The following classifications are made according to change in flow depth withrespect to time and space
Applied
Hydraulic Engineering: Uniform Types of
Flow
Types
of flow
The following classifications are made according to
change in flow depth withrespect to time and space
Steady and Unsteady: Time
is the criterion.
Flow is said to be
steady if the depth of flow at a particular point does not change or can be
Considered constant for the time interval under consideration. The flow is
unsteady if depth changes with time.
Uniform Flow: Space
as the criterion.
Open Channel flow is
said to be uniform if the depth and velocity of flow are the same at every
section of the channel. Hence it follows that uniform flow can only occur in
prismatic channels.
For steady uniform
flow, depth and velocity is constant with both time and distance. This
constitutes the fundamental type of flow in an open channel. It occurs when
gravity forces are in equilibrium with resistance forces.
Steady non-uniform flow.
Depth varies with
distance but not with time. This type of flow may be either (a) gradually
varied or (b) rapidly varied. Type (a) requires the application of the energy
and frictional resistance equations while type (b) requires the energy and
momentum equations.
Unsteady flow
The depth varies with
both time and space. This is the most common type of flow and requires the
solution of the energy momentum and friction equations with time. In many
practical cases the flow is sufficiently close to steady flow therefore it can
be analysed as gradually varied steady flow.