1、BRITISH STANDARD CONFIRMED APRIL1998 BS 3680-3D: 1980 ISO4369:1979 Methods of measurement of Liquid flow in open channels Part 3: Stream flow measurement Part 3D: Moving-boat method ISO title: Measurement of liquid flow in open channels Moving-boat method UDC 532.543:532.573.1BS3680-3D:1980 This Bri
2、tish Standard, having been prepared under the directionof the Industrial-process Measurement and Control Standards Committee, was published under the authority ofthe Executive Board and comesinto effect on 31October1980 BSI 11-1999 The following BSI references relate to the work on this standard: Co
3、mmittee reference PCL/3 Draft for comment 77/26415 DC ISBN 0 580 11657 3 Cooperating organizations The Industrial-process Measurement and Control Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: British Gas Corporation Bri
4、tish Industrial Measuring and Control Apparatus Manufacturers Association British Steel Corporation Cbmpe Control and Automation Manufacturers Association (BEAMA) Department of the Environment (Water Engineering Division including Water Data Unit)* Department of Industry (Computers Systems and Elect
5、ronics) Electrical, Electronic, Telecommunications and Plumbing Union Electricity Supply Industry in England and Wales Engineering Equipment Users Association Institute of Measurement and Control Institution of Gas Engineers Oil Companies Materials Association Post Office Engineering Union Scientifi
6、c Instrument Manufacturers Association* Sira Institute The organizations marked with an asterisk in the above list, together with the following, were directly represented on the Technical Committee entrusted with the preparation of this British Standard: Department of the Environment for Northern Ir
7、eland Department of the Environment (Hydraulic Research Station) Department of Industry (National Engineering Laboratory) Institution of Civil Engineers Institution of Water Engineers and Scientists National Water Council Natural Environment Research Council (Institute of Geological Science) Scottis
8、h Development Department South West Water Authority Co-opted expert Amendments issued since publication Amd. No. Date of issue CommentsBS3680-3D:1980 BSI 11-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii 1 Scope and field of application 1 2 References 1 3 Defi
9、nitions 1 4 Units of measurement 1 5 General 1 6 Principle of the moving-boat method 1 7 Limitations 3 8 Equipment 3 9 Measurement procedures 4 10 Computation of discharge 5 11 Accuracy of flow measurement 8 Annex A Description of the instruments and the functions of the crew members 21 Annex B A st
10、ep-by-step outline of the computation procedure whichreferstotheexamples of measurement notes for method1 andmethod2shownin Table 1 and Table 2 respectively as a guide to the computer 25 Figure 1 Sketch of stream with markers 14 Figure 2 General diagrams of velocity vectors 15 Figure 3 Definition sk
11、etch of midsection method of computation superimposedover a facsimile of an echo-sounder chart 16 Figure 4 Discharge hydrograph prepared from current meter measurementsand showing moving-boat check measurements; HudsonriveratPoughkeepsie, N.Y., August30,1966 17 Figure 5 Typical control panel of rate
12、 indicator and counter Method1 18 Figure 6 Comparison of actual and computed values of incremental widths 19 Figure 7 Compensation for deviations from cross-section or inthe directionofflow 20 Figure 8 Sketch of boat showing equipment Method1 24 Table 1 Sample of computation notes of a moving-boat m
13、easurement Method1 27 Table 2 Sample of computation notes of a moving-boat measurement Method2 28 Table 3 Rating table for moving-boat meter No.24 29 Table 4 Table of l b , in metres 30 Table 5 Sine of angle 30 Publications referred to Inside back coverBS3680-3D:1980 ii BSI 11-1999 National foreword
14、 This British Standard has been prepared under the direction of the Industrial-process Measurement and Control Standards Committee and is identical with ISO4369:1979“Measurement of liquid flow in open channels Moving-boat method” published by the International Organization for Standardization (ISO).
