[vronti]

Hello

I am running a simulation to get fully developed flow profile to use it in another simulation. The geometry is a rectangular duct (6x9x100)mm with top and bottom walls, side walls symmetric, inlet, and outlet.
I am using simpleFoam (modified pitzdaily case) with realizableKE RAS model.

I calculated entry length and get around 70mm, so, I ran the simulation with 100mm long duct. But when I ran a simulation with 500mm as length I got different peak velocity of fully developed flow. This is surprising because once the flow is developed, the velocity shouldn't rise/drop.
So, to further investigate I ran a simulation of Reynolds number 500 case (velocity - 0.069674m/s) with laminar and turbulent models. Both have different peak velocities. (laminar ~0.1 turbulent ~0.091)

Can someone please enlighten me with the theoretical understanding I am lacking?
It would be a great pleasure.

I am attaching the case to recreate. case - flowDevelop_500_2.zip
Best regards