| Leading-edge tubercles, inspired by humpback whale pectoral flippers, were used in an attempt to improve static and flapping wing performance. Wings with either sinusoidal tubercles or discrete leading-edge tubercles were tested. The best wing used eighteen discrete tubercles of amplitude 4.54% chord, increasing stall angle by 18%, CLmax by 7%, and decreasing drag by 8.4%. Decreased drag was seen only past the stall angle of the baseline case, suggesting that this was due mostly to stall delay. Computer simulations showed that the tubercles delayed stall by inducing boundary layer mixing, using two counter-rotating, stream-wise vortices. The discrete-tubercles on the flapping wing decreased thrust at alpha = 0° without affecting lift. However, at 6° AOA the tubercles reduced drag, but also decreased lift. The tubercles seemed only to benefit the performance of static wings, but this performance increase did not justify the added construction costs associated with their geometric complexity. |
