Wing-tip vortices, turbulence, and the distribution of emissions

Abstract

The decay of wing-tip vortices under the in uence of turbulence in a stably strati ed atmosphere is discussed by means of large-eddy simulations. The vortices originate from a B-747 aircraft in cruise. Atmospheric turbulence and turbulence originating from the boundary layer around the aircraft are distinguished. The former is weak and anisotropic with eddy sizes in the order of the wing span, whereas the latter is wrapped around the vortices with the maximum intensity at the core diameter. During their descent, the parallel vortex tubes approach each other because strati cation and turbulence detrain mass into the ambient air. The atmospheric eddies deform the trailing vortices such that their spacing varies. This, in turn, yields different mutually induced velocities that amplify the deformation quickly according to Crow's instability theorem. The bent vortex tubes link after about 1.5 min and form rings. The continuous trail of turbine exhaust is reorganized in a row of single puffs. Without any atmospheric turbulence the vortices approach each other but remain parallel. They start to dissolve after 2 min when they touch. This dissolution is triggered by the small-scale boundary-layer turbulence. The exhaust trail remains aligned along the ight track.

Large-eddy simulation of aircraft wake vortex deformation and topology

“…The numerical features of the LES code LESTUF are described in references [15] and [16]. For convenience, we briefly delineate the most important features.…”

Some thoughts on fallstreak holes

“…There is, however, another source of turbulence -the aircraft wake (Gerz and Holzapfel, 1999). The dynamics of aircraft wakes have been extensively studied by research aircraft using exhaust constituents as tracers of the flow, and by modelling (Dürbeck and Gerz, 1995;Fahey et al, 1995;Schumann et al, 1995;Baumgardner et al, 1998).…”

Influence of fuel sulfur on the composition of aircraft exhaust plumes: The experiments SULFUR 1–7

“…[23] In order to generalize the results to other aircraft, with more modern engines, and to search for sulfuric acid in the exhaust plume of cruising aircraft, an experiment was organized in which the Falcon could measure in the young exhaust plume of an Airbus A310 at cruise (plume ages 1 -4 s), and behind the ATTAS with refined instruments, at very close approach (plume age 0.5 -1 s), for situations with and without contrail formation and for a large range of FSC values (6 to 2830 mg/g) [Petzold et al, 1997]. The close approach of the Falcon to the ATTAS and Airbus aircraft was made possible by the Falcon pilots after learning about the nature of wake vortex formation [Gerz and Holzäpfel, 1999]. Steady flight conditions could be reached at some positions within the wake vortex as close as 25 m (during S6) behind the leading aircraft by expert pilots.…”