Experimental and numerical investigation of mooring line failure dynamic responses for a 15 MW hybrid floating offshore wind turbine

Abstract

Focusing on the integrated IEA 15 MW reference wind turbine and semi-submersible-spar hybrid foundation, this investigation evaluates the transient dynamic response of FOWT following a sudden mooring line failure. A novel 15 MW floating wind turbine platform was designed, employing a taut mooring system. A 1:50 scale model was subsequently fabricated and tested to investigate its performance. The dynamic behavior of the model was verified through free decay and mooring stiffness tests. A series of simulated instantaneous failures in different mooring lines were carried out to elucidate the resultant platform motions and the subsequent tension redistribution among the remaining lines. Results show after mooring failure, tension redistribution follows the proximity principle, with adjacent lines in the same cluster bearing the main additional load. Surge and sway displacements of the platform are the most sensitive, while heave motion remains dominated by wave loads. Pitch and roll motions fluctuate synchronously with mooring tension, reflecting system coupling effects. This investigation provides experimentally validated insights into the transient response mechanisms of a 15 MW-class FOWT under abrupt mooring failure and establishes a systematic numerical–experimental framework that can support mooring system safety design and risk assessment for large floating wind turbines, with quantitative responses corresponding to the investigated taut mooring configuration.