Flow velocity

The flow velocity of a liquid in pipes varies across the cross-section of the pipe. The flow velocity profile depends on whether the flow is laminar or turbulent.

With laminar flow, the velocity close to the pipe wall is close to zero, while relatively high in the middle of the pipe. With turbulent flow, the velocity is more even over the entire cross-section, however still a bit lower at the pipe wall. Friction losses are generated at the pipe wall. Velocity profiles of the two forms of flow are shown in the illustration.