Full-Aircraft Energy-Based Force Decomposition Applied to Boundary-Layer Ingestion

Abstract

This Paper introduces a generic force decomposition method derived from mechanical energy conservation. A transformation from relative to absolute reference frame captures the power transfer from pressure and skin-friction forces on aircraft surfaces to mechanisms in the flowfield. A unique flow-feature extraction procedure isolates these mechanisms into different regions including the jet-plume substructures as well as shocks and shear layers located externally to the jet. Featured is a novel shear-layer identification metric that captures both laminar and turbulent regions. The resulting energy balance is rearranged into a force decomposition formulation with contributions attributed to shocks, jets, lift-induced vortices, and the remaining wake. Boundary-layer ingestion is used to demonstrate the method where a potential for energy recovery factor is introduced and defines the amount of energy available at the trailing edge of an unpowered body. Computational fluid dynamics results of a fuselage suggest 10% of its drag power is available for reuse. Computational fluid dynamics studies of a boundary-layer ingesting propulsor show local minima in power consumption at a given thrust split for particular combinations of fan pressure ratio and amount of boundary layer ingested. A noteworthy finding reveals significant contributions of volumetric pressure work, a term often neglected in previous work.