1、Designation: D 4409 95 (Reapproved 2008)Standard Test Method forVelocity Measurements of Water in Open Channels withRotating Element Current Meters1This standard is issued under the fixed designation D 4409; the number immediately following the designation indicates the year oforiginal adoption or,
2、in the case of revision, 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 describes the design and use ofcup-type or vane-type vertical ax
3、is current meters andpropeller-type horizontal axis current meters for measuringwater velocities in open channels.1.2 This test method is intended primarily for those meterscustomarily used in open-channel hydraulic (as distinguishedfrom oceanographic) applications with an operator in atten-dance.1.
4、3 This test method is intended primarily for current metersthat measure one component or filament of flow.1.4 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not
5、 considered standard.1.5 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 t
6、o use.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 Water by Velocity-Area Method2.2 ISO Standards:3ISO 2
7、537 Liquid Flow Measurement in Open ChannelsRotating Element Current MetersISO 3454 Liquid Flow Measurement in Open ChannelsDirect Depth Sounding and Suspension EquipmentISO 3455 Liquid Flow Measurement in Open ChannelsCalibration of Rotating-Element Current Meters inStraight Open Tanks3. Terminolog
8、y3.1 Definitions: For definitions of other terms used in thistest method, refer to Terminology D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 current meteran instrument used to measure thespeed or velocity of flowing water at a point.3.2.2 Price-type current metersgeneric name for s
9、pecificvertical axis meters with a rotating element consisting of sixconical cups and constructed as described in Refs (1-3).43.2.3 spin test a test performed to check the bearings of acurrent meter. This test is used primarily with vertical axiscurrent meters.3.2.4 turbulenceirregular condition of
10、flow in which thevelocity exhibits a random variation with time and spacecoordinates so that statistically distinct average values can bediscerned.4. Summary of Test Method4.1 The angular velocity of the rotating element is afunction of water speed at the point of immersion. This angularvelocity is
11、determined from the meter output and its functionalrelation to the water speed is determined by calibration.5. Significance and Use5.1 This test method describes the design and use of varioustypes of current meters. These current meters are commonlyused to measure the velocity at a point in an open
12、channel crosssection as part of a velocity-area traverse to determine the1This 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 Oct. 1, 2008. Publis
13、hed November 2008. Originallyapproved in 1984. Last previous edition approved in 2003 as D 4409 95 (2003).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 standa
14、rds 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.4The boldface numbers refer to the list of references at the end of this testmethod.1Copyright ASTM International, 100 Barr Harb
15、or Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.flowrate of water. To this end it should be used in conjunctionwith Test Method D 3858.6. Interferences6.1 As with any intrusive flow measuring device, rotatingelement current meters are subject to damage by debris,especially in
16、high velocity flows, and to fouling by floatingmaterials such as aquatic growths and sewage.6.2 Owing to bearing friction, each rotating element currentmeter has a limiting low velocity below which it does notfunction reliably. This velocity is different for each type ofmeter but, in general, % erro
17、rs tend to become large as thevelocities decrease below 0.1 to 0.2 ft/s (0.03 to 0.06 m/s).7. Apparatus7.1 Current Meters Rotating element current meters con-sist of a rotating element with shaft and bearings, a mechanismfor detecting and registering revolutions, and a frame whichsupports the forego
18、ing elements and provides for suspension ofthe meter and the insertion of stabilizing fins if needed. Currentmeters covered by this test method do not customarily incor-porate direction-measuring devices.7.1.1 Rotor ConfigurationHorizontal-axis meters havepropeller-type rotors comprised of two or mo
19、re blades. Inter-changeable elements of different pitch or diameter can be usedto cover a wider range of velocities. Vertical-axis meters havea rotating wheel made up of several cup-type or vane-typeelements. Rotors employing six conical cups (for example,Price-type meters) are frequently used but o
