weird results with snappyHexMesh probably produced by (unrecognized) internal baffles
 

Hi Foamers,

I'm facing a rather strange issue when analyzing the fluid flow of a venturi nozzle. I have generated the mesh with snappyHexMesh and there are 22 Non-Othogonal faces wich are pointed out by the mesher after the final meshing stage. Besides this, all quality creterias seem to be matched (or ignored) by importing the mesh into a simpleFoam case.
However visualizing Non-orthogonal cells, they appear far away from the region of interest and the run converges very vell after a few iterations.

The problem now is, that the results are not reasonable (please see images), so I asked a colleague tu run the simulation in star with my mesh. Exporting it from openFoam (foamMeshToFluent) and importing it into star shows no error statistics and in star also the solution converges fine, but they (strange) solution is the same.

By reviewing the mesh carefully in star, there seams to be an internat baffle the region of the outflow nozzle, which could be a possible reason for the disturbance in the fluid flow.

Neither star, nor openFoam recognized the issue (or it's recpognized as a desired part of the mesh). The mesh passes quality checks in all solvers.

How can I spot out if there are internal baffles ? I can't identify them in paraview. Is there a general setting to avoid such problems ?
May some non orthogonal faces be the reason for this issue ?

Thank you ver much,

Jan

P.S.: I have attached a picture of the results as well as my snappyHexMesh and quality dict file in the attachment

The dictionary seems alright to me. By reviewing the velocity picture, I didn't find "baffle"; if there is a baffle, you can see vortex after the baffle. It could be caused by mesh size variation. Can you overlay the mesh on the velocity contour?

Thank you very much. I have finally reviewed everything carefully and could neither find errors nor vorteices within this region.

Have a nice day,

Jan