[Rakeshchandra]

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.

[ghorrocks]

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.

[Rakeshchandra]

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.

[ghorrocks]

Let me repeat:

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.

[Rakeshchandra]

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.

[ghorrocks]

There are a few tutorial examples which use it, and it is described in the CFX documentation.