An analytical method for predicting the lift and drag for slender sharp-edge delta wings in ground proximity

A potential flow lifting surface method is combined with a vortex lift concept and applied to slender sharp-edge delta wings. A multihorseshoe vortex lattice method incorporating an image technique is used to compute the potential flow normal force and axial force characteristics of delta wings in ground proximity. A free-air vortex lift concept based on a leading edge suction analogy is utilized to account for the lift increment due to the leading edge spiral vortex. A method is developed for combining the free air vortex lift concept with the potential flow theory results in ground proximity. A comparison of theoretical and experimental lift and drag for delta wings having a wide range of aspect ratios is made at selected angles of attack, The comparison indicates that this method provides a reasonably good prediction of the lift and drag in ground proximity for aspect ratios less than two in the angle of attack range from approximately 5° to 16°.