Aircraft icing, physical modeling and numerical simulation

Identified as a major risk from the very beginnings of aeronautics, icing remains to this day the leading cause of accidents excluding human factors.

Icing results from the more or less rapid capture and freezing of supercooled water droplets (liquids at a negative temperature) present in certain clouds crossed by aircraft. The water droplets strike the front of the aircraft's various structures, breaking the unstable state of supercooling and leading to the formation of ice. If left unprotected, this ice build-up can lead to major changes in the aerodynamic profiles of the canopies, as well as to engine shutdowns due to the ingestion of ice detached from the air intakes. Protection systems are available to limit the amount of ice deposited on the aircraft by mechanical or thermal means.

To study this phenomenon, optimize protection systems and verify their effectiveness throughout the flight envelope, while limiting the number of flight tests, two complementary methods are used: numerical simulation and icing wind tunnel testing. For numerical simulations, this document analyzes the various models and gives details of the terms neglected. For wind tunnel tests, the size of the model generally makes it impossible to work on a 1:1 scale, and it is therefore necessary to use a reduced-scale model. In the case of icing, the classical dimensional analysis approach does not allow exact similarity laws to be defined, which is why approximate similarity rules have been defined.