Frederick Jaouen & Willemijn Pauw f.jaouen@marin.nl


The CPF will be a permanently moored and column-stabilised production unit and the largest floating platform of this type in the world. The CPF model is one of the most detailed models that has ever been engineered and manufactured by MARIN. The modelling of the lower deck was especially detailed. This was necessary to model the structure-fluid interactions be- cause they can have a significant influence on the measured slamming forces, air-gap and green water. MARIN assisted the client in the detailed design of the CPF by provid- ing reliable measurements and advice.


The test campaign consisted of two phases. Seakeeping and towing tests were performed in MARIN’s Seakeeping and Manoeuvring Basin to investigate the motions, resistance and towing stability during transportation to the site. In the Offshore Basin in-place tests were performed with all 28 mooring lines and 25 risers connected. The real water depth was modelled but the CPF was moored using a horizontal equivalent (“trun- cated”) mooring system because the anchor footprint was larger than the dimensions of the basin at the tested scale. These mooring tests were performed in combinations of extreme waves, current and wind.


Detailed design In addition to mooring line loads and the CPF’s offsets, important aspects of the tests were the air-gap and slamming forces on the lower deck. To inves- tigate these, the highly accurate lower deck model was equipped with a large number of wave probes and slamming panels. The influence of the wave time-trace realisation on the slamming events was also assessed by testing many seeds. Furthermore, four cameras and one high-speed camera were used to correlate the measurements to the observations made in the basin.


This challenging project was successfully completed and it confirmed that the combi- nation of detailed modelling, accurate meas- urements and flow observation using video camera (including high-speed) is a great combination to help clients when they are working on the detailed design of a CPF.


0 deg. tilted nozzle


5 deg. tilted nozzle


7 deg. tilted nozzle


7 deg. tilted axis, 5 deg. tilted nozzle


7 deg. tilted axis, 7 deg. tilted nozzle


Model with mounted thrusters


Efforts to improve the modelling of thrusters continue


MARIN uses thrusters in many projects. For a typical model scale, around 1:50 to 1:60, rela- tively small thrusters are required. Thrusters for these models are available ranging from 50 mm to 80 mm nozzle diameters. Robert Heerink, r.heerink@marin.nl


In the past these thrusters were always modelled with a horizontal shaft. By tilting the nozzle, the closest possible match was achieved between the client specifications and the modelled thruster for the basin tests. Due to the ever-evolving process in improving the models, new thrusters were built witha 7-degree tilted thruster shaft. Special gears were made for a reliable and durable thruster model and with these new thrusters it is still possible to mount nozzles with a slightly different angle. See figures for examples.


The newly built thrusters give clients the ability to choose a more accurate representation of the thrusters used during model testing.


report 11


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