Eulerian-Lagrangian CFD-microphysics modeling of aircraft-emitted aerosol formation at ground-level

Aviation-induced particulate matter directly affects the climate, the atmospheric composition at flight altitudes, and local air quality near airports. Meeting environmental regulations is a key challenge for the future development of air transportation. To enhance the understanding of secondary aerosol formation in aircraft plumes, an innovative methodology combining flow dynamics in aircraft engine plumes with a particle-based microphysical model is proposed. To this end, 2D axisymmetric unsteady Reynolds-Averaged Navier-Stokes simulations were conducted behind a realistic aircraft engine geometry. The CFD model was coupled with a tabulated chemistry and a detailed microphysical model accounting for soot surface activation, condensation of organic vapors and sulfur species (H2SO4, SO3), as well as scavenging of sulfuric acid-water droplets on soot surfaces. The model's predictive capacity was validated against experimental data from APEX 1-2, encompassing plume aerothermodynamics properties and the evolution of gaseous species from low-idle (4%) to take-off (100%) power settings of the CFM56-2C1 aircraft engine. The predicted size distributions of total and nonvolatile particles matched reasonably well with measurements from APEX-1 within the near field (<= 30 m). The model reveals the engine power dependency of soot and the chemical composition of volatile particles, predominantly influenced by organic compounds downstream of the engine. Adsorption of gaseous species of organic compounds and sulfuric acid were identified as the most dominant mechanism for soot particle coatings in the near field, regardless of operating conditions.