1、Designation: D1941 91 (Reapproved 2013)Standard Test Method forOpen Channel Flow Measurement of Water with the ParshallFlume1This standard is issued under the fixed designation D1941; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 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 measurement of the volumetricflowrate of water and wastewater in open channels wi
3、th theParshall flume.1.1.1 Information related to this test method can be found inISO 1438 and ISO 4359.1.2 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
4、health practices and determine the applica-bility of regulatory limitations prior to use.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-
5、Channel Flow Measurementof Water by Velocity-Area Method2.2 ISO Standards:3ISO 555 Liquid Flow Measurements in Open ChannelsDilution Methods for Measurement of Steady FlowConstant Rate Injection MethodISO 1438 Liquid Flow Measurement in Open ChannelsUsing Thin-Plate Weirs and Venturi FlumesISO 4359
6、Liquid Flow Measurement in Open ChannelsRectangular Trapezoidal and U-shaped Flumes3. Terminology3.1 Definitions: For definitions of terms used in this testmethod, refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 free flowa condition where the flowrate is governedb
7、y the state of flow at the crest overfall and hence can bedetermined from a single upstream depth measurement.3.2.2 headthe height of a liquid above a specified point;that is, the flume crest.3.2.3 hydraulic jumpan abrupt transition from supercriti-cal to subcritical flow, accompanied by considerabl
8、e turbulenceor gravity waves, or both.3.2.4 normal depththe uniform depth of flow for a givenflowrate in a long open channel of specific shape, roughness,and slope.3.2.5 primary instrumentthe device (in this case, theflume) that creates a hydrodynamic condition that can besensed by the secondary ins
9、trument.3.2.6 scow floatan in-stream flat for depth sensing usuallymounted on a hinged cantilever.3.2.7 secondary instrumentin this case, a device whichmeasures the depth of flow at an appropriate location in theflume. The secondary instrument may also convert the mea-sured depth to an indicated flo
10、w rate.3.2.8 stilling wella small reservoir connected through aconstricted passage to the main channel, that is, the flume, sothat a depth measurement can be made under quiescentconditions.3.2.9 subcritical flowopen channel flow at a velocity lessthan the velocity of gravity waves in the same depth
11、of water.Subcritical flow is affected by downstream conditions, sincedisturbances are able to travel upstream.3.2.10 submerged flowa condition where the water stagedownstream of the flume is sufficiently high to affect the flowover the flume crest and hence the free-flow depth-dischargerelation no l
12、onger applies and discharge depends on two headmeasurements.3.2.11 supercritical flowopen channel flow at a velocitygreater than that of gravity waves in the same depth, sodisturbances cannot travel upstream, and downstream condi-tions do not affect the flow.3.2.12 throatthe constriction in a flume.
13、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. Published January 2013. Originallyapproved in 1962. Last previous edition approve
14、d in 2007 as D1941 91 (2007).DOI: 10.1520/D1941-91R13.2For 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 onthe ASTM website.3Availa
15、ble 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. United States14. Summary of Test Method4.1 Parshall flumes are measuring flumes
16、of specified ge-ometries for which empirical relations of the formQ 5 CHan(1)have been established so that the flowrate, Q, can bedetermined from a single depth measurement, Ha, in free flow.If the flow is submerged, an addition downstream depth, Hb,must be measured and suitable adjustments made.5.
