[AS_Aero]

Hi All

I have a lengthy turbine blade and I wanted to use a Symmetry Boundary condition at the mid surface. And there I have some issues , I have attached the image of the issue. I have shown the fluid part of the turbine to be meshed. So there I have an interface which is a small diameter greater than the turbine rotor diameter. In order to support the blades there is a disc at equal distance, so when I take the fluid volume this disc is subtracted and hence produces a shell kind of region and finally when I take the symmetry there is a thin ring like structure at the symmetry plane this is due to my interface. So here as shown in the image I give the top/outer dia as interface , then the symmety part is what I am not sure about, which all faces I should give ?
I have shown in the second image which surfaces I am talking about, its highlighted in green

Kindly help me on this issue.

Thanks in advance

[Far]

you cannot apply symmetry boundary conditions solely based on geochemistry.

[AS_Aero]

What are you talking about ? Where did geochemistry come from in this ?

[Far]

where you want to use symmetry?

[Gert-Jan]

You will have a symmetry plane in the stationary frame (the small ring on the outside) and you will have a symmetry plane in the rotating frame (the larger circle that intersects with your rotating blades.)

What is the problem?

The only thing I don't understand is: in your image you indicate something as "Thick". What is that?

[AS_Aero]

Actually I have the rotor blades and then theses blades are attahced with a metal disc of some thinckness, and I created a bigger diameter cylinder around this blade and subtracted the solid volume, so I have the fluid volume, where the outer face is interface. So when I subtract the solid part I get a hollow part at the disc region where exactly at the middle of a disc I made symmetry, so there will be a thickness of interface part right ? Which is my rotor part. The extreme outside face I can take as symmetry, then one part of the disc is there which is actually wall and my doubt is if I should give it as symmetry or wall. If I dont give it as symmetry how will it consider on the other side to have the same disc face ?
Then in between the disc wall and the interface outer diameter is what you see as a ring, where you have a thickness, which I dont know if it should be wall or symmetry . If I dont do symmetry its a hollow space right where there is not fluid or no mesh. I hope I made you clear

[Gert-Jan]

You should just set the thick part as a wall. Since it is a wall.
If it rotating in reality and it is the rotating domain, then it is just a no slip wall.
If it not rotating in reality and it is the rotating domain, then it should be counter rotating to effectively stand still in your simulation.

The symmety in the middle implies that you have a wall on the opposite side of the symmetry as well.

[AS_Aero]

Hi Gert
The projected part (Ring like part ) what you see in the image is basically the interface domain. But the problem here is my air domain is also ending there and hence i dont have an interface region on that side to match with this interface face. And I tried to keep it as wall and tried to run and just keeping the air domain side as symmetry, but CFX crashes with error, when I dont use symmetry the simulation works perfectly , so I guess this comes from the symmetry issue only.
Basically the problem here is the symmetry is applicable to both rotor domain whch has some interface face at the symmetry and the stator part which is basically a rectangle box which has a symmetry plane at the side and no interface.

[Gert-Jan]

Based on the text, I think it is to complicated to understand exactly, what you try to model, how it is setup, and what the problem is. If you can share your model (.def-file), I am willing to take a closer look in Pre. Send it through a private message.