1、Designation: D 5389 93 (Reapproved 2007)Standard Test Method forOpen-Channel Flow Measurement by Acoustic VelocityMeter Systems1This standard is issued under the fixed designation D 5389; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of flow rate ofwater in open channels, streams, and closed c
3、onduits with afree water surface.1.2 The test method covers the use of acoustic transmissionsto measure the average water velocity along a line between oneor more opposing sets of transducersby the time differenceor frequency difference techniques.1.3 The values stated in SI units are to be regarded
4、 as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use
5、. Specific precau-tionary statements are given in Section 6.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD 3858 Test Method for Open-Channel Flow Measurementof
6、 Water by Velocity-Area Method2.2 ISO Standard:3ISO 6416 Liquid Flow Measurements in Open ChannelsMeasurement of Discharge by the Ultrasonic (Acoustic)Method3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129.3.2 Definitions of Terms Specific to
7、 This Standard:3.2.1 acoustic paththe straight line between the centers oftwo acoustic transducers.3.2.2 acoustic path lengththe face-to-face distance be-tween transducers on an acoustic path.3.2.3 acoustic transducera device that is used to generateacoustic signals when driven by an electric voltag
8、e, andconversely, a device that is used to generate an electric voltagewhen excited by an acoustic signal.3.2.4 acoustic travel timethe time required for an acousticsignal to propagate along an acoustic path, either upstream ordownstream.3.2.5 dischargethe rate of flow expressed in units ofvolume of
9、 water per unit of time. The discharge includes anysediment or other materials that may be dissolved or mixedwith it.3.2.6 line velocitythe downstream component of watervelocity averaged over an acoustic path.3.2.7 measurement planethe plane formed by two or moreparallel acoustic paths of different
10、elevations.3.2.8 path velocitythe water velocity averaged over theacoustic path.3.2.9 stagethe height of a water surface above an estab-lished (or arbitrary) datum plane; also gage height.3.2.10 velocity samplingmeans of obtaining line veloci-ties in a measurement plane that are suitable for determi
11、ningflow rate by a velocity-area integration.4. Summary of Test Method4.1 Acoustic velocity meter (AVM) systems, also known asultrasonic velocity meter (UVM) systems, operate on theprinciple that the point-to-point upstream traveltime of anacoustic pulse is longer than the downstream traveltime andt
12、hat this difference in travel time can be accurately measuredby electronic devices.4.2 Most commercial AVM systems that measure stream-flow use the time-of-travel method to determine velocity alongan acoustic path set diagonal to the flow. This test method4describes the general formula for determini
13、ng line velocitydefined as (Fig. 1 and Fig. 2):1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.07 on Sediments, Geomor-phology, and Open-Channel Flow.Current edition approved June 15, 2007. Published July 2007. Originally
14、approved in 1993. Last previous edition approved in 2002 as D 5389 93 (2002).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page ont
15、he ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Laenen, A., and Smith, W., “Acoustic Systems for the Measurement ofStreamflow,” U.S. Geological Survey Water Supply Paper 2213, 1983.1Copyright ASTM Interna
16、tional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.VL5B2 cos uF1tCA21tACG(1)where:VL= line velocity, or the average water velocity at thedepth of the acoustic path,u = angle of departure between streamflow and theacoustic path,tAC = traveltime from A to C (up
17、stream),tCA = traveltime from C to A (downstream), andB = length of the acoustic path from A to C.4.3 The discharge measurement or volume flow rate deter-mination made with an AVM relies on a calibrated or theoreti-cal relation between the line velocity as measured by the AVMand mean velocity in the
18、 flow segment being measured. Takingmore line velocity measurements across the channel at differentelevations in the acoustic plane and performing a numericalintegration or weighted summation of the measured velocitiesand areas of flow can be used to better define the volume flowrate. The spacing be
19、tween acoustic paths, the spacing betweenthe top path and the liquid surface, and the spacing between thelowest path and the bottom are determined on the basis ofstream cross-section geometry or estimates of the vertical-velocity distribution and by the required measurement accu-racy. In addition to