17、Significance and Use5.1 Flume designs are available for throat sizes of 1 in. (2.54cm) to 50 ft (15.2 m) which cover maximum flows of 0.2 to3000 ft3/s (0.0057 to 85 m3/s) (1) and (2)4. They can thereforebe applied to a wide range of flows, with head losses that aremoderate.5.2 The flume is self-clea
18、nsing for moderate solids transportand therefore is suited for wastewater and flows with sediment.6. Interferences6.1 The flume is applicable only to open channel flow and isinoperative under full-pipe flow conditions.6.2 Although the flume has substantial self-cleansingcapacity, it can be clogged b
19、y debris or affected by accumula-tion of aquatic growth and cleaning or debris removal may berequired.7. Apparatus7.1 AParshall flume measuring system consists of the flumeitself (primary) and a depth-measuring device (secondary). Thesecondary device can range from a simple scale for manualreadings
20、to an instrument which continuously senses the depth,converts it to flowrate, and provides a readout or record ofinstantaneous flowrate or totalized flow, or both.7.2 The Flume:7.2.1 Parshall flumes are characterized by throat width;dimensions and flowrates for each size are given in Fig. 1 andTable
21、 1, respectively. The dimensions must be maintainedwithin 2 %, because the flume is an empirical device andcorrections for non-standard geometry are only estimates. Theinside surface of the flume should be at least as smooth as agood quality concrete finish.7.2.2 The measurement location for depth H
22、ais shown inFig. 1. In submerged flow a second depth, Hb, must bemeasured in the throat as indicated. However, in the 1, 2, and3-in. (2.54, 5.08, and 7.62-cm) flumes, this measurement ismade at Hcinstead, because disturbances have been observedat the Hblocation in these sizes (1) and (2). See Fig. 2
23、 for therelation between Hband Hc.7.3 Stilling Well and Connector :7.3.1 Stilling wells are recommended for accurate depthmeasurements; they are required when wire- or tape-supportedcylindrical floats are used or when the liquid surface isfluctuating.7.3.2 The lateral area of the stilling well is go
24、verned in partby the requirements of the depth sensor. For example, theclearance between a float and the stilling-well wall should be atleast 0.1 ft (3 cm) and should be increased to 0.25 ft (7.6 cm)if the well is made of concrete or other rough material, the floatdiameter itself being determined in
25、 part by permissible float lagerror (see 11.4.2). Other types of depth sensors may alsoimpose size requirements on the stilling well, and the maxi-mum size may be limited by response lag.7.3.3 Provision should be made for cleaning and flushingthe stilling well to remove accumulated solids. It may be
26、necessary to add a small purge flow of tap water to help keepthe well and any connector pipe and the sensor parts clean. Thisflow should be small enough for any depth increase in thestilling well to be imperceptible.7.3.4 The opening in the flume sidewall connecting to thestilling well either direct
27、ly or through a short perpendicularpipe must have a burr-free junction with the wall. The hole orpipe must be small enough to dampen surface disturbances; anarea of about 1/1000th of the stilling-well area is consideredadequate for this purpose. However, the diameter should not beso small (or the pi
