Dynamic analysis of a novel grand trine shared mooring system for floating wind farm

The shared mooring concept is still in the early-stage of development although it is been commonly recognized as a promising solution towards the cost reduction for floating offshore wind turbine (FOWT). However, there is tremendous lack of dedicated rules, standard, project experiences. Moreover, the coupling effects and the nonlinearity of multibody coupled system, the dynamic behavior of shared mooring systems remains uncertain and presents significant challenges. This paper proposes a novel grand trine shared mooring concept which possesses the favorable structural redundancy and can be assembled in modules. A 3-FOWT grand trine system with shared mooring lines and shared anchors has been designed and analyzed under both operating and survival conditions. The fully coupled analyses are conducted to investigate the performance, characteristics, and dynamic behaviors of the complicated system. Results indicate that FOWTs’ displacements and mooring line tensions in the shared mooring are greater than those in a similar single FOWT mooring. The downstream FOWTs exhibits greater offsets and larger natural periods than upstream ones. An oval-shaped displacement envelope is observed for the FOWTs, with limited mooring stiffness provided by shared mooring lines less affected by the in-phase FOWT motions. This study demonstrates the great potential of the grand trine concept for the development of floating wind farms. The 3-FOWT grand trine wind farm meets the engineering requirements for both FOWT displacement and line tension, ensuring the safety of employing shared mooring lines and shared anchors in mooring systems.