Abstract: Based on the Reynolds-Averaged Navier-Stokes equations with k-\omega SST turbulent model and coupled with the motion equationsfor an elastic supported system, the steady and unsteady flows for airfoilswith different incidences are simulated, specially, for high incidences whenseparated vortices exist. For the given Reynolds numbers and structureparameters considered in this paper, the frequencies of shedding vortex havea complicated relation with the airfoil vibration. The average aerodynamicforce may vary for some forced vibrations. For airfoils with thicknesslarger than 20\%, the aeroelastic response can lead to a separated flowfield from one balance state to another so that the aerodynamic forcechanges from one value to another. These results can explain the poorrepeatability of experimental results in these regions.