A study of numerical ship underwater noise prediction

• Underwater noise for an LNG carrier was predicted numerically
• Results were validated with field measurement data.
• The results from various modelling variations were compared.
• Results suggest that quadrupole sources cannot be neglected.
• Suitability of different variations depends on application.

Underwater noise has become a key area of concern to the marine industry, with pressure from government bodies and conservation groups urging the industry to examine and address the negative effects on marine fauna. Numerical methods are rapidly gaining popularity for hydroacoustic applications. These methods have the distinct advantage of allowing designers to understand the noise characterist"run_autics of a vessel during the design stages and therefore allowing corrective action to be taken promptly before the vessel is built. Numerical methods can provide highly accurate tools for noise level and propagation prediction, as well as giving insight into the flow field and other key aspects. This study uses a CFD-based URANS hydrodynamic prediction approach, coupled with the Ffowcs-Williams Hawkings (FWH) equation for noise propagation. Field measurement data for an LNG carrier was used for validation of the numerical results, and the same vessel was used in the numerical modelling. A variety of modelling variables were considered, to ascertain which should be modelled for different applications and required levels of prediction accuracy. These variables included the free surface and the capture of quadrupole noise sources, as well as a comparison of propeller representation approaches.