Simulation de la formation de traînée de condensation dans le champ proche d’un turboréacteur d’avion avec un modèle microphysique basé sur la solubilité des particules de suie

Abstract

The environmental impact of civil aviation, identified through the global energy balance, is largely caused by the greenhouse effect resulting from contrails, which are formed by the passage of an aircraft through the airspace and can, under the right ambient conditions, develop into persistent induced cirrus clouds. Consequently, the formation of contrails is a phenomenon that is difficult to measure experimentally, reinforcing the importance of modeling and simulation to quantify its impact. For this reason, studies have been conducted to better understand the physical phenomena and processes leading to the formation and growth of ice crystals, which result in the appearance of induced cirrus clouds. Computational Fluid Dynamics (CFD) is used to simulate the jet at the exit of the engine alone under cruise flight conditions. The Reynolds-Averaged Navier-Stokes (RANS) equations are solved in the near field of the jet. The simulations model a multiphase gas, composed of air and water vapor, which is compressible in a turbulent regime. A solid phase is added to model soot particles, originating from combustion in the engine, within the jet, thus allowing their movement to be tracked using a Lagrangian approach. Finally, the growth of these particles, evolving within the jet, is calculated using models developed by Kärcher for the liquid phase and by Fukuta and Walter for the solid phase. The results obtained explore the impact of various parameters related to the ambient environment and propulsion. They show that high temperatures (>225 [K]) prevent the formation of contrails, while lower temperatures (<215 [K]) promote it. Ambient humidity does not affect the development of contrails in the near field of the engine, as the water in the jet primarily comes from propulsion. Increasing the amount of water expelled by propulsion increases the amount of ice crystals formed by combustion. The soot particle emission index influences the maximum number of crystals that can be formed and the amount of water available in the domain. Finally, the initial radius of soot particles only affects the result if the ambient temperature approaches the threshold temperature (~225 [K]) for ice crystal formation.

Date	6 Dec 2024
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	François Garnier (Supervisor)