Force measurements and wake surveys of a swept tubercled wing

Abstract

Force measurements and wake surveys have been conducted on two swept NACA 0021 wings. One wing had a smooth leading edge, while the other wing had a tubercled leading edge. The force measurements and the wake survey results were in good agreement. Between 0 and 8° angles of attack, tubercles reduced the lift coefficient by 4–6%. For the same range of angles of attack, tubercles reduced the drag coefficient by 7–9.5%. Tubercles increased the lift-to-drag ratio of this wing by 2–6%, and increased the maximum lift-to-drag ratio by 3%. At angles of attack higher than 8°, tubercles typically decreased the lift coefficient and the lift-to-drag ratio, while substantially increasing the drag coefficient. The wake surveys revealed that tubercles reduced the drag coefficient near the wingtip and that they also spatially modulated the drag coefficient into local maxima and minima in the spanwise direction. Typically, tubercles reduced the drag coefficient over the peaks where the tubercle vortices produced downwash. Conversely, tubercles increased the drag coefficient over the troughs, where upwash occurred. The majority of the drag coefficient reduction occurred over the tubercled wingspan.