Simulation numérique des grandes échelles d’un jet propulsif en sortie de moteur d’avion avec modélisation microphysique des particules de glace

Abstract

The worldwide importance given to environmental problems and the prospect of future growth in air traffic led most developed countries to start important research programs on the aviation’s impact on the environment. The first concerns the impact on the global warning. It was followed by the establishment of regulatory measures which essentially reduce local pollution. More recently, the pollution in altitude as become a major topic of research. This latter impact was studied by some authors such as Paoli & Garnier (2005b) ; the author showed that the interaction process is mainly controlled by entrainment of the jet by the vortex flow and the turbulent diffusion of the jet . Although, in studies of the impact of aviation on climate change, contrails influence are among the most uncertain on the climate. In this context, the study aims to better describe the microphysical phenomena of the plume in the near field of an aircraft, these being able to condition the properties of the formed contrails. The main goal of the thesis is to deepen the understanding of the formation and growth of ice particles by using and modifying a high precision CFD code with an integrated microphysical model in order to understand the contrails formation at flight altitude. The turbulent round free jet using LES was widely studied in the last decade. Non-reflective conditions are used as boundary conditions for free jets, also, dynamic Smagorinsky model (DSM) give good results at low Mach number (0.2) and low Reynolds number compared to experiment and DNS data. In our work, simulations were run using a multidimensional Navier-Stokes solver (FLUDILES), to compute a free jet at atmospheric pressure and realistic Reynolds number (106). First, the accuracy and the stability of the model will be discussed for the mesh size and boundary conditions. The flow field results will be compared with experimental correlations on the mean and turbulent quantities and analytics results. On the second part of the thesis, we will discuss in detail the results of high-resolution numerical simulations of jet/soot particle interaction that include microscale turbulent mixing. The last part of the thesis will focus on the influence of the engine design on the particle growth. The essential scientific and technological impact of this work is to enable the precise understanding and quantification of the influence of effluents emitted by current aviation on the atmospheric environment. The digital tool thus developed will potentially allow technical modifications, from the very design of the engines and consequently reduce the environmental borrowing of aircraft engines.

Date	7 Jul 2021
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	François Garnier (Supervisor) & Emmanuel Montreuil (Co-supervisor)