Model test investigation of the influence of damping on the vortex induced motions of deep draft semi-submersibles

AuthorsJoost Sterenborg, Arjen Koop, Jaap de Wilde, Vimal Vinayan, Arun Antony, John Halkyard
Conference/JournalOMAE ASME 35th International Conference on Ocean, Offshore and Arctic Engineering, Busan, South Korea, 2016
DateJun 19, 2016
Model test investigation of the influence of damping on the vortex induced motions of deep draft semi-submersibles using a novel active damping device
Vortex Induced Motions (VIM) of semi-submersibles occur when the vortex shedding frequency is close to the natural frequency of the semi-submersible in the direction transverse to the current. Recent studies suggest that the magnitude of VIM predicted during model tests is higher than that observed in the field. Among others, the damping effect provided by the risers and mooring lines is regarded as one of the reasons for this difference. In this paper the setup and results are presented for model tests to investigate the influence of damping on VIM. For these model tests an active damping system was developed, which introduces an actively controlled external force mimicking a damping force. This applied damping force is based on the floater sway motion and sway velocity. With this system the introduced damping level can easily be controlled and verified without changing the stiffness of the system. In this paper the advantages and disadvantages of this active damping system are presented. The VIM tests were conducted for two semi-submersibles: a paired-column semi with eight columns and a four column semi. Reduced velocities ranged from Ur=3 to Ur=10 and different levels of additional linear damping were applied to the floaters in the direction transverse to the current dire

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Tags
stability, seakeeping and ocean engineeringwaves, impacts and hydrostructuralmeasurements and controldata sciencerenewablesoil and gasinfrastructuremarine systemslife at seamodel testingresearch and developmentloads and responsesmotionsvortex induced motions (vim)offshore engineeringresearch