Assessment of Measures to Mitigate URN Emissions from Ships

Paper in proceeding, 2026

As underwater radiated noise emission from shipping has been acknowledged as an environmental pressure to the ocean, implementation of mitigation measures is in progress. To do this effectively, there is need to improve our methods to assess the effect of different measures, from the aspect of a regulating body as well as for ship owner and technical supplier. This paper will start by briefly reviewing studies on different measures and methods to
assess the noise emissions. We will then focus on computational prediction methods and highlight some of the potential capabilities and issues in doing CFD-based assessment of ship noise. The radiated sound from cavitation on a sphere has been computed using both incompressible and compressible flow models, comparing different Ffowcs Williams and Hawkings (FW-H) set-ups, analysing the impact of neglecting flow compressibility and the choice of
surfaces for sound source sampling. Attention is then shifted to the prediction of cavitation noise from a ship in full scale, again looking at different FW-H set-ups; instead of comparing with direct compressible predictions, sea-trial and model scale experimental data are available. For both studies, we note a high sensitivity to how the simulation is performed and the FW-H set-up towards predicted noise emissions. This sensitivity needs to be carefully considered when assessing different mitigation techniques.