Numerical Investigation of Stall Flutter in a Pitching Airfoil at Low Reynolds Number

The present work investigates fluid–-structure instabilities and stall flutter of a pitching NACA0012 airfoil through numerical simulations. The flow is modeled using the compressible Navier–-Stokes equations in a non-inertial rotating reference frame, while the structural dynamics are represented by a torsional spring–-mass–-damper system. The analysis focuses on the effects of reduced velocity, equilibrium angle of attack, and elastic axis position on the aeroelastic behavior. The results show a transition from steady flow to vortex-shedding regimes and, at higher reduced velocities, to limit-cycle oscillations. Increasing the equilibrium angle of attack leads to an earlier onset of instability and stronger aerodynamic forcing, while moving the elastic axis downstream has a similar destabilizing effect due to the larger aerodynamic moment arm. Frequency analysis highlights the progressive coupling between fluid and structural dynamics: vortex shedding dominates at low reduced velocity, whereas the structural frequency governs the response in the limit-cycle regime. The study provides a consistent description of the mechanisms driving stall flutter and of the parameters influencing aeroelastic stability.