15、 Terminology and conventions. The text of the International Standard has been approved as suitable for publication, without deviation, as a British Standard. Some terminology and certain conventions are not identical with those used in British Standards; attention is especially drawn to the followin
16、g. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. Since the publi
17、cation of ISO4369, ISO5168has been published. Footnote1 on page1therefore no longer applies. The related standard for ISO3454:1975 is BS3680-8B:1973. The Technical Committee has reviewed the provisions of ISO4366:1979, for which there is no corresponding British Standard, and has decided that they a
18、re acceptable for use in conjunction with this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from leg
19、al obligations. Cross-references International Standard Corresponding British Standard BS3680 Methods of measurement of liquid flow in open channels ISO772:1978 Part 1:1979 Vocabulary and symbols (Technically equivalent) ISO748:1979 Part 3:1980 Stream flow measurement Part 3A:1980 Velocity-area meth
20、ods (Identical) ISO5168:1979 BS5844:1980 Measurement of fluid flow: estimation of uncertainty of a flow-rate measurement (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 30, an inside back cover and a back cover. This standard has b
21、een updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS3680-3D:1980 BSI 11-1999 1 1 Scope and field of application This International Standard specifies methods for measuring discharge in large rivers and e
22、stuaries by the moving-boat technique. In the following sections procedures applicable to this method and the general requirements of equipment are covered. A complete facsimile example of computation of a moving boat measurement is given in the annexes. 2 References ISO748, Liquid flow measurement
23、in open channels Velocity area methods. ISO772, Liquid flow measurement in open channels Vocabulary and symbols. ISO3454, Liquid flow measurement in open channels Sounding and suspension equipment. ISO4366, Liquid flow measurement in open channels Echo sounders. ISO5168, Calculation of the uncertain
24、ty of a measurement of flowrate 1) . 3 Definitions For the purpose of this International Standard the definitions given in ISO772apply. 4 Units of measurement The units of measurement used in this International Standard are SI units. 5 General Frequently, on large rivers and estuaries, conventional
25、methods of measuring discharge by current meters are difficult and involve costly and tedious procedures. This is particularly true at remote sites where no facilities exist, or during floods when facilities may be inundated or inaccessible. In those cases where unsteady flow conditions require that
26、 measurement be made as rapidly as possible, the moving-boat technique is applicable. It requires no fixed facilities and it lends itself to the use of alternate sites. The moving-boat technique uses a velocity-area method of determining discharge. The technique requires that the following informati
27、on be obtained: a) location of observation points across the stream with reference to the distance from an initial point; b) stream depth, d, at each observation point; c) stream velocity, v, perpendicular to the cross section at each observation point. The principal difference between a conventiona
28、l measurement and the moving-boat measurement is in the method of data collection. The mean velocity in the segments of a cross-section of the stream in the case of a conventional technique is determined by point velocities or an integrated mean velocity in the vertical. The moving-boat technique me
29、asures the velocity over the width of a segment by suspending the current meter at a constant depth during the traverse of the boat across the stream. The measured velocity and the additional information of the depth sounding gives the required data for determining the discharge. 6 Principle of the
30、moving-boat method The moving-boat measurement is made by traversing the stream along a preselected path that is generally normal to the streamflow (seeFigure 1). During the traverse an echo sounder records the geometry of the cross-section and a continuously operating current meter senses the combi
31、ned stream and boat velocities. A third set of data needed is obtained either by measuring at intervals the angle between the current meter, which aligns itself in a direction parallel to the movement of the water past it, and the preselected path or by measuring the distance to a fixed point on the
32、 bank. The velocity measurement observed at each of the observation points in the cross-section (v vin Figure 2) is the velocity of water past the current meter resulting from both stream flow and boat movement. It is the vector sum of the velocity of water with respect to the stream bed (v) and the
33、 velocity of the boat with respect to the stream bed (v b ). 1) At present at the stage of draft.BS3680-3D:1980 2 BSI 11-1999 The sampling data recorded at each observation point provide the necessary information to determine the velocity of the stream. There are two methods to obtain this velocity,
