Airfoil Passive Flow Control Strategies: Leading-Edge versus Surface Modifications

The aerodynamic and flow field characteristics of a NACA 0010 airfoil with and without modifications was investigated in flow with freestream turbulence intensity of 4%. The airfoil was modified with two different passive flow control strategies: leading-edge tubercles over the spanwise of the airfoil and surface-mounted rotating cylinders. The unmodified version of the airfoil was used as a baseline for comparison over a range of Reynolds numbers from 197,200 to 250,000 and various angles of attack ranging 0° to 24°. The experiments were carried out using two 6-axis force/torque transducers and Particle Image Velocimetry (PIV) in the low-speed wind tunnel facility at the University of Texas – Rio Grande Valley. The flow field data obtained using PIV showed large amount of turbulent mixing at the leading edge of the tubercle airfoil configuration. The PIV data revealed the presence of a recirculation bubble when the rotating cylinders on the surface of the airfoil were activated, giving rise to a faster adverse pressure gradient for the reattachment of the separated boundary layer. The recirculation greatly increased lift performance up to 50% within the pre-stall regime when compared to the unmodified airfoil and the tubercle airfoil.