Effects of average attack angle and amplitude on aerodynamic performance of an oscillating airfoil

The Reynolds average N-S equation enclosed by [k-ω SST] turbulence model and [γ-θ] transition model is adopted to do the numerical simulation for the unsteady flow field and lift characteristics of oscillating and static NACA0012 airfoils. The effects of average attack angle and amplitude on the average lift coefficient are studied in the case of Re=1.35×10⁵ and K=0.1, which is compared with lift characteristics of static airfoil and experimental values. The results show that the oscillatory motion of airfoil will decrease the average lift coefficient if the average attack angle is less than critical angle. And it will increase the average lift coefficient under the condition of the average attack angle greater than critical angle, while the minimal attack angle less than critical angle. In the range of 12° ~17°, the oscillating airfoil with amplitude of 6° can provide a better average lift coefficient compared with the static one, and the improvement value is about 30%~45.7%. When the minimal attack angle located in the light stall range of static airfoil, the average lift coefficient will step up during the process of generation of the leading edge vortex and concentrated vortex adhering on the pitching up airfoil. So the combination of static and oscillating airfoils could provide high lift and extend critical angle.