# Time based rotating condition

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 October 30, 2023, 07:37 Time based rotating condition #1 New Member   Rakeshchandra Join Date: Jul 2020 Posts: 13 Rep Power: 5 I'm trying to simulate a butterfly damper opening and closing condition for reference but i'm unable to write a condition such that the damper stops rotating when rotated to 90deg.

 October 30, 2023, 17:50 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,771 Rep Power: 143 There are many ways of doing this: 1) Rotating frame of reference: I suspect this is how you have done it. It is simple and easy to implement and computationally cheap, but you cannot control the rotation beyond a constant velocity. 2) Moving mesh with one domain: This is difficult to implement as the large deformation will make it difficult to deform the mesh and not fold it. I would not recommend this. 3) Moving mesh with two domains: This uses a similar mesh setup to the rotating frame of reference approach, but instead of using a rotating frame of reference to move the butterfly you use moving mesh. This is much more computationally expensive than RFR, but it does give you complete control over the motion. I suspect you will find option 3 as the most viable option. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

 October 30, 2023, 21:58 #3 New Member   Rakeshchandra Join Date: Jul 2020 Posts: 13 Rep Power: 5 Thanks for replying, I'm aware of these methods and I was successful to run it but i'm unable to stop rotation. I've provide angular velocity of 0.157 rad/s and I need to stop it's rotation at time of 10sec where the over all simulation is for 45sec. I tried using defining functions to halt it's rotation but wasn't successful. The function that I wrote is: tt = 45s dt = 0.25 s halt = if(tt >= 5 [s], 0 [radian s^-1], 0.15708 [radian s^-1] IDK where i'm doing wrong.

October 31, 2023, 04:49
#4
Super Moderator

Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,771
Rep Power: 143
Let me repeat:

Quote:
 you cannot control the rotation beyond a constant velocity.
So you cannot change the angular velocity during a run.

You have to use option 3 so you can change the angular velocity in a run.
__________________
Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

 October 31, 2023, 05:08 #5 New Member   Rakeshchandra Join Date: Jul 2020 Posts: 13 Rep Power: 5 oh thanks for clarifying, I didn't find much references regarding moving the mesh while running could you please share any references of the case.

 October 31, 2023, 16:38 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,771 Rep Power: 143 There are a few tutorial examples which use it, and it is described in the CFX documentation. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

 Tags ansys 14, cfx & stator & rotor, cfx 15, moving 3d mesh, moving boundary

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