Stall flutter mitigation mechanisms via active surface morphing: Quantitative insights from moment partitioning method

Stall flutter mitigation is crucial to ensure the stability and safety of aeroelastic systems. Our previous research has shown that active surface morphing can effectively reduce the energy transferred from the flow to the pitching airfoil, thereby mitigating stall flutter. This study aims to provide new quantitative insights into the underlying physical mechanisms of this control strategy. The adaptive variable density clustering-based moment partitioning method is implemented to quantitatively assess the contributions of distinct vortical structures to aerodynamic moments. The analysis reveals two primary mechanisms by which active surface morphing reduces the energy transferred to the pitching airfoil: (1) a delay and reduction of the moment peak during the pitch-up phase, driven by the phase lag in leading-edge vortex development and the formation of the shear-layer vortex, and (2) a significant increase in the moment trough during the pitch-down phase, resulting from the reinforcement of the second leading-edge vortex and the weakening of the trailing-edge vortex. These findings offer new insights into the effectiveness of active surface morphing for stall flutter control.