a philosophy question about rotating-stationary interface of turbo machinery?
 

As we know in turbo machinery such as axial or radial compressor, we just have an axial velocity which doesn't change with time so first I want to know if we don't want to model surge, off-design condition, trip or such things steady state solution is enough or not?
and second, unsteady interface (I mean unsteady frozen rotor) doas have any relationship with this unsteadiness of flow or it relates to just the relationship between rotating and stationary parts?:confused: