Computational domain for a blade cascade
 

Hello everybody,
I am going to analyze the flow within a compressor blade passage and I know about the possibility to study a single blade, and then applying the periodic boundaries to the upper and lower side of the domain. My questions are:
- which are the shapes of the surfaces on which I have to apply the periodicity?
- how are these shapes affecting the results, i.e. how is the periodicity acting at the interfaces?

I attach a picture of a domain corresponding to my blade geometry that I found on some articles. Thanks in advance for any help!

http://ars.els-cdn.com/content/image...00012-gr10.sml

Ideally the shape of the periodic boundary does not affect the results. There are a few pitfalls to avoid - like it should not cut through a blade (and if it has to it should do it perpendicular to the surface and not in a critical flow region), it should avoid the wake of the blade, and if possible it should avoid any shocks/rarefaction waves (but this can be very difficult to do, just minimise it as best you can).

But if you have a good mesh quality and a well converged solution you can get away with some of these sins.

Thanks for the help