12 m free-sailing model with 70 pressure gauges


Oasis of the Seas The next generation in cruising matched


by its equivalent in model testing Oasis of the Seas, the


largest cruise liner ever in the world, will set sail in December. As this magnificent ship


prepares for its maiden voyage, Report takes


the opportunity to focus on the measurement


techniques used in this interesting and


challenging project.


Giedo Loeff, Jaap van Heerd & Reint Dallinga g.loeff@marin.nl


M


ARIN partnered with the ship- yard, STX Europe in Finland, the owner RCCL, and engineering


team to meet the stringent performance requirements set for this 360 metre plus vessel to ensure efficiency, comfort and safety. In fact, STX Europe already started to work with MARIN on the development and design of this next-generation cruise liner back in 2005. This cooperation was based on a long-standing relationship between the shipyard and MARIN, which is also highlighted in this issue.


Flexural response in seaway One challenging task was to quantify the slam- ming-induced flexural response of the ship at an early stage of development and to compare this with the response of an exist- ing ship. The first step was to measure the wave-induced impact pressures. Over 70 pressure gauges were mounted on large- scale models (12 metres) of the reference ship and these were tested in a free-sailing model in the Seakeeping & Manoeuvring Basin. Associating each pressure with an area and an orientation, yielded input for dynamic finite element calculations on the structural vibrations of each ship. Hull girder vibrations were validated in two


ways. First of all STX Europe, which performed the finite element calculations, compared the calculated values with the shipyard’s continuous measurements at sea and the comparison showed excellent agreement. Secondly, results were com- pared with direct measurements with a segmented 7-metre, free-sailing model. In this model the vertical and horizontal two- and three-node bending modes were modelled with a simple flexible backbone. A new development here was the modelling of the first torsion mode. The prediction of slamming-induced, passenger discomfort required careful measurements on the vibration accelerations in each of the six segments. In addition, the horizontal and vertical bending and torsion moments were recorded by means of strain gauges.


Manoeuvrability With frequent calls to harbours, confined bays and passages through fairways and channels, the low speed manoeuvring capability of this enor- mous vessel had to meet stringent require- ments and was given the highest priority. MARIN’s Shallow Water Basin and Full Mis- sion Simulator were used to evaluate this. Measurements determined the forces and interactions on the vessel due to the 60MW


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