As the offshore wind industry moves toward deeper water, with larger turbines and correspondingly larger monopile foundations, nonlinear loads from steep waves may become more important for the ULS design. Nonlinear numerical wave tanks (NWTs) for generating wave kinematics, to be used as input to i.e. Morison’s equation, have been applied by several research groups, but further validation of the obtained wave kinematics is needed. Furthermore, the load models for larger diameters also need to be evaluated.
The present work first compares the wave elevation results from existing two-dimensional (2D) NWT tools. The nonlinear wave elevation is compared to experimental results from model tests of two regular waves. Several methods of wave generation are considered. The conclusion from the study is that the selected codes represent physics well, even though we see individual differences, which are discussed. Differences between codes are not necessarily only due to differences in the applied theory, but also modeling of wave flap, numerical beach etc.
Load (and response) estimates from using the NWT kinematics combined with the Morison load model are compared to experimental results, two sets of CFD simulations, and to simpler load models. Alternative methods of selecting the load coefficients for the simplified load models are also discussed.