Integration of mixed-fidelity aircraft/engine modelling to assess contrail mitigation strategies

Aviation’s environmental impact must be addressed in a multidisciplinary manner, further targeting improvements in CO₂ emissions whilst also ensuring reductions in short-term non-CO₂ radiative forcing, with particular focus on the largest contributor, aircraft contrails. Considering the challenges and cost associated with experimental measurements, to begin to formulate potential strategies to mitigate the impact of contrails, increased modelling fidelity and accuracy is required. Such work allows for the processes behind a contrail’s evolution to be better understood, whilst investigating key factors which dictate initial formation, particle properties, and climatic impact. From an engineering perspective, the key regions of interest are within the early regimes, covering contrail formation and early dynamics, where choices in aircraft and engine design can impact the initial contrail evolution.

To explore such effects, high fidelity RANS CFD with in-built contrail microphysics has been conducted on a fully featured aircraft geometry and its near-field wake. This allowed for accurate assessment of air vehicle performance, contrail formation, and aerodynamic interactions at cruise flight conditions. The CFD simulations incorporated a developed parametric aircraft model with realistic engine geometry to easily allow modifications in design to be studied and assessed in a multidisciplinary manner with respect to their environmental impact. To further increase the fidelity of the work, a detailed thermodynamic engine cycle model was coupled to the CFD boundary conditions and iterated upon throughout the simulations to ensure appropriate exhaust conditions for cruise flight were attained. Particle emissions at cruise were predicted by a machine learning model dependent on engine design and thrust setting. High level engine design choices, such as bypass ratio, were parametrised, with nacelle sizing requirements linked between the output of the engine model and CAD geometry to ensure installation effects and exhaust interactions were accurately captured, in addition to the required fuel burn and particle emissions. Simulation results from the early regime are intended to assess consistency with reduced fidelity model predictions, as well as to form a parametric input for longer term, global models.

Development of such models allows for aircraft/engine design exploration to be conducted to better understand pathways to potential mitigation of aviation’s environmental impact, inclusive of both CO₂ emissions and contrails.