A strange problem. A unstructured code works well with hexadral meshes, but fails for a full tetras. At last I found that some problem might exist for outlet B.C., since I repaced tetras near outlet with hexas, the code worked. the treatments of outlet in this two meshes should be completely different? or some trick is required? I would appreciate your comments.

Regards,

Harry

I did have this kind of problem, where the code was working for hexas but not for tetras.

The source of the problem was gradients. In case of tetras, cells are more skewed compared to hexas. Thus I had very high gradient values for tetra case. Using a good limiter solved the problem though.

I employ full tetra meshes, but only one layer of hexas for outlet, the code works. How to explain this situation?