ASTM D5389-93(2002)
(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
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 problems, 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D 5389 – 93 (Reapproved 2002)
Standard Test Method for
Open-Channel Flow Measurement by Acoustic Velocity
Meter Systems
This standard is issued under the fixed designation D 5389; 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 acoustic path length—the face-to-face distance be-
tween transducers on an acoustic path.
1.1 This test method covers the measurement of flow rate of
3.2.3 acoustic transducer—a device that is used to generate
water in open channels, streams, and closed conduits with a
acoustic signals when driven by an electric voltage, and
free water surface.
conversely, a device that is used to generate an electric voltage
1.2 Thetestmethodcoverstheuseofacoustictransmissions
when excited by an acoustic signal.
tomeasuretheaveragewatervelocityalongalinebetweenone
3.2.4 acoustic travel time—thetimerequiredforanacoustic
or more opposing sets of transducers—by the time difference
signal to propagate along an acoustic path, either upstream or
or frequency difference techniques.
downstream.
1.3 The values stated in SI units are to be regarded as the
3.2.5 discharge—the rate of flow expressed in units of
standard.
volume of water per unit of time. The discharge includes any
1.4 This standard does not purport to address all of the
sediment or other materials that may be dissolved or mixed
safety concerns, if any, associated with its use. It is the
with it.
responsibility of the user of this standard to establish appro-
3.2.6 line velocity—the downstream component of water
priate safety and health practices and determine the applica-
velocity averaged over an acoustic path.
bility of regulatory limitations prior to use. Specific precau-
3.2.7 measurementplane—theplaneformedbytwoormore
tionary statements are given in Section 6.
parallel acoustic paths of different elevations.
2. Referenced Documents 3.2.8 path velocity—the water velocity averaged over the
acoustic path.
2.1 ASTM Standards:
3.2.9 stage—the height of a water surface above an estab-
D 1129 Terminology Relating to Water
lished (or arbitrary) datum plane; also gage height.
D 2777 Practice for Determination of Precision and Bias of
3.2.10 velocity sampling—means of obtaining line veloci-
Applicable Methods of Committee D19 on Water
ties in a measurement plane that are suitable for determining
D 3858 Test Method for Open-Channel Flow Measurement
flow rate by a velocity-area integration.
of Water by Velocity-Area Method
2.2 ISO Standard:
4. Summary of Test Method
ISO 6416 Liquid Flow Measurements in Open Channels—
4.1 Acoustic velocity meter (AVM) systems, also known as
Measurement of Discharge by the Ultrasonic (Acoustic)
3 ultrasonic velocity meter (UVM) systems, operate on the
Method
principle that the point-to-point upstream traveltime of an
3. Terminology acoustic pulse is longer than the downstream traveltime and
that this difference in travel time can be accurately measured
3.1 Definitions—For definitions of terms used in this test
by electronic devices.
method, refer to Terminology D 1129.
4.2 Most commercial AVM systems that measure stream-
3.2 Definitions of Terms Specific to This Standard:
flow use the time-of-travel method to determine velocity along
3.2.1 acoustic path—the straight line between the centers of
an acoustic path set diagonal to the flow. This test method
two acoustic transducers.
describes the general formula for determining line velocity
defined as (Fig. 1 and Fig. 2):
This test method is under the jurisdiction of ASTM Committee D19 on Water
1 1
B
and is the direct responsibility of Subcommittee D19.07 on Sediments, Geomor-
t t
F G
V 5 2 (1)
CA AC
L
2 cos u
phology, and Open-Channel Flow.
Current edition approved April 15, 1993. Published June 1993.
Annual Book of ASTM Standards, Vol 11.01.
