Tug master in action during tow-out manoeuvre

there is an optimal transfer of knowledge from the earlier engineering phase by Dockwise to the operations phase.

A second objective is to model and test all the simulation components and to verify and document their hydrodynamic behaviour. The individual components for the float-over simulations consist of the spar, its asymmetric mooring system (three anchor pontoons, four tension barges, seven mooring lines), the S-Class vessels, assisting tugs and the topside itself. The simulation model of the spar with the mooring system used for the verification study is shown.

aNySIM can accurately simulate the behaviour of multiple floating bodies in conditions of combined swell, wind-seas, current and wind. The combined low frequency and wave frequency motions of each body are calculated in 6 degrees of freedom in the time-domain, using a retardation function approach. During the verification study, aNySIM is used to verify the properties of the complex composition of lines and fenders between the spar, the S-Class vessels and the topside during the mating operation in

10 report

detail to ensure the realistic behaviour of the complete system. An accurate simulation model is essential for this type of training programme. The hydrodynamic behaviour of the compo- nents of the simulation model is reflected in natural periods and damping of the moored spar and the stiffness of the fender system between the spar and the topside. By means of numerical decay and static load tests, the hydrodynamic behaviour of the components is calculated.

Results of the verification study are documented in a preparation report, which enables Dockwise to verify the simulation model against its design calculations, prior to the full mission simulation training.

Full mission simulations Following the verification study a workshop was carried out, in which the towmaster of Dockwise Hans Bosch, and a team comprising the superin- tendent, winch operators and tugmasters performed the operation on a set of MARIN bridge simulators. The newly developed DOLPHIN simulator system uses the same modelling technology as aNySIM. This means that the components, which were

validated in the verification study, could be imported directly into the simulator database. The workshop programme was jointly developed by MARIN and Dockwise. During meetings the input data was agreed and database development was coordinated. This resulted in a carefully thought-out simulation programme and corresponding set of scenarios. The database was also made available to the towmaster, who could simulate parts of the operation on his laptop using the same simulation software. In a four-day simulation session the crucial parts of the operation were executed under various weather conditions. Using the DOLPHIN software, scenarios could be amended at very short notice, allowing the programme to be adjusted whenever necessary.

The operations included the composition of the so-called ‘catamaran vessel’, consisting of the topside of Aasta Hansteen and two S-Class heavy lift vessels. Additionally, the transit with the catamaran vessel was practised with different tug combinations. But in the end, most attention was paid to the positioning of the topside on the spar.

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