Full-aircraft energy-based force decomposition applied to boundary layer ingestion

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 flow-field . 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. CFD results of a fuselage suggest 10% of its drag power is available for re-utilisation. CFD 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