20、 several line velocity measurements, it isnecessary to provide water level (stage) and cross-sectionalarea information for calculation of the volume flow rate (seeFig. 3).5. Significance and Use5.1 This test method is used where high accuracy of velocityor continuous discharge measurement over a lon
21、g period oftime is required and other test methods of measurement are notfeasible due to low velocities in the channel, variable stage-discharge relations, complex stage-discharge relations, or thepresence of marine traffic. It has the additional advantages ofrequiring no moving parts, introducing n
22、o head loss, andproviding virtually instantaneous readings (1 to 100 readingsper second).5.2 The test method may require a relatively large amountof site work and survey effort and is therefore most suitable forpermanent or semi-permanent installations.6. Interferences6.1 RefractionThe path taken by
23、 an acoustic signal willbe bent if the medium through which it is propagating variessignificantly in temperature or density. This condition, knownas ray bending, is most severe in slow moving streams withpoor vertical mixing or tidal (estuaries) with variable salinity.In extreme conditions the signa
24、l may be lost. Examples of raybending are shown in Fig. 4. Beam deflection for varioustemperatures and specific conductivities are shown in Fig. 5and Fig. 6.6.2 ReflectionAcoustic signals may be reflected by thewater surface or streambed. Reflected signals can interferewith, or cancel, signals propa
25、gated along the measurementplane. When thermal or density gradients are present, theplacement of transducers with respect to boundaries is mostcritical. This condition is most critical in shallow streams. Ageneral rule of thumb to prevent reflection interference is tomaintain a minimum stream depth
26、to path length ratio of 1 to100 for path lengths greater than 50 m.6.3 AttenuationAcoustic signals are attenuated by absorp-tion, spreading, or scattering. Absorption involves the conver-sion of acoustic energy into heat. Spreading loss is signalweakening as it spreads outward geometrically from its
27、 source.Scattering losses are the dominant attenuation factors inFIG. 1 Velocity Component Used in Developing Travel-TimeEquationsFIG. 2 Voltage Representation of Transmit and Receive Pulses atUpstream and Downstream TransducersD 5389 93 (2007)2streamflow applications. These losses are caused by air
28、bubbles, sediment, or other particle or aquatic materials presentin the water column. Table 1 presents tolerable sedimentconcentrations.6.4 Mechanical ObstructionsMarine growth or water-borne debris may build up on transducers or weed growth,boats, or other channel obstructions may degrade propagati
29、onand timing of acoustic signals.6.5 Electrical ObstructionsNearby radio transmitters,electrical machinery, faulty electrical insulators, or othersources of electromagnetic interference (EMI) can cause fail-ure or sporadic operation of AVMs.7. Apparatus7.1 The instrumentation used to measure open-ch
30、annel flowby acoustic means consists of a complex and integratedelectronic system known as an acoustic velocity meter (AVM).Three or four companies presently market AVM systemssuitable for measurement of open-channel flow. System con-figurations range from simple single-path to complex-multi-path sy
31、stems. Internal computation, transmission, and record-ing systems vary depending on local requirements. Most AVMsystems must include the capability to compute an acoustic linevelocity from one or more path velocities together with stage(water level) and other information related to channel geometryn
32、ecessary to calculate a flow rate per unit of time, usually cubicmillimetres per second (m3/s) or cubic feet per second (ft3/s).7.1.1 Electronics EquipmentThere are several methodsthat are currently being used to implement the electro-acousticfunctions and mathematical manipulations required to obta
33、in aline-velocity measurement. Whatever method is used mustinclude internal automatic means for continuously checking theaccuracy. In addition, provision must be included to preventerroneous readings during acoustic interruptions caused byriver traffic, aquatic life, or gradual degradation of compon
34、ents.7.1.2 Flow Readout EquipmentThis equipment is func-tionally separated into three subsystems. These subsystemsmay or may not be physically separable but are discussedseparately for clarity.7.1.3 Acoustic TranceiverThis system generates, re-ceives, and measures the traveltimes of acoustic signals
