Modeling of Droplet Deformation and Breakup in the Supercooled Large Droplet Regime

Droplet deformation and breakup is an important issue that involved in the aircraft and engine icing field especially in the case of the Supercooled Large Droplets (SLD). In this paper, the modes of SLD breakup were discussed in detail based upon the classical theories of droplet breakup and typical icing conditions. It was found that the breakup modes involved in SLD are mainly vibration breakup, bag-type breakup, multimode breakup and shear breakup. A breakup model composed of the typical SLD breakup types was proposed. In the proposed model, the transitions between different breakup modes depend on the Weber number; the droplet deformation was deemed as the displacement of the centre of the mass along the axis located at the centre of the droplet, and the movement of the centre of mass was obtained by solving the pressure balance equation; effects of the droplet deformation on the droplet external aerodynamic force were also considered in the model and droplet breakup occurs when the displacement of the mass centre was out of the scale described by the threshold function of Weber number; the sizes of the child-drops are depicted by the Saute Mean Diameter. The present breakup model was applied to predict SLD distortion and breakup around the clean and the “iced” airfoil in SLD regime. Effects of the surface shape on the properties of droplet deformation and breakup were discussed. Also, the effect of droplet breakup on the droplet collection efficiency was addressed.