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Old   July 13, 2012, 05:30
Default convergence problems
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Hello,

I have some serious convergence problems (especially p) with a mesh for a flow simulation around a building. To simulate multiple angles, I merged two meshes and combined them with AMI. So my question, is this mesh too bad to run? Here are the checkMesh results:

Quote:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 1901408
faces: 12673529
internal faces: 12307391
cells: 5669490
boundary patches: 10
point zones: 0
face zones: 1
cell zones: 1

Overall number of cells of each type:
hexahedra: 470000
prisms: 1352790
wedges: 0
pyramids: 10170
tet wedges: 0
tetrahedra: 3836530
polyhedra: 0

Checking topology...
Boundary definition OK.
Cell to face addressing OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
*Number of regions: 2
The mesh has multiple regions which are not connected by any face.
<<Writing region information to "0/cellToRegion"

Checking patch topology for multiply connected surfaces ...
Patch Faces Points Surface topology
inlet 2000 2091 ok (non-closed singly connected)
outlet 2000 2091 ok (non-closed singly connected)
symmetry 6800 7052 ok (non-closed singly connected)
top1 11750 11985 ok (non-closed singly connected)
bottom1 11750 11985 ok (non-closed singly connected)
outsideSlider 8000 8200 ok (non-closed singly connected)
building 271042 135919 ok (non-closed singly connected)
bottom2 37708 21346 ok (non-closed singly connected)
top2 7088 3645 ok (non-closed singly connected)
insideSlider 8000 8200 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-212 -250 -1.2547e-37) (638 250 150)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-1.92195e-17 -1.8619e-17 -1.2089e-15) OK.
Max cell openness = 3.09096e-15 OK.
Max aspect ratio = 121.1 OK.
Minumum face area = 0.000175324. Maximum face area = 100. Face area magnitudes OK.
Min volume = 1.62821e-05. Max volume = 687.1. Total volume = 6.37178e+07. Cell volumes OK.
Mesh non-orthogonality Max: 77.102 average: 18.3998
*Number of severely non-orthogonal faces: 7097.
Non-orthogonality check OK.
<<Writing 7097 non-orthogonal faces to set nonOrthoFaces
Face pyramids OK.
Max skewness = 3.78171 OK.
Coupled point location match (average 0) OK.

Mesh OK.

End
And here are my fvSchemes and fvSolution:
Quote:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
default steadyState;
}

gradSchemes
{
default Gauss linear;
grad(p) Gauss linear;
grad(U) Gauss linear;
grad(k) cellLimited Gauss linear 1;
grad(epsilon) cellLimited Gauss linear 1;
}

divSchemes
{
default none;
div(phi,U) Gauss upwind;
div(phi,k) Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,R) Gauss upwind;
div(phi,nuTilda) Gauss upwind;
div(R) 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 ;
}


// ************************************************** *********************** //
Quote:
solvers
{
p
{
solver PCG;
preconditioner DIC;
tolerance 1e-06;
relTol 0.01;
}

U
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 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 0;

residualControl
{
p 1e-2;
U 1e-3;
"(k|epsilon|omega)" 1e-3;
}
}

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


// ************************************************** *********************** //
I use simpleFoam and the k-e-realizable model for this simulation. I tried a simulation for zero angle of attack, everything works fine. But when I change the angle, I get problems with convergence.

I'll be really grateful for every advice.

Thanks,
slint
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