Jet-Wing Lifting-Surface Theory Using Elementary Vortex Distributions

Abstract

A lifting-surface theory for jet wings based on a finite-element method—the method of elementary vortex distribution or the EV D method—is presented. The method utilizes a set of independent but overlapped elementary horseshoe vortex distributions to represent the wing and jet sheet, and satisfies a set of mixed-type boundary conditions on both the wing and jet sheet. The solution includes chordwise and span wise loading distributions, from which sectional and total aerodynamic quantities (e.g., lift, pitching moment, induced drag, etc.) are derived. In view of the finite-element approach, the method can, in general, be applied to jet wings of arbitrary planform, camber, twist, partial-span flaps, and arbitrary trailing-edge jet-momentum distribution. The present method also reduces to a conventional lifting-surface theory when the jet momentum is zero. An extensive comparison has been made of solutions derived with the EVD method with other theoretical and experimental data for jet wings and conventional wings. Good agreement has been observed in the chordwise and span-wise loadings as well as total aerodynamic coefficients.