ISO 18481:2017 ハイドロメトリ — 自由落下のあるチャネルでの端部深さ法を使用した液体の流れの測定 | ページ 2

Foreword

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This document was prepared by Technical Committee ISO/TC 113, Hydrometry, Subcommittee SC 2, Flow measurement structures.

This first edition of ISO 18481 cancels and replaces ISO 3847:1977 and ISO 4371:1984, which have been merged and technically revised.

1 Scope

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:

• a) rectangular with confined and unconfined nappe;
• b) trapezoidal;
• c) triangular;
• d) circular;
• e) 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.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 772 apply.

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Bibliography