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Old   February 21, 2008, 14:45
Default Dear foamers, I have some c
Quinn Tian
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Dear foamers,

I have some convergence problem while running simpleFoam. Both pressure and velocity converges at the beginning to the order of 10^-3, then start to diverge until blowing out. I took a look at the pressure results before diverging and it looks reasonable and smooth. However,after that, I got huge pressure value at some locations, when simulation starts to diverge. Can someone please give me some guidance here? Thanks.

I had a hybrid mesh with fine hexahedra mesh in the wall region in order to use low Reynolds turbulence model.

Here is what I got from checkMesh,
Checking geometry...
Boundary openness in x-direction = -1.2949e-19
Boundary openness in y-direction = -2.43946e-18
Boundary openness in z-direction = 3.92812e-19
Boundary closed (OK).
Max cell openness = 1.0842e-19 Max aspect ratio = 33.7858. All cells OK.

Minumum face area = 1.85108e-08. Maximum face area = 0.00063044. Face area magnitudes OK.

Min volume = 2.9974e-11. Max volume = 5.37019e-06. Total volume = 0.36159. Cell volumes OK.

Number of non-orthogonality errors: 0. Number of severely non-orthogonal faces: 581.
Mesh non-orthogonality Max: 77.6364 average: 19.9435
Non-orthogonality check OK.

--> FOAM Warning :
From function primitiveMesh::checkFaceSkewness(const bool report, labelHashSet* setPtr) const
in file meshes/primitiveMesh/primitiveMeshCheck.C at line 838
Large face skewness detected. Max skewness = 256.281 percent.
This may impair the quality of the result.
37 highly skew faces detected.
Writing 37 skew faces to set skewFaces

Minumum edge length = 1.59999e-05. Maximum edge length = 0.0455865.

All angles in faces are convex or less than 10 degrees concave.

Face flatness (1 = flat, 0 = butterfly) : average = 0.999997 min = 0.997836
All faces are flat in that the ratio between projected and actual area is > 0.8

Geometry check done.

Number of cells by type:
hexahedra: 340824
prisms: 0
wedges: 0
pyramids: 28402
tet wedges: 0
tetrahedra: 1059899
polyhedra: 0
Number of regions: 1 (OK).

Here is what's inside fvSchemes and fvSolution

default Gauss upwind;
div(phi,U) Gauss upwind;
div(phi,k) Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,R) Gauss upwind;
div(R) Gauss linear;
div(phi,nuTilda) Gauss upwind;
div((nuEff*dev(grad(U).T()))) Gauss linear;

default Gauss linear limited 0.7;
laplacian(nuEff,U) Gauss linear limited 0.7; //Gauss linear corrected;
laplacian((1|A(U)),p) Gauss linear limited 1; //Gauss linear corrected; //Gauss linear limited 0.7;
laplacian(DkEff,k) Gauss linear limited 0.7;
laplacian(DepsilonEff,epsilon) Gauss linear limited 0.7;
laplacian(DREff,R) Gauss linear corrected;
laplacian(DnuTildaEff,nuTilda) Gauss linear limited 0.7;

p AMG 1e-08 0.01 200;
U BICCG 1e-08 0.0;
k BICCG 1e-06 0.0;
epsilon BICCG 1e-06 0.0;
R BICCG 1e-06 0.0;
nuTilda BICCG 1e-06 0.0;


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