Nikhil Narale
Ansys Employee



Can you post some images of your geometry and the existing mesh in the comments? 


I would recommend you to assign named selection to the rotor surfaces at the CAD level. With this, you can explicitly add boundary layers on the rotor surfaces (and not on hub).

Also, I would recommend you to use Ansys Fluent Meshing Watertight Workflow. 

Check out this free course on how to add boundary layers (inflation layers): Add Boundary Layers - ANSYS Innovation Courses