Parametric study of the response of varies wind turbines under F2 tornado wind loadings using a numerical model considering the effect of angle of twist

The global expansion of wind energy capacity, as reported by the International Energy Agency, has led to a significant rise in wind turbine farm installations. Most of the wind turbines, approximately 93%, are situated onshore, primarily in rural areas. This onshore placement exposes them to a heightened risk of encountering High-Intensity Wind events (HIW), including tornadoes. Tornadoes, due to their unpredictable and localized nature, present a formidable challenge for ensuring the structural integrity of onshore wind turbines. Remarkably, design guidelines for onshore wind turbines, such as the International Electrotechnical Commission (IEC) 61400-1, do not incorporate tornado wind loads. This study endeavors to fill the void by developing a numerical code to assess the structural response of three-blade onshore wind turbines subjected to 3D tornado wind loads, with a specific focus on the influence of the angle of twist. This research exclusively examines F2 tornado wind fields. The research methodology involves an extensive parametric study aimed at identifying critical F2 tornado configurations that induce maximum straining actions on both wind turbine blades and the supporting tower. Additionally, the study explores the optimal blade pitch angle that can mitigate the impact of these tornado-induced loadings. Three distinct wind turbines are analyzed, each with power capacities of 1.5MW, 5.0MW, and 10.0MW, respectively. The result shows that setting the blade pitch angle as 90 degrees could minimize the strain actions on the blade roots and the resultant bending moment at the tower base. With the presence of angle of twist, the resulted bending moments will be increased by 1% to 3% for all wind turbines considered in the current study. A comparison of the above findings with the design load cases given in IEC guidelines revealed that the flap-wise bending moments induced by F2 tornado wind loads exceed those calculated using standard design load cases for the wind turbines considered in this study.