The Aerodynamics of Curved and Straight Wings in Backward and Forward Sweep Orientations – Role of Forwardness vs. Curvature

We have previously reported that single curved wings that are backward swept (i.e. crescent-shaped) show classical lift behavior vs. angle of attack (AoA), namely an initial linear lift increase, followed by sudden stall (i.e. first stall, at ~ 12–18 degrees AoA), followed by increasing lift (i.e. recovery) past first stall and then a loss of lift (i.e. second stall) past 45 degrees AoA. Forward-swept curved wings however show a very different behavior with a reduction of first stall, an increase of lift in the recovery region and similar lift behavior at second stall. First stall can be essentially eliminated for strongly curved forward-swept wings. To address the question of the role of forwardness vs. curvature on this behavior, we provide results of numerical simulations using ANSYS-FLUENT on a NACA 0012 airfoil at a Re of 5.8e5 to compare a straight wing with a curved wing. Our results show that for the more common backward-swept case, the straight wing shows a reduced first stall behavior when compared to a curved wing, while for the forward-swept case a straight wing is nearly identical to a curved wing. This suggests that the forward placement of the wing's leading edge, rather than its curvature, plays the dominant role in alleviating the first stall behavior for the forward-swept case, but curvature plays a greater role in deepening the stall of a backward-swept case. For unswept configurations, the straight and curved wings show similar behaviors, but with a more sudden first stall behavior for the straight case.