Non-linear wave loads on next-generation offshore wind turbines

Abstract

In response to the escalating demand for renewable energy, wind turbines and their support structures have witnessed exponential growth in size in recent decades. However, this expansion presents substantial challenges, particularly in the face of severe storms and large waves, raising concerns about resonance-related issues. Accurate modeling of asymmetrical, non-linear waves generated during storms becomes crucial for safe and cost-effective wind turbine design. The prevalent approach embeds higher-order non-linear waves into linear theory, but recent studies have unveiled uncertainties in this method, necessitating innovative techniques for simulating non-linear waves. Some studies propose numerical wave models (NWMs) like SWASH and OceanWave3D, treated as numerical wave tanks (NWTs), as alternatives for predicting wave loads on offshore wind turbines. A comparative analysis between SWASH and OW3D reveals significant discrepancies, particularly in OW3D results, prompting further investigation into potential setup issues. Both non-linear models consistently report higher loads than the stream function method due to increased local accelerations, and differences in wave spectra underscore their ability to account for non-linear wave interactions. The study underscores the stream function's underestimation of loads, emphasizing the necessity of accurate non-linear wave modeling for predicting extreme loads. Recommendations for future research include extended convergence studies, user experience considerations, and a closer examination of non-linear effects on fatigue load predictions.