Developing a Numerical Framework for the High-Fidelity Simulation of Contrails: Sensitivity Analysis for Conventional Contrails

Abstract: Contrails have recently gained widespread attention due to their large and uncertain estimates of effective radiative forcing, i.e., warming effect on the planet, comparable to those of carbon dioxide. To study this aircraft-induced cloud formation in the context of current conventional fuels and future alternative fuels, we have developed a numerical framework for simulating the jet and early vortex interaction phases of contrail formation. Our approach consists of high-fidelity, 3D large-eddy simulations (LES) of an Eulerian-Lagrangian two-phase flow using the compressible flow solver charLES. We perform temporal simulations of the early contrail formation phases for a single linear contrail and compare the sensitivity of the results to modeling choices and atmospheric, aircraft, and engine parameters. Specifically, we discuss how these choices and parameters affect the number of nucleated ice crystals and estimated net radiative forcing (based on an optical depth parameterization). Our simulations show the most significant sensitivity to the aircraft size, followed by the soot number emission index and fuel consumption. Adding atmospheric aerosol as a precursor for future studies of sustainable fuels evidences a non-linear relation previously highlighted in the literature between number of emitted soot and nucleated ice crystals.