Effect of Internal Acoustic Excitation on Steady Wing Loads at Low Reynolds Numbers

The current study investigates the effectiveness of internal acoustic excitation as a method to manipulate steady aerodynamic loads on a NACA 0012 wing at low Reynolds numbers. By embedding thirty miniature speakers along the leading edge, the wing was subjected to a wide range of acoustic excitation frequencies across three flow regimes — attached, transitional, and separated. Theoretical estimates of Tollmien-Schlichting and Kelvin-Helmholtz instability frequencies informed the excitation range. Wind tunnel testing was conducted at Reynolds numbers of 60,000, 120,000, and 180,000, with lift, drag, and moment coefficients measured over varying angles of attack. Results indicate that acoustic excitation significantly reduces drag during attached flow and increases lift during separated flow, with peak effectiveness in the modified Strouhal number range of 0.02-0.03. These trends were consistent across Reynolds numbers and excitation frequencies. The findings reiterate the efficacy of internal acoustic excitation as a viable mechanism for aerodynamic efficiency enhancement in low Reynolds number flight applications.