A High-Resolution WRF Case Study of a Thunderstorm-Induced Cold Pool and Impacts on Wind Turbine Power Output, Wake Structure and Mechanical Loading

Convective cold-pool gust fronts represent extreme inflow conditions for wind-energy systems, yet their impacts on turbine wakes and loading remain poorly quantified. This study presents a high-resolution numerical case study of a strong cold-pool gust front simulated with the WRF model coupled to a generalized actuator disk representation of a wind turbine. The event is characterized by three distinct atmospheric-boundary-layer regimes: a marginally convective pre-gust boundary layer, a highly turbulent gust-front passage, and a strongly stabilized post-gust period.

During the gust front, hub-height wind speeds more than double relative to pre-gust conditions, reaching values close to 24 m/s. This wind ramp is accompanied by rapid wind direction changes and a near-surface temperature drop of approximately 6 K. The enhanced turbulence during the gust-front passage substantially reduces the turbine wake velocity deficit and accelerates wake recovery, while the stabilized post-gust environment leads to a stronger and more persistent wake. Changes in rotor-layer shear and veer during the event would have important implications for wake structure.

Analysis of the wake structure indicates that the cold-pool passage strongly modulates the turbine wake. In the marginally convective pre-gust environment, the wake deficit exhibits strong temporal variability. During the cold-pool gust front passage, due to the fact that turbine reaches rated power and due to enhanced turbulence dramatically reducing the wake velocity deficit, there is a smaller wake in terms of horizontal extent, indicating rapid wake recovery.

The analysis of out-of-plane blade root bending moments indicates that mechanical loading responds primarily to changes in turbine operating regime rather than directly to variations in wind shear associated with the gust-front passage. These results highlight the importance of convective cold-pool dynamics for wind-turbine performance and wake behaviour.

Comparisons to extreme observed cases at the DLR operated wind park, WiValdi, located in northern Germany, are presented.