An analytical model for early-stage mooring design in floating wind turbines

The design of mooring systems for Floating Offshore Wind Turbines presents significant engineering challenges, particularly in managing structural dynamics and fluid-structure interactions. While analytical models are less developed in this sector compared to experimental and numerical approaches, they offer key advantages in streamlining early-stage design by reducing time, costs, and errors. This study proposes a novel Linearized Single Degree of Freedom analytical model to efficiently predict the dynamic response of spar-type Floating Offshore Wind Turbines under hydrodynamic loads. While Morison-based and linear mooring formulations are well established, in this work a closed-form solution is derived to accurately estimate translational displacements and mooring tensions. Implemented in MATLAB R2022a, the proposed model was validated against wave-tank experiments and subsequently compared with OpenFOAM and OpenFAST simulations to evaluate its accuracy levels. Despite its reduced formulation, the model accurately captures stiffness, damping, and hydrodynamic forces. Frequency- and time-domain analysis show strong agreement with experimental data, confirming its reliability in predicting platform displacements and mooring line tensions. It has also been demonstrated that the analytical model is able to yield precise results regarding both maximum and minimum values of these parameters, while effectively capturing their relationships. The model, with significantly lower computational demands than numerical simulations and comparable accuracy, serves as a valuable tool for early-stage design and optimization. While the proposed model is restricted to spar-type floating platforms under regular wave conditions, future work will aim to incorporate aerodynamic loads, irregular waves, and alternative platform configurations, without compromising computational efficiency.