Experimental Investigation on the Interaction Between a Fluidic Oscillator Array and a Cross-flow

Active flow control (AFC) methods have been developed and widely studied for fluid mechanics in past decades. Among all the AFCs, the fluidic oscillators are one of the notable techniques that have been proven to yield significant efficiency improvements by preventing flow separation in various applications. While numerous researchers have explored the fluid oscillator, their focus has primarily been on the performance of single actuators. The fundamental knowledge of the multi-actuator interaction with the cross-flow, which is crucial to the optimization and reduce-order modeling of fluidic oscillator arrays, is yet limited. In the present study, an experimental investigation is conducted to evaluate the flow field characteristics of the oscillating jet array into free stream cross-flow. The actuator array is 3D printed using five oscillators with two feedback channels (i.e., sweeping jet actuator). Driven by a high-pressure air source, the actuator array is installed spanwise on a flat plate in a closed-circuit low-speed wind tunnel at the University of Alabama in Huntsville. Both the hotwire anemometer and the Particle Image Velocimetry (PIV) system are utilized in the experiments to quantify the fundamental flow behavior of a single actuator and mixing between different actuators at various mass flow rates of the actuator and different free-stream velocities. While the 2D PIV is used during the wind tunnel experiments to capture the streamwise mixing between emitting oscillating jet and cross-flow field, a stereoscopic PIV system is used to identify the spanwise vorticity structure between multiple actuators to further understand the mixing process between multiple actuators and cross flow. Our preliminary findings indicate that the operation of the multi-actuator array in the quiescent air can reduce the oscillation angle of every single actuator through the interaction between adjacent actuators. The mixing of the emitting jet takes place within the boundary layer. The stereoscopic PIV can clearly capture the vortex structure of the multiple jet interaction. This study aims to gain a more fundamental comprehension of the flow behavior when oscillating jets emit into the cross-flow, such that it provides more information for the flow control design in the future.