Rob
Ansys Employee

If you form a multibody part the zone connection becomes an interior. Otherwise the interface pair should be automatically created in Fluent to pass data over the boundary. Unless you NEED sliding mesh I'd aim for a conformal mesh as it's more efficient. 

https://forum.ansys.com/forums/topic/non-homogenous-velocity-contour-inside-bioreactor/ may answer a few questions too.