Physical properties of fluid and fluid transport in piping system
Laminar and turbulent flow in pipe
Flow in pipes and valves theory - full content
If the velocity of fluid inside the pipe is small, streamlines will be in straight parallel lines. As the velocity of fluid inside
the pipe gradually increase, streamlines will continue to be straight and parallel with the pipe wall until velocity is reached
when the streamlines will waver and suddenly break into diffused patterns. The velocity at which this occurs is called
"critical velocity". At velocities higher than "critical", the streamlines are dispersed at random throughout the pipe.
The type of flow when velocity is lower than "critical" is called laminar flow (or viscous or streamline flow). At laminar type
of flow the velocity is highest on the pipe axis, and on the wall the velocity is equal to zero.
When the velocity is greater than "critical", the type of flow is turbulent. In turbulent type of flow there is irregular
random motion of fluid particles in directions transverse to the direction on main flow. Velocity change in turbulent flow is
more uniform than in laminar.
In the turbulent type of flow, there is always a thin layer of fluid at pipe wall which is moving in laminar flow. That layer
is known as the boundary layer or laminar sub-layer.
<< Kinematic viscosity -- Flow mean velocity >>
|
