Turbulent State Operating Condition Assessment of Floating Offshore Wind Turbine Rotor using BEM and CFD

摘要

High and consistent wind resources at the deep waters are ideal locations for wind turbines. The offshore wind energy industries are seeking to exploit those locations by adopting the floating platform technologies that are prevalent in oil and gas industries. The floating offshore wind turbines are complex machines, due to coupled wind and wave forces leading to rotor motions in 6 degrees of freedom. The current study focuses on the dynamic effects of the platform pitching motion on the rotor aerodynamics for OC3 phase IV case 5.1 with modified wave height. High fidelity CFD (Computational Fluid Dynamics) software was employed along with the semiempirical tool, FAST, developed by NREL, USA by assuming the wind turbine as a rigid body. The hydrodynamic effects leading to the pitching motion of the turbine platform are obtained from FAST. These pitching motions are coupled with the rotating blades to study transient flow behaviors using CFD. The results are compared with the standard BEM based methods. The results show that the increased wave height induces very high velocity and acceleration of the platform motion and thereby on the rotor plane. Morever this confirms that the turbine is operating both in windmill and turbulent state under such conditions. BEM validity with Glauert correction and the appropriate tip loss model is to be further assessed for the application of floating offshore wind turbine performance and design predictions.