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The present paper aims to reproduce an extreme event extracted from an experimental time series relative to 2D long crested irregular waves. The experimental values are relative to the wave tank experiments at 1:80 scale, carried out on a stiff monopile within the Waveloads project. The monopile, modeled as a cylinder of constant diameter, is placed on a 1:25 slope and irregular waves are generated at the inlet with a mechanical paddle. In order to reproduce the time series and the consequent loads on the structure, a reconstruction of the wave elevation using a super position of 1st order components is done, the components are then imported to the aero-servo-elastic code 3Dfloat and the wave kinematics at the inlet for the computation fluid dynamics (CFD) simulations are obtained using 1st order formulation. Successively, the kinematics are imported as boundary conditions into the CFD commercial code STAR-CCM+. The free surface is modelled with the volume of fluid formulation and the k-ω turbulence model with the Menter formulation is used. In the experiments, a monopile of 0.75cm diameter (6m in full scale) is placed a distance of 7.75m (600m in full scale) from the inlet. The water depth at the model is 0.26cm (20m in full scale). Two different wave events of 25s extracted from two different time series are reproduced and compared with the experiments. The simulated wave elevation is measured at different locations and compared with the experiments. Good agreement between the simulations and the experiments is found.

The aero-servo-hydro-elastic Finite-Element-Method code 3DFloat is tailored for nonlinear, coupled time-domain simulations of offshore structures in general and offshore wind turbines in particular. This article describes the theory behind the structural model, aerodynamic and hydrodynamic load modules, control system and coupling with an optimizer. The verification and validation history includes the IEA OC3/OC4/OC5 projects, two wave tank tests and participation in commercial projects. Current development examples include implementation of advanced hydrodynamics in the DIMSELO project, implementation of soil/structure interaction super-elements in the REDWIN project, and optimization of large rotors with sweep in an industry project.

Detailed wake measurements with two similar model wind turbines, with a diameter of 0.9m, were performed in the wind tunnel. A single turbine arrangement and a tandem setup, where a wind turbine was operated in the wake of an upstream wind turbine, were tested. Measurements of the cross section in the near and far wake as well as measurements in axial direction are presented. A single hot-wire and a five-hole probe were used. The application of the five-hole probe enabled to measure a three-dimensional flow field providing detailed inspections of the rotation of the wake. A strong tower wake and a non-uniform velocity field and turbulence distribution were observed.