Influence of Boundary Layer Behavior on Aerodynamic Coefficients of a Swept-Back Wing

The effects of the Reynolds number and angle of attack on the boundary layer and the aerodynamic performance of a finite swept-back wing are studied experimentally. The cross-sectional profile of the wing is NACA 0012 (aspect ratio=10), and the sweep-back angle is 15 deg. The Reynolds number is set in the range of 30,000–130,000. The boundary layer field is visualized with surface oil-flow techniques. Six characteristic flow regimes—laminar separation, separation bubble, leading-edge bubble, bubble burst, turbulent separation, and bluff-body wake—are categorized and studied by considering the Reynolds numbers and angles of attack. The characteristic behaviors of boundary layer significantly affect the lift, drag, and moment coefficients. The bubble length shortens significantly in the separation bubble and leading-edge bubble regimes as the angle of attack rises. The aerodynamic performances demonstrate that the swept-back wing model has no hysteresis.