Bad quality mesh at external corners
 

Hey guys,

I'm trying to mesh a very simple case of a 2D square, using snappyHexMesh and then extrudeMesh to get a 2D slice. You can see the square cylinder STL and the final 2D mesh (Picture 1).

The issue is that even for such a simple case where the square walls are aligned with the grid, corners seem to have too skewed elements at the castellated step (picture 2), and somehow get distorted when applying the snapping (picture 3).

I don't know why this distortion appears and how to avoid it.

I've been playing with the quality parameters without success. The ones I've used to generate the mesh are the ones from the motorBike Tutorial.

How can I improve my corner mesh quality?

I attach the snappyHexMesh case with STL files, Allrun and Allclean files.

Any help will be much appreciated! Thanks!

The split cells you see are products of your paraview settings. When you load paraview select use VTKPolyhedron on the left, it will remove them.

castellatedMesh true;
snap true;
addLayers true;

Turn off snap and addLayers.
These will relax the mesh to try and improve its quality. In your case if the grid matches the geometry they aren't needed. I think you can also turn of a relaxation setting which should do the same.