoam. But again -> ocillating residuals.

Does anybody have an idea what we could have done wrong?

[MichiB]

Forgot the solution schemes

solvers {
p PCG {
preconditioner DIC;
tolerance 1e-05;
relTol 0.0002;
minIter 2; maxIter 5; };
pFinal PCG {
preconditioner DIC;
tolerance 1e-05;
relTol 0.0001;
minIter 2; maxIter 5; };
U BiCGStab {
preconditioner { type DILU; }
minIter 1; maxIter 10;
tolerance 1e-07;
relTol 0; };
k BiCGStab { // and epsilon
preconditioner { type DILU; }
minIter 1; maxIter 5;
tolerance 1e-07;
relTol 0; };
epsilon BiCGStab {
preconditioner { type DILU; }
minIter 1; maxIter 5;
tolerance 1e-07;
relTol 0; };
omega BiCGStab {
preconditioner { type DILU; }
minIter 1; maxIter 5;
tolerance 1e-07;
relTol 0; };
R GAMG
{
preconditioner GAMG;
tolerance 1e-06;
relTol 0.1;
agglomerator faceAreaPair;
nCellsInCoarsestLevel 10;
mergeLevels 1;
smoother GaussSeidel;
minIter 0;
maxIter 100;
cacheAgglomeration true;
nPreSweeps 0;
nPostSweeps 2;
nFinestSweeps 2;
};
nuTilda GAMG
{
preconditioner GAMG;
tolerance 1e-06;
relTol 0.1;
agglomerator faceAreaPair;
nCellsInCoarsestLevel 10;
mergeLevels 1;
smoother GaussSeidel;
minIter 0;
maxIter 100;
cacheAgglomeration true;
nPreSweeps 0;
nPostSweeps 2;
nFinestSweeps 2;
};
}
SIMPLE
{
nNonOrthogonalCorrectors 2;
}
PISO
{
momentumPredictor no;
nCorrectors 3;
nNonOrthogonalCorrectors 2;
nGammaCorr 1;
nGammaSubCycles 4;
cGamma 1;
}
relaxationFactors
{
p 0.3;
U 0.7;
k 0.7;
epsilon 0.7;
omega 0.7;
R 0.7;
nuTilda 0.7;
}

// ************************************************** *********************** //

[NickG]

Hi

Try running turbFoam on it first to get reasonable values for k and epsilon.

I have momentumPredictor yes; in my PISO loop. Don't know if that's going to make a difference but the initial turbulence model variables certainly affect the stability.

Good luck