Blocking/meshing
 

Dear ICEM Users,

because of my rather modest knowledge of ICEM I'm stuck and do not know how to continue.
In a picture below it can be seen a solid component(slice of exhaust turbine housing) upon which i added volume that represents fluid domain. Part is stationary and circumferentially periodic.

1.) I am wondering how to determine periodicity on the face edges of the casings (upper, bottom)? I do not have any reference rotation centerpoint i just have a periodic slice.

2.) When I approached blocking strategy it was unclear to me: when editing association > "edge - curve" what edge should I select? I am trying to devide domain around the blade/rib of a solid part. So should i take the inner edge of a rib/blade or outer.
Any help would be appreciated and lifesaving.

B.R.

Mesh
 

I am a beginner in icem and i have a lot of doubts about meshing and regarding fluent.. How do you relate the mesh domain to flow conditions? I am working on the following flow conditions:
Geometry: airfoil naca 4412
Chord length= 1m
C grid mesh
velocity= 18 m/s ie mach of about 0.05 (in compressible flow)
density=1.225 kg/m3
Model= spalart allamas

Thank you for your answers in advance.