| Supersale |
April 15, 2015 09:57 |
Noise in velocity graph
Hi all!
i am simulating a continuous ink-jet in OpenFOAM 2.1.1 using compressibleInterFoam
The geometry is basically a cilinder filled with ink that converges into a small nozzle and then exits into the atmosphere. The inlet is defined as a complex harmonical function of the pressure which in the first few time steps gradually increases from 0 to the required harmonical function (if the first time step is more than zero, the velocity experiences a sharp jump at the beginning).
The issue i am currently dealing with is that the velocity, which is induced by the pressure difference, seems to have some noice at the first time steps. later the graph becomes smooth and stable but for these first few time steps some areas with spikes can be seen. Did any of you experience something similar? Do you know where the problem might be?
I am using slightly modified files from the compressibleInterFoam tutorial cases:
fvSolution:
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
solvers
{
pcorr
{
solver PCG;
preconditioner
{
preconditioner DIC;
tolerance 1e-13;
relTol 0;
smoother DICGaussSeidel;
nPreSweeps 0;
nPostSweeps 2;
nFinestSweeps 2;
cacheAgglomeration false;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;
}
tolerance 1e-13;
relTol 0;
maxIter 100;
}
"(rho|rhoFinal)"
{
solver diagonal;
}
p_rgh
{
solver GAMG;
tolerance 1e-13;
relTol 0.01;
smoother DIC;
nPreSweeps 0;
nPostSweeps 2;
nFinestSweeps 2;
cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;
}
p_rghFinal
{
solver PCG;
preconditioner
{
preconditioner DIC;
tolerance 1e-13;
relTol 0;
nVcycles 2;
smoother DICGaussSeidel;
nPreSweeps 2;
nPostSweeps 2;
nFinestSweeps 2;
cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;
}
tolerance 1e-13;
relTol 0;
maxIter 20;
}
U
{
solver GAMG;
tolerance 1e-13;
relTol 0.01;
smoother DIC;
nPreSweeps 0;
nPostSweeps 2;
nFinestSweeps 2;
cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;
}
"(k|B|nuTilda)"
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-13;
relTol 0;
}
UFinal
{
solver PBiCG;
preconditioner
{
preconditioner DILU;
tolerance 1e-13;
relTol 0;
nVcycles 2;
smoother DICGaussSeidel;
nPreSweeps 2;
nPostSweeps 2;
nFinestSweeps 2;
cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;
}
tolerance 1e-13;
relTol 0;
maxIter 20;
}
}
PIMPLE
{
momentumPredictor yes;
nCorrectors 3;
nNonOrthogonalCorrectors 1;
nAlphaCorr 1;
nAlphaSubCycles 2;
cAlpha 1;
}
// ************************************************************************* //
fvSchemes:
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
ddtSchemes
{
default Euler;
}
gradSchemes
{
default Gauss linear;
}
divSchemes
{
div(rho*phi,U) Gauss SFCD;
div(phi,alpha) Gauss vanLeer;
div(phirb,alpha) Gauss interfaceCompression 1;
div(phi,p_rgh) Gauss SFCD; div(phi,k) Gauss vanLeer;
div((nuEff*dev(T(grad(U))))) Gauss linear;
}
laplacianSchemes
{
default Gauss linear corrected;
}
interpolationSchemes
{
default linear;
}
snGradSchemes
{
default corrected;
}
fluxRequired
{
default no;
p_rgh;
pcorr;
alpha1;
}
// ************************************************************************* //
i can not use an upwind scheme as this gives me constant noise. it needs to be second order.
Anyway, thanks for the help! |
