A multistage approach to computational modeling of large droplet breakup

Ice accretion on aircraft has been, and remains, a long-standing problem in the safe operation of flight vehicles. Ice can cause structural damage when ingested in engines and ice accretion diminishes the aerodynamic properties of lifting surfaces. Ice accretion is typically simulated using a large scale model of an aircraft, or wing, with droplets treated as a dispersed, secondary phase. The dynamics and impingement characteristics of these atmospheric water droplets are approximated by modeling. These models are tuned to match experimental data from in-flight and wind tunnel tests. Historically, icing generated by water droplets up to 50 µm in Mean Volumetric Diameter (MVD) has been considered; however, safety concerns have developed for droplets exceeding this size. Supercooled Large Droplets (SLD) are a class of droplets exceeding the 50 µm MVD limit. Increased droplet diameter complicates the physics of droplet impingement and deposition, breaking some of the assumptions present in models. This work attempts to provide a means of investigating the physics of an individual droplet, belonging to the SLD regime, as it approaches a body in a computationally efficient framework. This approach can enable higher fidelity modeling efforts in future work. A simple Galilean transformation is employed to isolate approximate droplet information from a model. Streamline data for this droplet is collected and then used as an input for an isolated droplet in a compact fluid domain. The droplet inside this domain is captured using a Volume of Fluid (VOF) formulation of the Navier-Stokes equations. Early results suggest that assumptions of the stability of large droplets is not as certain as previous literature has suggested, particularly in the context of impingement. This work can be used in any scenario where it is possible to capture droplet streamline information from a data set.