The stall characteristics of an airfoil under different vibrations

Based on the unsteady Reynolds-averaged Navier-Stokes equations, the flow field and aerodynamic characteristics of an airfoil at high incidences is investigated under the elastic structure vibration and different forced vibrations. It is shown that the aeroelastic vibration with certain amplitude near the critical flutter speed can cause large scale separation above the airfoil before the stall incidence, then, lead to the stall appearing at some lower incidence than the steady meaning stall incidence. Furthermore, the influences of three forced vibrations of the airfoil on the flow field at high incidences are considered. It is found that the forced plunging or pitching vibrations can also cause the large scale separation if the amplitudes of vibrations are large enough. The frequency and amplitude of the vibrations are important parameters.