[Tellur]

Hello everyone,

I just felt I'd share a bit of my struggles on this one in case they help someone in the future.

The case, as the title says, is fairly simple. A small room with only walls and a ceiling fan.

The set up is as you'd imagine, a rotating region around the fan and two mesh regions overall:

• Fluid Part: the part of the room that does not move. This is made by subtracting the rotating region from the room and consists of two boundaries, one for the wall of the rotating region and one for the rest of the fluid in the room.

• Rotating Part: the part of the room that moves. This is made by subtracting the fan geometry from the rotating region and consists of two boundaries, the wall of the rotating region and the fan.

Now this simple set up hasn't been working for days, under various models, mesh refinements, and whatever else I could think to change. Finally yesterday I managed to get results that make sense, with residuals that make sense. The model was a coarse mesh with k-epsilon, nothing to suggest that is the reason it works.

What I think did it was assigning proper reference frame to regions and boundaries. The set up was the following:

1. Internal interface between the two wall boundaries (the wall of rotating region).
2. Fan boundary: rotating reference frame.
3. Wall of rotating region: lab reference frame for both regions (no rotation).
4. Rest of the room: lab reference frame (no rotation).

Now what I am not sure about is item 3. It felt to me that the wall of the rotating region should be rotating, at least inside the rotating domain. So I changed it and is currently running. However it does seem that the flow developing is similar to the earlier case.

Is it that because this wall has been made into an interface between rotating and non-rotating regions? Is it that whatever I choose here will be 'overriden' by the interface itself? Or is one of the two ways the correct one?

Thanks in advance.

Kind regards,
Theodore.

[Xiang]

Hi Dasein,

Thanks for the great tips and suggestions. Appreciate it a lot. Sadly, I couldn't help you with your question as I'm still stuck at the meshing. The following is the error I had received after trying to adjust the element size and also adding the sharp angle. "The tolerance of the geometry is larger than the applied tessellation refinement tolerance. This might lead to an uneven mesh and/or to poor geometric accuracy of the mesh."


What would you recommend me to do?to get a good mesh

[prashant810]

Hi, I think the fluid mesh for room will be stable and only fan will move, so you can use MRF or Regid body motion to fan, you can give the fan speed in rpm.

[Xiang]

Hi prashant kadam,

It seems that you are pretty familiar with simulating the ceiling fan in a room. Could you help me with my setup?

Thanks