2 Replies Latest reply on Dec 11, 2013 9:12 PM by Jared Conway

    Axial Fan Rotating Region Not Working As Expected

    Will Seeber

      I created an internal simulation for an axial fan with inlet and outlet ducting.  I would like to determine the flow rate generated by the axial fan by setting the environmental pressures at the inlet and outlet of the ducting.  When I set the outlet pressure to atmospheric pressure and the inlet pressure to a little below atmospheric pressure, set my fan to rotate in the direction it does in real life, the results show flow from my oulet to the inlet.  So the flow is reversed!  When I change the direction of rotation of the fan, the direction of flow does not change in the results.  Still backwards.  However, by swapping the inlet and outlet pressures, I get flow in the correct direction.  But now the pressure differential across the fan is backwards and does not reflect reality since a fan MAKES pressure.  What am I missing here in setting this up to reflect reality where my fan creates flow from a lower to a higher pressure?

        • Re: Axial Fan Rotating Region Not Working As Expected
          Bill McEachern

          Set the pressur to same for both then messure he outlet BC and measure the static pressure. This could be a bit tricky but it should work.

          • Re: Axial Fan Rotating Region Not Working As Expected
            Jared Conway

            in an internal analysis if you set a pressure on both sides, you're defining the flow rate in the system. if you're using an internal flow simulation fan with a fan curve (vs a rotating region). you're going to see how well that fan works under those conditions.


            also, if you're using environmental pressure, remember that defines total pressure at the inlet and static pressure at the outlet, so you'll be generating a pressure difference that is higher than what you're actually expecting. something you might want to do before you move forward too far is just run the pipe without the fan to see how this part works.


            if you're using a rotating region because you're designing the fan yourself, i think you'll have to go to an external analysis. i ran an analysis like this recently and the developers agreed that the software wouldn't work well defining environmental pressure on both sides that are exactly the same. or static pressures that are the same.