Aircraft lift and drag decomposition in transonic flows

Abstract

A vorticity-based exact theory for the analysis of the aerodynamic force is here applied to three-dimensional aircraft configurations in steady transonic flow by postprocessing numerical solutions. A rigorous and unambiguous definition of lift-induced drag in compressible flows and its distinction from the profile component have been obtained. The equation is based on field integrals of the Lamb vector field highlighting the generation of the aerodynamic force in the rotational part of the flow only. Encountered numerical difficulties, arisen in high-transonic flow conditions, are first described. They have been overcome by a proper treatment of the numerical integration in the shock region where the accuracy of the numerical flow solution is poorer. Thus, a new exact formula is obtained for an accurate aerodynamic force computation in high-transonic and supersonic flows. In addition, a proper identification of the shock wave wake in the numerical solution allows for the decomposition of the profile drag in viscous and wave contributions. Applications are shown in the case of airfoil, elliptic wing and for the NASA Common Research Model wing–body configuration. Comparisons with classical drag breakdown methods are presented and the improvements obtained in the lift-induced drag analysis are discussed.