A criterion for minimum wave drag of a body

A method to obtain exact expression for the derivative of the wave-drag coefficient by using a specific global shape variation of a plane or axisymmetric body with a given fineness ratio was reported. This derivative determined how wave-drag coefficient changed when the body was replaced by a λ-equivalent body with a tail skirt. The study observed that the use of simple global variation of the contour of a plane or axisymmetric body of an arbitrary class with a given fineness ratio indicated the possibility of wave-drag reduction. The study concluded that weak and strong contour variations, which produced shock in the shock layer, helped to improve the body shape for reducing its wave drag. Body-shape variation with a positive kink angle of the longitudinal contour made a positive impact on the improvement of static margin.