Towards refined contrail simulations of formation flight scenarios

Abstract

Flying in formation reduces the climate effect of CO2 and non-CO2 emissions from passenger aircraft. In particular, the climate effect of contrail-cirrus can be substantially reduced. A comprehensive understanding of the contrail evolution and spreading is crucial. However, observational data are challenging to obtain, and previous simulations have often relied on idealized initialization settings, even for single-flight scenarios. In this study, we present large-eddy simulation (LES) of the early contrail evolution during the so-called contrail vortex phase, which is characterised by an interplay of ice microphysics and wake vortex dynamics. The objective of this study is to understand the sensitivity of the early contrail evolution to the initialization of the wake vortex flow field. In our previous LES studies, the description of the initial wake vortex flow was based on an analytical Lamb-Oseen vortex profile. In the present studies, the flow initialization is based on a priori Reynolds-Averaged Navier-Stokes simulations (RANS), which model the flow around the complete aircraft geometry, specifically of an A380 and A320. Our findings indicate that the initialization of the flow field has a substantial impact on the outcome when compared to simulations utilizing previous idealized initialization settings. Notably, not all ice crystals are captured within the RANS-initialized wake vortex system but remain at emission altitude. The analyses presented in this study are a major prerequisite for establishing more realistic contrail simulations behind aircraft formations. In an upcoming study, the contrail LES model will be initialized with a flow field behind a two-aircraft formation that is obtained from a RANS-LES model.