CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (http://www.cfd-online.com/Forums/openfoam-solving/)
-   -   Getting too many iterations by velocity solving (aborting). Changing U - Solver? (http://www.cfd-online.com/Forums/openfoam-solving/71936-getting-too-many-iterations-velocity-solving-aborting-changing-u-solver.html)

 suitup January 20, 2010 08:45

Getting too many iterations by velocity solving (aborting). Changing U - Solver?

Hi I have a problem by running my simulation (chtmultiregion), the simulation aborts after trying to solve the velocity in y-direction with over 1000 iterations.

Code:

Solving for solid region ss17
DICPCG:  Solving for T, Initial residual = 0.0170806, Final residual = 7.153049e-07, No Iterations 5
DICPCG:  Solving for T, Initial residual = 0.005342712, Final residual = 3.099503e-07, No Iterations 5
Min/max T:min(T) [0 0 0 1 0 0 0] 310.9295 max(T) [0 0 0 1 0 0 0] 310.9513
ExecutionTime = 47858.43 s  ClockTime = 48705 s

Region: domain0 Courant Number mean: 0.007054461 max: 0.2994233
Region: domain3 Courant Number mean: 0.02050585 max: 0.2296986
deltaT = 0.004454343
Time = 162.688

Solving for fluid region domain0
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 1.628197e-05, Final residual = 1.821337e-09, No Iterations 4
DILUPBiCG:  Solving for Uy, Initial residual = 3.892324e-05, Final residual = 3.410788e+97, No Iterations 1001
DILUPBiCG:  Solving for Uz, Initial residual = 1.160019e-05, Final residual = 6.464186e-09, No Iterations 3
DILUPBiCG:  Solving for h, Initial residual = 5.031973e-05, Final residual = 2.351623e-09, No Iterations 4
Min/max T:300.737 308.2481
GAMG:  Solving for p, Initial residual = 1, Final residual = 0.008969165, No Iterations 3
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (domain0): sum local = -1.376181e+16, global = 8.951178e+11, cumulative = 8.951178e+11
[0] [1] #0  Foam::error::printStack(Foam::Ostream&)[2] #0  Foam::error::printStack(Foam::Ostream&)[3] #0  Foam::error::printStack(Foam::Ostream&)[4] #0  Foam::error::printStack(Foam::Ostream&)[6] #0  Foam::error::printStack(Foam::Ostream&)[5] #0  Foam::error::printStack(Foam::Ostream&)[7] #0  Foam::error::printStack(Foam::Ostream&)#0  Foam::error::printStack(Foam::Ostream&) in  in "/root/OpenFOAM/OpenFOAM-1.6.x/lib/linux64GccDPOpt/libOpenFOAM.so"

I m using the GAMG solver for velocity, maybe I can solve the problem by using an other, but which one?

My solvers (fvSchemes):

Code:

solvers
{
rho
{
solver          PCG
preconditioner  DIC;
tolerance      1e-8;
relTol          0;
};
p
{
solver          GAMG;
tolerance        1e-8;
relTol          0.01;

smoother        GaussSeidel;

cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator    faceAreaPair;
mergeLevels      1;
};
pFinal
{
solver          GAMG;
tolerance        1e-8;
relTol          0;

smoother        GaussSeidel;

cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator    faceAreaPair;
mergeLevels      1;
};
U
{
solver          PBiCG;
preconditioner  DILU;
tolerance        1e-08;
relTol          0;
};

h
{
solver          PBiCG;
preconditioner  DILU;
tolerance        1e-08;
relTol          0.1;
};
hFinal
{
solver          PBiCG;
preconditioner  DILU;
tolerance        1e-08;
relTol          0;
};

k
{
solver          PBiCG;
preconditioner  DILU;
tolerance        1e-08;
relTol          0;
};
epsilon
{
solver          PBiCG;
preconditioner  DILU;
tolerance        1e-08;
relTol          0;
};
R
{
solver          PBiCG;
preconditioner  DILU;
tolerance        1e-08;
relTol          0;
};
}

PISO
{
momentumPredictor  off;
nOuterCorrectors    1;
nCorrectors    2;
nNonOrthogonalCorrectors 1;
pRefPoint      (-0.081 -0.0257 8.01);
pRefValue      1e5;
}

PIMPLE
{
momentumPredictor  on;
nCorrectors        2;
nNonOrthogonalCorrectors 0;
}

Or changing the discretisations?

(fvSchemes):
Code:

ddtSchemes
{
default Euler;
//default CoEuler phi rho 0.1;
}

{
default        Gauss linear;
//    grad(U)        cellLimited Gauss linear 1;
}

divSchemes
{
default        none;
div(phi,U)      Gauss upwind;
div(phiU,p)    Gauss linear;
div(phi,h)      Gauss upwind;
div(phi,k)      Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,R)      Gauss upwind;
div(R)          Gauss linear;
}

laplacianSchemes
{
default        none;
laplacian(muEff,U) Gauss linear limited 0.333;
laplacian((rho*(1|A(U))),p) Gauss linear limited 0.333;
laplacian(alphaEff,h) Gauss linear limited 0.333;
laplacian(DkEff,k) Gauss linear limited 0.333;
laplacian(DepsilonEff,epsilon) Gauss linear limited 0.333;
laplacian(DREff,R) Gauss linear limited 0.333;
}

interpolationSchemes
{
default        linear;
}

{
default        limited 0.333;
}

fluxRequired
{
default        no;
p;
}