Ansys Employee
OK, so you're moving the top section as a rigid body? Ie it's not deflecting. If it's not deflecting you only need layering and may want to rethink which parts move relative to the others: have a look at the tutorials and focus on the in-cylinder one(s) as that's close to what you want.
To add, a structured mesh may not be the best option in many cases. Here I'd go with a swept mesh where my source face(s) may be a mix of structured and unstructured quad and tri elements. We've not used full structured meshes for most tasks in years, but many text books (and lecturers) may be in need of updating as the technology has changed a lot in the 20 years I've been with Fluent and Ansys.