BS ISO 4359-2013 Flow measurement structures Rectangular trapezoidal and U-shaped flumes《流量测量 矩形 梯形和U形水槽》.pdf

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1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 4359:2013Flow measurement structures Rectangular, trapezoidal andU-shaped flumesBS ISO 4359:2013 BRITISH STANDARDNational forewordThis British Standard is the UK implement

2、ation of ISO 4359:2013. Itsupersedes BS ISO 4359:1983 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee CPI/113/2, Flow measurement structures.A list of organizations represented on this committee can beobtained on request to its secretary.This publicatio

3、n does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 70395 9ICS 17.120.20Compliance with a British Standard cannot confer immunity fromle

4、gal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 28 February 2013.Amendments issued since publicationDate Text affectedBS ISO 4359:2013 ISO 2013Flow measurement structures Rectangular, trapezoidal and U-shaped flumesStructures d

5、e mesure du dbit Canaux jaugeurs col rectangulaire, col trapzodal et col en UINTERNATIONAL STANDARDISO4359Second edition2013-02-15Reference numberISO 4359:2013(E)BS ISO 4359:2013ISO 4359:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwise

6、specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

7、or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 4359:2013ISO 4359:2013(E) ISO 2013 All rights reserved iiiContents PageForeword v1

8、Scope . 12 Normative references 13 Terms and definitions . 14 Symbols 25 Flume types and principles of operation 36 Installation . 66.1 Selection of site . 66.2 Installation conditions 87 Maintenance .108 Measurement of head .118.1 General 118.2 Location of head measurement(s) 118.3 Gauge wells . 11

9、8.4 Zero setting . 129 General equations for discharge .129.1 Discharge based on critical flow in the flume throat 129.2 Discharge based on observed upstream head 139.3 Calculation of stage-discharge relationships .279.4 Approach velocity and coefficient of velocity 279.5 Selection of flume size and

10、 shape 2810 Rectangular-throated flume 3010.1 Description 3010.2 Location of head measurement section 3010.3 Provision for modular flow . 3010.4 Evaluation of discharge for a given observed upstream head 3110.5 Computation of stage-discharge relationship .3510.6 Limits of application 3511 Trapezoida

11、l-throated flumes 3611.1 Description 3611.2 Location of head measurement section 3611.3 Provision for modular flow . 3711.4 Evaluation of discharge Coefficient method 3711.5 Computation of stage-discharge relationship .4011.6 Limits of application 4212 U-throated (round-bottomed) flumes .4312.1 Desc

12、ription 4312.2 Location of head measurement section 4412.3 Provision for modular flow . 4412.4 Evaluation of discharge Coefficient method 4412.5 Computation of stage-discharge relationship .4812.6 Limits of application 5013 Uncertainties of flow measurement 5113.1 General 5113.2 Combining measuremen

13、t uncertainties . 5213.3 Percentage uncertainty of discharge coefficient u*(C) for critical-depth flumes .5413.4 Uncertainty budget. 5414 Example of uncertainty calculations 5514.1 General 55BS ISO 4359:2013ISO 4359:2013(E)iv ISO 2013 All rights reserved14.2 Characteristics Gauging structure 5514.3

14、Characteristics Discharge calculation . 5514.4 Characteristics Discharge coefficient 5514.5 Characteristics Gauged head instrumentation 5614.6 Characteristics Throat width 5614.7 Overall uncertainty in discharge 57Annex A (informative) Simplified head-discharge relationships for flume 58Annex B (inf

15、ormative) Introduction to measurement uncertainty .63Annex C (informative) Sample measurement performance for use in hydrometric worked examples 72Annex D (informative) Spreadsheets for use with this International Standard .75Bibliography .77BS ISO 4359:2013ISO 4359:2013(E)ForewordISO (the Internati

16、onal Organization for Standardization) is a worldwide 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

17、 established has the right to be represented on that 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 standa

