BS 3680-2A-1995 Measurement of liquid flow in open channels - Dilution methods - General《明渠液流测量 第2A部分 稀释法 总则》.pdf

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1、BRITISH STANDARD BS3680-2A: 1995 ISO9555-1: 1994 Measurement of liquid flow in open channels Part 2: Dilution methods Part 2A: GeneralBS3680-2A:1995 This British Standard, having been prepared under the directionof the Electrotechnical Sector Board, was published underthe authority of the Standards

2、Board and comes into effect on 15 January1995 BSI 06-1999 The following BSI references relate to the work on this standard: Committee reference PCL/3 Draft for comment 92/34385 DC ISBN 0 580 23541 6 Committees responsible for this British Standard The preparation of this British Standard was entrust

3、ed by the Electrotechnical Sector Board to Technical Committee PCL/3, upon which the following bodies were represented: Clyde River Purification Board Department of the Environment Institute of Measurement and Control Institution of Water and Environmental Management National Rivers Authority Water

4、Services Association of England and Wales Welsh Office The following bodies were also represented in the drafting of the standard, through subcommittees and panels: Institute of Hydrology Water Research Centre Amendments issued since publication Amd. No. Date CommentsBS3680-2A:1995 BSI 06-1999 i Con

5、tents Page Committees responsible Inside front cover National foreword ii Introduction 1 1 Scope 1 2 Normative reference 1 3 Definitions 1 4 Symbols and units 4 5 Principles of the different dilution methods 5 6 Characteristics common to both methods 6 7 Choice of tracer 11 8 Choice of measuring rea

6、ch 12 9 Procedure for the constant rate injection method 20 10 Procedure for the sudden injection method 25 11 Comparison between the two dilution methods 30 12 Estimation of uncertainties 32 Annex A (normative) Standard dilutions using pipettes and flasks 46 Annex B (normative) Standard dilution ra

7、nges obtained with a micrometer-type microburette 47 Annex C (normative) Analysis for variance as a test of non-randomness 49 Annex D (informative) Bibliography 50 Figure 1 Relation between and c 2 12 Figure 2 Curves of appearance and disappearance of tracer for a sudden injection Shapes of curves o

8、f concentration against time and distance 18 Figure 3 Curves of appearance and disappearance of tracer used to determine a suitable duration of injection T ifor a gauging by the constant rate injection method Shapes of curves of concentration against time and distance 19 Figure 4 Constant level tank

9、 for the injection of tracer solution at constant rate 22 Figure 5 Use of a constant-rate pump for injection of tracer solution at constant rate 23 Figure 6 Mariotte constant head vessel 24 Figure 7 Floating siphon device 24 Figure 8 Typical sampling curves 27 Figure 9 Obtaining mean samples 28 Figu

10、re 10 Obtaining several mean samples 31 Figure 11 Pump with manifold for multiple sampling 32 Table 1 Values of the coefficient k 15 Table B.1 Preparation of standard dilution ranges using a micrometer-type microburette 48 Table B.2 Micrometer turns for ranges with mid-values N 0 48 Table C.1 Instru

11、ment readings 49 Table C.2 Sums of squares of values from Table C.1 49 Table C.3 Instrument readings 50 Table C.4 Sum of squares of values from Table C.3 50 List of references Inside back coverBS3680-2A:1995 ii BSI 06-1999 National foreword This Part of BS3680 has been prepared under the direction o

12、f the Electrotechnical Sector Board. It is identical with ISO9555-1:1994 Measurement of liquid flow in open channels Tracer dilution methods for the measurement of steady flow Part1: General, published by the International Organization for Standardization (ISO). This is one of a series of Parts of B

13、S3680 on dilution methods, as follows: Part 2A:1994: General; Part 2B:1993: Radioactive tracers; Part 2C:1993: Chemical tracers; Part 2D:1993: Fluorescent tracers. These four Parts of BS3680 supersede BS3680-2A:1964, BS3680-2B:1986, and BS3680-2C:1983 which are withdrawn. Cross-references The Techni

14、cal Committee has reviewed the provisions of ISO772:1988, to which normative reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. Informative reference is also made to the following standard: A British Standard does not purport to include

