Aero Hydro Elastic Simulation of a Semi Submersible Floating Wind Turbine

Abstract

This paper presents an aerohydroelastic model of a semisubmersible floating wind turbine. A specific attention is drawn to hydrodynamic modeling options and their effect on the dynamic response of the platform. The NREL 5 MW reference wind turbine mounted on the historical concept of semisubmersible platform Dutch trifloater is considered. A specific hydrodynamic model of loads on a semisubmersible platform is used within the wind turbine design code FAST from NREL. This hydrodynamic model includes nonlinear hydrostatic and FroudeKrylov forces, diffraction/radiation forces obtained from linear potential theory, and Morison forces to take into account viscous effects on the braces and damping plates. The effect of the different hydrodynamic modeling options is investigated. As one could have expected, it is found that the effect of viscous drag on braces, and nonlinear FroudeKrylov loads, becomes larger with increasing wave height. Their effect remains of small order. Simulations also are run with directional waves, it is found that wave directionality induces larger transverse motions.