Project description
 (see also the EU database entries here and here)














Fundamental Research on Aircraft Wake Phenomena



Project type

Specific Targeted Research Project (STReP)

Contract number



01 February 2005


40 months


3.84 Million Euro (final)

EU support

1.98 Million Euro


17 organisations in 8 countries


This 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.


The 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

The FAR-Wake project contains four major work packages (WP), in which the following subjects are investigated:

WP1 - Vortex instabilities and decay

            Waves on vortices: vortex meandering, end effects, vortex bursting
            Vortex instabilities: short-wave elliptic instabilities, medium- and longwave instabilities

WP2 - Vortex interactions with jets and wakes

            Jets: cold engine jets, hot engine jets and compressibility effects
            Wakes: fuselage wake, wakes of wing elements (engine nacelle, landing gear, ...)

WP3 - 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

WP4 - Synthesis and assessment

In 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

A description 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.


This 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 represent a 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.



Left: Ingestion of jet turbulence (red) into a vortex (yellow). Dye visualisation in a water channel.

Right: 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.