Representing the Dispersion of Emissions From Aircraft on Runways
Year: 2008
Type: conference-paper
Abstract: : Aircraft in their takeoff ground run constitute an unavoidable strong source of emissions subject to a highly variable motion. The intermittent nature of release makes it difficult to measure the emissions and establish their impact on mean concentrations in the vicinity of airports. Practically, it is also difficult to perform experimental studies near taxiways and runways. Remote observations have nevertheless recently been obtained by a rapidly-swept UV Lidar, and analysis of these has necessitated and informed a parallel modelling effort. Aircraft exhausts disperse in a complex manner, as they are subject not only to transport processes of the ambient atmosphere, but also to those associated with the aircraft itself (with diffusion in ambient turbulence to be expected once turbulence resulting from the aircraft falls to ambient levels). They have a downstream Lagrangian momentum associated with the engine thrust, and steadily acquire a vertical momentum as a result of their buoyancy. Exhaust streams merge and interact strongly with the ground to form a common emission plume within about a wingspan downstream of engines ’ exits. Before the aircraft reaches a threshold speed, is rotated upward and lifts off, the downstream (thrust) forcing and upstream source acceleration are approximately constant, and a first-order nonlinear partial differential equation may be expressed capturing the turbulent diffusion of the plume in the reference frame of the source. The downstream forcing exceeds the buoyant forcing, so the plume remains in contact with the ground, but is heightened and narrowed by buoyant rise. During rotation and liftoff, the net downstream forcing declines as a significant airframe drag arises, and the source acceleration plummets. More importantly, lift on the airframe and the associated shed circulation cause exhausts to move downward and, in proximity to ground, outward, so their
Authors: A. Graham, Michael Bennett, Simon Christie
Institution: Manchester Metropolitan University
Language: English
Topic: Wind and Air Flow Studies
Subfield: Environmental Engineering
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2193766340