The wave forces on a monopile are compared among the classical random wave models and the state-of-the-art fully nonlinear random wave model. Forces are calculated in terms of Morison’s equation up to the wave crest zone. Linear random wave model with constant stretching, second-order random wave model with linear extrapolation from the still water level and, the third-order nonlinear wave model are adopted in time-domain simulations.
The simulation results show that the third-order random model is able to produce accurate predictions of extreme wave crest and quasi-static wave forces when compared with the fully nonlinear model. The linear random model with constant stretching behaves better than the commonly used Wheeler stretching. The second-order random wave model is suggested to enter the mainstream application of industrial design for shallow-water offshore structures as it provides wave forces whose quality is only inferior to the third-order model, but with much less computational effort than both the third-order model and the fully nonlinear model.