Eulerian method for Super-Cooled Large-Droplet Ice-Accretion on aircraft wings

Abstract

Many research has been done to provide scientists and aviation engineers with tools to predict ice accretions on in ight aircraft. The ice accretion problem is often sudden, its eects can be dramatic, leading to aircraft accidents with possible loss of lives. Until now this eld has been relatively steady. It has proven to be fairly easy to model ice accretions for clouds with droplets of relatively small droplet diameter (< 50 μm). However, a recent trend is to investigate supercooled large droplets, with diameters ranging from 50 μm through 1000 μm or larger. These large droplets have been found to be more prominent in nature than previously thought. Ice accretions caused by these droplets have been identied as the likely cause for several aviation incidents during the last decade. Ice accretion by sld are far more dicult to predict than those by smaller droplets. Development of ice accretion models for sld has found renewed focus and was the central research theme in the European Commission FP7 extice project. Much of the research in this thesis has its origins, or has been inspired by, this project. A new sld ice accretion method has been developed, incorporating: droplet size distributions, droplet deformation, droplet splashing, and droplet rebound. This method has been validated against experimental catching eciencies and experimental ice accretions shapes. Furthermore, this method has been extended from a Lagrangian method for two-dimensional ow to an Eulerian method for three-dimensional ow. Validation results show an accuracy of droplet catching eciencies within 10%. The ice accretion shapes are more dicult to accurately predict, but without a boundary layer lm ow model the ice accretion thickness can also be predicted within approximately 10% accuracy.