ASTM D5242-21

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D5242 − 21
Standard Test Method for
Open-Channel Flow Measurement of Water with Thin-Plate
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Weirs
This standard is issued under the fixed designation D5242; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
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1. Scope 2.2 ISO Standards:
ISO1438 FlowMeasurementinOpenChannelsUsingWeirs
1.1 This test method covers measurement of the volumetric
and Venturi Flumes—Part 1: Thin-Plate Weirs
flow rate of water and wastewater in channels with thin-plate
ISO 555 Liquid Flow Measurement in Open Channels,
weirs. Information related to this test method can be found in
Delusion Methods for Measurement of Steady Flow-
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Rantz (1) and Ackers (2).
Constant Rate Injection Method
1.2 The values stated in inch-pound units are to be regarded
3. Terminology
as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only
3.1 Definitions:
and are not considered standard.
3.1.1 For definitions of terms used in this standard, refer to
Terminology D1129.
1.3 This standard does not purport to address all of the
3.2 Definitions of Terms Specific to This Standard:
safety concerns, if any, associated with its use. It is the
3.2.1 crest, n—the bottom of the overflow section or notch
responsibility of the user of this standard to establish appro-
of a rectangular weir.
priate safety, health, and environmental practices and deter-
3.2.2 head, n—theheight of aliquidaboveaspecifiedpoint,
mine the applicability of regulatory limitations prior to use.
for example, the weir crest.
1.4 This international standard was developed in accor-
3.2.3 hydraulic jump, n—an abrupt transition from super-
dance with internationally recognized principles on standard-
critical flow to subcritical or tranquil flow.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 3.2.4 nappe, n—the curved sheet or jet of water overfalling
mendations issued by the World Trade Organization Technical the weir.
Barriers to Trade (TBT) Committee.
3.2.5 notch, n—the overflow section of a triangular weir or
of a rectangular weir with side contractions.
2. Referenced Documents
3.2.6 primary instrument, n—the device (in this case the
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2.1 ASTM Standards:
weir) that creates a hydrodynamic condition that can be sensed
D1129 Terminology Relating to Water
by the secondary instrument.
D2777 Practice for Determination of Precision and Bias of
3.2.7 scow float, n—an in-stream float for depth sensing,
Applicable Test Methods of Committee D19 on Water
usually mounted on a hinged cantilever.
D3858 Test Method for Open-Channel Flow Measurement
3.2.8 secondary instrument, n—in this case, a device that
of Water by Velocity-Area Method
measures the depth of flow (referenced to the crest) at an
appropriate location upstream of the weir plate. The secondary
instrument may also convert the measured depth to an indi-
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This test method is under the jurisdiction of ASTM Committee D19 on Water
cated flow rate.
and is the direct responsibility of Subcommittee D19.07 on Sediments,
3.2.9 stilling well, n—a small free-surface reservoir con-
Geomorphology, and Open-Channel Flow.
Current edition approved Dec. 15, 2021. Published January 2022. Originally
nected through a constricted channel to the approach channel
approved in 1992. Last previous edition approved in 2013 as D5242 – 92 (2013).
upstreamoftheweirsothatadepth(head)measurementcanbe
DOI: 10.1520/D5242-21.
made under quiescent conditions.
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The boldface numbers in parentheses refer to a list of references at the end of
the text.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
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D5242 − 21
3.2.10 subcritical flow, n—open channel flow in which the
average velocity is less than the square root of the product of
the average depth and the acceleration due to gravity; some-
times called tranquil flow.
3.2.11 submergence, n—a condition where the water level
on the downstream side of th
...