Characteristic flow patterns and aerodynamic performance on a forward-swept wing

Abstract

This investigation elucidates the effects of Reynolds number (Re) and angle of attack (α) on the boundary-layer flow patterns, aerodynamic performance, flow behaviors and vortex shedding. This investigation applies a finite NACA 0012 forward-swept wing with the forward-sweep angle (φ) of 15°. The Reynolds numbers were tested in the range of 4.6 × 104 < Re < 105. The wing chord length is 6 cm and the semi-wing span is 30 cm, such that the full-span wing aspect ratio is 10. The surface oil-flow scheme was utilized to visualize the boundary-layer flow structures. The hot-wire anemometer was applied to measure the vortex-shedding frequency behind the forwardswept wing. Furthermore, a force-moment sensor was applied to measure the aerodynamic loadings. The surface oil-flow patterns are classified into six characteristic flow modes — separation, separation bubble, secondary separation, leading-edge bubble, bubble extension and bluff-body wake modes. Additionally, the output of force-moment sensor and the visualized boundary-layer flow configurations indicate that the aerodynamic performance is closely related to the boundary-layer flow behaviors. Furthermore, the boundary-layer flow stalled in the leading-edge bubble mode. Moreover, the vortex-shedding frequency behind the forward-swept wing shows that the vortexshedding frequency at low α exceeds that at high α.