1、Designation: D 1941 91 (Reapproved 2007)Standard Test Method forOpen Channel Flow Measurement of Water with the ParshallFlume1This standard is issued under the fixed designation D 1941; 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 (e) 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
3、 with 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 a
4、nd health practices and determine the applica-bility of regulatory limitations prior to 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
5、 Open-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
6、 4359 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 D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 free flowa condition where the flowrate is go
7、vernedby 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 cons
8、iderable 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 second
9、ary instrument.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 indica
10、ted flow 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
11、 depth 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-dischargerelati
12、on no longer applies and discharge depends on two headmeasurements.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 J
13、une 2007. Originallyapproved in 1962. Last previous edition approved in 2001 as D 1941 91 (2001).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 Docum
14、ent 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.11 supercritical f
15、lowopen 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.4. Summary of Test Method4.1 Parshall flumes are measuring flumes of specified ge-
16、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. Significance and
17、 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-cleansing for modera
18、te 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-cleansing capac-ity, it can be clogged by debris or af
19、fected by accumulation ofaquatic growth and cleaning or debris removal may be re-quired.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 to an instrume
20、nt 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 1, respective
21、ly. 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 Hais shown inFi
22、g. 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 for therelati
23、on 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 governed in partb
24、y 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 part by permis
25、sible 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 benecessary to ad
26、d 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 directly or through a
27、 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 pipe so long) tha
28、t 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 occur. The int
29、ake dimensions cited in thisparagraph should be regarded as suggestions only.7.4 Depth-Discharge Relations:4The boldface numbers in parentheses refer to a list of references at the end ofthis test method.FIG. 1 Parshall FlumeD 1941 91 (2007)27.4.1 Free FlowThe values of C and n for use with Eq 1are
30、given in Table 2, along with approximate limiting flow-rates. The maximum submergence ratios, Hb/Ha, for which freeflow will occur are:Hb/Ha 0.5, for 1, 2, and 3-in. (2.54, 5.08, andTABLE 1 Dimensions and Capacities of Standard Parshall FlumesNOTE 1Flume sizes 3 in. through 8 ft have approach aprons
31、 rising at 25 % slope and the following entrance roundings: 3 through 9 in., radius = 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 walllengthCA,ftGage Points, ftFree
32、-flow Capacities,ft3/sThroat,WTUpstreamend, WC,ftDown-streamend, WD,ftConverg-ing Sec-tion, 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 0.1
33、52 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 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
34、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 0.25 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
35、 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 1.30 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
36、 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 3.50 139.510 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 2
37、5.0 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 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 1
38、9.33 . . 25 3280AFor sizes 1 to 8 ft, C = WT/2 + 4 ft.BHClocated 2/3 C distance from crest 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
39、Parshall Flumes(See Eq 1)Throat Width CAnQ,minBQ, maxBft-in cminch-poundSI ft3/sm33103/sft3/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
40、 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 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 2.4
41、26-0 182.88 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 85.0 121.4 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
42、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 1500 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 incubic feet per second. Listed value
43、s of C (metric) should be used with Haincentimetres to obtain flowrate in litres per second.BFrom Ref (1).D 1941 91 (2007)37.62-cm) flumes;Hb/Ha 0.6, for 6 and 9-in. (15.24 and 22.86-cm) flumes;Hb/Ha 0.7, for 1 to 8-ft (30.48 to 243.8-cm) flumes;Hb/Ha 0.8, for 10 to 50-ft (304.8 to 1524.0-cm) flumes
44、.7.4.2 Submerged Flow:7.4.2.1 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 published curve
45、s (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 (Table 17,
46、 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 designed
47、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 thenormal depth of
48、 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. For this pur
49、pose,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 is formed at
