Load distribution patterns and structural effects of IEA 15MW wind turbine under downburst wind field

Abstract

Downbursts, which are intense, short-duration, highly non-stationary and non-synoptic outflows generated by severe thunderstorms, pose a significant threat to the structural safety of large-scale wind turbines, particularly in regions with abundant wind resources but frequent convective storms. Although numerical approaches have been widely used to assess downburst-induced loads, experimental investigations remain limited due to the challenges of reproducing realistic transient non-synoptic wind fields in controlled environments. In this study, a combined wind tunnel and numerical simulation framework is developed to quantify the aerodynamic load distribution and structural responses of a 15 MW reference wind turbine under downburst conditions. Scaled wind tunnel tests were conducted to reproduce representative downburst wind fields with varying turbulence intensities, enabling high-fidelity measurements of unsteady surface pressures and global aerodynamic forces. The experimental data were incorporated into an aeroelastic-structural coupling framework that links OpenFAST aerodynamic load simulations with detailed FEM analyses to evaluate stress distributions, displacement responses and potential failure modes. By comparing these results with those obtained under synoptic wind conditions, the study reveals the substantially more severe aerodynamic loading and structural instability induced by downbursts. A systematic investigation was conducted on the effects of radial position, wind profile type, turbulence intensity, and operational conditions on blade responses and tower stability, highlighting the importance of incorporating downburst-related wind fields into wind turbine design standards and operational strategies to enhance the structural resilience of turbines in regions susceptible to convective storms, like downbursts, tornadoes, etc.