20、ther configurationsare permissible provided the following requirements are met:7.1.1.1 The relation between velocity and rotation rate mustbe stable, that is, there should be no significant uncertainties inthe meters rating curve due to unstable flow separations at thecups or similar hydrodynamic ca
21、uses.7.1.1.2 If fractions of revolutions are to be registered, theangular movement of the rotor must be the same during eachmeasured fraction.7.1.2 Bearings:7.1.2.1 Bearing design shall permit the meter to be used insediment-laden water, without affecting the accuracy of themeter.7.1.2.2 If a partic
22、ular oil is required for bearing lubrication,the supplier shall furnish it with the instrument. Information forobtaining replacement oil shall also be furnished.7.1.2.3 At the highest velocity claimed for the meter,properly maintained bearings shall function without adverselyaffecting meter performa
23、nce for a period of time customarilyassociated with normal use or for the period of time betweenrecommended recalibrations. If bearing replacement is neededto meet this requirement, such replacement shall be possible inthe field.7.1.2.4 At the lowest velocity claimed for the meter, prop-erly maintai
24、ned bearings shall function consistently and notcontribute to undue deviations in meter response.7.1.2.5 No breaking-in period for the bearings shall berequired after meter delivery.7.1.3 Registering RevolutionsThe current meter shall beequipped with a mechanism which detects and signals eithersingl
25、e revolutions of the rotor or known fractions or multiplesthereof. This detection can be by mechanical-electric contact,by magnetic, optical, or other methods, and shall produce asignal which is audible, visible, or recordable by other means.7.1.3.1 Amechanical-electric contact device shall not add
26、inany significant manner to the internal friction at the lowestvelocity claimed for the meter.7.1.3.2 The contact device must always actuate the signal atprecisely the same position in each revolution (fraction ormultiple).7.1.3.3 If the revolution count is to be made manually by theoperator, the au
27、dible or visual signals (as distinguished fromrecorded signals) shall not occur at a frequency greater than 3,and preferably 2.75, cps.7.1.3.4 A timing device is a necessary adjunct to the meterso that the revolution rate can be determined from therevolution count. In the simplest configuration this
28、 system canconsist of a manual stopwatch for timing audible or visualsignals.7.1.3.5 If the current meter system has a direct readout invelocity units, the user must be furnished an accuracy state-ment which includes the readout. Also, the user must beprovided with a procedure to check for system ma
29、lfunctions.7.1.4 FrameThe frame houses the current-meter elementsand provides for suspending the meter in the flow. Dependingupon the intended use of the meter, the frame can be designedfor suspension by rigid rod only, by cable-and-weight only, orit can provide for both types of suspension.7.1.4.1
30、The connection for rod mounting shall provide, inconjunction with the rod, rigidity and vibration-free perfor-mance at the highest velocity claimed for the meter, and shallprovide for adjustable meter position along the rod. Fixed rodposition is necessary for some applications, such as formeasuring
31、through ice cover. Rods must be provided withsuitable fixtures to accommodate fins as specified in 7.1.4.3.7.1.4.2 The connection for cable suspension shall permit themeter to swivel in a vertical plane so that it can seek andmaintain a horizontal orientation.7.1.4.3 FinsMeters to be suspended by ca
32、ble must pro-vide for stabilizing fins to be inserted into the frame. Provisionshall be made for balancing the meter-fin unit about its pivotwhile immersed in water, so that it can operate in a levelposition at all velocities claimed for the meter.7.1.5 Other General Requirements:7.1.5.1 The meter d
33、esign and construction shall be suffi-ciently sturdy for normal field use and the materials shall beusable in normally encountered fresh and saline waters withoutundue corrosion or wear.7.1.5.2 The meter shall offer low resistance to the flow andmust be able to maintain a stable position with respec
34、t to theflow.7.1.5.3 Meter parts shall be interchangeable among othermeters of the same model and manufacturer. The manufacturershall state which parts can be replaced without requiringrecalibration.7.1.5.4 Design features which permit minor repairs or partsreplacement by the user in the field are e
