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- Numerical and Physical Characterization of a TwoWay Coupling Approach for the Simulation of Fluid Flows under Cryogenic ConditionsPublication . Meireles, Rúben Diogo Silva Oliveira; Silva, André Resende Rodrigues daThe crystallization of water droplets is a ubiquitous phenomenon, which plays a fundamental role in many natural and artificial processes. This phenomenon gained particular interest in the aeronautical industry due to ice accretion on lifting surfaces and engine intakes. Additionally, the aerospace sector also uses this phenomenon for the development of cryogenic rocket engines. This dissertation aimed at studying the cooling of water droplets, at different diameters and air humidity ratios, through the conversion of a preexistent inhouse computational tool for that purpose. In order to predict the behavior of discrete particles, a mathematical model that accounted for the physics behind the cooling phenomenon of liquid water droplets was incorporated into the existing code. To predict the convective effects experienced by the droplets two correlations were used: the RanzMarshall classical formulation and an empirical transient formulation that corrects the first one. The results obtained were compared with a numerical study that used a oneway coupling model and experimental data available in the literature. To understand how these results are integrated into a complete freezing process, an analytical study of a fullscale fourstage freezing model was performed and further compared with experimental data. The numerical results showed that for, high humidity content, the interaction between the particle and the surrounding environment becomes predominant and needs to be accounted for. When considering low humidity content, this interaction can be neglected since the oneway coupling resembles the experimental data in a better way. Additionally, it was concluded that the complete mixing model, which does not account for deformations and vibrations of droplets, is an acceptable assumption when considering low or high humidity ratios and that for intermediate humidity content, the mixing model assumption, which accounts for those effects, shows close agreement with experimental data. The analytical model implemented for the fullscale supercooling freezing of water droplets was able to predict the phenomenon.