15、 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 legal obligations. ISO 8363:1986 BS3680 Measurement of liquid flow in open channels Part 3G:1990 General g

16、uidelines for the selection of methods Summary of pages This document comprises a front cover, an inside front cover, pagesi and ii, pages1to50, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated

17、 in the amendment table on the inside front cover.ISO9555-1:1994(E) BSI 06-1999 1 Introduction The former standard series ISO555 was subdivided into parts on the basis of the method of field measurement, i.e.constant-rate injection method and integration (sudden injection) method. Since the choice o

18、f the type of tracer to be used in a field measurement will often depend on the expertise and the laboratory facilities available, this new series of standards ISO9555 is divided into parts based on the type of tracer used. This revision has enabled the unnecessary repetition of text of the various

19、parts to be avoided and will, it is hoped, prove to be a more convenient form of presentation for the user. ISO9555 deals with the measurement of steady flow in open channels by dilution methods using tracers. The methods described may also be applied to the measurement of slowly varying flow, but t

20、hey may only be used when flow conditions ensure adequate mixing of the injected solution throughout the flow. For the measurement of very large flows, tracer methods can be onerous in terms of tracer costs and measurement times. However, the use of tracers often reduces danger to personnel during f

21、lood periods. ISO9555-1 presents the general principles of the methods of constant rate injection and integration (sudden injection). ISO9555-2, ISO9555-3 and ISO9555-4 deal with the specific aspects of the use of radioactive, chemical and fluorescent tracers, respectively, as well as specific analy

22、tical procedures. This approach has been adopted for the following reasons: to facilitate subsequent updating, additions or revisions which concern only ISO9555-2, ISO9555-3 or ISO9555-4; to provide a more practical document for the user, who is often obliged to choose the tracer best suited to the

23、available analytical equipment. 1 Scope This part of ISO9555 concerns principles of the constant rate injection method and the sudden injection method (integration method), and the principles of injection, sampling and analysis which apply for all types of tracer. It is important to note that the tr

24、acers used and their concentrations should be compatible with the legislation of each country regarding the occasional and short-duration discharges of foreign substances into natural waters. They should also take into account possible short-term or long-term influences on flora and fauna, both natu

25、ral and domestic. In the absence of appropriate regulations, the World Health Organizations (WHO) Guidelines for drinking water quality should serve as a guide, taking account of the brief nature of the measurement and of the use that is to be made of water receiving the injected tracer. 2 Normative

26、 reference The following standard contains provisions which, through reference in this text, constitute provisions of this part of ISO9555. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this part of ISO9555 are

27、encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO772:1988, Liquid flow measurement in open channels Vocabulary and symbols. 3 Definitions For the pur

28、poses of this part of ISO9555, the definitions given in ISO772 and the following definitions apply. 3.1 tracer ion, compound or radionuclide introduced into a flow system to follow the behaviour of some component of that system. It is necessary that the tracer, which can be observed, behave in exact

29、ly the same fashion as the component to be followed, whose behaviour cannot easily be observed 3.2 dilution method method in which the discharge is deduced from the determination of the ratio of the concentration of the tracer injected to that of the tracer at the sampling cross-section (see also3.9

30、)ISO9555-1:1994(E) 2 BSI 06-1999 3.3 constant rate injection method method of measuring the discharge in which a tracer is injected at a constant and known rate at one cross-section and its dilution is measured at another section downstream where complete mixing has taken place and the concentration

31、 plateau has been reached 3.4 sudden injection method; integration method method of measuring the discharge in which a known volume of tracer is injected over a short time at one cross-section and its dilution is measured at another cross-section downstream where complete mixing has taken place, ove

32、r a period sufficient to allow all the tracer to pass that cross-section, so that the mean dilution of tracer during this period can be determined 3.5 multiple injection simultaneous injection of tracer at several points in the injection cross-section, with the aim of improving transverse mixing in

33、a given measuring reach 3.6 constant level tank equipment for the injection of the concentrated solution at constant rate, in which, using an overflow weir, a constant head is maintained above a selected nozzle or orifice 3.7 Mariotte vessel equipment for injection of the concentrated solution at co

