Parametric study of the quasi-static response of wind turbines in downburst conditions using a numerical model

Many research studies were conducted on wind turbine towers subjected to either seismic loads or synoptic wind loading, such as: hurricanes, typhoons, and tropical cyclones. However, the behavior of wind turbines under localized high-intensity wind events (HIW), such as downbursts, is not well-understood. The localized nature of downbursts makes the prediction of critical loads on wind turbines quite challenging. In the current study, a numerical model is developed and validated to investigate the effect of downburst wind loading on wind turbines. This model incorporates a previously developed Computational Fluid Dynamics (CFD) model for the downburst wind field coupled with a newly developed wind turbine structural model. The numerical model is capable of predicting the effect of downbursts on wind turbines taking into consideration the different downburst parameters such as the jet velocity, the size of the downburst and its location relative to the wind turbine. The model also accounts for the change in the pitch angle of the blades, which is a parameter typically used to control the blades rotation and the power generation. An extensive parametric study is conducted using the developed numerical model to determine the peak moments at the tower base and the roots of the blades considering a large number of downburst configurations and different blade pitch angles. Downburst critical configurations for different pitch angles are obtained and the optimum pitch angle which minimizes the downburst effect on the wind turbine is recommended.