Aircraft contrails contribute to climate change through global radiative forcing. As part of the general effort aimed at developing reliable decision-making tools, this paper demonstrates the feasibility of implementing a Lagrangian ice microphysical module in a commercial CFD code to characterize the early development of near-field contrails. While engine jets are highly parameterized in most existing models in a way that neglects the nozzle exit-related aspects, our model accounts for the geometric complexity of modern turbofan exhausts. The modeling strategy is based on three-dimensional URANS simulations of an aircraft nozzle exit involving a bypass and a core jet (Eulerian gas phase). Solid soot and ice particles (dispersed phase) are individually tracked using a Lagrangian approach. The implemented microphysical module accounts for the main process of water-vapor condensation on pre-activated soot particles known as heterogeneous condensation. The predictive capabilities of the proposed model are demonstrated through a comprehensive validation set based on the jet-flow dynamics and turbulence statistics in the case of compressible, turbulent coaxial jets. Simulations of contrail formation from a realistic nozzle-exit geometry of the CFM56-3 engine (short-cowl nozzle delivering a dual stream jet with a bypass rate of 5.3) were also carried out in typical cruise flight conditions ensuring contrail formation. The model provides reliable predictions in terms of the plume dilution and ice-particle properties as compared to available in-flight and numerical data. Such a model can then be used to characterize the impact of nozzle-exit parameters on the optical and microphysical properties of near-field contrails.

飞机凝结尾迹通过全球辐射强迫助长了气候变化。作为旨在开发可靠的决策工具的一般工作的一部分，本文证明了在商业CFD代码中实施拉格朗日冰微物理模块以表征近场凝结尾迹早期发展的可行性。尽管在大多数现有模型中对发动机喷气机进行了高度参数化，而忽略了与喷嘴出口相关的方面，但我们的模型考虑了现代涡轮风扇排气装置的几何复杂性。该建模策略基于飞机喷嘴出口的三维URANS模拟，该喷嘴涉及旁路和核心射流（欧拉气相）。使用拉格朗日方法分别跟踪固体烟尘和冰粒（分散相）。实施的微物理模块解决了水蒸气在预活化烟尘颗粒上凝结的主要过程，即所谓的异相凝结。在可压缩湍流同轴射流的情况下，通过基于射流动力学和湍流统计数据的综合验证集，可以证明所提出模型的预测能力。在典型的巡航飞行条件下，还从CFM56-3发动机的实际喷嘴出口几何形状（短流形喷嘴以5.3的旁通率提供双流喷射的短罩喷嘴）模拟了转换轨迹，以确保转换轨迹的形成。与可用的机载数据和数值数据相比，该模型就烟羽稀释度和冰粒性质提供了可靠的预测。