[Davitt]

Hello fellow Fluid Dynamicists...

I'm using COMSOL 5.1 and I'm trying to create a 'Rotating Interior Wall' boundary but for some reason I'm not able to select the boundary (surface) that I want to select.
Actually I can't select any surface when I'm trying to make the Rotating Interior Wall boundary.

Has anyone ever encountered this before.

Any assistance will be greatly appreciated.

Thank you,
David

[LionMan]

Hi David,
"rotating wall" must be within a "rotating domain" , then you can select boundaries as RW.
For instance, draw a circle with diameter bigger than RW, make flow continuity pairs and boundaries can be selected as RW. make sure rotating domain and RW centers are aligned, or it will rotate awkward.

hope that helps,
Serzat

[leovante]

Hi Serzat,
can you help me with same problem?

its 1/4 part of mixer. I am beginner in comsol.
i attach file
https://1drv.ms/u/s!Aj_rp8CXnx_yhIo6BLCruUw0AmG4UQ
rotating domain is created. Comsol 5.2a

I will be glad of any help

Thank you,
Dmitry

[LionMan]

Hi Dmitry,
I'll include a short abstract of the topic FYI.
Rotating Domain is used to define mesh inside the domain respect to a stationary coordinate. So it rotates as a solid body. Then you can choose various rotation options for body movement. I think that is adequate for modeling definition.
But due to motion happening in a fluid, you have to define boundary conditions for rotating domain. You have 2 options for this;
1) Rotating Wall: directly applying boundary conditions to external boundaries of a rotating domain. Then you can choose corresponding wall functions.
2) Rotating Interior Wall: Same principle with above. But instead, it applies boundary conditions on both sides of an internal boundary. It is useful to avoid meshing thin geometries. Infinite thin geometry (curve or surface) definitions allow shell meshing as part of rotating domain.

As fas as I understand from your model is, rotating domain definition is true.
During import, because of assembling of CAD software or import features, component is accepted as whole 3D geometry without thin curves or surfaces. That is why you can't select interior wall in my opinion, please check it.
Regarding to explanation above, you can just simply use Rotating Wall for boundaries including 9-10-...-40.
Delete rotating interior wall.

Then you can get some results.
https://1drv.ms/u/s!AvWDjBV-jqr-imDryMtJCPf4qpJx

Hope that helps,

Regards,
Serzat

[leovante]

Hi Serzat,
Thank you for detailed answer and attach file. I understand you, but my eanglish is bad.
If you now, about multiphase rotating machinery, how i can change periodic flow conditions boundary? this option is not in the list.

Thank you,
Dmitry

[LionMan]

Hi Dmitry,
I was busy and my phone app didn't work well, I noticed your post a bit late.
Will take a look for periodic flow conditions. Is it related to your model ?

regards,
Serzat