Setting up Periodic Boundaries
 

Background - I am using Ansys Fluent to run simulation on a wind turbine blade. The model was made in SolidWorks and imported across as a step file. Spaceclaim was used to make the flow domain area. The playlist below outlines the steps taken. https://www.youtube.com/playlist?lis...euAWEaqdhtTr8n

When trying to set the periodic boundaries the following error appears.

Error: Periodicity could not be automatically calculated. The selections that you provided are non-planar. Use Manual option
Error Object: #f

I know I can do this manually, but it would be good to know what is causing this error and how it could be avoided/fixed.