Qi Zhang, Ould el Moctar, Changqing Jiang
Offshore wind turbines consist of slender cylindrical members whose fatigue and ultimate strength govern both structural safety and cost. Accurate design requires reliable prediction of wave–structure interactions, including hydroelastic effects, which are often neglected in traditional rigid-body or decoupled analyses. This study implements a fully coupled CFD-FEM framework to investigate hydroelastic responses of a top-fixed flexible cylinder, representative of offshore wind turbine foundations. The framework combines a finite-volume Navier–Stokes solver with a nonlinear structural dynamics solver, validated against benchmark experiments for both rigid hydrodynamics and flexible structural behavior. Results demonstrate that structural flexibility fundamentally alters wave-induced loads, particularly when wave excitation frequencies approach the cylinder’s natural modes. Spectral analysis shows that rigid assumptions overpredict higher-order harmonics in short waves but underpredict key harmonics (2nd, 3rd) in long waves, leading to potentially non-conservative fatigue estimates. Increasing wave steepness amplifies nonlinear interactions and higher-order vibrations, which dominate fatigue-critical responses. These findings highlight the necessity of accounting for hydroelasticity in the design and lifetime assessment of offshore wind support structures to ensure both safety and cost efficiency. • A coupled CFD-FEM framework is validated for predicting hydroelasticity of flexible support structures in offshore wind turbines. • Hydroelastic effects significantly alter wave-induced loads near structural natural frequencies, where rigid-body models fail. • Flexibility reshapes the spectral content of loads, leading to contrasting errors in fatigue assessment under short and long waves. • Increasing wave steepness amplifies nonlinear forcing and higher-order vibrations, highlighting fatigue-critical design scenarios.