[nicasch]

Dear OpenFoamers,

I have noticed some strange behavior of refineMesh utility. I have created an axisimetric 2D slice, using blockMesh, consisting of uniform hexahedra, here how it looks like:



After applying refineMesh I obtained a refined mesh, but it seems a little strange near the axis of symmetry. The mesh seems to be not refined in a 2x2 manner through the middle of edges, as the refineMeshDict says. I tried various combinations of HexTopology and geometricCut entries, but I was never able to get a fine 2x2 refined mesh. My refined meshes looks like this:






My blockMeshDict and refineMeshDict are:

// blockMesh mesh description file
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
FoamFile
{
version 2.0;
format ascii;
root "";
case "";
instance "";
local "";
class dictionary;
object blockMeshDict;
}
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
convertToMeters 0.001;

vertices
(
(0 0 0)
(45 0 1.96474)
(45 0 -1.96474)
(0 45 0)
(45 45 1.96474)
(45 45 -1.96474)
);

blocks
(
hex (0 1 2 0 3 4 5 3) (45 1 45) simpleGrading (1 1 1)
);

patches
(
wedge wedgeFront
(
(4 3 0 1)
)
wedge wedgeBack
(
(5 2 0 3)
)
patch atmosphereTop
(
(3 4 5 3)
)
patch wallBottom
(
(0 2 1 0)
)
wall wallRightSide
(
(5 4 1 2)
)
empty centralAxis
(
(0 0 3 3)
)
);

mergePatchPairs
(
);
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */


// refineMesh description file
FoamFile
{
version 2.0;
format ascii;
root "";
case "";
instance "";
local "";
class dictionary;
object refineMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
// Cells to refine; name of cell set
set c0;
// Type of coordinate system:
// - global : coordinate system same for every cell. Usually aligned with
// x,y,z axis. Specify in globalCoeffs section below.
// - patchLocal : coordinate system different for every cell. Specify in
// patchLocalCoeffs section below.
coordinateSystem global;
//coordinateSystem patchLocal;
// .. and its coefficients. x,y in this case. (normal direction is calculated
// as tan1^tan2)
globalCoeffs
{
tan1 (1 0 0);
tan2 (0 1 0);
}
patchLocalCoeffs
{
patch outside; // Normal direction is facenormal of zero'th face of patch
tan1 (1 0 0);
}
// List of directions to refine
directions
(
tan1
tan2
);
// Whether to use hex topology. This will
// - if patchLocal: all cells on selected patch should be hex
// - split all hexes in 2x2x2 through the middle of edges.
useHexTopology no;
// Cut purely geometric (will cut hexes through vertices) or take topology
// into account. Incompatible with useHexTopology
geometricCut no;
// Write meshes from intermediate steps
writeMesh yes;
// ************************************************** *********************** //

Does anyone knows what is wrong? Is this due to some internal control of OF, which does not allow 2x2 refinement of axisymetric meshes?

Best Regards

[nicasch]

sorry, the images are here:

[mattijs]

The cells at the wedge axis are not hexes and that might give you problems. Either
- start off from all hexes, refine and only then make into wedge (wasn't there a makeAxialMesh on the Wiki?) or
- try the geometricCut yes to not take into account any topology. Your mesh will have to be symmetric in the x-y plane.

[nicasch]

Thanks Mattijs!

I tried out the makeAxialMesh utility, it worked just fine