ASTM D5389-1993(2013) Standard Test Method for Open-Channel Flow Measurement by Acoustic Velocity Meter Systems《用传声速度计系统测试明渠流量的试验方法》.pdf

1、Designation: D5389 93 (Reapproved 2013)Standard Test Method forOpen-Channel Flow Measurement by Acoustic VelocityMeter Systems1This standard is issued under the fixed designation D5389; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio

2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 cond

3、uits 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 as

4、 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. S

5、pecific precau-tionary statements are given in Section 6.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3858 Test Method for Open-Channel Flow Measurementof Water

6、 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 D1129.3.2 Definitions of Terms Specific to This S

7、tandard: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 voltage, andc

8、onversely, 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 water

9、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 elevati

10、ons.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 determiningflo

11、w 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 andthat thi

12、s difference in travel time can be accurately measuredby electronic devices.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.07 on Sediments,Geomorphology, and Open-Channel Flow.Current edition approved Jan. 1, 2013. Publi

13、shed January 2013. Originallyapproved in 1993. Last previous edition approved in 2007 as D5389 93 (2007).DOI: 10.1520/D5389-93R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informat

14、ion, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Unit

15、ed States14.2 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 determining line velocitydefined as (Fig. 1 and Fig. 2):VL5B2cosF1tCA21tACG(1)wher

16、e:VL= line velocity, or the average water velocity at thedepth of the acoustic path, = angle of departure between streamflow and the acous-tic path,tAC = traveltime from A to C (upstream),tCA = traveltime from C to A (downstream), andB = length of the acoustic path from A to C.4.3 The discharge meas

17、urement 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 flow segment being measured. Takingmore line velocity measurements across the channel at differentelevations in the aco

18、ustic 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 between acoustic paths, the spacing betweenthe top path and the liquid surface, and the spacing between thelowest path and

19、 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 several line velocity measurements, it isnecessary to provide water level (stage) and cross-sectionalarea information f

20、or 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 long period oftime is required and other test methods of measurement are notfeasible due to low velocities in the channel,

21、variable stage-discharge relations, complex stage-discharge relations, or thepresence of marine traffic. It has the additional advantages ofrequiring no moving parts, introducing no head loss, andproviding virtually instantaneous readings (1 to 100 readingsper second).5.2 The test method may require

22、 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 an acoustic signal will bebent if the medium through which it is propagating variessignificantly in temperature or dens

23、ity. 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 signal may be lost. Examples of raybending are shown in Fig. 4. Beam deflection for varioustemperatures and specific conducti

24、vities are shown in Fig. 5and Fig. 6.4Laenen, A., and Smith, W., “Acoustic Systems for the Measurement ofStreamflow,” U.S. Geological Survey Water Supply Paper 2213, 1983.FIG. 1 Velocity Component Used in Developing Travel-TimeEquationsFIG. 2 Voltage Representation of Transmit and Receive Pulses atU

25、pstream and Downstream TransducersD5389 93 (2013)26.2 ReflectionAcoustic signals may be reflected by thewater surface or streambed. Reflected signals can interferewith, or cancel, signals propagated along the measurementplane. When thermal or density gradients are present, theplacement of transducer

26、s 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 to path length ratio of 1 to100 for path lengths greater than 50 m.6.3 AttenuationAcoustic signals are atte

27、nuated byabsorption, spreading, or scattering. Absorption involves theconversion of acoustic energy into heat. Spreading loss issignal weakening as it spreads outward geometrically from itssource. Scattering losses are the dominant attenuation factorsin streamflow applications. These losses are caus

28、ed by airbubbles, 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

29、propagationand 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 measur

30、e open-channel 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-mult

31、i-path systems. 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

32、geometrynecessary 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 require

33、d to obtain 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

34、of components.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, receives,and measures the traveltimes of acoustic

35、signals. The acousticsignals travel between the various pairs of acoustic transducersand form the acoustic paths from which line velocities aredetermined.7.1.4 ProcessorThe processor performs the mathematicaloperations required to calculate acoustic line velocities, makesdecisions about which acoust

36、ic paths 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

37、any otherinformation 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) depe

38、nding on 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 pathelevation, length, and angle to flow. The transducers andcabling must be sufficiently rugge

39、d to withstand the handlingand operational 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 methods formeasuring stage and inputting thi

40、s information to the system.The actual method used depends on the particular installationFIG. 3 Example of Acoustic Velocity/Flow Measuring SystemD5389 93 (2013)3requirements. Some examples include visual measurement/manual keyboard entry, float/counterweight or bubbler systemsFIG. 4 Signal Bending

41、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 beyond thebeam width but at a weak level. In the shaded area the detection is so great that signals cannot be received directly f

42、or any transducer beam width.FIG. 5 Beam Deflection From Linear Temperature Gradients for Different Path LengthsD5389 93 (2013)4with servo manometers connected to analog conversion equip-ment or digital encoders, upward looking acoustic transducers,or other electronic pressure sensors.7.4 Power Supp

43、lySeveral 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.7.5 CablingAll interconnected cabling to and from trans-ducers shall

44、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 acrossthe stream after a predetermined time interval. A responder isused where direct wire connection i

45、s impractical. A typicalresponder system is shown in Fig. 78. Sampling8.1 Sampling, as defined in Terminology D1129,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 t

46、en channelNOTE 1Transducer directivity or beam width determined at the 30-dB level of the transmitted signal pattern. The signal is propagated beyond thebeam 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 widt

47、h.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 mi

48、lligrams per litre.SelectedTransducerFrequency(kHz)Path distance (m)5 20 50 100 200 300 500 10001000 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 35030 8800 5700 3200 1500FIG. 7 Responder SystemD5389 93 (2013)5widths up

49、stream 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 pathwhere 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