Lift enhancement by wavy leading edges at Reynolds numbers between 700,000 and 3,000,000

摘要

An experimental investigation has been undertaken to study the wavy leading edge phenomena on rectangular wing of aspect ratio 4 with a NACA 0020 airfoil at Reynolds number range from 700,000 to 3,000,000. Force measurements for various shapes of sinusoidal leading edge indicate smaller amplitude and shorter wavelength configuration (A3λ11) presenting a substantial increase in aerodynamic performance at entire range of Reynolds number tested when compared to baseline configuration, as result achieving 28.3 % of increasing in maximum lift coefficient. Oil flow visualizations reveal that tubercles with smaller amplitude have the role of delaying trailing edge flow separation. At high angles of attack, the A3λ11 configuration is shown to present spanwise wavelengths for which the optimal generation of streaks in turbulent boundary layers is expected according to previous experimental works. The appearance of such streaky boundary layers is a possible reason for the delay in flow separation and increase of maximum lift coefficient.