34、 referred to as method1 and method2. Method1consists of measuring the angle between the selected path of the boat and a vertical vane which aligns itself in a direction parallel to the movement of the water past it. An angle indicator attached to the vane assembly indicates angle . Method2consists o
35、f measuring the distance from the observation points to a fixed point on the bank from which the width of the traversed segment can be determined along with the simultaneous measurement of time. From these data, the velocity component of the boat, v b , can be computed and by means of the measuremen
36、t of total velocity, v v , the velocity component, v, of the stream perpendicular to the selected boat path is determined. The reading from the rate indicator unit in pulses per second is used in conjunction with a calibration table to obtain the vector magnitude v v . Normally, data are collected a
37、t30or40observation points in the cross-section for each run. Where practicable, automatic and simultaneous readings of all required parameters may be recorded. 6.1 Determination of stream velocity By method1the stream velocity v, perpendicular to the boat path (true course) at each observation point
38、1,2,3,., can be determined from the relationship The solution of equation (1) yields an answer which represents that component of the stream velocity which is perpendicular to the true course even though the direction of flow may not be perpendicular. By method2the stream velocity can be determined
39、from where v bis obtained from (seeFigure 3) where 6.2 Determination of distance between observation points From the vector diagram, (seeFigure 2) it can be seen that where %l bis the distance which the boat has travelled along the true course between two consecutive observation points, provided the
40、 stream velocity is perpendicular to the path. Where the velocity is not perpendicular, an adjustment is required as explained in10.3. If it is assumed that is approximately uniform over the relatively short distance which makes up any one increment, then it may be treated as a constant. Therefore a
41、pplying method1, equation (4) becomes v = v vsin . (1) . (2) . (3) i is the observation point order; l i is the distance from observation point i to a fixed point on the bank; l i is the time required to traverse the width of a segment. . (4) . (5)BS3680-3D:1980 BSI 11-1999 3 Now where %l vis the re
42、lative distance through the water between two consecutive observation points as represented by the output from the rate indicator and counter. Therefore for the ith relative distance the total width, B, of the cross sectional area is If method2is applied, then the width of the interval between obser
43、vation points should be computed as the difference between successive distance measurements from a fixed point on one of the banks as shown in equation (3). 6.3 Determination of stream depth The stream depth at each observation point should be obtained by adding the transducer depth to the depth fro
44、m the echo sounder chart, unless the transducer is set to read total depth. 7 Limitations The method is normally employed on rivers over300m wide and over2m in depth. The minimum width which is required depends on the number of segments into which the cross-section is divided and the minimum time to
45、 pass these segments to obtain a sufficiently accurate measurement. The number of segments should be at least25. The width to be taken for each segment depends on the accuracy with which the velocity in each segment can be measured. The interval between two observation points should be sufficient to
46、 allow the observer to read the instruments and record the results. The minimum speed of the boat should be such as to ensure that the boat may traverse the section in a straight line. For the best results this speed should be of the same order as the velocity of the stream. The river should be of s
47、ufficient depth to allow for the draught of the boat and the requirement of easy manuvring during the traverse of the cross-section. Shallow locations may cause damage to the instruments as the current meter and/or vane extend about1m below the boat. The stream should not have an under-current, as c
48、an be the case in tidal-flow, where the direction is opposite to the flow in which the velocity is measured. In such cases the velocity distribution in the vertical is unknown and the mean velocity cannot be satisfactorily correlated to the measured velocity. During the time that the boat traverses
49、the stream the discharge should not change to such an extent that an unreliable measurement is obtained. For unsteady flow conditions on tidal streams, it will normally be desirable not to average the results from a series of runs, but rather to keep them separate so as to better define the discharge cycle (seeFigure 4). 8 Equipment 8.1 General The equipment required is similar no matter which of the two methods is used (see clause6). Essentials of the equipment required for both methods are given below. A more det
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