ASTM D5389-93(2013)
(Test Method)Standard Test Method for Open-Channel Flow Measurement by Acoustic Velocity Meter Systems
Standard Test Method for Open-Channel Flow Measurement by Acoustic Velocity Meter Systems
SIGNIFICANCE AND USE
5.1 This test method is used where high accuracy of velocity or continuous discharge measurement over a long period of time is required and other test methods of measurement are not feasible due to low velocities in the channel, variable stage-discharge relations, complex stage-discharge relations, or the presence of marine traffic. It has the additional advantages of requiring no moving parts, introducing no head loss, and providing virtually instantaneous readings (1 to 100 readings per second).
5.2 The test method may require a relatively large amount of site work and survey effort and is therefore most suitable for permanent or semi-permanent installations.
SCOPE
1.1 This test method covers the measurement of flow rate of water in open channels, streams, and closed conduits with a free water surface.
1.2 The test method covers the use of acoustic transmissions to measure the average water velocity along a line between one or more opposing sets of transducers—by the time difference or frequency difference techniques.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 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. Specific precautionary statements are given in Section 6.
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Standards Content (Sample)
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Designation: D5389 − 93 (Reapproved 2013)
Standard Test Method for
Open-Channel Flow Measurement by Acoustic Velocity
Meter Systems
This standard is issued under the fixed designation D5389; 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.
1. Scope 2.2 ISO Standard:
ISO 6416 Liquid Flow Measurements in Open Channels—
1.1 This test method covers the measurement of flow rate of
Measurement of Discharge by the Ultrasonic (Acoustic)
water in open channels, streams, and closed conduits with a
Method
free water surface.
1.2 Thetestmethodcoverstheuseofacoustictransmissions
3. Terminology
tomeasuretheaveragewatervelocityalongalinebetweenone
3.1 Definitions—For definitions of terms used in this test
or more opposing sets of transducers—by the time difference
method, refer to Terminology D1129.
or frequency difference techniques.
3.2 Definitions of Terms Specific to This Standard:
1.3 The values stated in SI units are to be regarded as the
3.2.1 acoustic path—the straight line between the centers of
standard.
two acoustic transducers.
1.4 This standard does not purport to address all of the
3.2.2 acoustic path length—the face-to-face distance be-
safety concerns, if any, associated with its use. It is the
tween transducers on an acoustic path.
responsibility of the user of this standard to establish appro-
3.2.3 acoustic transducer—a device that is used to generate
priate safety, health, and environmental practices and deter-
acoustic signals when driven by an electric voltage, and
mine the applicability of regulatory limitations prior to use.
conversely, a device that is used to generate an electric voltage
Specific precautionary statements are given in Section 6.
when excited by an acoustic signal.
1.5 This international standard was developed in accor-
3.2.4 acoustic travel time—the time required for an acoustic
dance with internationally recognized principles on standard-
signal to propagate along an acoustic path, either upstream or
ization established in the Decision on Principles for the
downstream.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.2.5 discharge—the rate of flow expressed in units of
Barriers to Trade (TBT) Committee.
volume of water per unit of time. The discharge includes any
sediment or other materials that may be dissolved or mixed
2. Referenced Documents
with it.
2.1 ASTM Standards: 3.2.6 line velocity—the downstream component of water
velocity averaged over an acoustic path.
D1129 Terminology Relating to Water
D2777 Practice for Determination of Precision and Bias of
3.2.7 measurement plane—the plane formed by two or more
Applicable Test Methods of Committee D19 on Water
parallel acoustic paths of different elevations.
D3858 Test Method for Open-Channel Flow Measurement
3.2.8 path velocity—the water velocity averaged over the
of Water by Velocity-Area Method
acoustic path.
3.2.9 stage—the height of a water surface above an estab-
lished (or arbitrary) datum plane; also gage height.
This test method is under the jurisdiction of ASTM Committee D19 on Water
and is the direct responsibility of Subcommittee D19.07 on Sediments,
3.2.10 velocity sampling—means of obtaining line veloci-
Geomorphology, and Open-Channel Flow.
ties in a measurement plane that are suitable for determining
Current edition approved Jan. 1, 2013. Published January 2013. Originally
flow rate by a velocity-area integration.
approved in 1993. Last previous edition approved in 2007 as D5389 – 93 (2007).
DOI: 10.1520/D5389-93R13.
