Underwater radiated noise investigations of cavitating propellers using medium size cavitation tunnel tests and full-scale trials

There has been a growing recent concern on the environmental impact to be caused by Underwater Radiated Noise (URN) from the worldwide increase in shipping traffic. In order to address this concern several collaborative European research projects have been started including the SONIC project under the umbrella of the 7 th Framework Programme (FP) of the EU. As one of the participants in SONIC (Suppression Of Noise Induced by Cavitation) Newcastle University has been involved in various full-scale trials and model-scale testing campaigns using their own research catamaran " The Princess Royal " and medium size cavitation tunnel " The Emerson Cavitation Tunnel ". The full-scale trial campaign was conducted in the North East region of England and involved various on-board and off-board measurements including the URN from suspended arrays of hydrophones and propeller cavitation observations. The cavitation tests were conducted using a 1/3.5 scale dummy model of the starboard side demi-hull of The Princess Royal and simulated some of the full-scale trial runs covering a range of non-cavitating and cavitating conditions. This paper presents the details of the cavitation tunnel tests with a specific emphasis on the comparisons of the extrapolated URN data recorded during these tests and full scale measurements. The comparisons indicated that, whilst the ideal experimental approach was to conduct involved tests with a full-hull model in large cavitation tunnels, the medium size facilities, using dummy-hull models with wake screens, can still provide a very useful means for the URN investigations with rapid turn around and an economical way of conducting such tests.