Direct numerical simulation of secondary atomization of a vaporizing drop

The secondary breakup of a freely moving volatile drop in a uniform high-speed and high-temperature gas stream is investigated through direct numerical simulation. 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 energy of each phase, with an immersed Dirichlet boundary condition at the interface to implicitly account for the latent heat absorption. The model is implemented in the open-source solver, Basilisk, which uses adaptive octree mesh for spatial discretization and will allow for adaptive mesh refinement. The code has been validated by a series of test cases, including the vaporization of a spherical water drop with a very low Weber number. The simulation results agree well with the experimental results. The validated code were then used to simulate the secondary breakup of a volatile drop at moderate Weber numbers. The drop is initially stationary and at saturation temperature and is suddenly exposed to a uniform high-speed superheated gas stream. Through the simulation results, we will investigate the correlation between droplet deformation and the rate of droplet vaporization and will also characterize the effect of vaporization on the drop breakup dynamics.