Final answer:
In a fully developed turbulent pipe flow, the axial velocity profile is flatter in the center and decreases towards the pipe walls with chaotic eddies and swirls present, which enhance mixing and even out velocity variations.
Step-by-step explanation:
In turbulent pipe flow that is fully developed, the axial velocity profile is characterized by irregular and fluctuating velocities throughout the cross-section of the pipe. Unlike laminar flow, where the velocity profile is parabolic and the flow is organized in layers, turbulent flow consists of chaotic eddies and swirls which cause mixing of fluid particles across different layers.
The velocity in turbulent flow is highest at the center and decreases towards the pipe walls. However, the velocity profile is flatter in the center compared to laminar flow which means the difference in velocity between the center and the outskirts of the pipe isn't as pronounced. This is because the mixing induced by turbulence tends to even out the velocity variations. The velocity at the walls is not precisely zero due to the turbulent boundary layer but it is significantly lower compared to the center.
To further understand turbulent flow, it is essential to consider concepts such as Reynolds number, which predicts the onset of turbulence. A Reynolds number greater than 4000 generally indicates turbulent flow, while a number below 2000 suggests laminar flow, with values in between being transitional.