Applied Hydraulic Engineering: Uniform Types of Flow

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.