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Correcting unreliable velocity distributions in short culverts and canal reaches

Date

2002-07

Authors

Replogle, John, author
U.S. Committee on Irrigation and Drainage, publisher

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Abstract

Irrigation water management increasingly depends on good water flow measurement. Too frequently, flow disturbances from upstream elbows, the well pump, or other pipe fittings, produce distorted flow profiles that are detrimental to the proper installation and operation of common flow meters used in pipes, and the flumes and weirs used in canals associated with irrigated agriculture. Field conditions often force installation of pipe flow meters and flumes closer to these upstream disturbances than specified by standard installation recommendations. Special methods to condition flows to generate usable flow profiles over short distances are commercially offered for pipes meters. Less expensive methods have been used in irrigation applications, but have been only partially studied to define their application limits. The historical installation recommendations for pipe meters and flumes are summarized and still recommended for inclusion in future constructions. For retrofit situations the field experiences and limited laboratory information on alternate approaches are presented. Suitable flow profiles for acceptable metering results in pipes can be obtained at distances about one-half to one-third the usual, historical, pipe-length requirements. These profiles, while nearly symmetrical, may be more uniform, or piston-like, than the fully developed shape.

Description

Presented at the 2002 USCID/EWRI conference, Energy, climate, environment and water - issues and opportunities for irrigation and drainage on July 9-12 in San Luis Obispo, California.

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