Creo Simulate > Reference Links > Fix and Flip Normals
  
Fix and Flip Normals
If your shell is not part of a volume or part of a shell pair in a midsurface compressed model, these options appear on the SIM SELECT menu after you select a surface for the Refine Model > Shell or Home > Pressure:
Fix Normals—Use this option to adjust all surfaces so that the normal directions in each element are consistent across the model. Creo Simulate changes the normal direction of some surfaces to make the normals as consistent as possible.
For certain models, it is not possible to generate a completely consistent set of directions. Review the normals and use Flip to fine-tune the global fix.
Flip Normals—Use this option to change the direction of the normal in selected surfaces.
Select the surfaces. Creo Simulate flips the direction of the arrow for each surface you selected.