OPTIMUM LOADING ON NONPLANAR WINGS AT MINIMUM INDUCED DRAG

Abstract : A numerical technique was developed for computing the optimum spanwise load distribution on nonplanar wings of arbitrary shape. Munk's criterion for minimum induced drag was used. The problem is solved in the two- dimensional Trefftz plane. The two-dimensional shed vortex sheet is assumed to have the same shape as the nonplanar wing from which it was shed. The vortex sheet in the Trefftz plane is subdivided into 2N segments. Each vortex sheet segment is assumed to have a linear vorticity distribution. The velocity induced at N-Q stations is determined with the Biot-Savart law. The problem is then reduced to solving a set of linear algebraic equations. The technique was applied to nonplanar wings with various dihedral angles and locations of the nonplanar wing sections. It was concluded that if the span is the limiting factor then it may be advantageous to use nonplanar wings. On the other hand, if the wing total peripheral length is limited, then the planar wing is always the most desirable configuration, with the highest lift over drag ratio.