Boundary Type for the rotation Axis in CFX-Pre
 

What type of boundary should i take for the rotation axis in a 2.5D model.:)
thank you very much for the help
PS: i use periodic interface for the both sides

Assuming by 2.5D by mean an 2D axisymmetric simulation with an out-of-plane swirl component, or a 2D planar simulation with an out-of-plane component - then this can be done using a periodic boundary.

but-...
 

thank you
but cfx-solve says there is no boundary at the xxx-position(where the rotation axis is). my question is which bounday should i select for the xxx(rotation axis)? symmetrie? free slip wall?

If your geometry is a wedge then you do not need to define any boundary at the rotation axis. CFX does not have linear boundary conditions, only surface boundary conditions. Can you post an image of your geometry?