Hydrodynamic responses of the triangle-shaped semi-submersible platform under wave loadings by an incompressible material point method and finite element method model

Floating platforms are essential foundations that enable the stable operation of floating offshore wind turbines (FOWTs). This paper employs a coupled model that combines the Incompressible Material Point Method and Finite Element Method (IMPM-FEM) to analyze the hydrodynamic behavior of the foundation of China's first deep-sea FOWT, 'Fuyao,' a triangle-shaped semi-submersible platform (Tri-SSP), under regular and irregular wave loadings. The experimental results about the impact of dam-break waves on an elastic baffle and the hydrodynamic responses of the OC4-DeepCwind platform are used to validate the proposed IMPM-FEM model. Then, the influence of regular wave impact on the mooring system and Tri-SSP is studied, revealing increased tensions in the leading mooring lines (i.e. Fairlead Group 1), along with a 180 degrees phase difference between surge and pitch motions and an approximately 90 degrees phase difference between surge and heave motions. The effects of the incidence angle of 1-h irregular waves on the Tri-SSP's hydrodynamic characteristics are also investigated and it is found that both the surge and pitch motions exhibit notable variations depending on the wave conditions and incidence angles. Furthermore, the extreme tensions reaching nearly 8000 kN at 2858 s observed in Fairlead Group 1 when exposed to an incidence angle of 0 degrees underscore the need for mooring line reinforcement to withstand wave-induced forces. The study emphasizes the importance of considering wave incidence angles in platform design and highlights the asymmetrical effects on platform dynamics.