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Göteborg, Sweden

Gaggero S.,University of Genoa | Gaggero T.,University of Genoa | Villa D.,University of Genoa | Rizzuto E.,University of Genoa | Hallander J.,SSPA
Towards Green Marine Technology and Transport - Proceedings of the 16th International Congress of the International Maritime Association of the Mediterranean, IMAM 2015

A numerical investigation of the impact of the speed reduction achieved by pitch or propeller Revolutions Per Minute (RPM) variations on propeller performances is proposed. A test case is selected from the European Project AQUO, for which experimental data are available. Numerical selfpropulsion analyses are carried out to assess the off-design propeller functioning conditions of the propeller. Results, in terms of self-propulsion points and predicted pressure pulses in the various conditions under investigation (design speed at design pitch, reduced speed at reduced pitch and at reduced RPM), are compared with the available experimental measurements. On the basis of the predicted pressure pulses and cavitation volumes, conclusions are drawn about the acoustic impact of different strategies for realizing off-design operative conditions and on the possibility of ranking them by numerical methods. © 2015 Taylor and Francis Group. Source

Audoly C.,DCNS S.A. | Rousset C.,DCNS S.A. | Rizzuto E.,UNIGE | Mullor R.S.,Tecnicas y Servicios de Ingenieria | And 2 more authors.
MTS/IEEE OCEANS 2015 - Genova: Discovering Sustainable Ocean Energy for a New World

The European AQUO project started in October 2012, in the scope of the FP7 European Research Framework, for three years duration. The final goal is to provide policy makers with practical guidelines and solutions, in order to mitigate underwater noise footprint due to noise radiation from ships. For a maritime area under consideration, mitigation solutions can be split into two categories: the first one is to reduce the underwater noise emission of the noisiest vessels sailing in the area, and the second one is related to ship traffic management. The present paper addresses the first type, and the purpose is to assess the efficiency of different mitigation measures, corresponding to the dedicated task 5.2 of AQUO Project. First, an overview of a comprehensive list of possible mitigation measures is presented. Then, study cases corresponding to reference vessels are defined and several mitigation measures are tested in order to give an estimation of the reduction of ship source level (underwater radiated noise). To achieve this task, different modeling techniques and experimental results from previous tasks of AQUO Project are used. Special care must be taken on the relative importance of the part of radiated noise due to internal machinery and engines, and the part due to propeller(s). The analysis of the result allow identifying the most promising solutions. © 2015 IEEE. Source

Tani G.,University of Genoa | Viviani M.,University of Genoa | Hallander J.,SSPA | Johansson T.,SSPA | Rizzuto E.,University of Genoa
Applied Ocean Research

The prediction of propeller induced pressure fluctuations and underwater radiated noise is a subject of great and increasing interest in marine engineering. Nevertheless, the full-scale prediction of these negative effects, even though based on dedicated model scale tests represents still a challenging task. This is due to different phenomena, among which scale effects on cavitation and ship wake, confined environment and near field effects in model tests play an important role; the analysis of these problems is made difficult by the rather limited amount of available data from sea trials and to the complexities of the phenomena, most of which related to cavitation on the propeller blades, that are present in the measurements carried out in cavitation tunnels, depressurized towing tanks or circulating channels. In the present work, the subject has been studied with reference to a four blades conventional CP propeller of a coastal tanker. Cavitation tunnel tests have been carried out in two rather different facilities, at UNIGE cavitation tunnel and at SSPA large cavitation tunnel. Results from model scale tests processed with different treatments are then compared with full scale measurements performed by SSPA on the same propeller in terms of cavitation extension and radiated noise. The analysis is aimed at assessing the effectiveness of different experimental setups, testing procedures and scaling laws. © 2016 Elsevier Ltd. Source

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