Numerical Implications of Spanwise Camber on Minimum Induced Drag Configurations

Abstract

Lifting line and Euler techniques have indicated that an elliptical planform cambered in the spanwise direction appears to have a lower induced drag than the uncambered, planar configuration, when both of then have identical arc lengths and the same wetted areas. In other words, a wing geometry with a lower projected span than the planar wing, only because of spanwise cambering, has been found to have a lower induced drag than the corresponding planar case. It was also noted that in the Euler solutions the theoretical minimum induced drag was not achieved on a planar configuration without applying a twist distribution. The increased efficiency of the non-planar configuration is due to induced lift and without accounting for this induced lift, the induced drag is larger then that of the corresponding unfolded planar wing. Induced lift and aerodynamic efficiency of the spanwise cambered configuration was observed to increase with reduced aspect ratio.