SUMMARY

The design and performance of transport aircraft are influenced substantially by the effectiveness of the aerodynamic control system, affecting characteristics such as maximum takeoff weight, required runway length and fuel consumption. Many conventional control systems are complex and consist of multiple elements with intricate positioning mechanisms that are designed to maximize performance and efficiency. Active flow control (AFC) provides a means for reducing weight, part count and fabrication cost while improving cruise efficiency, creating the potential for significantly enhanced performance compared to what is possible using conventional technologies. Our research demonstrates how AFC can be used by means of fluidic actuation to manipulate the aerodynamic characteristics of several airfoil models without moving control surfaces. Aerodynamic effects including drag reduction, pitching moment control and high-lift performance improvement are demonstrated using actuation provided by fluidic oscillators or synthetic jet actuators that are integrated to the airfoil surface. The actuators function by engendering and manipulating concentrations of vorticity near the surface, affecting both accumulation and shedding. The effectiveness of the actuation and the resulting changes in concentrations of trapped vorticity are varied by altering the momentum coefficient and other actuator operating conditions, leading to changes in the flow around the entire airfoil and the associated aerodynamic forces and moments. The actuator operating conditions, including location, momentum coefficient and duty cycle, are optimized to maximize the effectiveness of the AFC. The related AFC-induced changes in aerodynamic characteristics are investigated using hotwire anemometry and particle image velocimetry (PIV) in the airfoil wake and boundary layer and in the vicinity of the actuator.