Booklet 7 - Flow Measurement Methods in Open Channels

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−−−a visual assessment of effluent flow by an experienced individual;an instant measurement of effluent flow (ex. depth/velocity);determination of the approximate diameter and slope of sewer pipes, indication of the network’smaximum capacity.If plant activities cause major fluctuations in flow and the only indication of flow available is an average flowvalue. This flow value should be increased by a factor of 2.5 to determine the maximum discharge, to reflectpeak periods.1.12.4. Tolerance of fluctuations in flowIf a measuring device has been installed correctly, it should continue to have the same precision duringfluctuations in flow. It is therefore important to verify how systems react during fluctuations.In the control section of a measuring device, a drop or increase in discharge should not cause turbulence andcause the flowrate to vary. It should instead show up essentially as a variation of water depth in the primarydevice.1.12.5. Flume widthIf a flow channel is too wide or too narrow, the possibility of restricting or enlarging the flow area should beexamined, to allow measuring equipment to be installed and to ensure that equipment can operate correctly.The flow channel should be at least as wide as the measuring device and no wider than the width of themeasuring element plus 10 m. Figure 4 illustrates this type of setup.1.12.6. Loss of chargeBefore installing a measuring device, it is important to verify the allowable maximum drop in charge.Different measurement methods create different drops in charge. For a particular measuring instrument, themaximum loss of depth corresponds to the maximum flow.Loss of charge for flumes is generally less than that caused by weirs. The difference is approximately 30 %.Page 28 of 223Booklet 7 - Flow Measurement Methods in Open Channels
FIGURE 4 - FLUME - FLUME AND FLOW CHANNEL LAYOUTBooklet 7 - Flow Measurement Methods in Open Channels Page 29 of 223
Page 1: Centre d’expertise en analyse env
Page 5: FOREWORDThis Sampling Guide for Env
Page 8 and 9: 4.4. Area/velocity method..........
Page 10 and 11: LIST OF ILLUSTRATIONSFigure 1 - Wei
Page 13 and 14: 1. GENERAL1.1. Definition of flowra
Page 15 and 16: Note: If effluents have different d
Page 17 and 18: This equation shows that water dept
Page 19 and 20: Sizes vary according to the type an
Page 21 and 22: FIGURE 1 - WEIR COMPONENTSFlow is d
Page 23 and 24: 1.10. Reference measurementIf a mea
Page 25 and 26: FIGURE 2 - PALMER-BOWLUS - FLUME CH
Page 27 and 28: TABLE 1 - DIMENSIONS FOR PALMER-BOW
Page 29: 1.12. Choosing a measurement method
Page 33 and 34: TABLE 3 - CHART FOR COMPARING THE M
Page 35 and 36: TABLE 4 - DIMENSIONS FOR STILLING W
Page 37 and 38: 2. DESCRIPTION OF FLUMESThe section
Page 39 and 40: 2.1.2. Operating principleA Parshal
Page 41 and 42: TABLE 5 - PARSHALL FLUME - STANDARD
Page 43 and 44: TABLE 6 - PARSHALL FLUME - RECOMMEN
Page 45 and 46: 2.1.7. PrecisionThe margin for erro
Page 47 and 48: channel at maximum flow (H c ), bef
Page 49 and 50: FIGURE 8 - PARSHALL FLUME - JUNCTIO
Page 51 and 52: FIGURE 9 - PARSHALL FLUME - EFFECTS
Page 53 and 54: 2.1.12. Discharge equation in a sub
Page 55 and 56: FIGURE 11 - LOSS OF HEAD - PARSHALL
Page 57 and 58: To monitor the total rise, follow t
Page 59 and 60: A Palmer-Bowlus flume, as experimen
Page 61 and 62: FIGURE 13 - SHAPE OF A PALMER-BOWLU
Page 63 and 64: TABLE 10 - PALMER-BOWLUS FLUME - ST
Page 65 and 66: Because some manufacturers do not a
Page 67 and 68: −use of the depth/flow table2.2.1
Page 69 and 70: For temporary systems, a simple ver
Page 71 and 72: Q is the flowrate in liters or US g
Page 73 and 74: FIGURE 15 - SHAPE OF LEOPOLD-LAGCO
Page 75 and 76: 2.3.7. Measurement capacity of a fl
Page 77 and 78: 2.3.11. Installation specifications
Page 79 and 80: 2.4.2. Operating principleCutthroat
Page 81 and 82:
TABLE 14 - CUTTHROAT FLUME - STANDA
Page 83 and 84:
TABLE 15 - CUTTHROAT FLUME - RECOMM
Page 85 and 86:
TABLE 16 - CUTTHROAT FLUME - VALUES
Page 87 and 88:
TABLE 18 - CUTTHROAT FLUME - DISCHA
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Since a number of other cutthroat f
Page 91 and 92:
where:Q is the flowrate in cubic me
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Example: To measure a 0.6 m 3 (21 C
Page 95 and 96:
