Simulation with a rotating frame within another?

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 August 22, 2016, 06:08 #2 Member   Ruud Caljouw Join Date: Dec 2012 Posts: 40 Rep Power: 7 Hi siw, did you eventually solve this problem? I am also working on a similar problem. Thanks

 August 22, 2016, 09:45 #3 New Member   Join Date: Aug 2016 Posts: 17 Rep Power: 3 I don't think there is any necessity to use one rotating frame within another. this probably a fluid-structure integrated problem.

 August 22, 2016, 19:59 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,214 Rep Power: 110 You can't put a rotating frame of reference inside another one. In CFX RFR needs a fixed rotation axis. So you are going to have to do this by moving mesh. Also I would not recommend doing this as a rigid body or FSI simulation to get the rotation speed. Only use FSI if you are modelling the blade deflection due to aerodynamic loads. It is far easier to get the rotation speed by running a series of assumed and fixed rotation speeds and establishing the system torque versus speed characteristic. Then you can interpolate to zero net torque based on the system load. This approach requires several simple simulations. kabuforever likes this.

August 23, 2016, 02:57
#5
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Ruud Caljouw
Join Date: Dec 2012
Posts: 40
Rep Power: 7
Yes, I noticed this. How would that work with the moving mesh.

I read on another website the following text on how to do this? Would you agree with this. My (brief) efforts to apply this have not been successful yet

Quote:
 In general, specifying a rotating domain inside a rotating domain in CFX-Pre does not move the axis of the rotated domain. This needs to be done as a moving mesh case. Let's say that a larger outer cylinder is spinning around a global z axis and smaller inner cylinders are rotating around their own local z axis (as well as around a global z axis). Then the solid body rotation of the large cylinder needs to be defined as a moving mesh and the local rotation of smaller cylinders as a number of individual rotating domains. The larger cylinder needs to be connected to the surrounding stationary domain by a standard GGI interface which will automatically update the reintersecting moving mesh. The smaller (inner) rotating cylinders must be connected to the larger (outer) cylinder by transient rotor-stator interfaces. Defining an interface, creates two separate BCs patches, one for each domain. These patches need to move with the same mesh displacement as the volume mesh of the larger (outer) cylinder, therefore mesh motion has to be defined for them as well.

 August 23, 2016, 05:59 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,214 Rep Power: 110 I don't understand the quote's second paragraph. The domain which has a simple rotation about a fixed axis should be made a rotating domain and the domains which have a moving rotation axis have to be moving mesh. I can't see how it can be done any other way. Other than the quote seems correct.

August 23, 2016, 14:37
#7
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Stuart
Join Date: Jul 2009
Location: Portsmouth, England
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Quote:
 Originally Posted by bolus13 Hi siw, did you eventually solve this problem? I am also working on a similar problem. Thanks
This was over three years ago and I do not recall what I did in the end - I have worked on so many other projects since then

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