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1、INTERNATIONAL STANDARD ISO 4377 Third edition 2002-10-01 Reference number ISO 4377:2002(E) ISO 2002 Hydrometric determinations Flow measurement in open channels using structures Flat-V weirs Dterminations hydromtriques Mesure de dbit dans les canaux dcouverts au moyen de structures Dversoirs en V ou
2、vert Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/11/2007 20:22:55 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 4377:2002(E) ii ISO 2002 All rights re
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6、 ISO 2002 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in
7、the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.ch Web www.iso.ch Printed in Switzerland Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA
8、 Technical Standards 1/9972545001 Not for Resale, 04/11/2007 20:22:55 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 4377:2002(E) ISO 2002 All rights reserved iii Contents Page 1Scope . 1 2Normative references . 1 3Terms and definitions 1 4Symbols 3 5Characteristics of
9、 flat-V weirs . 4 6Installation 4 7Maintenance . 7 8Measurement of head(s) 8 9Discharge relationships 12 10Computation of discharge . 25 11Uncertainties in flow measurement 27 12Examples 30 Annex AVelocity distribution 35 Copyright International Organization for Standardization Provided by IHS under
10、 license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/11/2007 20:22:55 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 4377:2002(E) iv ISO 2002 All rights reserved Foreword ISO (the International Organization for Standardization) is a world
11、wide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on t
12、hat committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in
13、 accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Atten
14、tion is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International Standard ISO 4377 was prepared by Technical Committee ISO/TC 113, Hydrometric
15、determinations, Subcommittee SC 2, Notches, weirs and flumes. This third edition cancels and replaces the second edition (ISO 4377:1990), which has been technically revised to give a rigorous version of the basic discharge equation for a weir operating under drowned flow conditions. The successive a
16、pproximation method for calculating discharges is reintroduced. Annex A forms a normative part of this International Standard. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/11/2007 20:
17、22:55 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARDISO 4377:2002(E) ISO 2002 All rights reserved 1 Hydrometric determinations Flow measurement in open channels using structures Flat-V weirs 1Scope This International Standard describes the methods of
18、 measurement of flow in rivers and artificial channels under steady or slowly varying conditions using flat-V weirs (see Figure 1). Annex A gives guidance on acceptable velocity distribution. 2Normative references The following normative documents contain provisions which, through reference in this
19、text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most
20、recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 772, Hydrometric determinations Vocabulary and symbols ISO/T
21、R 5168, Measurement of fluid flow Evaluation of uncertainties Guide to the expression of uncertainty in measurement (GUM), BIPM, IEC, IFCC, ISO, IUPAC, INPAP and OIML 3Terms and definitions For the purposes of this International Standard, the terms and definitions given in ISO 772 apply. Copyright I
22、nternational Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/11/2007 20:22:55 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 4377:2002(E) 2 ISO 2002 All rights reserved Key 1Head
23、gauging section 2Upstream tapping 3Stilling wells 4Crest tapping 5Flow 6Downstream tapping 7 above stilling basin level 8Permissible truncation a but equal or greater than b but equal or greater than Figure 1 Triangular profile flat-V weir 100 mm 10H?3Hmax 25H?3Hmax Copyright International Organizat
24、ion for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/11/2007 20:22:55 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 4377:2002(E) ISO 2002 All rights reserved 3 4Symbols The following is a list
25、 of symbols used, with the corresponding units of measurement. SymbolaMeaningUnits Area of cross-section of flow Width of approach channelm Crest widthm Coefficient of dischargeNon-dimensional Drowned flow reduction factorNon-dimensional Coefficient of approach velocityNon-dimensional Uncertainty in
26、 head measurementm Uncertainty in gauge zerom Uncertainty in head correction factorm Gravitational acceleration (standard value) Total head above lowest crest elevationm Maximum total head above crest elevationm Gauged head above lowest crest elevationm Separation pocket headm Effective separation p
27、ocket head relative to lowest crest elevationm Difference between lowest and highest crest elevationsm ConstantsNon-dimensional Head correction factorm Crest cross-slope (1 vertical: horizontal)Non-dimensional Number of measurements in a setNon-dimensional Difference between mean bed level and lowes
28、t crest elevationm Discharge Standard deviation of the mean of several head readingsm Mean velocity at cross-sectionm/s Mean velocity in approach channelm/s Percentage uncertainty in discharge coefficientNon-dimensional Percentage uncertainty in coefficient of velocityNon-dimensional Percentage unce
29、rtainty in drowned flow reduction factorNon-dimensional Percentage uncertainty in head measurementNon-dimensional Percentage uncertainty in discharge measurementNon-dimensional Shape factorsNon-dimensional Coriolis energy coefficientNon-dimensional Subscript 1denotes upstream value 2denotes downstre