It consists of two sections: approa
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FIGURE 18 - H FLUME - PHYSICAL CHAR
Page 99 and 100:
Although this type of flume can be
Page 101 and 102:
TABLE 21 - H FLUME - STANDARD DIMEN
Page 103 and 104:
TABLE 23 - H FLUME - RECOMMENDED MI
Page 105 and 106:
CoefficientsandexponentsTABLE 24 -
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−erosion at the outlet of the flu
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2.5.13. Flume modificationTo obtain
Page 111 and 112:
Example:For a rectangular weir wher
Page 113 and 114:
−−−−−−−the presence o
Page 115 and 116:
TABLE 25 - WEIR CALIBRATION - VOLUM
Page 117 and 118:
FIGURE 20 - RECTANGULAR WEIR WITHOU
Page 119 and 120:
TABLE 26 - RECTANGULAR WEIR WITHOUT
Page 121 and 122:
Inadequate approach velocityThe app
Page 123 and 124:
FIGURE 21 - RECTANGULAR WEIR WITH C
Page 125 and 126:
The Kindsvater-Carter equation take
Page 127 and 128:
3.3.5. PrecisionIn free flow condit
Page 129 and 130:
TABLE 28 - RECTANGULAR WEIR WITH CO
Page 131 and 132:
FIGURE 22 - TRAPEZOIDAL WEIR (CIPOL
Page 133 and 134:
TABLE 29 - TRAPEZOIDAL WEIR (CIPOLL
Page 135 and 136:
Length of contractionsIf side contr
Page 137 and 138:
In addition to the information prov
Page 139 and 140:
The discharge equation resulting fr
Page 141 and 142:
3.6. Combined weirTo obtain a preci
Page 143 and 144:
In addition to the information prov
Page 145 and 146:
3.6.5. PrecisionIn free flow condit
Page 147 and 148:
FIGURE 25 -COMPOUND WEIR - PHYSICAL
Page 149 and 150:
TABLE 32 - COMPOUND WEIR - MEASUREM
Page 151 and 152:
4.1.1.2 Characteristics of tracersT
Page 153 and 154:
S gis the specific weight of the tr
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4.1.2.1.4 Disadvantages of the meth
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When selecting a sampling point, it
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4.1.2.2.8 Detection and measurement
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Dyes are well suited to flow measur
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4.1.2.3.8 Detection and measurement
Page 165 and 166:
4.1.2.4.3 Preparation of radioactiv
Page 167 and 168:
4.1.2.4.9 Preliminary testsBefore c
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4.1.3.1.3 Advantages of the method
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Testing procedures are as follows:T
Page 173 and 174:
Use the following formula to determ
Page 175 and 176:
The discharge equation is therefore
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• Choosing a tracerExamine the di
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Sampling must be carried out during
Page 181 and 182:
−−contamination of sampling con
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Instantaneous injections1 2 3 4 5nP
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tracer is lost due to splashing, by
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The concentration of tracers is usu
Page 189 and 190:
4.1.3.3.7 Causes of errorThe princi
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4.2.4. DisadvantagesThe principal d
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−If the dimensions cannot be meas
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4.3.7. DisadvantagesFlow measuremen
Page 197 and 198:
4.3.8.2 Calculation of pumping time
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4.3.8.4 Number of testsWhen a pumpi
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−−−−−requires a number of
Page 203 and 204:
4.4.9. Flow areaMeasurement of the
Page 205 and 206:
Velocity measurements should be tak
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considering only the source of erro
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There are also other causes of bias
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12. GRANT, D. M., ISCO Open Channel
Page 213:
36. INTERNATIONAL STANDARD ORGANISA
Page 216 and 217:
CHANDRA, U., Aoki, P. E., Ramos e S
Page 218 and 219:
HAMMER, Mark J., Water and Waste-Wa
Page 220 and 221:
Resources Instrumentation, June 4-6
Page 222 and 223:
REPLOGLE, John A., Meyers, Lloyd E.
Page 224 and 225:
TRIESTE, Douglas J., Evaluation of
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Booklet 7 - Flow Measurement Methods in Open Channels

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