[buzzybee]

I am interested to hear from people who have modelled an axial flow fan in a duct, to find out what shape of inlet they have found works best to determine the correct velocity profile in front of the fan.

In my case, I have a fan with a 2mm tip clearance placed into a duct 25 mm down from the duct entrance - see http://img218.imageshack.us/img218/7379/domain.jpg

As can be seen from this image, the domain in front of the fan is a dome shape with the 25mm of duct in front of the fan intruded and 'cut out' from the dome shape, where 1 and 2 are non-slip walls. I have been trying different combinations of inlet and outlet boundary conditions and have been getting quite different results when visualising the flow over the blades. I believe that a mass flow on the outlet and a total pressure of 0 atm (relative domain pressure is 1 atm), best physically simulates my experimental setup. However I get backflow when using these boundary conditions (with more than 60% wall off to maintain the inlet boundary condition).

As far as I am concerned the outlet is far enough away from the inlet (10 diameters, which it was in the physical experiment). I have been looking at the effect of the inlet varying the size of the dome, but would like to hear from anyone who has modelled a similar physical setup to find what shape inlet they have successfully used.

Thanks in advance for any advice/suggestions.

Jenny