ISO 20233-1:2018 船舶および海洋技術—船舶設計におけるプロペラキャビテーション騒音評価のモデル試験方法—パート1：ソースレベルの推定 | ページ 2

Foreword

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This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology, SC 8, Ship design.

Introduction

In order to reduce shipping noise, the characteristics of ship noise should be understood. Propeller noise, which is the major noise source in commercial ships, is mainly due to its turns as spectral harmonics and to cavitation as broadband noise. Special ships such as fishery research vessels and military vessels require quiet propellers with less or no cavitation in their operating conditions.

The propeller cavitation noise can be assessed by experimental and/or numerical methods in the propeller design stage. The numerical method such as CFD or empirical formulae might be a good alternative to propeller cavitation noise evaluations. However, the model tests are still used widely to predict the full-scale acoustic source strength of the propeller cavitation for a wide range of frequencies.

This document was developed to provide a standardized model test method for propeller cavitation noise evaluation. This document is aimed for appropriate evaluation of the propeller cavitation noise characteristics at the early design phase via model tests.

1 Scope

This document specifies a model test method for propeller cavitation noise evaluation in ship design.

The procedure comprises reproduction of noise source, noise measurements, post processing and scaling. The target noise source is propeller cavitation. Thus, this document describes the test set-up and conditions to reproduce the cavitation patterns of the ship based on the similarity laws between the model and the ship. The propeller noise is measured at three stages. The measurement targets for each stage are propeller cavitation noise, background noise, and transmission loss. For the source level evaluations, corrections for the background noise and the transmission loss are applied to the measured propeller cavitation noise. Finally, the full-scale source levels are estimated from the model scale results using a scaling law.

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 following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

3.3

cavitation number

σ_n

non-dimensional quantity defined as

	p0	is the total static pressure;
	pv	is the vapour pressure;
	ρ	is the density of the fluid;
	n	is the propeller rotational speed (rps);
	D	is the diameter of the propeller.

Bibliography