Unexpected results for rotating geometry with no slip condition

Here we can see the velocity magnitude of my new wind turbine design, as expected velocity is zero at the centre. However, unexpectedly velocity increases at the surface the further away it is from the centre. This would be the expected result (in my head) of the AMI, however, for an MRF where the geometry is not physically rotating, I would expect 0m/s at the surface with no slip?

Thoughts welcome :slight_smile:
Darren