The entrance length needed for pipe and channel flows to re-adjust from a uniform to a fully-
developed velocity profile is typically defined as the length required for the centreline
velocity to reach 99% of its fully-developed value. This definition may be quite inaccurate in
non-Newtonian flows with almost flat fully-developed velocity distributions near the
centreline. Shear-thinning and viscoplasticity may cause the flow close to the centreline to
evolve faster than that closer to the walls. Thus, alternative definitions of the entrance length …