High-fidelity simulation and analysis of a floating offshore wind turbine under extreme wave and wind conditions

Abstract

A high-fidelity simulation environment is developed based on a coupled methodology of MBS and CFD solvers. The methodology provides an integrated analysis of floating offshore wind turbines with consideration of aero- and hydrodynamics, structural dynamics as well as mooring and control system. A numerical wave tank is build in CFD. Experimental data from a wave tank model test, conducted in the course of the EU FP7 FLOATGEN project, are used to validate the simulation approach. The MBS model of a generic 2.2 MW wind turbine is simulated under extreme wave and wind conditions using a deterministic, phase-focused wave group based on representative metocean conditions with 50-year return period. A steady extreme wind speed model is used for computation of aerodynamic loads on the flexible rotor using BEM theory and wind drag forces on the flexible tower. Platform surge is highly excited by extreme wave conditions and significant wave run-up at the transition piece is observed. However, maximum inclinations and accelerations of the nacelle and tower are still within acceptable survival design margins of a barge-type floating substructure. The results demonstrate that the developed high-fidelity MBS-CFD simulation environment can fill the gap between engineering models and experiments for the design of floating offshore wind turbines. The methodology provides results, which cannot be obtained from other simulation techniques, such as wave run-up and pressure distributions under extreme conditions.