Abstract
Upscaling of the standard three-bladed upwind design is one of the main options for reducing the levelized cost of energy for floating offshore wind. As a result of this upscaling, the rotor-nacelle assembly (RNA) is subjected to higher aerodynamic loads and weight. Simultaneously, efforts to reduce material costs are leading to lighter floaters. These concurrent trends are challenging the traditional assumption of a rigid floater, now proven to be unrealistic. While extensive studies exist on both blades and tower flexibility, introducing floater flexibility changes the dynamic behavior of the structure. This study aims to improve the understanding of interactions between floater elasticity and the rest of the structure. A key objective is to identify the deformation modes of the platform and link them to certain RNA modelling parameters. To investigate these interactions, simulations were conducted using two models: one with a rigid hull and another with a fully flexible hull. For each model, a sensitivity analysis of the eigenmodes was performed by varying the blade bending stiffness. Results of the eigenvalue analysis were compared using the Modal Assurance Criterion, taking the initial flexible model as a reference. Doing so helped identify pure platform modes as well as coupling modes influenced by blade bending stiffness. These results provide a foundation for more accurate fatigue load predictions and support the development of cost-effective floating wind turbine designs.