3 4
Available from the American National Standards Institute, 11 W. 42nd Street, Laenen, A., and Smith, W., “Acoustic Systems for the Measurement of
13th Floor, New York, NY 10036. Streamflow,” U.S. Geological Survey Water Supply Paper 2213, 1983.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5389 – 93 (2002)
FIG. 1 Velocity Component Used in Developing Travel-Time
Equations
FIG. 3 Example of Acoustic Velocity/Flow Measuring System
4.3 The discharge measurement or volume flow rate deter-
mination made with anAVM relies on a calibrated or theoreti-
cal relation between the line velocity as measured by theAVM
and mean velocity in the flow segment being measured.Taking
morelinevelocitymeasurementsacrossthechannelatdifferent
elevations in the acoustic plane and performing a numerical
integration or weighted summation of the measured velocities
and areas of flow can be used to better define the volume flow
rate. The spacing between acoustic paths, the spacing between
thetoppathandtheliquidsurface,andthespacingbetweenthe
lowest path and the bottom are determined on the basis of
stream cross-section geometry or estimates of the vertical-
velocity distribution and by the required measurement accu-
racy. In addition to several line velocity measurements, it is
necessary to provide water level (stage) and cross-sectional
area information for calculation of the volume flow rate (see
Fig. 3).
FIG. 2 Voltage Representation of Transmit and Receive Pulses at
Upstream and Downstream Transducers
5. Significance and Use
5.1 Thistestmethodisusedwherehighaccuracyofvelocity
where:
or continuous discharge measurement over a long period of
V = line velocity, or the average water velocity at the
L time is required and other test methods of measurement are not
depth of the acoustic path,
feasible due to low velocities in the channel, variable stage-
u = angle of departure between streamflow and the
discharge relations, complex stage-discharge relations, or the
acoustic path,
presence of marine traffic. It has the additional advantages of
t
AC = traveltime from A to C (upstream),
requiring no moving parts, introducing no head loss, and
t
CA = traveltime from C to A (downstream), and
providing virtually instantaneous readings (1 to 100 readings
B = length of the acoustic path from A to C.
per second).
D 5389 – 93 (2002)
FIG. 4 Signal Bending Caused by Different Density Gradients
5.2 The test method may require a relatively large amount Scattering losses are the dominant attenuation factors in
of site work and survey effort and is therefore most suitable for streamflow applications. These losses are caused by air
permanent or semi-permanent installations.
bubbles,sediment,orotherparticleoraquaticmaterialspresent
in the water column. Table 1 presents tolerable sediment
6. Interferences
concentrations.
6.1 Refraction—The path taken by an acoustic signal will
6.4 Mechanical Obstructions—Marine growth or water-
be bent if the medium through which it is propagating varies
borne debris may build up on transducers or weed growth,
significantly in temperature or density. This condition, known
boats, or other channel obstructions may degrade propagation
as ray bending, is most severe in slow moving streams with
and timing of acoustic signals.
poor vertical mixing or tidal (estuaries) with variable salinity.
6.5 Electrical Obstructions—Nearby radio transmitters,
In extreme conditions the signal may be lost. Examples of ray
electrical machinery, faulty electrical insulators, or other
bending are shown in Fig. 4. Beam deflection for various
sources of electromagnetic interference (EMI) can cause fail-
temperatures and specific conductivities are shown in Fig. 5
ure or sporadic operation of AVMs.
and Fig. 6.
6.2 Reflection—Acoustic signals may be reflected by the
7. Apparatus
water surface or streambed. Reflected signals can interfere
7.1 The instrumentation used to measure open-channel flow
with, or cancel, signals propagated along the measurement
by acoustic means consists of a complex and integrated
plane. When thermal or density gradients are present, the
placement of transducers with respect to boundaries is most electronic system known as an acoustic velocity meter (AVM).
