# Can a domain be transformed (rotated) in CFX 11 in a transcient simulation?

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 December 7, 2009, 12:24 Can a domain be transformed (rotated) in CFX 11 in a transcient simulation? #1 New Member   Dan Burke Join Date: Dec 2009 Posts: 1 Rep Power: 0 I am currently running CFX-11. I have a moving domain that needs only to be rotated about the rotation axis - not remeshed. Is there any way to set up a rule to do this between time steps? Dan

 December 7, 2009, 18:18 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,638 Rep Power: 98 Use a rotating frame of reference. Then you don't need to use the dynamic meshing stuff and your simulation will be much faster.

December 8, 2009, 07:01
#3
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Roland Rakos
Join Date: Mar 2009
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Quote:
 Originally Posted by ghorrocks Use a rotating frame of reference. Then you don't need to use the dynamic meshing stuff and your simulation will be much faster.
I agree with you that the rotating frame is simple method and the simulation time is not too long but in my opinion there is some situation where this approach is not exact.
In the rotating domain a tangential velocity component will appear in every cells . For example: there are a wind turbine which rotates very slowly (RPM:1 rev/s). In the case of application of the rotating frame these tangential components can be seen in every cells of the rotating domain but I think that in the reality these components is much smaller between two blades than along the blades.
In short it is not correct approach that every cells are rotating with the turbine...

What do you think about this?

December 8, 2009, 07:20
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Glenn Horrocks
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Quote:
 What do you think about this?
Sounds like rubbish to me

For a rotating frame of reference you are simply using a different frame of reference for your velocities, nothing more than that. And for the case you state where the object is rotating but the flow remains mainly on the stationary frame of reference you use the "alternate rotation model" - look it up in the documentation.

December 8, 2009, 13:32
#5
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Quote:
 Originally Posted by dburke I am currently running CFX-11. I have a moving domain that needs only to be rotated about the rotation axis - not remeshed. Is there any way to set up a rule to do this between time steps? Dan
I have a similiar project to be simulated. However, I need this domain, like yours to be rotating, but is magnetically levitated and hence, its positioning is affected by the fluid dynamics surrounding this domain.

What may be the best approach to do this? Use dynamic meshing for the rotation and at the same time define its 6DOF?

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