Dynamic stability analysis of a trimaran-type floating structure with large appendages

Trimaran platforms provide enhanced stability and structural efficiency, making them attractive candidates for floating structures for marine energy systems. However, the integration of large appendages may alter the platform's hydrodynamic behaviour and influence mooring performance. This study investigates the dynamic response of a delta-trimaran floating platform designed to support an ocean-current turbine. The platform is stabilised by a spread mooring system, and four mooring configurations are evaluated: catenary, catenary-clump weight, soft-chain, and semi-taut. Two mooring line compositions are considered, namely chain-polyester rope-chain and chain-wire rope-chain. Coupled hydrodynamic simulations based on the boundary element method are performed using ANSYS® AQWA under combined environmental conditions. Platform motions, mean offsets, and mooring line tensions are analysed. Results show that soft-chain configurations produce the largest offsets, while the semi-taut system limits the mean offset to below 1 m. Peak mooring tensions range from 180 to 375 kN, remaining well below the minimum breaking load.