[RalfBecker]

Hello,

I am facing problems building a hybrid mesh (hex/tet) in a quarter of a geometry (90 degree) with rotational symmetry. The attached picture shows a detail. The geometry is build from a larger block (green) with hex elements and a smaller cylindrical cutout with Tet-elements. The yellow elements are the interface between hex and tet elements. Periodicity is defined at the edges along the y-axis and z-axis.

I have tried the merge with different mesh sizes on the interface, with smoothing, building a new mesh on a smoothed surface mesh and so on. The number of bad elements varies, but I never got a "valid" result of the merge. Best results I have obtained by dropping the periodicity constraint before the merge, but this is only an option if I could restore the periodicity afterwards.

I read and practiced the hybrid mesh tutorial in the docs and searched in this forum, but I am still stuck.

As you can see in the picture, after the merge are a lot of irregular elements along the periodic edges left and the periodicity of the above triangular surface mesh (not shown) is violated (Even if periodicity is defined in "Global Mesh Setup")
My questions:

1. Which possibilities do I have to correct the bad elements?
2. Is there a way to restore the periodicity?
3. How can I avoid this problems?

Kind regards,
Ralf