BS ISO 22098:2020 pdf free.Ships and marine technology – Full-scale test method for propeller cavitation 0 bservation and hull pressure measurement.
BS ISO 22098 This document specifies a full-scale test method for propeller cavitation observation and hull pressure measurement. The objective of the test is to investigate the propeller cavitation behaviour and its effects on the hull vibration problems.The test method comprises the specification of the test instrumentation and implementation, construction requirements to ensure structural safety, test and measurement procedures, and reporting documentation.This document is applicable to ships in the following stages: 一before or during sea-trial, prior to delivery stage (vessels under constructions), and after delivery stage.When the ship for full-scale test is in “after delivery stage”, the measurement section on the ship shells,where the observation windows shall be located, shall be designed and constructed not as a part of the ship shell, but as a“sea chest”. The thickness of the shell plates shall be carefully designed.The observation windows shall be considered as “side scuttles”, as a practicable construction that shall meet the applicable requirements, such as IACS UI LL62[3] and/or IMO Resolution MSC. 143(77)[4]:
The observation windows together with their glasses, deadlights and storm covers, if fitted, shall be of approved design, and substantial construction of structural strength safety including water-tightness in accordance with, or equivalent to, recognised national or international standards. Non-metallic frames are not acceptable.When the measurement of the pressure fluctuation and the observation of the cavitation pattern using high-speed cameras are planned at the same time, it is recommended to conduct both simultaneously so that the measured pressure signal can directly be correlated with the observed cavitation pattern[5].Regarding hull pressure measurements, data should be recorded in the time domain and spectrum analysed. The most commonly used data treatment is harmonic analysis after averaging the measured values. From the frequency domain analysis, the signal amplitude can be determined for the harmonics of blade frequency. Thus, the amplitudes and the corresponding phase angles for the signals, such as maximum, minimum, mean and per cent highest amplitude, are determined.In order to analyse the fluctuating pressure signal induced by the propeller, frequency analysis is performed for each blade frequency component. Since the pulse sensor is installed on the propeller rotary shaft, one pulse in the pulse signals corresponds to exactly one rotation period of the propeller.BS ISO 22098 pdf download.