Contrails, which appear behind aircraft engines in flight, represent a significant contribution to the radiative forcing associated with civil aviation. This phenomenon becomes particularly critical when contrails evolve into induced cirrus clouds, whose extended lifetime amplifies their climatic impact. However, large uncertainties remain due to the variability of atmospheric conditions and the complex spatial and temporal scales involved. Moreover, the difficulty of obtaining representative experimental measurements makes numerical simulations a particularly suitable approach for studying these phenomena. In this context, this work aims to analyze the interaction between the engine exhaust jet and the wingtip vortex generated by the aircraft’s wing, to better understand their role in the formation and evolution of contrails.
To model this phenomenon, computational fluid dynamics is employed under cruise flight conditions. The Reynolds-Averaged Navier–Stokes equations are solved over a one-kilometre domain downstream of the engine, first in steady state and then in unsteady mode. The exhaust plume is represented as a Lagrangian phase of soot particles evolving in a compressible and turbulent mixture of air and water vapour, allowing both spatial and temporal evolution to be tracked. This evolution is modelled using Kärcher’s formulation for the liquid phase and the Fukuta and Walter model for the solid phase.
Parametric studies were conducted to assess the influence of various flow parameters on contrail formation and development. The presence of the wing, which generates the wingtip vortex, induces significant plume dilution, increasing the contrail cross-section by up to a factor of two compared to the single-engine configuration. In addition, higher ambient temperatures (>225 K) limit contrail formation, while lower temperatures (<215 K) favour it. The initial radius of soot particles at the engine exit shows no significant influence for the considered conditions. Finally, the emission index directly affects the size of the ice crystals within the plume and, consequently, the overall visibility of the contrail.
| Date | 24 Nov 2025 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | François Garnier (Supervisor) |
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Brégeot, V. (Author),
Garnier (Supervisor),
24 Nov 2025Student thesis: Master's thesis › Master in Engineering: Engineering