Flume

For other uses, see Flume (disambiguation).

File:Hävla bruk sågverket.jpg

Log flume in Sweden, August 2010

A flume is a human-made channel for water, in the form of an open declined gravity chute whose walls are raised above the surrounding terrain, in contrast to a trench or ditch. Flumes lead water from a diversion dam or weir to their desired location.

Many flumes took the form of wooden troughs elevated on trestles, often following the natural contours of the land. Originating as a part of a mill race, they were later used in the transportation of logs in the logging industry. They were also extensively used in hydraulic mining and working placer deposits for gold, tin and other heavy minerals.

Flumes are not to be confused with aqueducts, which are built with the goal of transporting the water, whereas a flume would use the flowing water to transport other materials.

Etymology

The term flume comes from the Old French word flum, from the Latin flumen, meaning a river. It was formerly used for a stream, and particularly for the tail of a mill race. It is used in America for a very narrow gorge running between precipitous rocks, with a stream at the bottom, but more frequently is applied to an artificial channel of wood or other material for the diversion of a stream of water from a river for purposes of irrigation, for running a sawmill, or for various processes in the hydraulic method of gold-mining.

Types of flumes

Bull Run Hydroelectric Project diversion flume, carrying water from one reservoir to another.

File:Irrigation Flume.jpg

Working to replace parts on operational irrigation flume in the East Kootenay, British Columbia Canada. This flume runs 8km to provide water to a few dozen farms. Built in 1912.

Millrace

A diversionary flume is used to transfer water from one body to another, such as between two reservoirs.

Log flume

Main article: Log flume

Log flumes use the flow of water to carry cut logs and timber downhill, sometimes many miles, to either a sawmill or location for further transport.

Flow measurement flume

File:Flume, Hafren Forest - geograph.org.uk - 228904.jpg

Measuring flume in the UK

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Flume outflow

File:Creek diversion above the southern portal of Woy Woy tunnel.jpg

A temporary flume in New South Wales

Some varieties of flumes are used in measuring water flow of a larger channel. When used to measure the flow of water in open channels, a flume is defined as a specially shaped, fixed hydraulic structure that under free-flow conditions forces flow to accelerate in such a manner that the flow rate through the flume can be characterized by a level-to-flow relationship as applied to a single head (level) measurement within the flume. Acceleration is accomplished through a convergence of the sidewalls, a change in floor elevation, or a combination of the two.

Flow measurement flumes typically consist of a converging section, a throat section, and a diverging section. Not all sections, however, need to be present. In the case of the Cutthroat flume, the converging section directly joins the diverging section, resulting in a throat section of no length (hence the term "Cutthroat"). Other flumes omit the diverging section (Montana and HS / H / HL -flumes).

Flumes offer distinct advantages over sharp-crested weirs:

• For the same control width, the head loss for a flume is about one-fourth of that needed to operate a sharp-crested weir
• The velocity of approach is part of the calibration equations for flumes
• Unauthorized altering of the dimensions of constructed flumes is difficult (and therefore unlikely)
• Most flume styles readily allow for the passage of sedimentation and floating debris – reducing the time and effort associated with maintaining a flume installation

Styles of flow measurement flumes include: Cutthroat, HS / H / HL-type, Khafagi, Montana, RBC, Palmer-Bowlus, Parshall, Trapezoidal, and Venturi Flume.

Flow measurement flumes can be installed in earthen channels, concrete canals, below ground chambers, or factory integrated into Packaged Metering Manholes.

Navigable Canal Flume

File:Bypass Flume Lock 7 C and O Canal.jpg

A bypass flume on the Chesapeake and Ohio Canal

In some 19th-century canals, a bypass flume diverted water around a lift lock from the level (or pound) above to the level below the lock, so that the level below would have sufficient water.

Recreational flumes

See also: Log flume (ride)

In competitive swimming, specialized flumes with transparent sides are often employed by coaches to analyze a swimmer's technique. The speed of the flow is variable to accommodate the full spectrum of swimming styles and ability.

See also

• Mill race
• Acequia
• Aqueduct (watercourse)
• Canal
• Leat
• Log flume

Further reading

• http://www.openchannelflow.com/blog/article/sections-of-a-flume-their-location-and-function Sections of a Flume - Their Location and Function
• http://www.openchannelflow.com/blog/article/anatomy-of-a-flume Anatomy of a Flume

External links

• Pictures of flow measurement flumes

•  One or more of the preceding sentences incorporates text from a publication now in the public domain: 
• Flumes, Openchannelflow.com
• Sections of a Flume - Their Location and Function, Openchannelflow.com
• p. 270