ISSUES: Rotating VS Non-Rotaing Domains

gigiboumba · April 25, 2014, 06:10

Hi all!

I am setting up a simulation of a wind turbine: the model contains a tower, a nacelle with the hub, and three blades.

To simulate the non rotating fluid I have a spherical domain containing the whole model. The nacelle and the tower are made as wall boundaries.

To simulate the rotating domain (hub and three blades) I have a cylindrical domain containing the hub and the three blades. The axis of rotation and the angular velocity are specified. The blades and the hub are made as wall boundaries in the rotating domain.

Then a fluid fluid interfance is created between the two domain.

My problem is that a small part of the nacelle goes into the roating domain, however I don't want that to rotate. When I try to create a wall boundary on that small part in the non-rotating frame, the piece does not appear on the parts list because for CFX it is in the rotating domain (I can find it there a Primitive 2D).
So I can create a wall boundary in the rotating domain, however won't that make the bit of the nacelle to rotate with the domain?

How do I set the small nacelle part that is into the rotating domain into the non-rotating one? Do I have to remesh the whole assembly changing my domain specification (during the mesh I specified on ICEM a volume rotating to the rotating domain and volume to the non-rotating on)?

Many thanks in advance,
Edoardo

ghorrocks · April 26, 2014, 07:29

Note that in a rotating domain the mesh rotates all together. So if the stationary bit is axially symmetric that is fine (then you set it as a counter-rotating wall), but if it is not axially symetric then it should not be modelled in a rotating frame of reference.

gigiboumba · April 26, 2014, 07:39

Dear ghorrocks,

thank you very much for your help. The small bit is not axially symmetric unfortunately: so I will need to redefine my domain on ICEM and remesh everything right?

Many thanks,
Edoardo

ghorrocks · April 26, 2014, 08:22

That is one option.

Another option is if the difference is small and not in an important part of the flow then you can ignore it and just assume it is axisymmetric.

April 25, 2014, 06:10	ISSUES: Rotating VS Non-Rotaing Domains	#1
gigiboumba New Member Edoardo Join Date: Feb 2014 Posts: 13 Rep Power: 12	Hi all! I am setting up a simulation of a wind turbine: the model contains a tower, a nacelle with the hub, and three blades. To simulate the non rotating fluid I have a spherical domain containing the whole model. The nacelle and the tower are made as wall boundaries. To simulate the rotating domain (hub and three blades) I have a cylindrical domain containing the hub and the three blades. The axis of rotation and the angular velocity are specified. The blades and the hub are made as wall boundaries in the rotating domain. Then a fluid fluid interfance is created between the two domain. My problem is that a small part of the nacelle goes into the roating domain, however I don't want that to rotate. When I try to create a wall boundary on that small part in the non-rotating frame, the piece does not appear on the parts list because for CFX it is in the rotating domain (I can find it there a Primitive 2D). So I can create a wall boundary in the rotating domain, however won't that make the bit of the nacelle to rotate with the domain? How do I set the small nacelle part that is into the rotating domain into the non-rotating one? Do I have to remesh the whole assembly changing my domain specification (during the mesh I specified on ICEM a volume rotating to the rotating domain and volume to the non-rotating on)? Many thanks in advance, Edoardo

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April 26, 2014, 07:29		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Note that in a rotating domain the mesh rotates all together. So if the stationary bit is axially symmetric that is fine (then you set it as a counter-rotating wall), but if it is not axially symetric then it should not be modelled in a rotating frame of reference.

April 26, 2014, 07:39		#3
gigiboumba New Member Edoardo Join Date: Feb 2014 Posts: 13 Rep Power: 12	Dear ghorrocks, thank you very much for your help. The small bit is not axially symmetric unfortunately: so I will need to redefine my domain on ICEM and remesh everything right? Many thanks, Edoardo

April 26, 2014, 08:22		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	That is one option. Another option is if the difference is small and not in an important part of the flow then you can ignore it and just assume it is axisymmetric.