Three-Dimensional Effects in Transonic Wing Flutter: Insights from Direct Numerical Simulations*

Aeroelastic wing flutter poses a persistent challenge for high-performance aircraft, especially in the transonic regime, where the critical flutter speed can decrease due to the "transonic dip." Additionally, aerodynamic instabilities and non-linear damping, often caused by shock formations, can lead to limit-cycle oscillations that fatigue the aircraft and affect targeting and pilot comfort in military applications. To address these issues, a deeper understanding of shock-fluid interactions is needed. In this presentation, we consider a three-dimensional NACA0012 wing which encounters shock-stall flutter at a Reynolds number of 10,000 and Mach number of 0.7. Direct numerical simulations are based on a high-order immersed boundary code utilizing prescribed sinusoidal motion. The main aim of this study is to examine how three-dimensional shock and flow features impact energy extraction mechanisms, compared to previous two-dimensional results. Spanwise incoherence, changes in shock formation and shock trajectory are shown to influence the predicted flutter boundary. Futhermore, it is found that the assumption of two-dimensional flow results in secondary energy extraction mechanisms not observed in three dimensions.