18、rdization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for vo

19、ting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all suc

20、h patent rights.ISO 4359 was prepared by Technical Committee ISO/TC 113, Hydrometry, Subcommittee SC 2, Flow measurement structures.This second edition cancels and replaces the first edition (ISO 4359:1983), which has been technically revised. It also incorporates the Technical Corrigendum ISO 4359:

21、1983/Corr.1:1999. ISO 2013 All rights reserved vBS ISO 4359:2013BS ISO 4359:2013Flow measurement structures Rectangular, trapezoidal and U-shaped flumes1 ScopeThis International Standard specifies methods for the measurement of flow in rivers and artificial channels under steady or slowly varying fl

22、ow conditions, using certain types of standing-wave, or critical-depth, flumes.A wide variety of flumes has been developed, but only those which have received general acceptance after adequate research and field testing, and which therefore do not require in situ calibration, are considered.The flow

23、 conditions considered are uniquely dependent on the upstream head, i.e. subcritical flow must exist upstream of the flume, after which the flow accelerates through the contraction and passes through its critical depth (see Figure 1). The water level downstream of the structure is low enough to have

24、 no influence upon its performance.This International Standard is applicable to three commonly used types of flumes, covering a wide range of applications, namely rectangular-throated, trapezoidal-throated and U-throated. Typical field installations are shown in Figure 2. Site conditions are importa

25、nt and Figure 3 shows acceptable velocity profiles in the approach channel.Detailed illustrations of the three types of flumes covered by this International Standard are given as follows:a) rectangular-throated (see Figure 4);b) trapezoidal-throated (see Figure 5);c) U-throated, i.e. round-bottomed

26、(see Figure 6).It is not applicable to a form of flume referred to in the literature sometimes called a “Venturi” flume in which the flow remains subcritical throughout.NOTE This form is based on the same principle as a Venturi meter used within a closed conduit system and relies upon gauging the he

27、ad at two locations and the application of Bernoullis energy equation.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated reference

28、s, the latest edition of the referenced document (including any amendments) applies.ISO 772, Hydrometry Vocabulary and symbols3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 772 apply.INTERNATIONAL STANDARD ISO 4359:2013(E) ISO 2013 All rights reserve

29、d 1BS ISO 4359:2013ISO 4359:2013(E)4 SymbolsUnits of measurement are metres (m) and seconds (s) or derivatives of these.Symbol Quantity Unit of measurementA area of cross-section of flow m2B width of approach channel (width at bed if trapezoidal) mb width of flume throat (width at bed if trapezoidal

30、) mC overall coefficient of discharge (rectangular flumes) non-dimensionalCccoefficient of contraction non-dimensionalCDcoefficient of discharge non-dimensionalCsshape coefficient for trapezoidal throated and U-throated flumes non-dimensionalCvcoefficient allowing for the effect of approach velocity

31、 non-dimensionalD diameter of base of U-throated flume md depth of flow mE specific energy (relative to local invert) mFr Froude number non-dimensionalg gravitational acceleration m/s2H total head (relative to a specified datum, such as a flume invert) mH*correction to the total head mh gauged head

32、mksequivalent sand roughness of surface, after Nikuradse mmL length of prismatic section of the contraction at a flume mL1length of bellmouth entrance mL2length of slope (if present) between throat and downstream still-ing basin or channel floormL3length of stilling basin (if present) mm side-slope

33、(m horizontal to 1 vertical) non-dimensionaln number of measurements in series non-dimensionalP wetted perimeter of flow cross-section mp height of flume invert above the invert of the approach channel mQ discharge m3/sR radius mRe Reynolds number non-dimensionalrpradius of hump mR1radius of bellmou

34、th entrance mS standard deviation Sstandard error of the mean Vaverage velocity through a cross-section, defined by Q/A m/sw water surface width m2 ISO 2013 All rights reservedBS ISO 4359:2013ISO 4359:2013(E)Symbol Quantity Unit of measurementu*(Q)68overall percentage uncertainty in the determinatio

