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

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