21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-2.10.1

MODELING EXHAUST JET DILUTION IN AIRCRAFT WAKES: APPLICATION TO THE CONTRAIL FORMATION

Garnier F., Laverdant A.
ONERA, France

Keywords: modeling, exhaust jet dilution, aircraft wakes, contrail formation

In order to investigate the process of contrail formation, an integral model and a two-dimensional direct numerical simulation have been performed to analyze the mixing and entrainment processes of the engine exhaust through. their interaction with the vortex wake of various aircraft. The objective of this study is to evaluate the partial vapor pressure of water and temperature in the near field of subsonic and supersonic aircraft. Results are presented involving the relative humidity calculation by post-processing solution fields and provide a qualitative indicator of the condensation process. After testing numerical algorithm with some success, this study was performed for three transport subsonic aircraft: A-330, B-737 and DC-9; for twin-engine ATT AS of DLR and for the Anglo-French supersonic Concorde. For subsonic aircraft, in the early wake, the distance where the saturation is reached depends only upon the engine jet characteristics. For the supersonic aircraft, a low relative humidity has been shown in the plume centerline. However, the wing-tip vortices contributes largely to increase the mixing and dispersion of the exhaust plume. Consequently the persistence or evaporation processes is clearly changed by the vortical structure. Effects of aerodynamics parameters are analyzed and discussed.

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