Reducing Climate Impact through Formation Flying: A Refined Approach to Contrail Simulation and Wake Vortex Analysis

Given the significant environmental impacts associated with global aviation, this sector must transition towards being more climate-friendly. Emissions from CO₂ and NO_x contribute substantially to climate change, while contrails also have a high negative impact. The establishment of formation flight configurations involving two or more passenger aircraft can support the reduction of the climate footprint, without the need for revolutionary technological improvements. By retrieving the energy generated from the wake vortex of the leading aircraft, subsequent aircraft experience reduced induced drag, thereby decreasing fuel consumption and emission (e.g., -5% CO₂ and  -15% NO_x). As a consequence of atmospheric saturation effects, this approach also reduces the impact of contrails, resulting in an overall reduction in climate impact of approximately 25%. 
The evolution of contrails depends on the dynamics of the wake vortices, as the aircraft exhaust and the resulting contrail ice crystals are captured within the wake vortex system and transported downwards. When flying in formation, the wake vortex system of the leading aircraft is affected by the interference with the wing and fuselage of the following aircraft. The complex interaction between the four wake vortex tubes requires a realistic modeling of the wake vortex dynamics behind a formation configuration. However, existing simulations have been limited to idealized scenarios.
To address this limitation, we develop a novel, refined and more realistic initialization method for our early contrail simulations. Firstly, we conduct RANS-LES simulations with two wings flying in formation, followed by the extraction of a velocity field downstream of the second wing. Subsequently, we initialize our early contrail simulations using this velocity field. This approach will be compared with previous analytical methods and with the contrail behavior of individual aircraft to quantify the potential for climate impact mitigation.
The work is performed as part of the EU project GEESE, which aims to demonstrate the operational feasibility of commercial formation flights over the North Atlantic and continental European airspace.