Room Fan

I would like to now try and simulate a spinning room fan in a room, let say, 12 ft by 12 ft by 9 ft.

The fan is a three bladed room circulation fan mounted 16" below the ceiling.

1. Can I model accurately a non-symetrical thing like with Caedium? I have already done the spinning wheel tutorial.

2. Can I model this using a time variant condition in the room?

3. In modeling this should I create the fan center motor and blades as a single closed volume and insert it into a room volume and subtract it from the room volume leaving a void in the room then use the surfaces of that void as my rotating object?

4. If I can do this in time variant will I see the blades turning or just the effect on the air?

Ken

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Use Moving Reference Frame (MRF)

To model a non-axi-symmetric object, such as a fan, you will have to use a Moving Reference Frame (MRF) within a multiple-volume flow domain. Note the rotating wheel tutorial is axi-symmetric, so it is modeled with a simple angular velocity assigned to the wheel faces.

To simplify your geometry I suggest you only model the rotating fan blades, i.e., omit the shaft and motor housing.

For your ceiling fan simulation:

  1. Enclose the entire fan within a cylinder - an axi-symmetric volume.
  2. Keep a copy of the cylinder.
  3. Subtract the fan from the original cylinder to form the MRF volume.
  4. Subtract the copy of the cylinder from the room to give a void that perfectly matches the MRF volume.
  5. Use the Faces->Connect tool on the Geometry Tool Palette to connect the faces between the 2 volumes.
  6. Create a group of the 2 volumes and assign the Substance to the group.
  7. Setup the MRF by assigning Conditions->Angular Velocity to the MRF volume.
  8. Setup up all faces excluding the internal connected faces as Conditions->Walls.

MRF is for steady-state simulations, so you will not see the blades moving. It's as if the fan is spinning and you take a snapshot at an instant for the current fan position. MRF is also known as the frozen rotor method.

More on MRF

fan

This is interesting. I will give it a try. thanks

Requesting for the procedure of the fan CFD analysis

Dear Ken,

I read your comment and understood that you intended on performing a CFD analysis for a ceiling fan. I am glad to know that because i want to do the same. I am new to CFD and i request you to give me information regarding how did you carry out the analysis (Assuming you successfully completed the analysis), it will be of great help to me.

Thanks and regards,
Balaji.

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