28、pe so long) that it is difficult to keep open ora lag is introduced in the response to changing flows (3); holeand pipe diameters of about12 in. (1.3 cm) should beconsidered a minimum. If changes are made in pipe sizes, theyshould be done sufficiently removed from the flume wall thatno drawdown will
29、 occur. The intake dimensions cited in thisparagraph should be regarded as suggestions only.7.4 Depth-Discharge Relations:7.4.1 Free FlowThe values of C and n for use with Eq 1are given in Table 2, along with approximate limiting flow-rates. The maximum submergence ratios, Hb/Ha, for which freeflow
30、will occur are:Hb/Ha 0.5, for 1, 2, and 3-in. (2.54, 5.08, and7.62-cm) flumes;Hb/Ha 0.6, for 6 and 9-in. (15.24 and 22.86-cm) flumes;4The boldface numbers in parentheses refer to a list of references at the end ofthis test method.FIG. 1 Parshall FlumeD1941 91 (2013)2Hb/Ha 0.7, for 1 to 8-ft (30.48 t
31、o 243.8-cm) flumes;Hb/Ha 0.8, for 10 to 50-ft (304.8 to 1524.0-cm) flumes. 7.4.2 Submerged Flow:TABLE 1 Dimensions and Capacities of Standard Parshall FlumesNOTE 1Flume sizes 3 in. through 8 ft have approach aprons rising at 25 % slope and the following entrance roundings: 3 through 9 in., radius =
32、1.33ft; 1 through 3 ft, radius = 1.67 ft; 4 through 8 ft, radius = 2.00 ft.Widths Axial lengths, ftWallDepth inCon-vergingSection,D,ftVertical distance be-low crest, ftConverg-ing walllength CA,ftGage Points, ftFree-flow Capacities,ft3/sThroat,WTUpstreamend, WC,ftDown-streamend, WD,ftConverg-ingSect
33、ion,LCThroatsection,LTDivergingsection,LDDip atThroat, NLower endof flume,KHC, walllength up-stream ofcrestBHTabMinimum Maximum1 in. 0.549 0.305 1.17 0.250 0.67 0.50.75 0.094 0.062 1.19 0.79 0.026 0.042 0.005 0.152 in. 0.700 0.443 1.33 0.375 0.83 0.500.83 0.141 0.073 1.36 0.91 0.052 0.083 0.01 0.303
34、 in. 0.849 0.583 1.50 0.500 1.00 1.002.00 0.188 0.083 1.53 1.02 0.083 0.125 0.03 1.906 in. 1.30 1.29 2.00 1.00 2.00 2.0 0.375 0.25 2.36 1.36 0.167 0.25 0.05 3.909 in. 1.88 1.25 2.83 1.00 1.50 2.5 0.375 0.25 2.88 1.93 0.167 0.25 0.09 8.901.0 ft 2.77 2.00 4.41 2.0 3.0 3.0 0.75 0.25 4.50 3.00 0.167 0.2
35、5 0.11 16.11.5 ft 3.36 2.50 4.66 2.0 3.0 3.0 0.75 0.25 4.75 3.17 0.167 0.25 0.15 24.62.0 ft 3.96 3.00 4.91 2.0 3.0 3.0 0.75 0.25 5.00 3.33 0.167 0.25 0.42 33.13.0 ft 5.16 4.00 5.40 2.0 3.0 3.0 0.75 0.25 5.50 3.67 0.167 0.25 0.61 50.44.0 ft 6.35 5.00 5.88 2.0 3.0 3.0 0.75 0.25 6.00 4.00 0.167 0.25 1.
36、30 67.95.0 ft 7.55 6.00 6.38 2.0 3.0 3.0 0.75 0.25 6.50 4.33 0.167 0.25 1.60 85.66.0 ft 8.75 7.00 6.86 2.0 3.0 3.0 0.75 0.25 7.0 4.67 0.167 0.25 2.60 103.57.0 ft 9.95 8.00 7.35 2.0 3.0 3.0 0.75 0.25 7.5 5.0 0.167 0.25 3.00 121.48.0 ft 11.15 9.00 7.84 2.0 3.0 3.0 0.75 0.25 8.0 5.33 0.167 0.25 3.50 13
37、9.510 ft 15.60 12.00 14.0 3.0 6.0 4.0 1.12 0.50 9.0 6.00 . . 6 30012 ft 18.40 14.67 16.0 3.0 8.0 5.0 1.12 0.50 10.0 6.67 . . 8 52015 ft 25.0 18.33 25.0 4.0 10.0 6.0 1.50 0.75 11.5 7.67 . . 8 90020 ft 30.0 24.00 25.0 6.0 12.0 7.0 2.25 1.00 14.0 9.33 . . 10 134025 ft 35.0 29.33 25.0 6.0 13.0 7.0 2.25
38、1.00 16.5 11.00 . . 15 166030 ft 40.4 34.67 26.0 6.0 14.0 7.0 2.25 1.00 19.0 12.67 . . 15 199040 ft 50.8 45.33 27.0 6.0 16.0 7.0 2.25 1.00 24.0 16.00 . . 20 264050 ft 60.8 56.67 27.0 6.0 20.0 7.0 2.25 1.00 29.0 19.33 . . 25 3280AFor sizes 1 to 8 ft, C = WT/2 + 4 ft.BHClocated23 C distance from crest
39、 for all sizes; distance is wall length, not axial.NOTE 11 ft = 30.48 cmFIG. 2 Relation Between Hband Hcfor 1, 2, and 3-in. (2.54, 5.08,and 7.62-cm) flumes (Reference (2)TABLE 2 Free-Flow Values of C and n for Parshall Flumes(See Eq 1)Throat Width CAnQ,minBQ, maxBft-in cminch- poundSI ft3/sm3103/sft
