Spanwise control authority of synthetic jets on a stalled airfoil

Abstract

This study investigates the aerodynamic effects of low- and high-frequency synthetic jet control strategies on a National Advisory Committee for Aeronautics (NACA) 0025 airfoil. Visualizations and measurements are employed to assess the stability of the flow, focusing on the shear layer and wake dynamics under two forcing frequencies. High-frequency actuation is found to induce steadier flow reattachment and more favorable aerodynamic characteristics compared to low-frequency control. Flow structures resulting from high-frequency actuation, notably vortex rings, are identified and their significance in flow control is evaluated. The spanwise control authority of the synthetic jet array is evaluated, revealing that the aerodynamic stability decreases significantly away from the midspan. Additionally, the effective control length is limited to approximately 40% of the length of the array. Insights from modal analysis provide additional understanding of flow structures and their evolution across different spanwise planes.