Question: Develop a solution for the friction coefficient and velocity profile in the entry region of a flat duct, assuming that the velocity is uniform over the flow cross section at the entrance, that the boundary layer that develops on the two surfaces is turbulent from its very beginning, and that Eq. is an adequate approximation for the velocity profile both in the can be divided into two parts: a uniform-velocity core region and a boundary layer that ultimately engulfs the entire core. Note that the uniform velocity in the core region accelerates because of the displacement of the boundary layer, and that part of the pressure drop in the entry region is due to this acceleration. Determine the length of the entry region.
u+ = 8.6y+1/7