Analysis Methods and Design Measures for the Reduction of Noise and Vibration Induced by Marine Propellers

The development of numerical methods for the prediction of underwater radiated noise by marine propellers within the ProNoVi project has resulted in the following automated CFD tools that can be employed at different stages of the design process: - Ship resistance simulation with extraction of information regarding time-varying nominal wake field; - Ship propulsion simulation using a simplified model of propeller represented by an actuator disk with extraction of effective wake field on propeller; - Open water propeller simulation with prediction of cavitation using phase transfer modelling, and prediction of radiated noise using Ffowcs Williams-Hawkings (FW-H) acoustic analogy. - Ship propulsion simulation with prediction of cavitation and radiated noise using the same methods; free surface may also be included in the analysis. The aforementioned numerical methods have been validated against the experimental data acquired during the ProNoVi test campaigns at the two model testing facilities. The methods have been applied to the analysis of propeller cavitation and acoustic performance for several target ship cases studied in the project. Being based on the latest developments of multi-phase flow models and acoustic models, and implementing Scale Resolving Simulation approach to the modelling of turbulence, the developed tools are seen as a considerable step beyond state-of-the-art in industrial CFD simulations. It is of practical importance that the said tools come in the form of automated templates which reduce significantly the effort associated with pre-, post-processing and execution of such simulations. The developed numerical methods can also be applied to the analysis of acoustic performance of other blade systems such as for example wind turbines and tidal turbines, which is an important part of the environment oriented design approach. With these developments realized, the project ProNoVi provides appreciable contribution to the overall objectives of Green Platform Initiative by the RCN and EU Green Deal Initiative.

The project ProNoVi has significantly contributed to the improvements of the experimental and numerical methods to the prediction of noise radiated by ship propulsion systems. This has resulted in better services offered by the R&D providers such as SINTEF Ocean in the field of marine hydroacoustics. Practical experience gained by the industrial partners (Helseth AS) ensures advancement in the design of propellers, rudders and appendages, leading to more environment friendly solutions. The numerical developments in ProNoVi reveal a clear interdisciplinary impact, since the same methodology is applicable to the analysis of noise emitted by tidal energy devices, wind turbines or aircraft propellers. The international collaboration has further strengthened long-term ties between the research and industrial partners from Norway, Germany and Italy, provided platform for new joint initiatives on European arena, and increased visibility of project results to the main stakeholders.

Efficient mitigation of noise and vibrations induced by ships and propellers is seen today as one of the key technologies in achieving the goal of environment friendly shipping worldwide. The propeller cavitation noise is identified as the dominating noise source in the low frequency band of emission, which coincides with important frequencies of perception of baleen whales and fish and thus may have negative impact on their natural activities. The highest levels of on-board noise are frequently noted in the same lower-frequency bands representing health hazards and compromising safety and comfort for crew and passengers. The noise emissions at higher frequencies may interfere with acoustic sensors used by naval, research and oceanographic vessels and underwater monitoring systems. The project ProNoVi is a joint research initiative by SINTEF Ocean (Norway), TUHH (Germany), CNR INSEAN (Italy), Lürssen (Germany), Schottel (Germany) and Helseth (Norway) within the MarTERA ERA-NET Cofund program. Its overall objective is to improve the numerical and experimental methods for the prediction of noise and vibrations induced by a propeller operating behind ship hull in full scale conditions, and to elaborate practical recommendations for the reduction of noise and vibration levels for single and twin-screw vessels of different size and speed range. In addressing this complex, multidisciplinary problem, the project aims at delivering a better understanding of fundamental physical mechanisms related to turbulence, induced vorticity and cavitation dynamics which play a decisive role in generation of tonal and broadband propeller noise. The design oriented tools and advanced CFD methods developed in the project will be used by the researchers and ship and propeller designers, while findings and recommendations are expected to contribute into the development of noise mitigation guidelines by the classification societies.