Abstract
Aerodynamic interactions of the model NREL 5 MW offshore horizontal axis wind turbines (HAWT) are investigated using a high-fidelity computational fluid dynamics (CFD) analysis. Four wind turbine configurations are considered; three-bladed upwind and downwind and two-bladed upwind and downwind configurations, which operate at two different rotor speeds of 12.1 and 16 RPM. In the present study, both steady and unsteady aerodynamic loads, such as the rotor torque, blade hub bending moment, and base the tower bending moment of the tower, are evaluated in detail to provide overall assessment of different wind turbine configurations. Aerodynamic interactions between the rotor and tower are analyzed, including the rotor wake development downstream. The computational analysis provides insight into aerodynamic performance of the upwind and downwind, two- and three-bladed horizontal axis wind turbines.
Highlights
Wind turbines are designed to extract kinetic energy from the wind, usually to drive an electric generator
The upwind configuration has the rotor upwind of the tower, whereas the downwind configuration has the rotor downwind of the tower where the rotor rotates through the disturbed air produced by the tower’s aerodynamic shadow
On the other hand, do not typically need a yaw control mechanism if the rotor and nacelle have a suitable design to make the nacelle passively align with the wind
Summary
Wind turbines are designed to extract kinetic energy from the wind, usually to drive an electric generator. The boundary layer gradient together with a rotating rotor can lead to a yawing moment on the tower to a nonintuitive result Effects such as flow separation and wake interaction with the tower make computational fluid dynamics (CFD) modeling and simulation of wind turbine flows an appropriate choice to investigate the unsteady aerodynamics. The actuator disk models [7], effective in studying the general aerodynamics between the rotor and tower, are unable to capture the time-accurate unsteady phenomenon and impulsive loadings associated with each individual blade motion, which is critical in deterring the blade structural response and fatigue life of the whole wind turbine system.
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