AS 3778.4.6-1991

1 - AS 3778.4.6-1991 MEASUREMENT OF WATER FLOW IN OPEN CHANNELS - MEASUREMENT USING FLOW GAUGING STRUCTURES - FLAT-V WEIRS
4 - PREFACE
6 - 1 Scope
6 - 2 General
6 - 3 Normative references
6 - 4 Definitions and symbols
6 - 5 Installation
6 - 5.1 Selection of site
7 - 5.2 Installation conditions
7 - 5.2.1 General requirements
7 - 5.2.2 Approach channel
9 - 5.3 Weir structure
9 - 5.4 Downstream of the structure
9 - 6 Maintenance - General requirements
9 - 7 Measurement of head(s)
9 - 7.1 General requirements
9 - 7.2 Gauge wells
10 - 7.3 Zero setting
10 - 7.4 Location of head measurement sections
11 - 8 Discharge relationships
11 - 8.1 Discharge equation
11 - 8.2 Discharge coefficient
11 - 8.3 Velocity of approach factor
12 - 8.4 Shape factor
12 - 8.5 Drowned flow reduction factor
12 - 8.6 Limits of application
15 - 9 Computation of discharge
15 - 9.1 Computation steps
15 - 9.2 Accuracy
15 - 10 Errors in flow measurement
15 - 10.1 General
15 - 10.2 Sources of error
16 - 10.3 Types of error
16 - 10.4 Errors in quantities given in this Inter-The national Standard
17 - 10.5 Errors in quantities measured by the user
17 - 10.6 Combination of uncertainties
17 - 10.7 Presentation of results
17 - 11 Examples
17 - 11.1 Modular flow at low discharge
17 - 11.1.1 Basic data
17 - 11.1.2 Calculation of discharge
18 - 11.1.3 Random uncertainty in calculated discharge
18 - 11.1.4 Systematic uncertainty in calculated discharge
18 - 11.1.5 Total uncertainty in the discharge
18 - 11.2 Drowned flow at high discharge
18 - 11.2.1 Basic data
18 - 11.2.2 Calculation of discharge
19 - 11.2.3 Random uncertainty in calculated discharge
19 - 11.2.4 Systematic uncertainty in calculated discharge
19 - 11.2.5 Total uncertainty in the discharge
20 - Annex A - Nomenclature
21 - Annex B - Velocity distribution
23 - Annex C - Bibliography

Specifies methods for the measurement of water flow in rivers and artificial channels using flat-V weirs under steady or slowly varying flow conditions. It is technically identical with and reproduced from ISO 4377:1990.

This International Standard deals with the measurement of flow in rivers and artificial channels using flat-V weirs under steady or slowly varying flow conditions. 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 weir can be used in both the modular (undrowned) and the drowned ranges of flow. In the modular (undrowned) flow range, discharges depend solely on the upstream water levels and a single measurement of the upstream head will suffice. In the drowned flow range, discharges depend on both the upstream and the downstream water levels and two independent head measurements are required. For the standard flat-V weir, these area) the upstream head;b) the head developed within the separation pocket which forms just downstream of the crest.

First published as AS 3778.4.6-1991.