Effect of hydrodynamic coupling of floating offshore wind turbine and offshore support vessel

摘要

The hydrodynamic coupling of Semi-submersible floating wind turbine and offshore support vessel during walk-to-work operation is studied, which is aimed at investigating the interaction of seakeeping and stationkeeping on both floating structures. The complex multi-body hydrodynamic problem is analyzed by 3-D diffraction and radiation computation in the frequency domain. To identify and evaluate coupling effects, three strategies are proposed in the modeling of the time domain simulation i.e. fully-coupling, no-coupling, and semi-coupling which ignores the interactive wave damping terms between the wind turbine and support vessel. The dynamic and mechanical properties of the wind turbine such as nonlinear mooring tension and damping are validated and reach a good agreement with existing measurements. A series of sea-state that combining different wave conditions and wave headings are taken into account in the study. By analyzing the maximum and spectrum of dynamic response, the surge and sway of support vessel show over-predicted motion due to the overestimate of drift force if hydrodynamic interaction was ignored. Under the following sea, the apparent 'splitting' phenomenon can be observed that makes both structures drift towards opposite directions. The sway and roll of the wind turbine reduce significantly by up to 40% because of the 'shielding effect' that 'cut down' both linear and nonlinear wave forces in the entire frequency range. Sway and heave of support vessel present behavior of 'gap resonance' where different modes of peak or trough are observed whose occurrence is however opposite to sway and heave.