Abstract: Interaction problem between the airframe and the propulsion system of a modern large civil aircraft is one of the key points that is extremely important and must be carefully dealt with in the process of aerodynamic design. For a long time, commercial and in-house Computational Fluid Dynamics (CFD) solvers construct aerodynamic models to simulate the interference flow field of turbofan engine, by setting up the total pressure ratio and the total temperature ratio at exhaust plane and the mass flow ratio at inlet.Based on the current aerodynamic model and the idea of designating the external duct as the characteristic boundary, we present a new approach of modeling turbofan engine with power. Verification and validation are conducted by simulating the flow field around an axisymmetric ultra-high bypass ratio turbofan simulator, a turbine powered simulator and a typical civil aircraft with turbofan engine.The solutions show that, the traditional and the new model have both simulated the propulsion effects of turbofan engine with power properly, and the surface pressure coefficient distributions coincide well with the experiment data, illustrating the correctness, reliability and engineering applicability of both models. Moreover, our newly presented model is much more suitable for high bypass ratio turbofan engine and the evaluation of dynamic characteristics with unknown total pressure ratio and total temperature ratio at bypass. Hence, the new model has wider engineering application compared to traditional models.

Key words: computational fluid dynamics, large civil aircraft, turbofan engine, propulsion performance, unstructured grid