Stream Function Wave Embedment into Linear Irregular Seas: A New Method Based on the Hilbert Transform

摘要

As monopiles tend to grow larger in diameter, extreme hydrodynamic loads from fault and idling cases are becoming design drivers for o shore wind turbines foundations. In order to take into account the nonlinearity of the loads induced by large, extreme waves, it is common practice to embed a nonlinear wave into a linear wave realization. In this work, a new procedure to embed a stream function wave into a linear wave realization is presented. The algorithm is based on the calculation of the Hilbert transform on a subset of the original time series containing the extreme event, from which a so-called strong analytical signal can be derived. If the subset of the time series containing the extreme event has a narrow banded spectrum, one can identify extreme events from the analytical signal and calculate the embedment parameters, namely the period T and the amplitude A of the embedded stream function wave. The embedment routine was used to reproduce the force and wave elevation of an extreme event in a model experiment. The model cylinder had a diameter of D = 0:075 m, and was exposed to a long crested wave spectrum with signi cant waves height of HS = 0:104 m and peak period TP = 1:409 s, but at a water depth of h = 0:51 m.