Large-eddy simulations (LES) have been employed to investigate the far-field four-vortex wake vortex evolution over 10min behind an aircraft formation. In formation flight scenarios, the wake vortex behaviour was found to be much more complex, chaotic and also diverse than in the classical single aircraft case, depending very sensitively on the formation geometry, i.e. the lateral and vertical offset of the two involved aircraft. Even though the case-by-case variability of the wake vortex behaviour across the various formation flight scenarios is large, the final plume dimensions after vortex dissolution are in general substantially different from those of single aircraft scenarios. The plumes are around 170 to 250m deep and 400m to 680m broad, whereas a single A350/B777 aircraft would produce a 480m deep and 330m broad plume. Formation flight plumes are thus not as deep, yet they are broader, as the vortices do not only propagate vertically but also in span-wise direction. Two different LES models have been employed independently and show consistent results suggesting the robustness of the findings. Notably,$CO_{2}$emissions are only one contribution to the aviation climate impact among several others like contrails and emission of water vapour and nitrogen oxides, which would be all affected by the implementation of formation flight. Thus, we also highlight the differences in ice microphysical and geometrical properties of young formation flight contrails relative to the classical single aircraft case.

中文翻译：

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两架飞机编队飞行的远场尾涡演化及其对年轻尾迹的影响

大涡模拟 (LES) 已被用于研究飞机编队后 10 分钟内的远场四涡尾涡演化。在编队飞行场景中，发现尾涡行为比经典的单一飞机情况更加复杂、混乱和多样化，这非常敏感地取决于编队几何形状，即两架相关飞机的横向和垂直偏移。尽管在各种编队飞行情景中尾涡行为的逐例变化很大，但涡流溶解后的最终羽流尺寸通常与单个飞机情景中的大不相同。羽状物深约 170 至 250m，宽 400m 至 680m，而一架 A350/B777 飞机将产生 480m 深和 330m 宽的羽状物。因此，地层飞行羽流没有那么深，但它们更宽，因为涡流不仅垂直传播，而且沿展向方向传播。两种不同的 LES 模型已独立使用，并显示出一致的结果，表明研究结果的稳健性。尤其，$CO_{2}$排放只是对航空气候影响的一种贡献，如凝结尾迹以及水蒸气和氮氧化物的排放，这些都会受到编队飞行的影响。因此，我们还强调了年轻编队飞行轨迹相对于经典单机情况的冰微物理和几何特性的差异。