Numerical research on the effect of variable droop leading-edge on oscillating NACA 0012 airfoil dynamic stall

Dynamic stall occurs when an airfoil is in unsteady motion and the angle of attack is far beyond the static-stall angle. In dynamic stall, lift and pitching moment will fluctuate in a wide range, and the performance of airfoil will get worse. By using the variable droop leading-edge (VDLE), local angle of attack near the leading-edge dynamically decreases when the overall angle of attack gets too large, then the adverse pressure gradient can be reduced. As a result, the formation of leading-edge vortex will be restricted, as well as the flow separation and dynamic stall. In this paper, two VDLE modes are proposed and a series of investigations are performed on the effect of different modes and parameters on dynamic stall control of NACA 0012 airfoil in pitching oscillation. The unsteady Reynolds-averaged Navier-Stokes equations and γ-Reθ turbulence model are employed as the governing equations, and the shape modification is realized by the DCP-RBF mesh deformation method. The results suggest that the VDLE modes proposed in this paper can effectively reduce the dynamic stall and significantly improve the aerodynamic characteristics of NACA 0012 airfoil.