Three or four companies presently market AVM systems
critical. This condition is most critical in shallow streams. A
general rule of thumb to prevent reflection interference is to suitable for measurement of open-channel flow. System con-
figurations range from simple single-path to complex-multi-
maintain a minimum stream depth to path length ratio of 1 to
100 for path lengths greater than 50 m. path systems. Internal computation, transmission, and record-
ing systems vary depending on local requirements. MostAVM
6.3 Attenuation—Acousticsignalsareattenuatedbyabsorp-
tion, spreading, or scattering. Absorption involves the conver- systemsmustincludethecapabilitytocomputeanacousticline
sion of acoustic energy into heat. Spreading loss is signal velocity from one or more path velocities together with stage
weakening as it spreads outward geometrically from its source. (waterlevel)andotherinformationrelatedtochannelgeometry
D 5389 – 93 (2002)
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
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
necessarytocalculateaflowrateperunitoftime,usuallycubic 7.1.2 Flow Readout Equipment—This equipment is func-
3 3
millimetres per second (m /s) or cubic feet per second (ft /s). tionally separated into three subsystems. These subsystems
7.1.1 Electronics Equipment—There are several methods
may or may not be physically separable but are discussed
that are currently being used to implement the electro-acoustic
separately for clarity.
functions and mathematical manipulations required to obtain a
7.1.3 Acoustic Tranceiver—This system generates, re-
line-velocity measurement. Whatever method is used must
ceives, and measures the traveltimes of acoustic signals. The
includeinternalautomaticmeansforcontinuouslycheckingthe
acoustic signals travel between the various pairs of acoustic
accuracy. In addition, provision must be included to prevent
transducers and form the acoustic paths from which line
erroneous readings during acoustic interruptions caused by
velocities are determined.
rivertraffic,aquaticlife,orgradualdegradationofcomponents.
D 5389 – 93 (2002)
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
7.1.4 Processor—The processor performs the mathematical
operations required to calculate acoustic line velocities, makes
decisions about which acoustic paths should be used on the
basis of stage, performs error checking, calculates total volume
flow rate, and totalizes volume flow.
7.1.5 Display/Recorder—Generally, the output of the sys-
tem is a display or a recorder, or both. The recorder normally
includes calendar data, time, flow rate, stage, and any other
information deemed desirable, such as error messages. Equip-
ment of this type is often connected to other output devices,
such as telemetry equipment.
7.2 AcousticTransducers—Transducersmaybeactive(con-
taining Transmitter and first stage of amplification) or passive
(no amplification) depending on path length and presence of
FIG. 7 Responder System
electromagnetic interference EMI. Acoustic transducers must
be rigidly mounted in the channel wall or bottom. Means must
be provided for precise determination of acoustic path eleva-
8. Sampling
tion, length, and angle to flow. The transducers and cabling
8.1 Sampling, as defined in Terminology D 1129,isnot
must be sufficiently rugged to withstand the handling and
applicable to this test method.
operational environment into which they will be placed.
Additionally, provision shall be made for simple replacement
9. Preparation of Apparatus
of transducer or cable, or both, in the event of failure or
damage. 9.1 Site Selections:
7.3 Stage Measuring Device—There are several methods 9.1.1 Channel Geometry—The gaged site should be in a
for measuring stage and inputting this information to the section of channel that is straight for three to ten channel
system. The actual method used depends on the particular widths upstream and one to two channel widths downstream.
installation requirements. Some examples include visual Thebanksshouldbeparallelandnotsubjecttooverflow.There
should be minimal change in cross-section area between the
measurement/manual keyboard entry, float/counterweight or
bubbler systems with servo manometers connected to analog upstream and downstream transducer locations. Calibrating
discharge measurements must be made along the acoustic path
conversion equipment or digital encoders, upward looking
acoustic transducers, or other electronic pressure sensors. where large differences exist in cross-sectional area between
7.4 Power Supply—Several venders currently offer battery- the upstream and downstream transducers. AVMs are not
powdered AVMs as well as systems operating on 110 V ac usually suitable for wide shallow channels, except by using
standard commercial electric power. Availability of electricity multiple horizontal paths.
should be considered during site evaluation prior to equipment 9.1.2 Channel Stability—The cross sections should not be
selection. subject to frequent shifting and the relationship between stage
7.5 Cabling—All interconnected cabling to and from trans- and cross-section area must be stable or frequently measured.
ducer
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.