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-   -   SimpleFoam - Interpretation of Residuals (http://www.cfd-online.com/Forums/openfoam-solving/112907-simplefoam-interpretation-residuals.html)

despaired student February 7, 2013 08:36

SimpleFoam - Interpretation of Residuals
 
3 Attachment(s)
Hi,

I need comments on my residuals-plots. They look pretty ...linear. I've never had such residuallines before. How to interpretate them and how does it come?

The configuration files are the following:

ControlDict:
Quote:

FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application simpleFoam;

startFrom latestTime;

startTime 0;

stopAt endTime;

endTime 6000;

deltaT 1;

writeControl timeStep;

writeInterval 50;

purgeWrite 0;

writeFormat ascii;

writePrecision 6;

writeCompression on;

timeFormat general;

timePrecision 6;

runTimeModifiable true;
fvSchemes:
Quote:

FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
default steadyState;
}

gradSchemes
{
default Gauss linear;
grad(p) Gauss linear;
grad(U) Gauss linear;
}

divSchemes
{
default none;
div(phi,U) Gauss linear; //upwind;
div(phi,k) Gauss linear;
div(phi,epsilon) Gauss linear;
div(phi,R) Gauss linear;
div(R) Gauss linear;
div(phi,nuTilda) Gauss linear;
div((nuEff*dev(T(grad(U))))) 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(DREff,R) Gauss linear corrected;
laplacian(DnuTildaEff,nuTilda) Gauss linear corrected;
}

interpolationSchemes
{
default linear;
interpolate(U) linear;
}

snGradSchemes
{
default corrected;
}

fluxRequired
{
default no;
p ;
}
fvSolution:
Quote:

FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
p
{
solver PCG;
preconditioner DIC;
tolerance 0; //1e-06
relTol 0.001; //0.01
}

U
{
solver PBiCG;
preconditioner DILU;
tolerance 0; //1e-05
relTol 0.001; //0.1
}

k
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0.1;
}

epsilon
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0.1;
}

R
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0.1;
}

nuTilda
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0.1;
}
}

SIMPLE
{
nNonOrthogonalCorrectors 2; //0

residualControl
{
p 1e-12; // 1e-3
U 1e-12; // 1e-4
"(k|epsilon|omega)" 1e-3;
}
}

relaxationFactors
{
p 0.3;
U 0.7;
k 0.7;
epsilon 0.7;
R 0.7;
nuTilda 0.7;
}

sfigato February 8, 2013 03:06

Hi Soren,

I am dealing with the same issue...your residuals are pretty low, though they do not reach the steady state (i think so). They are going on to decrease. I suggest to you to let the simulation run for more iterations!

Regards
Marco

sfigato February 8, 2013 03:21

Hi Soren,


Why have you used a tolerance equal to 0 for U and p?

Regards
Marco

despaired student February 8, 2013 08:39

My superwiser told me that I should use for U and p a tolerance of 0.


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