PhD defense - L. Nybelen

Numerical study of aircraft wake vortex

Delivered by Paul Sabatier Toulouse III University
Speciality: Fluid dynamics

June 10, 2008 - CERFACS

Abstract

The wake of an aircraft is composed of intense vortices whose lifetime may be of the order of several minutes in calm air. The may represent a significant danger to any following aircraft as they may cause an upset in roll or down wash. The aim of the present work is to contribute to the knowledge of the wake vortex behaviour, studying different flow configurations by direct numerical and large-eddy simulations. The first one concerns the wave propagation and collision along a single vortex, modelling the end-effects and vortex bursting phenomena, respectively.

The wave propagation characteristics and its consequences were analysed. Moreover, an objective criterion of appearance of the vortex bursting has been established. Then, the interaction between a vortex and jet has been simulated by temporal large-eddy simulations for the three flight conditions. In cruise condition, the interaction has for consequences to reduce the velocity extrema of the wing tip vortex. This effect is less important if the separation distance is large. For the take-off and approach phases, the study deals with the vortex emanating from a flap just above the engine jet. The results showed that the jet may be sufficient strong to lead to the complete loss of the vortex structure.

The third phenomenon studied is the merging of two co-rotating vortices, which governs the dynamics in the extended near-field of an aircraft wake. The temporal approach allowed to analyse the process in stable and unstable conditions, without axial flow and for two realistic vortex models. The boundary conditions has been adapted to perform spatial simulations. These simulations are more representative and let to take into account the torsion of the system and the effects of axial flow. Two vortex flow configurations were simulated showing the complexity of the mechanisms.

Jury

J.E. Weisfreid	Senior researcher - LPMMH of ESPCI, Paris	President
J.M. Chomaz	Senior researcher - LadHyX-Ecole Polytechnique, Palaiseau	Referee
P. Comte	Professor - LEA-ENSMA, Poitiers	Referee
A. Antkowiak	Assistant professor - IJLRA Paris VI	Member
F. Laporte	Coordinator A380 - Airbus France, Toulouse	Member
R. Paoli	Researcher - CERFACS, Toulouse	Member
P. Brancher	Assistant professor - IMFT-UPS Toulouse III	Advisor
A. Giovannini	Professor - IMFT-UPS Toulouse III	Advisor