Global Aeroelastic Stability Analysis of a NACA0012 Airfoil in Transitional Reynolds Regime

The onset of pitch-oscillations of a NACA0012 airfoil mounted on a torsion-spring is investigated by the means of a global fluid-structure linear stability analysis (LSA). Experimental studies from literature have shown this configuration undergoing on a flutter behaviour for a close range of Reynolds. This phenomenon is attributed to the laminar character of the boundary layer on the airfoil surface and to its detachment, transition and subsequent reattachment. In this regard, we carried out a global fluid-structure LSA of a mean flow field, issued from a time and spanwise averaged Direct Numerical Simulation, at different incidences, α, for Re = 50 000. The LSA at α = 0 • predicts a static divergence behaviour of the airfoil from its equilibrium position, whereas the LSA at different incidences predicts the stabilisation of the static mode, associated to the existence of a laminar separation bubble over the upper surface of the airfoil.