Effect of camber on the aerodynamics of adaptive-wing micro air vehicles

Four microair vehicle wind-tunnel models were built with 3, 6, 9, and 12% camber, all based upon the S5010-TOP24C-REF thin, cambered-plate airfoil. These models were tested in the Low Speed Wind Tunnel at angles of attack ranging from 0 to 35 deg and velocities of 5, 7.5, and 10 m/s, corresponding to mean aerodynamic chord Reynolds numbers of 5 × 10⁴, 7.5 × 10⁴, and 1 × 10⁵, respectively. Aerodynamic coefficients C_L, C_D, C_M and lift-to-drag ratio (L/D) were obtained and plotted vs angle of attack for all of the cambers at each velocity. Large positive, nose-up pitching moment coefficients were found with all cambers at the lowest Reynolds number. These results have been verified with flight tests of micro air vehicles utilizing these airfoils. The 3% camber wing gives the best lift-to-drag ratio of the four cambers and theoretically would be the optimal choice for high-speed, efficient flight. It is theorized that the 6 and 9% camber wings will give the best low-speed performance because of their high lift-to-drag ratios and mild pitching moments near their stall angles of attack.