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
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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D5389 − 93 (2013)
FIG. 1 Velocity Component Used in Developing Travel-Time
Equations
4. Summary of Test Method
4.1 Acoustic velocity meter (AVM) systems, also known as
ultrasonic velocity meter (UVM) systems, operate on the FIG. 2 Voltage Representation of Transmit and Receive Pulses at
Upstream and Downstream Transducers
principle that the point-to-point upstream traveltime of an
acoustic pulse is longer than the downstream traveltime and
rate. The spacing between acoustic paths, the spacing between
that this difference in travel time can be accurately measured
by electronic devices. thetoppathandtheliquidsurface,andthespacingbetweenthe
lowest path and the bottom are determined on the basis of
4.2 Most commercial AVM systems that measure stream-
stream cross-section geometry or estimates of the vertical-
flow use the time-of-travel method to determine velocity along
4 velocity distribution and by the required measurement accu-
an acoustic path set diagonal to the flow. This test method
racy. In addition to several line velocity measurements, it is
describes the general formula for determining line velocity
necessary to provide water level (stage) and cross-sectional
defined as (Fig. 1 and Fig. 2):
area information for calculation of the volume flow rate (see
1 1
Fig. 3).
B
t t
F G
CA AC
V 5 2 (1)
L
2cosθ
5. Significance and Use
where:
5.1 Thistestmethodisusedwherehighaccuracyofvelocity
V = line velocity, or the average water velocity at the
or continuous discharge measurement over a long period of
L
depth of the acoustic path,
time is required and other test methods of measurement are not
θ = angle of departure between streamflow and the acous-
feasible due to low velocities in the channel, variable stage-
tic path,
discharge relations, complex stage-discharge relations, or the
t
AC = traveltime from A to C (upstream),
presence of marine traffic. It has the additional advantages of
t
CA = traveltime from C to A (downstream), and
requiring no moving parts, introducing no head loss, and
B = length of the acoustic path from A to C.
providing virtually instantaneous readings (1 to 100 readings
4.3 The discharge measurement or volume flow rate deter- per second).
mination made with anAVM relies on a calibrated or theoreti-
5.2 The test method may require a relatively large amount
cal relation between the line velocity as measured by theAVM
of site work and survey effort and is therefore most suitable for
and mean velocity in the flow segment being measured.Taking
permanent or semi-permanent installations.
morelinevelocitymeasurementsacrossthechannelatdifferent
elevations in the acoustic plane and performing a numerical
6. Interferences
integration or weighted summation of the measured velocities
6.1 Refraction—Thepathtakenbyanacousticsignalwillbe
and areas of flow can be used to better define the volume flow
bent if the medium through which it is propagating varies
significantly in temperature or density. This condition, known
as ray bending, is most severe in slow moving streams with
Laenen, A., and Smith, W., “Acoustic Systems for the Measurement of
Streamflow,” U.S. Geological Survey Water Supply Paper 2213, 1983. poor vertical mixing or tidal (estuaries) with variable salinity.
D5389 − 93 (2013)
6.5 Electrical Obstructions—Nearby radio transmitters,
electrical machinery, faulty electrical insulators, or other
sources of electromagnetic interference (EMI) can cause fail-
ure or sporadic operation of AVMs.
7. Apparatus
7.1 The instrumentation used to measure open-channel flow
by acoustic means consists of a complex and integrated
electronic system known as an acoustic velocity meter (AVM).
Three or four companies presently market AVM systems
suitable for measurement of open-channel flow. System con-
figurations range from simple single-path to complex-multi-
path systems. Internal computation, transmission, and record-
ing systems vary depending on local requirements. MostAVM
systemsmustincludethecapabilitytocomputeanacousticline
velocity from one or more path velocities together with stage
(waterlevel)andotherinformationrelatedtochannelgeometry
necessarytocalculateaflowrateperunitoftime,usuallycubic
3 3
millimetres per second (m /s) or cubic feet per second (ft /s).
7.1.1 Electronics Equipment—There are several methods
that are currently being used to implement the electro-acoustic
functions and mathematical manipulations required to obtain a
line-velocity measurement. Whatever method is used must
includeinternalautomaticmeansforcontinuouslycheckingthe
accuracy. In addition, provision must be included to prevent
erroneous readings during acoustic interruptions caused by
rivertraffic,aquaticlife,orgradualdegradationofcomponents.
7.1.2 Flow Readout Equipment—This equipment is func-
tionally separated into three subsystems. These subsystems
FIG. 3 Example of Acoustic Velocity/Flow Measuring System
may or may not be physically separable but are discussed
separately for clarity.