35、. Theacoustic signals travel between the various pairs of acoustictransducers and form the acoustic paths from which linevelocities are determined.7.1.4 ProcessorThe processor performs the mathematicaloperations required to calculate acoustic line velocities, makesdecisions about which acoustic path
36、s should be used on thebasis of stage, performs error checking, calculates total volumeflow rate, and totalizes volume flow.7.1.5 Display/RecorderGenerally, the output of the sys-tem is a display or a recorder, or both. The recorder normallyincludes calendar data, time, flow rate, stage, and any oth
37、erinformation deemed desirable, such as error messages. Equip-ment of this type is often connected to other output devices,such as telemetry equipment.7.2 Acoustic TransducersTransducers may be active (con-taining Transmitter and first stage of amplification) or passive(no amplification) depending o
38、n path length and presence ofelectromagnetic interference EMI. Acoustic transducers mustbe rigidly mounted in the channel wall or bottom. Means mustbe provided for precise determination of acoustic path eleva-tion, length, and angle to flow. The transducers and cablingmust be sufficiently rugged to
39、withstand the handling andoperational environment into which they will be placed.Additionally, provision shall be made for simple replacementof transducer or cable, or both, in the event of failure ordamage.7.3 Stage Measuring DeviceThere are several methodsfor measuring stage and inputting this inf
40、ormation to thesystem. The actual method used depends on the particularinstallation requirements. Some examples include visualmeasurement/manual keyboard entry, float/counterweight orbubbler systems with servo manometers connected to analogconversion equipment or digital encoders, upward lookingacou
41、stic transducers, or other electronic pressure sensors.7.4 Power SupplySeveral venders currently offer battery-powdered AVMs as well as systems operating on 110 V acstandard commercial electric power. Availability of electricityshould be considered during site evaluation prior to equipmentselection.
42、7.5 CablingAll interconnected cabling to and from trans-ducers shall be armored or protected, or both, to minimizedamage during installation and operation.7.6 RespondersA responder is an electronic device thatreceives an acoustic signal and then retransmits it back acrossFIG. 3 Example of Acoustic V
43、elocity/Flow Measuring SystemD 5389 93 (2007)3the stream after a predetermined time interval. A responder isFIG. 4 Signal Bending Caused by Different Density Gradients4NOTE 1Transducer directivity or beam width determined at the 30-dB level of the transmitted signal pattern. The signal is propagated
44、 beyond thebeam 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 LengthsD 5389 93 (2007)4used where direct wire connection is impr
45、actical. A typicalresponder system is shown in Fig. 78. Sampling8.1 Sampling, as defined in Terminology D 1129,isnotapplicable to this test method.9. Preparation of Apparatus9.1 Site Selections:9.1.1 Channel GeometryThe gaged site should be in asection of channel that is straight for three to ten ch
46、annelwidths upstream and one to two channel widths downstream.The banks should be parallel and not subject to overflow. Thereshould be minimal change in cross-section area between theupstream and downstream transducer locations. Calibratingdischarge measurements must be made along the acoustic pathw
47、here large differences exist in cross-sectional area betweenthe upstream and downstream transducers. AVMs are notusually suitable for wide shallow channels, except by usingmultiple horizontal paths.9.1.2 Channel StabilityThe cross sections should not besubject to frequent shifting and the relationsh
48、ip between stageand cross-section area must be stable or frequently measured.Sites with unstable vertical velocity profiles should be avoided,NOTE 1Transducer directivity or beam width determined at the 30-dB level of the transmitted signal pattern. The signal is propagated beyond thebeam width but
49、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 LengthsTABLE 1 Estimates of Tolerable Sediment Concentrations forAVM System Operation Based on Attenuation From SphericalSpreading and From Scattering From the Most Critical ParticleSizeNOTE 1Sediment concentrations in milligrams per litre.SelectedTransducerFrequency(kHz)Path distance (m)5 20 50 100 200 300 500 10001000 6300 1200 400
