project is the continuation of a recent effort, on a European level, to
characterize, understand and control aircraft wake turbulence. Aircraft
in flight leave behind large-scale swirling flows (vortices), which can
represent a significant hazard to following aircraft, and therefore are
of great importance for practical applications concerning safety and
capacity of air transport.
main objective is to gain new knowledge on unresolved aspects of vortex
dynamics relevant to aircraft wakes, and to provide a more systematic
description than previously achieved, of the phenomena involved in
aircraft wake dynamics. These fundamental developments are necessary to
achieve major advances in this domain, in view of a successful
application of existing or future strategies for wake characterisation,
prediction, and alleviation.
Description of the work
FAR-Wake project contains four major work packages (WP), in which the
following subjects are investigated:
- Vortex instabilities and decay
Waves on vortices: vortex meandering, end effects, vortex
Vortex instabilities: short-wave elliptic instabilities,
medium- and longwave instabilities
- Vortex interactions with jets and wakes
Jets: cold engine jets, hot engine jets and compressibility
Wakes: fuselage wake, wakes of wing elements (engine
nacelle, landing gear, ...)
- Wake evolution near the ground
Idealised conditions (lab or simulation): uniform and
spatially evolving wakes
Real conditions (including atmospheric effects): data from
previous flight tests
Real-time modelling of vortices in ground effect
- Synthesis and assessment
the majority of the cases, emphasis was put on the study of simplified
geometries and generic vortex configurations, which facilitates the use
of different complementary approaches. In support of new experimental
and numerical investigations, theoretical/analytical treatment was
applied, with the aim of obtaining a systematic description and
comprehension of the phenomena. Furthermore, extensive use was made of
results and data from previous projects or available data bases. The
confrontation and comparison of different sets of results validate the
findings and make the description of the studied phenomena more
complete. At the end, an effort was made to provide a synthesis of all
the new fundamental results that were obtained, and to assess their
relevance for the wake turbulence problem for real aircraft. Certain
features found to be promising for the acceleration of wake decay, such
as flows with multiple wake vortices, were analysed and tested in a
realistic configuration, using numerical simulations and experiments in
a large-scale towing tank facility.
Summary of results achieved
of the main results achieved in this project, including the complete
list of all related publications and presentations can be found in the
Final Activity Report.
project has generated systematic results and physical understanding
concerning previously unresolved issues related to aircraft trailing
wakes, including the role of vortex instabilities, the influence of
engine jets and fuselage wakes, and ground effects. These results
solid knowledge base for future applications aiming at the reduction of
wake turbulence hazards. Concerning ground effects, the project has in
addition produced improved tools for the real-time prediction of wake
vortex behaviour, for potential use in the domain of Air Traffic Management.
Due to the mostly fundamental character of the research, the results
are also relevant in various other areas of fluid mechanics.
Vortices in the wake of a civil transport aircraft.
Optimal perturbation for
the excitation of vortex core deformations, possibly relevant for
understanding vortex meandering. Isosurfaces of axial vorticity at
initial and optimal times.
Long- and short-wave instabilities in a vortex pair.
Dye visualisation in a water tank.
Short-wave instability of a trailing vortex with axial core flow.
Dye visualisation in a water channel.
Ingestion of jet turbulence (red) into a vortex (yellow).
Dye visualisation in a water channel.
Ingestion of a hot jet into a vortex. Isoncontous of temperature from
wind tunnel experiments.
Structure of a landing gear wake. From RANS calculations.
Vortex pair in ground effect: instability of secondary vortices.
Results from Direct Numerical Simulation.
Vortex pair in ground effect with turbulent cross-wind.
Isosurfaces of vorticity from Large-Eddy Simulations.