centrifugal fan modeling
 

hi all
i am modeling a centrifugal fan with two domains using a frozen rotor domain interface approach.i have got a frozen rotor for fan blades and one for stator(take a look at attached images).i am using a relative zero pressure inlet and a zero static pressure outlet to have the total dynamic pressure duo to fan rotation and air velocity.(i think the problem emerges right here but not sure!)
i am trying to investigate the effect of increasing the number of rotor blades and RPM in pressure and flow(h-q graph).
there is a weird error in this study.the cfx-solver runs and reported good results the first time but as i changed the model geometry(increasing blade number) and keeping all physical BC's and conditions the same , cfx turs out with some error's about domain interface(attached).i dont know what is the error's source:confused::confused:. do you have any idea?

best regards

Which is interface 1?

Interface 1 is the one that conects the top of rotor domain to stator.in another word it is a flat surface

I suspect mesh buildup error. Did you build it up in ICEM? Are you sure your mesh is fully in a planer section (no nodes slightly off plane?)

Are you sure your coord frame is dead on in the center? It didnt get altered a bit with new mesh?

Also, recheck the surfaces in the interfaces. Are you sure they are the same as the first run?

I was facing exactly the same problem. Solution was to specify the Pitch angle instead of using the Automatic function (however in contrast to your setup i am modelling only one passage, but maybe it is worth a try)

Tnx pemo for sharing your experience. But one question,What do you mean by pitch angle?where can i define that?

Pitch Angle defines the Angle between the domains (for instance if your modelling one of total 15 blades with a full draft tube (diffusor) the blade pitch angle is 360/15=24deg while the draft tube angle is 360deg. Most of the time it is sufficient to keep the automatic function, but sometimes its not :).
You find it in the Interface section direct beneath the Frame Change (Frozen Rotor Model). The Correct name is Pitch Change

Your pitch angle in your interface should be set to "None" for your case.

Tnx singer.problem solved.i am going to hange your comment on my room's wall ;-) .

Tnx pemo your clue also really helped.