PIV Measurements in Thruster-interaction Research

AuthorsHans Cozijn and Rink Hallmann (MARIN)
Conference/JournalMTS Dynamic Positioning Conference 2014, Houston
DateOct 1, 2014

During DP operation the thrusters of the vessel counteract the wind, wave and current forces, so that the vessel can maintain its required position and heading. However, the generated forces can be significantly smaller than what would be expected based on the thrusters' bollard pull characteristics. This is a result of thruster-interaction (or thrust degradation) effects, which occur as a result of interactions with the hull, current and the wake of neighboring thrusters. The understanding and quantification of these interaction effects is essential for an accurate evaluation of the station-keeping capabilities of DP vessels.The wake flow behind azimuthing thrusters was investigated in 5 different situations; (1) in open water, (2) under a flat plate, (3) under a schematical barge, (4) a semi-submersible with 8 azimuthing thrusters and (5) a drill ship with 6 azimuthing thrusters. PIV measurements were carried out for all 5 cases. The wake flow behind a ducted azimuthing thruster shows a circular pattern in the measured cross sections. The wake flows horizontally for the 'Normal' thruster (90 deg gear angle) and is directed slightly downwards for the 'Tilted' thruster (97 deg gear angle).The wake of the 'Normal' thruster under the plate is affected by the presence of the p

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