ASTM D1941-91(2001)
(Test Method)Standard Test Method for Open Channel Flow Measurement of Water with the Parshall Flume
Standard Test Method for Open Channel Flow Measurement of Water with the Parshall Flume
SCOPE
1.1 This test method covers measurement of the volumetric flowrate of water and wastewater in open channels with the Parshall flume.
1.1.1 Information related to this test method can be found in ISO 1438 and 4359.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D 1941 – 91 (Reapproved 2001)
Standard Test Method for
Open Channel Flow Measurement of Water with the Parshall
1
Flume
This standard is issued under the fixed designation D 1941; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.2 head—the height of a liquid above a specified point;
that is, the flume crest.
1.1 This test method covers measurement of the volumetric
3.2.3 hydraulic jump—an abrupt transition from supercriti-
flowrate of water and wastewater in open channels with the
caltosubcriticalflow,accompaniedbyconsiderableturbulence
Parshall flume.
or gravity waves, or both.
1.1.1 Information related to this test method can be found in
3.2.4 normal depth—the uniform depth of flow for a given
ISO 1438 and 4359.
flowrate in a long open channel of specific shape, roughness,
1.2 This standard does not purport to address all of the
and slope.
safety concerns, if any, associated with its use. It is the
3.2.5 primary instrument—the device (in this case, the
responsibility of the user of this standard to establish appro-
flume) that creates a hydrodynamic condition that can be
priate safety and health practices and determine the applica-
sensed by the secondary instrument.
bility of regulatory limitations prior to use.
3.2.6 scow float—an in-stream flat for depth sensing usually
2. Referenced Documents
mounted on a hinged cantilever.
3.2.7 secondary instrument—in this case, a device which
2.1 ASTM Standards:
2
measures the depth of flow at an appropriate location in the
D 1129 Terminology Relating to Water
flume. The secondary instrument may also convert the mea-
D 2777 Practice for Determination of Precision and Bias of
2
sured depth to an indicated flow rate.
Applicable Methods of Committee D-19 on Water
3.2.8 stilling well—a small reservoir connected through a
D 3858 Test Method for Open Channel Flow Measurement
2
constricted passage to the main channel, that is, the flume, so
of Water by Velocity-Area Method
that a depth measurement can be made under quiescent
2.2 ISO Standards:
conditions.
ISO 555 Liquid Flow Measurements in Open Channels—
3.2.9 subcritical flow—open channel flow at a velocity less
Dilution Methods for Measurement of Steady Flow—
3
than the velocity of gravity waves in the same depth of water.
Constant Rate Injection Method
Subcritical flow is affected by downstream conditions, since
ISO 1438 Liquid Flow Measurement in Open Channels
3
disturbances are able to travel upstream.
Using Thin-Plate Weirs and Venturi Flumes
3.2.10 submerged flow—a condition where the water stage
ISO 4359 Liquid Flow Measurement in Open Channels—
3
downstream of the flume is sufficiently high to affect the flow
Rectangular Trapezoidal and U-shaped Flumes
over the flume crest and hence the free-flow depth-discharge
3. Terminology
relation no longer applies and discharge depends on two head
measurements.
3.1 Definitions: For definitions of terms used in this test
3.2.11 supercritical flow—open channel flow at a velocity
method, refer to Terminology D 1129.
greater than that of gravity waves in the same depth, so
3.2 Definitions of Terms Specific to This Standard:
disturbances cannot travel upstream, and downstream condi-
3.2.1 free flow—a condition where the flowrate is governed
tions do not affect the flow.
by the state of flow at the crest overfall and hence can be
3.2.12 throat—the constriction in a flume.
determined from a single upstream depth measurement.
4. Summary of Test Method
1
This test method is under the jurisdiction ofASTM Committee D-19 on Water
4.1 Parshall flumes are measuring flumes of specified ge-
and is the direct responsibility of Subcommittee D19.07 on Sediments, Geomor-
ometries for which empirical relations of the form
phology, and Open-Channel Flow.
n
Current edition approved Jan. 25, 1991. Published March 1991. Originally
Q 5CH (1)
a
e 2
published in 1962. Last previous edition D 1941 – 67 (1975) .
2
Annual Book of ASTM Standards, Vol 11.01.
3
Available from American National Standards Institute, 11 W. 42nd St., 13th
Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D 1941 – 91 (2001)
corrections for non-standard geometry are only estimates. The
inside surface of the flume should be at least as smooth as a
good quality concrete finish.
7.2.2 The measurement location for depth H is shown in
a
Fig. 1. In submerged flow a second depth, H , must be
b
measured in the throat as indicated. However, in the 1, 2, and
3-in. (2.54, 5.08, and 7.62-cm) flum
...
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