Aerodynamic performance of an airfoil with step-induced vortex for lift augmentation

Physical and numerical experiments on flow developments around an NACA-0012 airfoil were conducted to explore the possibility of enhancing the airfoil's aerodynamic performance by vortex lift augmentation. The paper focuses on the effects of the separated flow and subsequent vortex formation, generated by backward-facing steps on pressure distributions and corresponding flow occurrences around the airfoil. Various step configurations are examined to determine their effect on lift and on lift-to-drag ratios. A discussion of the effects of main geometrical parameters of upper and lower surface steps on the airfoil performance, based on computational and physical flow visualization experiments, are presented. The results suggest that incorporation of backward-facing steps on the lower surface that are located at the midchord and extend back to the trailing edge with 50% depth of the airfoil chord may lead to considerable enhancements in lift coefficients and lift-to-drag ratios. The data produced may serve as a reference for future studies on the possible use of separated vortex structures in enhancing the aerodynamic or hydrodynamic performance of vehicles and structures.