Dynamic stall alleviation using a deformable leading edge concept - A numerical study

Dynamic stall calculations were carried out for an airfoil with a dynamically deformed leading-edge (DDLE) shape at a freestream Mach number of 0.3. The surface deformations were done about a baseline NACA 0012 airfoil, effectively increasing the airfoil leading-edge radius and thickness at high angles of attack. It was found that the DDLE airfoil had a slightly dynamic stall behavior compared to the baseline NACA 0012 airfoil. In particular, the lift, drag, and pitching-moment hysteresis loops were milder for the DDLE airfoil compared to the baseline airfoil. It was also found that a static shape that corresponds to the thickest deformed shape performed just as well as the DDLE shape, indicating that the shape itself, and not its time rate of change, was the reason for the improved performance. At higher Mach numbers around 0.4, the DDLE shape exhibited a strong dynamic stall triggered by a shock-induced separation, offsetting any benefit from the change in the shape of the airfoil. Additional work is needed on the development of DDLE shapes that will perform well at higher speeds.