Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

This paper presents improvements to the CIRAAMIL ice accretion software developed at AMIL (Anti-Icing Materials International Laboratory) in a joint project with CIRA (Italian Aerospace Research Center). The software is based on a panel method for flow field, Lagrange formulation for water droplet trajectories and the ice accretion thermodynamic model is similar to existing ones. The distinctive characteristic of the code is the analytical model used to calculate the object surface roughness during ice accretion which is based on the water behavior at the surface such as bead and water film. The local roughness height is calculated from two analytical formulations simulating bead formation and water film. In this version, the minimum bead height is calculated from the incoming droplet diameter and the water film thickness calculation is independent of time. Also, the object surface is characterized with a finer definition. The accretion model is calibrated with icing profiles obtained experimentally in wind tunnel by Shin and Bond for a NACA0012 and validated with 20 runs from 19 test series at the NASA Icing Research Tunnel between 1991 and 1998. Based on the final icing shapes, the CIRAAMIL code generated the complex ice shapes observed experimentally with good precision. However, in the majority of the cases, the predicted horn thickness is slightly larger than the measured and its orientation is poorly predicted for mid temperatures (-7 to -12°C). Also, at about the same temperatures and at lower speed (67 m/s), runback water is over predicted on the lower part of the wing. The improvements in the geometry code and physical model to predict surface roughness result in a better ice accretion software, but work is still need to improve the film roughness model. Also, without a proper water shedding model, it will be difficult to predict the ice shape with excellent accuracy.