Open-channel flow: Difference between revisions

Revision as of 10:08, 9 January 2017

Revision as of 07:37, 23 August 2017

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'''Open-channel flow''', a branch of [[hydraulics]] and [[fluid mechanics]], is a type of [[liquid]] flow within a conduit with a free surface, known as a [[Stream channel|channel]]. The other type of flow within a conduit is [[pipe flow]]. These two types of flow are similar in many ways, but differ in one important respect: the free surface. Open-channel flow has a [[free surface]], whereas pipe flow does not.

==Classifications of flow==

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::''Varied flow'' - The depth of flow changes along the length of the channel. Varied flow technically may be either steady or unsteady.

:: Varied flow can be further classified as either rapidly or gradually varied.

:::''Rapidly varied flow'' - The depth changes abruptly over a comparatively short distance. Rapidly varied flow is known as a local phenomenon. Examples are the [[hydraulic jump]] and the hydraulic drop.

:::''Gradually varied flow'' – The depth changes over a long distance.

::''Continuous flow'' - The discharge is constant throughout the [[Reach_(geography)|reach]] of the channel under consideration. This is often the case with a steady flow. This flow is considered continuous and therefore can be described using the continuity equation for continuous steady flow.

::''Spatially varied'' or discontinuous flow - The discharge of a steady flow is nonuniformnon-uniform along a channel. This happens when water enters and/or leaves the channel along the course of flow. An example of flow entering a channel would be a road side gutter. An example of flow leaving a channel would be an irrigation channel. This flow can be described using the continuity equation for continuous unsteady flow requires the consideration of the time effect and includes a time element as a variable.

==Summary of the classification of open-channel flow==

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==States of flow==

The behavior of open channel flow is governed by the effects of [[viscosity]] and gravity relative to the [[inertia|inertial]] forces of the flow. Surface tension has a minor contribution, but does not play a significant enough role in most circumstances to be a governing factor.

Depending on the effect of viscosity relative to inertia, as represented by the [[Reynolds number]], the flow can be either [[laminar flow|laminar]], [[turbulent flow|turbulent]], or [[Laminar-turbulent transition|transitional]].