SEA modelling of a large ship
For this recent project, ISVR Consulting was asked to predict the noise levels in the critical areas of a ship, including crew or passenger accommodation, work and machinery rooms. The ship was a large tanker and the task was undertaken using Statistical Energy Analysis (SEA) techniques.
Statistical Energy Analysis was used to model the critical accommodation and work spaces of the ship, to predict the noise levels from engines and machinery reaching critical areas via airborne and structure-borne paths, and to deduce whether the noise levels would meet the International Maritime Organization (IMO) Guidelines for noise levels on board ships.
The figure shows the SEA model of part of the tanker. The structural subsystem layout of the model was built from AutoSEA2 elements, such as uniform plates, rib-stiffened plates, and singly curved shell elements. The model had approximately 2,500 nodes and 850 structural subsystems, while 65 acoustical subsystems were used to represent the critical work, machinery and accommodation areas.
A user-defined database was generated for standard trim configurations in the critical areas of the ship. The trim was only applied to the structural elements forming part of any respective acoustic subsystem. Finally, a 'semi-infinite fluid', energy sink was used to model the radiation into the sea water and subsystems were connected to this sink to provide the correct effective surface area for each of the different loading conditions of the ship.