The effect of partial flexibility on aerodynamic performance of finite wing

In this thesis, the aerodynamic effects of partially flexible surface coverage applied to a NACA 0018 airfoil operating in low Re regimes were experimentally investigated. The flexible surface, made of latex material, was placed along a specific chordwise region of the wing, and four different wings with varying spanwise flexibility ratios were tested. Wind tunnel experiments were conducted in the Re range of 3 x 10⁴ to 10 x 10⁴, measuring lift (CL) and drag (CD) coefficients. Additionally, surface oil and tuft flow visualization techniques were used to analyze flow structures. The findings revealed that the partially flexible surface significantly suppressed the laminar separation bubble (LSB), delayed stall, and enhanced lift coefficient, thereby improving aerodynamic efficiency, particularly at lower Re. However, the effectiveness of the flexible surface diminished as the Re increased. These results contribute to the literature by demonstrating the potential of partial flexibility in optimizing passive flow control methods for UAV applications.