Abstract
An unsteady tightly-coupled icing model is established in this paper to solve the numerical simulation problem of unsteady aircraft icing. The multi-media fluid of air and droplets is regarded as a single medium fluid with variable material properties. Taking the droplet concentration as the phase parameter and the droplet resistance coefficient as the interphase force, the mass concentration distribution of the droplet is obtained by solving the Cahn–Hilliard equation. Fick’s law is introduced to improve the Cahn–Hilliard equation to predict the droplet shadow zone. On this basis, the procedure of the unsteady numerical simulation method for aircraft icing is established, including grid generation, the dual-time-step method to realize the unsteady calculation of the air and droplet tightly-coupled mixed flow field, and the improved shallow water icing model. Finally, through the comparative analysis of numerical examples, the effectiveness of the new model in predicting the droplet impact characteristics and the droplet shadow zone are verified. Compared with other icing models, the ice shapes predicted by the unsteady tightly-coupled model were found to be the most consistent with the experiments. In the icing comparison conditions in this manuscript, the prediction accuracy of the ice thickness at the stagnation point of the leading edge was up to 35% higher than that of LEWICE.
Highlights
The aircraft icing problem has been one of the most important problems in flight safety [1]
A number of mature icing numerical simulation codes have been developed and widely used in industry, such as LEWICE developed by NASA [5,6], FENSAP-ICE developed by NTI (Newmerical Technologies International) [7,8], TRAJICED developed by DRA [9], IGLOO2D and IGLOO3D developed by ONERA [10] and so on
It can be seen from the figure that the boundary of the sheltered area obtained by the numerical simulation is the same as the experimental results, which proves the accuracy of the tightly-coupled model in this paper in predicting the shadow zone of droplets, and shows the correctness of the calculation results of water droplet trajectory
Summary
The aircraft icing problem has been one of the most important problems in flight safety [1]. Zhu [27] proposed an adaptive Cartesian method combined with the ghost cell method for the aircraft unsteady icing problem This numerical method calculates the airflow field by solving Eulerian equations and uses the Lagrangian method to obtain the droplet trajectories, and the solution of the droplet trajectories is still steady. In view of this situation, in this paper, we propose a numerical simulation method of the unsteady tightly-coupled icing process.
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