- Critical Velocity :
The velocity at which the flow changes from laminar to turbulent is known as Critical Velocity.
It is further divided into two types.
- Lower critical velocity :
A velocity at which laminar flow stops.
The velocity at which the flow enters from laminar to transition period is known as lower critical velocity.
There is a transition period in between laminar and turbulent flow. It has been experimentally found that when a laminar flow changes into turbulent, it does not change abruptly. But there is transition period between two types of flows. This experiment was first performed by Prof. Reynold Obsorne in 1883.
- Upper critical velocity :
A velocity at which turbulent flow starts.
A velocity in which flow enters from transition period to turbulent flow is known as upper or higher critical velocity.