Developing a numerical framework for high-fidelity simulation of contrails: sensitivity analysis for hydrogen contrails*

Contrails are a non-CO2 effect with an uncertain but high radiative forcing impact.

As aviation decarbonizes and moves toward using sustainable aviation fuels and hydrogen, the impact of contrails grows more uncertain. This is especially true for hydrogen, where larger emissions of water vapor may lead to more widespread contrail formation in the presence of suitable ice nuclei.

 

In this work, we simulate the initial phases of contrail formation, jet and vortex phases, for Jet A and hydrogen-fueled aircraft. The main distinguishing parameters are water vapor emissions, aerosol location, concentration, and hygroscopicity.

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 use aerosol-to-ice microphysics modeling (water droplet activation, growth, freezing, and ice crystal growth) and add a bypass to the idealized core flow to simulate the aircraft jet exhaust.

 

A sensitivity analysis showcases the impact of the aircraft size, atmospheric temperature, and aerosol number on ice crystal mean size and number.

We compare the warming potential of contrails from conventional and alternative fuels with optical depth and radiative forcing estimates.