Multi-fidelity Analyses of Rotor Loads of Floating Offshore Wind Turbines with Wind/Wave Misalignment

Abstract

Reliable predictions of the aero- and hydrodynamic loads of fixed-bottom and floating offshore wind turbines are paramount for assessing fatigue life and designing load and power control systems. However, significant uncertainty affecting aerodynamic predictions still exists. This study presents cross-comparative analyses of the predictions of aerodynamic loads and power of fixed-foundation and floating wind turbine rotors with and without yaw errors using time- and frequency-domain Navier-Stokes Computational Fluid Dynamics, and the Blade Element Momentum theory. The considered test case is the National Renewable Energy Laboratory 5 MW reference turbine, assumed to be mounted in the floating case on a semi-submersible platform and undergoing pitching motion about the tower base. Although the overall qualitative agreement of the low- and high-fidelity predictions is found to be fair in all cases, for the considered regimes the agreement between the two methods is better for the pitching rotor in aligned wind than for the yawed flows regardless of the tower motion.