34、nstant rate. The constant rate injection is achieved by means of an airtight vessel that is provided with an orifice plate or nozzle at its bottom portion. The liquid flows through the restriction and air enters the vessel through a tube, maintaining atmospheric pressure at the lower end of the tube

35、, set at a determined height above the restriction. The head on the restriction and consequently the discharge from the vessel remain constant, independently of the level of the liquid in the vessel 3.8 floating siphon equipment for injection of the concentrated solution at constant rate. The soluti

36、on is taken from a vessel by means of a siphon that is fixed on a float. The lower end of the siphon is fitted with an orifice plate or nozzle. The head on the restriction and consequently the discharge from the vessel remain constant, independently of the level of the liquid in the vessel 3.9 dilut

37、ion ratio; dilution factor 1) For the constant rate injection method, the ratio between the concentration of the injected tracer solution and the concentration of added tracer detected at the sampling cross-section when steady conditions have been reached. 2) For the sudden injection method, the rat

38、io between the concentration of the injected tracer solution and the mean, over the sampling period, of the concentration of added tracer detected at the sampling cross-section. 3.10 sampling cross-section; sampling station cross-section of an open channel downstream of the injection cross-section,

39、at which samples are taken or in which the concentration is directly measured 3.11 reach length of open channel between two defined cross-sectionsISO9555-1:1994(E) BSI 06-1999 3 3.12 degree of mixing measure of the extent to which mixing has been achieved in a cross-section downstream of the injecti

40、on of tracer, varying from near zero in a cross-section immediately downstream of the injection to100% at a cross-section in which the tracer has been completely mixed across the whole cross-section 3.13 mixing length distance, measured along the general path of flow, between the injection cross-sec

41、tion and the downstream cross-section at which the specified degree of mixing is obtained. For given conditions, this mixing length is not a fixed value: it varies according to the admissible values for the degree of mixing. The higher the specified degree of mixing, the longer the mixing lengthISO9

42、555-1:1994(E) 4 BSI 06-1999 4 Symbols and units 4.1 Symbols The symbols used in this part of ISO9555 are given below. Other symbols not listed here are used only in passing and are defined where used. 4.2 Subscripts NOTE 1A bar () is used above the symbol to indicate an averaging process; further av

43、eraging is indicated by a double bar (=). NOTE 2For convenience in the use of this part of ISO9555, some of the symbols and their definitions are not consistent with those defined in ISO772. Symbol Explanation Average stream surface width between the injection and sampling cross-sections c o Backgro

44、und concentration of tracer c 1 Concentration of tracer in injection solution c 2 Concentration of added tracer c9 1 Concentration of diluted injection solution (c9 1 = c 1 /D9) c9 ri Relative concentration corresponding to standard dilution D9 D Dilution factor D9 Estimated dilution factor used in

45、dilution of injection solution D9 i Standard dilution Average depth of flow between injection and sampling cross-sections E Transverse mixing coefficient G Instrument response g Acceleration due to gravity L Mixing length M, m Mass m Number of sampling points n Number of samples or measurements Q St

46、ream discharge Q9 Estimated stream discharge q Injection rate r h Mean hydraulic radius S Energy slope T c Duration of steady state concentration T i Duration of injection T p Time of passage of tracer through the sampling cross-section t Elapsed time, usually taking as the origin the start of injec

47、tion t a Time of arrival of first molecule of tracer at a given sampling cross-section t* Mean time of travel V Volume of tracer solution injected Mean velocity v * Shear velocity, equal to (gr h S) 1/2 x Degree of mixing Level of accuracy of analysis Lowest temperature likely to be met during gaugi

48、ng c Concentration z Exponent b d vISO9555-1:1994(E) BSI 06-1999 5 4.3 Units of measurement The units of measurement used in this part of ISO9555 are those of the International System of Units (SI). 5 Principles of the different dilution methods The basic principle of dilution methods is the additio

49、n of a suitably selected tracer to the flow. Downstream of the injection point, when vertical and lateral dispersion throughout the flow is complete, the discharge may be calculated from the measurement of the dilution of the tracer. If this tracer, or a substance with analytical characteristics similar to the injected tracer, was present in the flow before the injection, the increase in concentration of tracer due to the injection is known as the “concentration of added tracer”. The methods set out in this part