35、ncouraged. Anyspecial purpose tools needed for such repairs or replacementshall be furnished with the meter.D 4409 95 (2008)27.1.5.5 For high-inertia, vertical-axis meters, spin test dura-tions shall be recommended for effective use of the meters attheir lowest claimed velocity. See Refs (1-3) for P
36、rice-typemeters. Users shall be provided with alternative procedures forqualitative indications of internal friction in meters that are notamenable to spin testing.7.1.5.6 The user shall be provided with the means (detaileddimensions, templates, or forms) to ascertain gradual changesin rotor configu
37、ration, where appropriate. See also 10.2.7.1.5.7 Information on depth (pressure) limitation on metersubmergence and on temperature effects, if any, on meterperformance shall be furnished by the manufacturer.7.2 Suspension EquipmentDescription and requirementsfor suspension equipment are available in
38、 Refs (2, 3) andISO 3454. This test method includes only those elementswhich directly affect the meter performance.7.2.1 RodsThe rod for which the meter rating is valid, ifnot furnished with the meter, shall be precisely specified withregard to dimensions and configuration.7.2.2 Cable and Weight:7.2
39、.2.1 The cable suspension system for which the meterrating is valid, if not furnished with the meter, shall beprecisely specified with regard to dimensions and configura-tion, including dimensions of the sounding weight, its distancefrom the meter, connecting strap details, cable dimensions, etc.7.2
40、.2.2 The weight shall offer minimal resistance to the flowand should be able to maintain a stable and level position. Itshall be so shaped that the current meter is not subject to shededdies or other instabilities; and it shall be heavy enough toavoid excessive downstream deflection of the cable, pa
41、rticu-larly in deep and swift currents. If some deflection is unavoid-able, tables for air-line and wet-line corrections are available.7.2.2.3 The suspension cable preferably shall be reverse-laysounding cable to minimize torque on the immersed meter andweight. However, even this type of cable may c
42、ause or allowmeter yaw and subsequent meter registration errors for Price-type current meters in velocities below 1.00 ft/s (0.305 m/s).7.2.2.4 For protection of the meter it is preferable that theweight be mounted below the meter.8. Sampling8.1 Sampling, as defined in Terminology D 1129,isnotapplic
43、able in this test method. Sampling to obtain a reliablemeasurement of average velocity in a cross section is coveredin Test Method D 3858.9. Calibration9.1 General Calibration Requirements:9.1.1 The range of calibration velocities ideally includes theminimum and maximum velocities claimed for the me
44、ter.Practically, most calibration (rating) facilities cannot achievethis range of velocities and are limited to 0.10 ft/s (0.03 m/s) to12 ft/s (3.66 m/s). Calibrations at those minimum and maxi-mum possible velocities, along with enough intervening points,typically describe a rotation rate-velocity
45、relation that bracketsvalues commonly found in flowing streams. For the rare caseswhere current meters are used to measure faster velocities,linear upward extension can be made with minimal accuracydegradation. Downward extrapolation may result in largererrors, due to variable stall rates of individ
46、ual meters. Providethe rating to the user in the form of an equation, table, or graph.Furnish an estimate of the accuracy.9.1.2 Make individual calibrations, using the same suspen-sion with which the meter is to be used in the field. See 7.2.1and 7.2.2.1.9.1.3 If a propeller meter is intended to res
47、pond only to thevelocity component along the meter axis, provide calibrationinformation on this capability for the usable range of approachangles claimed for the meter.9.1.4 Recalibrate meters when their performance is suspect.Some organizations establish routine recalibration policies,such as annua
48、lly or based on hours of use. In the case ofinstruments made to stringent specifications, repairs and partsreplacement may be made without recalibration requirements.9.2 Towing Tank CalibrationCurrent meters usually arecalibrated (rated) in a towing tank. Guidelines for this type ofcalibration are g
49、iven in ISO 3455.9.3 Water Tunnel CalibrationCurrent meters also can becalibrated in flowing waterin a facility that provides auniform velocity distribution in a test area large enough toavoid blockage effects, provided that the accuracy of thesystem is demonstrably high. If this procedure is used, providesome indication of the scale and intensity of the turbulence.9.4 Group Ratings A rating equation provided by amanufacturer for a specific type of current meter is sometimesused in place of an individual calibration equation.9.4.1 Base group ratings can be made,
