Regal1975,

The word 'turbulence' is used to mean different things. What you need to do to get turbulence-free flow depends a little bit on what you consider to be turbulence. Generally, turbulent flow has some kind of disturbances that cause it to be unsteady ( changing from one moment to the next ). The main distinction to make is the size of the disturbances. If you want to get rid of the large disturbances, which essentially vortices, then turning vanes, as mentioned by BMatthews, might be all you need. If you want to get rid of all disturbances, large and small, you need something more elaborate. First, you need a fairly fine screen, to make sure that you get small vortices throughout the flow ( this is the role of the fabric BMatthews mentions ). This is because the small vortices damp themselves out very quickly. Immediately downstream from the screen you need some kind of flow straighteners. Some kind of honeycomb-like passage is a good way to go. I don't know the ideal dimensions for the screen holes or the honeycomb. Downstream of the honeycomb, you need some open area, to allow the small vortices ( turbulence to damp out ). I don't know how long this section has to be either, but I don't think it is much more than one diameter of the duct.

As BMatthews says, wind tunnels take a lot of juice to run. If you have some kind of flow that just needs to be really smooth, you don't need much more power than you currently use. The only increase would be due to the pressure drop of the screen & straighteners. I don't know what the setup is, bit it sounds like you might be able to get away with adding the screen & honeycomb upstream of the area where you want smooth flow, with no other changes.

I may be able to find more info. in some old textbooks next week when I return from a business trip. PM me if you like.

banktoturn