High-fidelity simulation and modeling of aerodynamic breakup of vaporizing droplets

The aerodynamic breakup and vaporization of a droplet are investigated through high-fidelity interface-resolved simulations. The droplet is initially stationary and at saturation temperature, and is suddenly subjected to a uniform superheated vapor stream. The sharp liquid-gas interface is tracked using the geometric Volume-of-Fluid (VOF) method. The incompressible Navier-Stokes equations are solved in conjunction with a two-fluid model for thermal energy advection and conduction, with an embedded Dirichlet boundary condition for temperature at the interface. The phase-change model is implemented in the adaptive multiphase flow solver, Basilisk, in which an adaptive quadtree/octree mesh is used for spatial discretization. Different drop liquids, including water, acetone, and armonoia, are considered. Parametric simulations were performed for different Weber (We) and Stefan (St) numbers, which characterize the droplet deformation and vaporization. The range of We covers the vibrational, bag, and multi-mode breakup modes. Particular attention is focused on characterizing the interaction between droplet deformation and vaporization. The results indicate an increase in the droplet vaporization rate with We, and a novel droplet vaporization model for the Nusselt number is developed. We have also observed a significant variation of critical Weber number with St.