35、n of discharge expressed as a percentage standard deviation at 68 % confi-dence limitsnon-dimensionalu*(b) percentage uncertainty in b (or D) non-dimensionalu*(C) percentage uncertainty in the combined coefficient value non-dimensionalu*(h) percentage uncertainty in h non-dimensionalu*(m) percentage

36、 uncertainty in m non-dimensional kinetic energy correction coefficient (taking into account non-uniformity of velocity distribution)non-dimensional coefficient dependent on mean curvature of stream lines non-dimensional, , coefficients in the uncertainty computation * boundary layer displacement th

37、ickness m a numerical coefficient related to the sideslope angle in trapezoi-dal flumesnon-dimensional kinematic viscosity of the fluid m2/s semi-angle subtended at the centre of curvature of the invert of a U-throated flume between the water surface and the verticalnon-dimensional semi-angle subten

38、ded at the centre of curvature of the invert of a U-throated flume between the water surface and the horizontalnon-dimensionalSubscripts a values in approach channel c values at critical flow d values downstream of the flume e effective values after making allowance for boundary layer effects1 value

39、s assuming an ideal frictionless fluid M maximum value 5 Flume types and principles of operation5.1 The flumes covered by this International Standard are often known as “long-throated” or “critical-depth” flumes and rely fundamentally on the occurrence of critical flow in the flume throat. When this

40、 occurs, there is a unique relationship, for a given flume geometry, between the upstream head and the discharge, that is independent of the conditions downstream of the flume throat. Figure 1 shows a simplified sketch of where the critical depth typically occurs in a critical depth flume and the co

41、nsequent water surface profile through a long-throated trapezoidal flume, together with key hydraulic and geometrical parameters.a) ISO 2013 All rights reserved 3BS ISO 4359:2013ISO 4359:2013(E)b) Section in approach channel upstream from throatc) Section at downstream end of throatKey1 total energy

42、 line2 typical flow profile3 edge of boundary layer displacement thickness* has been exaggerated.Figure 1 Trapezoidal-throated flume showing key geometrical parameters, water surface profile and development of boundary layer displacement thickness (after Figure 8.1, Ref.9)5.2 Because the flume desig

43、n is based on critical flow, this International Standard is largely based on fundamental hydraulic theory, without the need for the large-scale volumetric testing that has been used to derive the coefficients for other forms of flow measurement structure. In order to obtain critical flow within the

44、throat of the flume, the following conditions shall be satisfied.a) The throat of the flume shall be long enough for the flow to be virtually parallel with the flume invert, so that hydrostatic pressure conditions occur at the control section.b) The entrance to the flume throat shall be shaped so th

45、at there are virtually no energy losses between the point where the head is gauged and the point where critical flow occurs.c) The flume throat shall constrict the channel severely enough to raise the energy level in the throat sufficiently high above the energy level downstream to ensure that the f

46、lume is “modular”.5.3 Figure 2 shows examples of flow in rectangular-throated, trapezoidal-throated and U-throated flumes. The choice of flume type from these three depends upon several factors, such as the range of discharge to be measured, the accuracy required, the head available and whether or n

47、ot the flow carries sediment that is liable to accrete. The graphs in Annex A give the user of this International Standard a means of quickly comparing the idealized performance of a range of flume designs, to aid a preliminary choice of the size and form of flume needed to deliver the required disc

48、harge capacity and stagedischarge relationship.4 ISO 2013 All rights reservedBS ISO 4359:2013ISO 4359:2013(E)a) Rectangular-throated flume b) Trapezoidal-throated flume c) U-throated flumeFigure 2 Examples of rectangular-throated, trapezoidal-throated and U-throated flumes5.4 The rectangular-throate

49、d flume is the simplest to construct. It generally proves necessary to raise the invert of the flume throat above the bed of the channel upstream, in order to generate a constriction that is sufficiently severe to allow low flows to be gauged. However, this may result in a regime of cyclic sediment accretion and erosion upstream, which would affect the accuracy and consistency of gauging.5.5 The trapezoidal-throated flume is more appropriate where a wide range of discharge is to be measured with c