Abstract
Abstract. A simplified approach has been applied to analyse the mixing and entrainment processes of the engine exhaust through their interaction with the vortex wake of an aircraft. Our investigation is focused on the near field, extending from the exit nozzle until about 30 s after the wake is generated, in the vortex phase. This study was performed by using an integral model and a numerical simulation for two large civil aircraft: a two-engine Airbus 330 and a four-engine Boeing 747. The influence of the wing-tip vortices on the dilution ratio (defined as a tracer concentration) shown. The mixing process is also affected by the buoyancy effect, but only after the jet regime, when the trapping in the vortex core has occurred. In the early wake, the engine jet location (i.e. inboard or outboard engine jet) has an important influence on the mixing rate. The plume streamlines inside the vortices are subject to distortion and stretching, and the role of the descent of the vortices on the maximum tracer concentration is discussed. Qualitative comparison with contrail photograph shows similar features. Finally, tracer concentration of inboard engine centreline of B-747 are compared with other theoretical analyses and measured data.
Highlights
The interaction of engine exhausts with the trailing vortices of an aircraft is an important topic for aviation impact on the atmosphere
Garnier e-mail: fgarnier@onera.fr 1996; Taleb et al, 1996) have shown the important part played by the system water vapour-sulphuric acid on aerosol formation in the wake
One reason is the lack of knowledge of accurate partial vapour pressures of dierent species in the wake vortex
Summary
The interaction of engine exhausts with the trailing vortices of an aircraft is an important topic for aviation impact on the atmosphere. For favourable ambient relative humidity and temperature, these emissions can lead to ice nucleation and growth processes that will form contrails in the atmosphere. These contrails may have an impact on cloudiness and may modify the Earth's radiative budget balance (Fortuin et al, 1995; Ponater et al, 1996). One reason is the lack of knowledge of accurate partial vapour pressures of dierent species (mainly water and sulphuric acid) in the wake vortex To assess these local variables which control the dispersion and dilution of the aircraft emissions, we have had to investigate the mixing process throughout the wake. In this study we focus on a simpli®ed analysis of the mixing and dispersion of the engine jet in the near ®eld of an aircraft
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