30、am value edenotes “effective” and implies that corrections for fluid effects have been made to the quantity a In cases where the subscript of a symbol also contains a subscript, it is house style to write the second subscript on the same line after a comma. Thus is written , and is written Am2 B b C
31、D Cdr Cv eh eh,0 ek,h gm/s2 H Hmax h hp hpe h?,H? K1,K2 kh mm n p Qm3/s sh v va XC,D XC,v XC,dr Xh XQ Zh,ZH ekhek,hXCdrXC,dr Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/11/2007 20:22
32、:55 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 4377:2002(E) 4 ISO 2002 All rights reserved 5Characteristics of flat-V weirs The standard flat-V weir is a control structure the crest of which takes the form of a shallow V when viewed in the direction of flow. The st
33、andard weir is of a triangular profile with an upstream slope of 1 (vertical): 2 (horizontal) and a downstream slope of 1:5. The cross-slope of the crest line shall not be steeper than 1:10. The cross-slope shall lie in the range of 0 to 1:10 and, at the limit when the cross-slope is zero, the weir
34、becomes a two dimensional triangular profile weir. The weir can be used in both the modular and drowned ranges of flow. In the modular flow range, discharges depend solely on upstream water levels and a single measurement of upstream head is sufficient. In the drowned flow range, discharges depend o
35、n both upstream and downstream water levels, and two independent head measurements are required. For the standard flat-V weir, these are: the upstream head; the head developed within the separation pocket which forms just downstream of the crest or, as a less accurate alternative, the head measured
36、just downstream of the structure. The flat-V weir will measure a wide range of flows and has the advantage of high sensitivity at low flows. Operation in the drowned flow range minimizes afflux at very high flows. Flat-V weirs shall not be used in steep rivers, particularly where there is a high sed
37、iment load. There is no specified upper limit for the size of this structure. Table 1 gives the ranges of discharges for three typical weirs. The flat-V weir can be designed to minimize the obstruction to the passage of fish in the appropriate flow range. Flow is concentrated towards the centre of t
38、he downstream face and this provides the depth of water required by migratory fish. 6Installation 6.1Selection of site 6.1.1The weir shall be located in a straight section of the channel, avoiding local obstructions, roughness or unevenness of the bed. 6.1.2A preliminary study of the physical and hy
39、draulic features of the proposed site shall be made, to check that it conforms (or can be constructed or modified to conform) to the requirements necessary for measurement of discharge by the weir. Particular attention shall be paid to the following: a)the adequacy of the length of channel of regula
40、r cross-section available (see 6.2.2.2); b)the uniformity of the existing velocity distribution (see annex A); c)the avoidance of a steep channel (see 6.2.2.6); d)the effects of increased upstream water levels due to the measuring structure; e)the conditions downstream (including such influences as
41、tides, confluences with other streams, sluice gates, mill dams and other controlling features, such as seasonal weed growth, which might cause drowning); Table 1 Ranges of discharge Elevation of crest above bed Crest/cross-slope ratio WidthRange of discharge 0,21:1040,015 to 5 0,51:20200,030 to 180
42、(within maximum head of ) 1,01:40800,055 to 630 (within maximum head of ) mmm3/s 3 m 3 m Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/11/2007 20:22:55 MDTNo reproduction or networking
43、 permitted without license from IHS -,-,- ISO 4377:2002(E) ISO 2002 All rights reserved 5 f)the impermeability of the ground on which the structure is to be founded and the necessity for piling, grouting or other means of controlling seepage; g)the necessity for flood banks, to confine the maximum d
44、ischarge to the channel; h)the stability of the banks, and the necessity for trimming and/or revetment; i)the uniformity of the approach channel section; j)the effect of wind on the flow over the weir, especially when it is wide and the head is small and when the prevailing wind is in a transverse d
45、irection. 6.1.3If the site does not possess the characteristics necessary for satisfactory measurements, or if an inspection of the stream shows that the velocity distribution in the approach channel deviates appreciably from the examples shown in Figure 2, the site shall not be used unless suitable
46、 improvements are practicable. a)b) c)d) e)f) Figure 2 Examples of velocity profiles in the approach channel ? left right 1 ? 100=6,9 % ? left right 1 ? 100=9,0 % ? left right 1 ? 100=12,3 % ? left right 1 ? 100=1,2 % ? left right 1 ? 100=0,6 % ? left right 1 ? 100=0,9 % Copyright International Orga
47、nization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/11/2007 20:22:55 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 4377:2002(E) 6 ISO 2002 All rights reserved 6.2Installation conditions
48、6.2.1General requirements The complete measuring installation consists of an approach channel, a weir structure and a downstream channel. NOTE 1The condition of each of these three components affects the overall accuracy of the measurements. Installation requirements include such features as the surface finish of the weir, the cross-sectional shape of the channel, channel roughness and the influe