Numerical analysis of near-field flow and particle characteristics of condensation tail for a separate-exhaust aeroengine

Aircraft condensation trails (contrails), particularly persistent ones in ice-supersaturated regions, significantly contribute to aviation-induced climate forcing. This study conducts RANS-based numerical simulations with particle microphysics model to analyze near-field flow dynamics and particle characteristics in the condensation trail of a full-scale, separate-exhaust turbofan engine. A validated computational framework integrates compressible flow dynamics, Shear-Stress Transport (SST) k - ω turbulence modeling, and Lagrangian particle tracking with detailed heterogeneous condensation physics. Simulations cover 0–100 fan diameters ( D b ) downstream, resolving coupled turbulent flow structures, temperature decay, supersaturation fields, and particle growth. Key findings reveal rapid particle diffusion from the core to freestream regions, driven by shear-induced turbulence, with ambient relative humidity (RH) critically governing particle activation and growth kinetics. Results show that turbulent flows drive rapid radial dispersion, with over 75% of particles transported to the freestream within 100 Db downstream, leading to a width expansion to approximately 1.5 D b . The maximsum supersaturation ( S ≈ 3.5) occurs radially near 1.1 D b under RH = 60%. In sub-saturated conditions (RH ≤ 60%), particle diameter increases nearly 25 times, with minor variation between RH = 0% and RH = 60%. Under supersaturation (RH = 120%), the average particle size increased while the size distribution became more uniform. This work underscores the necessity of providing detailed and accurate initial conditions for simulating the initial-stage contrails.