Refine mesh vertex in a simple step tube CFD problem

Greetings everyone!

I would like a simple suggestion to refine the mesh in vertex step in SALOME 9.9.0.
You can find in the attached file (steptube.hdf) the steps I used, and the coarser local mesh at the corner.
I’m looking for a simple solution using the GUI interface of SALOME, for a beginner CFD group.

Thanks in advance,

steptube.hdf (1,7,MB)