[cutter]

Hi Foamers!

First of all: Many thanks to Dr. Franjo Juretic for providing cfMesh under an OSS license! It's a really impressing mesher. I've obtained amazingly good meshes for really complex geometries in almost no time.

I've got a specific geometry that's causing some trouble though. Please have look at the attached screenshots and the sample case! I played with various settings and discretizations, but had no luck so far. Especially the finer discretizations that are required in my case are resulting in the worst cells. What could I try to obtain higher quality meshes?

These are the parameters used for the screenshots:

surfaceFile "TestGeometry.fms";
maxCellSize 0.25;
boundaryCellSize 0.125;

surfaceFile "TestGeometry.fms";
maxCellSize 0.05;
boundaryCellSize 0.025;

keepCellsIntersectingBoundary 1;

surfaceFile "TestGeometry.fms";
maxCellSize 0.05;
boundaryCellSize 0.025;

//keepCellsIntersectingBoundary 1;

I used surfaceFeatureEdges -angle 25 TestGeometry.stl TestGeometry.fms to convert my surface triangulation and extract the feature edges.


BTW: What's the correct forum/subforum for cfMesh related issues? Maybe someone could create a special area and move the already existing entries!

Many Thanks
Cutter

[franjo_j]

Hello,

This geometry seems simple, and the settings are simple. However, the mesher has hard time deciding how to adapt the mesh onto the geometry. Please check the following figure generated by using maxCellSize 0.25, boundaryCellSize 0.125 and keepCellsIntersectingBundary 0:


You can notice that the mesh and the template are not similar and it is difficult to choose a suitable corner. When the mesh is refined it gets a bit better, and the result is shown here:

The problem is still similar, and it will not go away only by mesh refinement. The solution is to generate the template matching the geometry as much as possible.

I order to resolve the problem you need to modify the template such that you get a candidate for each problematic corner as close as possible to the geometry. Can you please try using:

keepCellsIntersectingPatches
{
Face_9
{
keepCells 1;
}
}
The mesher will then use the cells intersected by Face_9 in the mesh, and my impression is that it should make the mesh more similar to the geometry.
In addition, can you please try to refine the mesh locally near the problematic corners by using objectRefinements? I would try with lines and boxes to localize the problem.
Furthermore, you can analyze what is going on in the process by writing out the mesh after surfacePreparation and mapMeshToSurface functions in cartesianMeshGenerator.C

I hope this helps.

Regards,

Franjo

[cutter]

Hi,

thanks for the suggested changes.

I did not use these parameters before and played a little while with them. The mesh now conforms somewhat better to the geometry but still contains some really bad shaped cells. I'm going to keep an eye at this issue, this kind of geometry occurs frequently in my projects.

I finally changed the geometry for this case. I moved the hole away from the sharp feature edge to allow the mesher to add better shaped polyhedrons there. This is of course not possible for every project.

Many Thanks
Cutter