Influence of non-linear wave load models on monopile supported offshore wind turbines for extreme conditions

This paper investigates the influence of non-linear wave loads on the response and design of a monopile supported DTU 10 MW offshore wind turbine during extreme conditions. Morison’s equation with linear wave theory is compared to an experimental based Stokes-type approach and the Rainey force model, both currently considered state-of-the-art. These comparisons show that models incorporating non-linearity significantly impact structural response due to higher harmonic loading coinciding with natural periods. The Stokes-type model method is shown to predict the largest loading and response. These models are compared to the widely used constrained wave approach, showing that significant differences are predicted for steel and geotechnical design checks. This suggests that the industry standard approach may be inappropriate for the design of monopile structures against extreme wave loads.