BS ISO 18481:2017
$142.49
Hydrometry. Liquid flow measurement using end depth method in channels with a free overfall
| Published By | Publication Date | Number of Pages |
| BSI | 2017 | 28 |
This document specifies a method for the estimation of the sub-critical flow of clear water in a smooth, essentially horizontal channel (or a gently sloping channel), abruptly discontinued at bottom by a hydraulic structure, with a vertical drop and discharging freely. Such an overfall forms a control section and offers a means for the estimation of flow using the end depth measurement method. A wide variety of channel cross-sections with overfall have been studied, but only those which have received general acceptance after adequate research and testing, and therefore do not require in situ calibration, are considered. This document covers channels with the following types of cross-sections:
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rectangular with confined and unconfined nappe;
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trapezoidal;
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triangular;
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circular;
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parabolic.
The flow at the brink is curvilinear; therefore, the measured depth at the drop is not equal to the critical depth as computed by the principle based on assumption of parallel flow. However, the end depth and the critical depth (as in the case of the assumption of parallel flow) have unique relation, which is used to estimate the flow through these structures.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 2 | undefined |
| 7 | Foreword |
| 8 | 1 Scope 2 Normative references 3 Terms and definitions |
| 9 | 4 Symbols and abbreviated terms 5 Principle 6 Installation 6.1 General 6.2 Selection of site |
| 10 | 7 Measurement of end depth 7.1 General 7.2 Head measuring devices 7.3 Gauge datum 8 Maintenance 8.1 General |
| 11 | 8.2 Types |
| 12 | 8.3 Specifications for the drop structure |
| 13 | 8.4 Specifications for installation 8.5 Determination of gauge zero 8.6 Discharge relationship 8.7 Coefficient of discharge 8.7.1 Confined nappe 8.7.2 Unconfined nappe 8.8 Practical limitations |
| 14 | 8.9 Uncertainty of measurement 9 Triangular channel drop structure 9.1 Specifications for the drop structure 9.2 Specifications for installation 9.3 Specifications for head measurement 9.3.1 General 9.3.2 Determination of channel angle |
| 15 | 9.3.3 Determination of gauge zero 9.4 Discharge formula — Unconfined 9.5 Practical limitations 9.6 Uncertainty of measurement |
| 16 | 10 Trapezoidal channel drop structure 10.1 Specifications for the drop structure 10.2 Specifications for head measurement 10.2.1 General 10.2.2 Determination of gauge zero 10.3 Discharge formula — Unconfined |
| 17 | 10.4 Practical limitations 10.5 Uncertainty of measurement |
| 18 | 11 Circular channel drop structure 11.1 Specifications for the drop structure 11.2 Specifications for head measurement 11.2.1 General 11.2.2 Determination of gauge zero 11.3 Discharge formula — Unconfined |
| 20 | 11.4 Practical limitations 11.5 Uncertainty of measurement |
| 21 | 12 Parabolic channel drop structure 12.1 Specifications for the drop structure 12.2 Specifications for head measurement 12.2.1 General 12.2.2 Geometry 12.2.3 Determination of gauge zero |
| 22 | 12.3 Discharge formula — Unconfined 12.4 Practical limitations 13 Uncertainties of flow measurement 13.1 General 13.2 Sources of error |
| 23 | 13.3 Kinds of error 13.4 Uncertainties in coefficient values |
| 24 | 13.5 Uncertainties in measurements made by the user 13.6 Combination of uncertainties to give total uncertainty on discharge 13.7 Example |
| 27 | Bibliography |
