Sensitivity of High-Fidelity Contrail Simulations to Model Choices and Input Parameters

The study of contrails has gained widespread attention because their effective radiative forcing (ERF) is comparable to that of carbon dioxide from aviation, yet current ERF estimates remain highly uncertain. To enhance predictions of contrail formation for both conventional and alternative fuels, we have developed a high-fidelity numerical framework for the simulation of the jet and vortex interaction phases of contrails. Our approach combines three-dimensional large-eddy simulations of an Eulerian–Lagrangian two-phase flow in the compressible flow solver charLES with detailed mixing, turbulence, and microphysics models. We conduct temporally resolved simulations of early single contrail formation and compare the effects of atmospheric, aircraft, engine, and modeling parameters on the number of nucleated ice crystals and estimated net radiative forcing. Adding bypass flow shifts the plume away from the ideal core-atmosphere mixing line and reduces the number of initially nucleated ice crystals, while a more complete microphysics treatment alters the nucleation rate but has a limited lasting effect for sufficiently low atmospheric temperatures. Our simulations show the strongest sensitivity to aircraft size, followed by the soot number emission index and atmospheric temperature. Atmospheric aerosols also produce a nonlinear low-soot regime, indicating that ambient aerosol can contribute appreciably to ice crystal formation.