Aerodynamic performance of a two-bladed downwind turbine using a new nacelle tilt control concept is numerically investigated based on a Computational Fluid Dynamics analysis. High fidelity, unsteady full Navier-Stoke viscous flow simulations are performed for wind turbines at different nacelle tilt angles to investigate the mean and unsteady aerodynamic loads under two operating conditions: (1) a power-unregulated mode at a rated wind speed of 11.4 m/s, and (2) a power-regulated mode at a rated power of 5 MW. The rotor power, blade and tower bending moments are among the key parameters to evaluate the effect of this new wind turbine control method. A dynamic moving grid method is used to simulate the relative motion and unsteady interaction between the rotor and the tower. Computational results indicate favorable mean bending moments obtained on the turbine blades and tower. However, increased unsteady loadings are experienced by wind turbines at high nacelle tilt angles. The current investigation provides quantitative assessments of the aerodynamic loads and performance of downwind turbines, as well as insight into reducing the costs of offshore horizontal axis wind turbines using an alternative power control method.

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