Non-Spherical Particle Trajectory Modelling for Ice Crystal Conditions

摘要

Aircraft icing is a significant issue for aviation safety. In this paper, recent developments for calculating the trajectory of non-spherical particles are used to determine the trajectory and impingement of ice crystals in aircraft icing scenarios. Two models are used, each formulated from direct numerical simulations, to give the drag, lift and torque correlations for various shaped particles. Previously, within the range of Reynolds number permitted in this study, it was only possible to model the trajectory and full rotational progression of cylindrical particles. The work presented in this paper allows for analysis of a wider range of ice shapes that are commonly seen in icing conditions, capturing the dynamics and behaviours specific to ice crystals. Previous limitations relate to the in ability to account for particle rotation and the dependency of force correlations on the measure of particle sphericity - which are now overcome. The method also provides an opportunity for new analysis - the creation of catch bounds for mixed clouds of particles. The above models are applied to two geometries and compared with drag only cases for spheres and non-spherical particles as parameterized by sphericity. The analysis shows that taking the worst- and best-case scenarios provide a range of values for the catch, which can help to understand better the extent over which particles impinge. Hence a catch-limit for a mixed cloud of particles of different shaped particles and different sized particles may be easily gained. The methods are also able to capture rotations and trajectories in three dimensions. Incorporating new methods for modelling the trajectory, rotation and orientation of non-spherical particles into the modelling of aircraft icing opens new avenues for industrial analysis. In turn this may aide several areas of aircraft design related to engine design and flight instrumentation system design as well as informing the aircraft certification process.