AS 3778.4.7-1991

1 - AS 3778.4.7-1991 MEASUREMENT OF WATER FLOW IN OPEN CHANNELS - MEASUREMENT USING FLOW GAUGING STRUCTURES - RECTANGULAR...
4 - PREFACE
6 - 1 Scope and field of application
6 - 2 References
6 - 3 Definitions and symbols
6 - 4 Units of measurement
6 - 5 Selection of the type of flume
7 - 6 Installation
7 - 6.1 Selection of site
7 - 6.2 Installation conditions
7 - 6.2.1 General requirements
7 - 6.2.2 Approach channel
8 - 6.3 Flume structure
8 - 6.4 Downstream conditions
8 - 7 Maintenance - General requirements
8 - 8 Measurement of head
8 - 8.1 General requirements
9 - 8.2 Gauge well
9 - 8.3 Zero setting
9 - 9 Determination of discharge
9 - 9.1 General equations for discharge
10 - 9.2 Calculation of discharge from observed head
10 - 9.3 Calculation of stage-discharge relationships
11 - 9.4 Approach velocity
11 - 10 Rectangul ar throated flume
11 - 10.1 Description
12 - 10.2 Location of head measurement section
12 - 10.3 Provision for modular flow
12 - 10.4 Evaluation of discharge
13 - 10.5 Computation of stage-discharge relationship
13 - 10. 6 Limits of application
13 - 10.7 Uncertainty of measurement
13 - 11 Trapezoidal throated flumes
13 - 11.1 Description
14 - 11.2 Location of head measurement section
14 - 11.3 Provision for modular flow
14 - 11.4 Evaluation of discharge
15 - 11.5 Computation of stage-discharge relationship
16 - 11.6 Graphical approach to design
16 - 11.7 Limits of application
17 - 11.8 Uncertainty of measurement
17 - 12 U-throated (round-bottomed) flumes
17 - 12.1 Description
17 - 12.2 Location of head measurement section
17 - 12.3 Provision for modular flow
18 - 12.4 Evaluation of discharge
19 - 12.5 Computation of stage-discharge relationship
20 - 12.6 Limits of application
20 - 12.7 Uncertainty of measurement
20 - 13 Errors in flow measurement
20 - 13.1 General
20 - 13.2 Sources of error
21 - 13.3 Kinds of error
21 - 13.4 Errors in coefficient values
21 - 13.5 Errors in measurement
22 - 13.6 Combination of uncertainties to give overall uncertainty on discharge
23 - Annex A - Guide for the selection of weirs and flumes for the measurement of the discharge of water in open channels
23 - A.1 Scope and field of application
23 - A.2 Types of standard weirs and flumes
23 - A.3 criteria for sel ection of standard weirs or flumes
25 - Annex B - Symbols and units
27 - Annex C - Velocity distribution
28 - Annex D - Computation of discharge using boundary layer theory
28 - D.1 General
28 - D.2 Rectangular throated flume
28 - D.3 Trapezoi dal throated flumes
29 - D.4 U-throated (round-bottomed) flumes
31 - Annex E - Examples illustrating methods for the computation of discharge
31 - E.1 Calculation of single discharge for a trapezoidal throated flume
31 - E.2 Calculation of single discharge for a trapezoidal throated flume; boundary layer corrections
32 - E.3 Calculation of stage-discharge curve for trapezoidal flume
32 - E.4 Calculation of stage-discharge curve for trapezoidal throated flume; boundary layer corrections
33 - E.5 Calculation of single discharge for a U-throated flume;
33 - E.6 Calculation of single discharge for a U-throated flume; boundary layer corrections
34 - E.7 Calculation of stage-discharge curve for a U-shape throated flume
34 - E.8 Calculation of stage-discharge curve for a U- throated flume; boundary layer corrections
35 - Annex F - Example of the computation of the overall uncertainty of discharge measurement
36 - Annex G - Determination of height of hump - Rectangular throated flumes
36 - G.1 Stage-discharge relation

This Standard specifies methods for the measurement of water flow in rivers and artificial channels under steady or slowly varying flow conditions, using certain types of standing-wave (or critical depth) flumes. It is technically identical with and reproduced from ISO 4359:1983.

This International Standard deals with the measurement of flow in rivers and artificial channels under steady or slowly varying flow conditions, using certain types of standing-wave (or critical depth) flumes. A wide variety of flumes have been designed 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. Three types of flumes, covering a wide range of applications are recommended as follows:a) Rectangular-throated (see figure 1). b) Trapezoidal-throated (see figure 4). c) U-throated, i.e. round-bottomed (see figure 5).The flow 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, and the water level beyond the structure is low enough to have no influence upon its performance.Annex A gives the guidelines for the selection of weirs and flumes for the measurement of the discharge of water in open channels.

First published as AS 3778.4.7-1991.