Behavior of Wind Turbine Towers and Blades Under Tornado Wind Fields

The installation rate of wind turbines around the world is increasing significantly. Therefore, wind turbine farms are constructed in plentiful wind resources areas that put a considerable number of wind turbine towers under severe wind conditions. As a result, failures due to unexpected wind loads on either the blades or the tower are increasing. In addition, wind turbines are designed to resist synoptic wind loads as per the current guidelines, which do not consider high-intensity wind (HIW) events such as tornadoes. The built-in-house numerical code “HIW-WT” has been developed in this study to model wind turbines under three-dimensional wind fields such as tornadoes. Extensive analysis has been conducted with the goal of determining the critical tornado wind field for wind turbines considering different tornado structures. The methodology depends on identifying the critical location of the tornado that will cause peak straining actions on the tower and blades, and the optimal pitch angle that will minimize the effects of that tornado. Design wind profiles for tornadoes are developed in this study taking into account several factors. The proposed wind profiles are presented as wind speeds in the rotor plane and perpendicular to the rotor plane at different heights. The development of the tornado design wind profile took into consideration several tornado wind fields with different tornadic structures. It also accounted for the configuration of the blades (pitch angle changes), various airfoil sections, the rotor configuration (yaw angle changes), the supporting tower’s height (hub height), and the base diameter of the supporting tower. The proposed wind profile can be applied on wind turbines by design engineers for tornado hazard assessment and it has the potential to be implemented in structural design codes and guidelines for future designs