[hmasenger]

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. do you have any idea?

best regards

[singer1812]

Which is interface 1?

[hmasenger]

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

[singer1812]

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?

[PeMo]

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)

[hmasenger]

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

[PeMo]

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

[singer1812]

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

[hmasenger]

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

[hmasenger]

Tnx pemo your clue also really helped.