Comparative Study of the Flow Control Physics Using Different Fluidic Actuators

Active flow control (AFC) methods have been widely studied for UAV aerodynamics in the past decades. Among all the AFCs, the fluidic actuators are one of the notable techniques that have been proven to yield significant efficiency improvements. Our previous study demonstrated the interaction between the fluidic actuator and incoming freestream flow on a flat plate. However, the flow control physics on various types of actuators over the airfoil still needs detailed investigation. In the present study, a comparative study is conducted to evaluate the flow control behavior of the fluidic actuator array on both the flat plate and the NACA 0018 airfoil. Three different types of the actuator array (i.e., sweeping jet actuator, straight jet actuator, divergent jet actuator) were selected in the present study. While the actuator array is 3D printed using five oscillators for the flat plate study, the modular-designed NACA 0018 aifoil with an actuator array in a different configuration is manufactured. Driven by a high-pressure air source, the actuator arrays operate at various mass flow rates in a closed-circuit low-speed wind tunnel at the University of Alabama in Huntsville. The Particle Image Velocimetry (PIV) system, pressure, and force sensor are utilized in the experiments to quantify the fundamental flow control effect and efficiency on both the flat plate and the airfoil. While the 2D PIV is used during the wind tunnel experiments to capture the streamwise mixing between the emitting jet and the cross-flow field, a stereoscopic PIV system is used to identify the spanwise flow structure to further understand the mixing process between multiple actuators and the cross-flow. Our preliminary findings indicate that the fluidic oscillator behaves unsteadily with maximum TKE values compared with the other two steady actuators. The straight jet can induce the strongest steady counter-rotating vortex pair. The stereoscopic PIV can clearly capture the vortex structure of the multiple jet interaction. The study on the airfoil can reveal the key parameters that decide the flow control efficiency, such as unsteadiness, induced vortices, and momentum injection. This study aims to gain more insights into flow control algorithms using different actuators and provides more information for the flow control design in the future.