Tips for 3D tetra mesh quality for Fluent transient run. Rotary Engine
 

Dear all,

I am in a critical stage of my project modelling a Wankel engine concept and I need to achieve a good quality mesh with a reasonable amount of cells and a quality that will not go off after a few time-steps in Fluent transient.

Therefore I am seeking for some tips establishing a viable meshing strategy.

You can see the geometry in the first pic. The nodes are displayed too.
The purpose is to have a good quality mesh and maintain the gap between the rotor tips and the housing as small as possible. In this case it's 1mm.

For the rotor curves, I thought setting Fullcosinus bunching would ensure I get finer mesh at the tips which it really didn't as can be seen in picture 2.

Actually, the mesh doesn't seem to respect the node bunching at all.
Reducing the surface mesh size results in unacceptably high number of elements without really improving the quality.

Anyway, I can achieve a tGrid skewness rating of 60% to 65% which I guess is OK for Fluent in general, but after the first time step I get negative volume errors etc.

Reducing the time step in Fluent could fix this but it is already a heavy - slow model and running it even slower will violate my time constraints.

Any help would be most appreciated!

All the best,
Thanos