40、3/s m3/s0-1 2.54 0.338 0.0479 1.55 0.01 0.28 0.2 0.00570-2 5.08 0.676 0.0959 1.55 0.02 0.56 0.5 0.0140-3 7.62 0.992 0.141 1.55 0.03 0.85 1.1 0.0310-6 15.24 2.06 0.264 1.58 0.05 1.42 3.9 0.110-9 22.80 3.07 0.393 1.53 0.09 2.55 8.9 0.251-0 30.48 4.00 0.624 1.522 0.11 3.1 16.1 0.461-6 45.72 6.00 0.887
41、1.538 0.15 4.2 24.6 0.692-0 60.96 8.00 1.135 1.550 0.42 11.9 38.1 0.933-0 91.44 12.00 1.612 1.566 0.61 17.3 50.4 1.424-0 121.92 16.00 2.062 1.578 1.3 36.8 67.9 1.925-0 152.40 20.00 2.500 1.587 1.6 45.3 85.6 2.426-0 182.88 24.00 2.919 1.595 2.6 73.6 103.5 2.937-0 213.36 28.00 3.337 1.601 3.0 85.0 121
42、.4 3.448-0 243.84 32.00 3.736 1.607 3.5 99.1 139.5 3.9510-0 304.8 39.38 4.709 1.6 6 170 200 5.612-0 365.8 46.75 5.590 1.6 8 227 350 9.919-0 457.2 57.81 6.912 1.6 8 227 600 17.020-0 609.6 76.25 9.117 1.6 10 283 1000 28.325-0 762.0 94.69 11.32 1.6 15 425 1200 34.030-0 914.4 113.13 13.53 1.6 15 425 150
43、0 42.540-0 1219.2 150.00 17.94 1.6 20 566 2000 56.650-0 1524.0 186.88 22.35 1.6 25 708 3000 84.9AListed values of C should be used in Eq 1 with Hain feet to obtain flowrate in cubicfeet per second. Listed values of C (metric) should be used with Hain centimetresto obtain flowrate in litres per secon
44、d.BFrom Ref (1).D1941 91 (2013)37.4.2.1 Discharge rates for submerged-flow conditions aregiven for 1, 2, 3, 6, and 9-in. (2.54, 5.08, 7.62, 15.24, and22.86-cm) flumes in Table 3, Table 4, Table 5, Table 6, andTable 7 (Table 8, Table 9, Table 10, Table 11, and Table 12),which were compiled from publi
45、shed curves (2).7.4.2.2 For all larger flumes, that is, 1 to 50 ft (30.48 to 1524cm) throat widths, flowrates under submerged-flow conditionsare given as corrections to be subtracted from the free-flowdischarge at the same Ha. These corrections are found in Table13, Table 14, Table 15, and Table 16
46、(Table 17, Table 14, Table18, and Table 16), which were compiled from published curves(2).7.4.2.3 It is recommended that submergence be avoided ifpossible and that ratios not be allowed to exceed 0.95.7.5 Installation Requirements:7.5.1 It is highly desirable that the Parshall flume installa-tion be
47、 designed for free flow. The depth-discharge relationsfor free flow are more accurate than those for submerged flow,particularly at high submergence ratios. Further, the secondaryinstrumentation for free flow is simpler and more readilyavailable. Design for free flow requires an estimate of thenorma
48、l depth of flow in the channel downstream of the flumeand the assumption that the resulting surface elevation prevailsapproximately at the Hblocation. Design examples are avail-able in the References.7.5.2 The flow entering the flume should be tranquil anduniformly distributed across the channel. Fo
49、r this purpose,uniform velocity distribution can be defined as that associatedwith fully developed flow in a long, straight, moderatelysmooth channel. As a general guideline, a straight upstreamapproach length of 10 to 20 times the throat width will meetthis entrance condition. The adequacy of the approach flowmust be demonstrated on a case-by-case basis using current-meter traverses, experience with similar situations, or analyti-cal approximations.7.5.3 If the approach flow is supercritical, the installationshould be designed so that a hydraulic jump
