Set fully developed turbulent flow at inlet using openfoam
 

Hi For a university assignment, I am trying to simulate the effect of inserting a cylinder-shaped turbulator (in transverse) into a square duct in order to enhance the heat transfer.
I tried to implement a fully developed turbulent flow in the inlet of the duct where the heat is transferred. But it seemed that too much computational effort would be required to simulate it in 3D if I extend the length of duct for it. So I searched and found that I could set the parabolic velocity as a boundary condition in the inlet.
However, I am still confused. If I set a parabolic velocity to the inlet, a fully developed flow would be implemented within the entire duct?
Or are there any other tips to reduce simulation time for this problem?
The method I was thinking of was to implement it in 2D, but I think this would be less accurate considering the walls on both sides of duct and the transverse cylinder structure. Because the effect in flow due to walls on both sides are not taken into account. Or, if there is another way to implement a fully developed turbulent flow, that would be a good answer as well.