AS 3778.4.5:2022 identically adopts ISO 4360:2020, which specifies methods for the measurement of the flow of water in open channels under steady flow conditions using triangular profile weirs. The flow conditions considered are steady flows which are uniquely dependent on the upstream head and non-modular (drowned) flows which depend on downstream as well as upstream levels.
Table of contents
Header
About this publication
Preface
Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Principle
6 Installation
6.1 General
6.2 Selection of site
6.3 Installation conditions
6.3.1 General
6.3.2 Measuring structure
6.3.3 Approach channel
6.3.4 Downstream channel
7 Maintenance
8 Measurement of head(s)
8.1 General
8.2 Location of head measurement(s)
8.2.1 Modular (free) flow
8.2.2 Non-modular (drowned) flow
8.3 Gauge wells
8.4 Zero setting
8.5 Dimensions
9 Discharge characteristics
9.1 Formulae of discharge
9.1.1 Modular (free) flow
9.1.2 Non-modular flow
9.2 Coefficients
9.2.1 Coefficient of discharge, Cd
9.2.2 Coefficient of velocity for modular flow, Cv
9.2.3 Non-modular flow reduction factor, f, with crest tappings
9.2.4 Non-modular flow reduction factor, f, with tailwater recorder
9.3 Limitations
10 Uncertainties of flow measurement
10.1 General
10.1.1
10.1.2
10.1.3
10.1.4
10.1.5
10.2 Combining measurement uncertainties
10.3 Uncertainty of discharge coefficient u(Cd) for the triangular profile weir
10.4 Uncertainty budget
11 Example
11.1 General
11.2 Characteristics — Gauging structure
11.3 Characteristics — Gauged head instrumentation
