Ice accretion prediction with mixed phase cloud particles

2017
Ayan, Erdem
Existence of ice crystals in convective clouds has become one of the major threats for flight safety. Several flight incidents have been reported in the last decades due to ice accretion around heated surfaces like air probes or on engine components. Ice accretion due to water droplets is a well studied issue. However, ice accretion due to ice particles is a relatively new aspect and the physics are not yet fully understood. Hence adequate models for representing the physical phenomena are very scarce. Withinthe recent years, several projects and groups have focused on this topic. High Altitude Ice Crystals (HAIC) project is one of them which has started in 2012 and completed in January 2017. HAIC FP7 European project is a large-scale integrated project and ice crystal accretion prediction is one of the issues within the scope of this project. It is observed in these studies that differing from water droplets, ice crystals generally pose a threat once they reach heated surfaces and either when they are partially melted or when water film is already accreted on the surface. Ice crystals can either melt completely during their trajectories by convection or melt upon impact on warmer components. Thus, the height of the liquid film on corresponding components increases resulting in more ice crystals sticking. This scenario causes reduction in local surface temperature and enhances the probability of in flight incidents by developing suitable conditions for iceaccretion. Within the scope of this thesis, one aim is to enhance capabilities of an in-house developed tool TAICE by including models related to ice crystals accretion. Drag coefficient, heat transfer, phase change, impingement, erosion and accretion models have been implemented to TAICE. Some of them have been modified and further calibrated thanks to the available experimental results in literature. Another aim is to extend the two-layer ice accretion model (ExtendedMessingerModel) for mixed phase and glaciated icing conditions. In two layer method, instead of predicting the equilibrium temperature in Original Messinger Model, temperature variation is modeled within the ice and water layers to improve accuracy of the prediction. Extension of the Messinger Model has not been performed up to now in the literature for ice crystal accretion and this motivates the study. All of the implemented models are detailed in theory part and validation of the tool has been performed by using NASA-NRC, COX and TUBS experiments. Moreover, some 2D and 3-D industrial applications like ice accretion prediction on engine inlet and pitot-tube have been included in this thesis. 
Citation Formats
E. Ayan, “Ice accretion prediction with mixed phase cloud particles,” Ph.D. - Doctoral Program, Middle East Technical University, 2017.