Wake integration for three-dimensional flowfield computations: Theoretical development

This paper examines the analytical, experimental, and computational aspects of the determination of the drag acting on an aircraft in flight, with or without powered engines, for subsonic/transonic flow. Using a momentum balance approach, the drag is represented by an integral over a crossflow plane at an arbitrary distance behind the aircraft. Asymptotic evaluation of the integral shows the drag can be decomposed into three components corresponding to streamwise vorticity and variations in entropy and stagnation enthalpy, These are related to the established engineering concepts of induced drag, wave drag, profile drag, and engine power and efficiency. This decomposition of the components of drag is useful in formulating techniques for accurately evaluating drag using computational fluid dynamics calculations or experimental data.