In extreme conditions the signal may be lost. Examples of ray
7.1.3 Acoustic Tranceiver—This system generates, receives,
bending are shown in Fig. 4. Beam deflection for various
and measures the traveltimes of acoustic signals. The acoustic
temperatures and specific conductivities are shown in Fig. 5
signals travel between the various pairs of acoustic transducers
and Fig. 6.
and form the acoustic paths from which line velocities are
6.2 Reflection—Acoustic signals may be reflected by the
determined.
water surface or streambed. Reflected signals can interfere
7.1.4 Processor—The processor performs the mathematical
with, or cancel, signals propagated along the measurement
operations required to calculate acoustic line velocities, makes
plane. When thermal or density gradients are present, the
decisions about which acoustic paths should be used on the
placement of transducers with respect to boundaries is most
basis of stage, performs error checking, calculates total volume
critical. This condition is most critical in shallow streams. A
flow rate, and totalizes volume flow.
general rule of thumb to prevent reflection interference is to
maintain a minimum stream depth to path length ratio of 1 to 7.1.5 Display/Recorder—Generally, the output of the sys-
100 for path lengths greater than 50 m. tem is a display or a recorder, or both. The recorder normally
includes calendar data, time, flow rate, stage, and any other
6.3 Attenuation—Acoustic signals are attenuated by
information deemed desirable, such as error messages. Equip-
absorption, spreading, or scattering. Absorption involves the
ment of this type is often connected to other output devices,
conversion of acoustic energy into heat. Spreading loss is
such as telemetry equipment.
signal weakening as it spreads outward geometrically from its
source. Scattering losses are the dominant attenuation factors
7.2 Acoustic Transducers—Transducers may be active (con-
in streamflow applications. These losses are caused by air
taining Transmitter and first stage of amplification) or passive
bubbles,sediment,orotherparticleoraquaticmaterialspresent
(no amplification) depending on path length and presence of
in the water column. Table 1 presents tolerable sediment
electromagnetic interference EMI. Acoustic transducers must
concentrations.
be rigidly mounted in the channel wall or bottom. Means must
be provided for precise determination of acoustic path
6.4 Mechanical Obstructions—Marine growth or water-
borne debris may build up on transducers or weed growth, elevation, length, and angle to flow. The transducers and
boats, or other channel obstructions may degrade propagation cabling must be sufficiently rugged to withstand the handling
and timing of acoustic signals. and operational environment into which they will be placed.
D5389 − 93 (2013)
FIG. 4 Signal Bending Caused by Different Density Gradients
NOTE 1—Transducer directivity or beam width determined at the 30-dB level of the transmitted signal pattern. The signal is propagated beyond the
beam width but at a weak level. In the shaded area the detection is so great that signals cannot be received directly for any transducer beam width.
FIG. 5 Beam Deflection From Linear Temperature Gradients for Different Path Lengths
Additionally, provision shall be made for simple replacement 7.3 StageMeasuringDevice—Thereareseveralmethodsfor
of transducer or cable, or both, in the event of failure or measuring stage and inputting this information to the system.
damage. The actual method used depends on the particular installation
D5389 − 93 (2013)
NOTE 1—Transducer directivity or beam width determined at the 30-dB level of the transmitted signal pattern. The signal is propagated beyond the
beam width but at a weak level. In the shaded area the deflection is so great that signals cannot be received directly for any transducer beam width.
FIG. 6 Beam Deflection From Linear Conductivity Gradients for Different Path Lengths
TABLE 1 Estimates of Tolerable Sediment Concentrations for
AVM System Operation Based on Attenuation From Spherical
Spreading and From Scattering From the Most Critical Particle
Size
NOTE 1—Sediment concentrations in milligrams per litre.
Selected Path distance (m)
Transducer
Frequency
5 20 50 100 200 300 500 1000
(kHz)
1000 6300 1200 400 — — — — —
500 — 3500 1200 530 230 — — —
300 — 7900 2800 1300 560 350 — —
200 — 11 000 4000 1800 830 520 280 —
100 — — 10 000 4600 2200 1400 770 350
30 — — — — 8800 5700 3200 1500
requirements. Some examples include visual measurement/
manual keyboard entry, float/counterweight or bubbler systems
with servo manometers connected to analog conversion equip-
ment or digital encoders, upward looking acoustic transducers,
or other electronic pressure sensors.
7.4 Power Supply—Several venders currently offer battery-
powdered AVMs as well as systems operating on 110 V ac
standard commercial electric power. Availability of electricity
should be considered during site evaluation prior to equipment
selection.
7.5 Cabling—All interconnected cabling to and from trans-
ducers shall be armored or protected, or both, to minimize
FIG. 7 Responder System
damage during installation and operation.
7.6 Responders—A responder is an electronic device that
receives an acoustic signal and then retransmits it back across
8. Sampling
the stream after a predetermined
...
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