Due to concerns about its effect on marine life, shipping noise is receiving increasing attention within the maritime industry. The primary noise source is known to be the cavitating propeller. In order to check compliance with class rules and upcoming environmental regulations, underwater radiated noise can be predicted during the design of a vessel using model-scale measurements, such as those performed at MARIN’s Depressurized Wave Basin.
As a means to better understand the accuracy and reliability of underwater radiated noise measurements, a round robin test campaign was organised within the Community-of-Practice Noise of the HydroTesting Forum, with the aim of comparing results between several institutes for an open water propeller test setup.
This paper reports the test campaign carried out at MARIN, including details of the experimental setup, data analysis methods and resulting noise levels. Noise was measured using a hydrophone fixed on a bottom-mounted mast, with a dedicated silent towing carriage used to minimise background noise. The effect of applying electrolysis as a means to improve cavitation inception was investigated, and found to be more important for high cavitation numbers. Differences in the radiated noise levels between different test conditions were found to depend largely on the dynamics of the cavitating tip vortex. In general a primary broadband hump was seen, the frequency of which is affected by propeller loading and cavitation number. The spectral shape at higher frequencies could not so easily be related to a clear physical origin however.
Following further data analysis, the results will be compared to those from the other participants in the round robin test campaign.
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For more information contact Frans Hendrik Lafeber.