Investigation on aerodynamic behaviors at the extreme angle of attack of Two-dimensional wing

To investigate aerodynamic behaviors of two dimensional wings at the extreme angle of attack the traditional lift and drag force measurements were carried out during one revolution angle of attack by using the dynamic balance in the wind tunnel, and their flow visualizations were also performed. Five different wings were used to measure basically lift and drag coefficients and their polar plots, and their comparisons were also made. It was found that most wings have a second peak in the lift profile even after the stall angle with comparable magnitude to the first peak. At more than 90 degrees of angle of attack, the trailing edge vortex became main vortex to lead the wake structure. Especially, near the 140 degrees angle there appeared drag jumps for most wings. It was interesting feature that the polar plot of the flat wing has an profile very close to an elliptic curve.