Prediction and experimental evaluation of planar wing spanloads for minimum drag

An evaluation and analysis of optimum wing spanloads was conducted by comparing wing performance values obtained from theoretical models and experimental wind-tunnel measurements. Three wing spanloads were designed for a prescribed wing-root bending moment using a Lagrange multiplier optimization method, with and without incorporating a representative viscous effect. Wind-tunnel models were constructed for each spanload, and experiments were conducted to determine the relative difference in drag measured as changes were made to the design constraints. The results indicate that significant decreases in drag from an elliptically-loaded wing are achievable for an optimized spanload having equal lift and wing-root bending moment of the elliptic wing. Experimental 5-hole probe wake-survey measurements were reduced into total lift and drag, as well as spanwise lift distributions, which lend insight into how measurements of the viscous-and inviscid-optimized wing configurations compared to predicted values.