Laminar Flow and Turbulence
At low speeds liquid flow is smooth and 'laminar'. The flow occurs in parallel layers, with minimal disruption between these layers.
The flow is greatest at the centre and diminishes towards the periphery. This makes the laminar flow describe a bullet shaped velocity profile shown in red below:
Turbulent flow occurs in rough tubes and at higher flow rates.
The flow is not streamlined. There is a lot of swirling of the fluid and a lot of energy is wasted overcoming the internal forces of the fluid.
The flow is not greatest at the centre. Thus, as shown in red below, the velocity profile of turbulent flow is more regular than that caused by laminar flow.