A Drag Reduction Method for Wings of Fixed Plan Form

A method is given for reducing the drag of wings of fixed plan form, while maintaining constant some property such as wing lift or wing volume. This drag reduction is accomplished through adjustment of the wing twist and camber if lift is fixed or by adjustment of the thickness distribution if the volume is fixed. As an example, the drag due to lift of flat rectangular wings and flat delta wings is studied. For the rectangular wings, it was found that no drag reduction could be obtained with twist, while camber led to a drag reduction that was negligible for high effective aspect ratios and large for low effective aspect ratios. The camber was most effective near the wing tips. Twist was found to be useful in reducing the drag due to lift of delta wings. For delta wings with supersonic or sonic leading edges, a uniform camber (constant across the span) produced no improvement. The interference drag for two superimposed pressure distributions comes from the pressures of one distribution acting on the local angles of attack for the other distribution. Two pressure distributions are called orthogonal if their interference drag is zero. The drag due to lift of any pressure distribution may be reduced by combining it with an orthogonal pressure distribution whose lift is not zero. This combined distribution can in turn be improved by a similar process. A procedure for constructing orthogonal distributions is given.