Extreme vortex-gust encounters by a square wing

This study examines extreme vortex gust encounters by a square wing at a chord-based Reynolds number of Re = 600. We numerically simulate flows around a square NACA0015 wing being impacted by a spanwise-oriented gust vortex with a gust ratio G > 1. During the extreme aerodynamic events, the wing experiences significant lift fluctuations. Through a detailed analysis of vortex dynamics around the wing, we identify two opposing effects of the tip vortices on the large lift change in the extreme interaction. First, tip vortices interact with the incoming gust vortex, leading to the strengthening of low-pressure tip vortex cores near the wing surface, which contribute to significant lift surge. Second, the tip vortices reduce lift fluctuations by their enhanced downwash and distortion of vortical structure around the wing corners. The second effect can overwhelm the first effect, leading to reduced transient lift fluctuation on the square wing compared to the analogous 2D wing. This indicates that further strengthening the tip vortices during interaction may further reduce the large transient lift change. These findings provide foundational insights into three-dimensional extreme vortex-gust-finite-wing interactions, suggesting potential strategies to leverage tip vortices for attenuating large transient lift variations at higher Reynolds numbers.