Vaporization of liquid droplet with large deformation and high mass transfer rate, II: Variable-density, variable-property case

Highlights: • A physically based vaporization model for multiphase flows is developed. • Difficulties related to large deformation and high density ratios are circumvented. • Effects of variable density in liquid and gas phases are well addressed. -- Abstract: A novel approach for treating vaporization of liquid droplets with large deformation and high mass transfer rate is developed. The formulation is based on decomposed vaporization mechanisms and accommodates the effects of density and property variations in both the gas and liquid phases. In this model, the mass and energy transfer across the interface are realized by a source layer in the gas phase and a sink layer in the liquid phase around the interface. The flow field in each phase is described by a set of unified conservation equations in the low Mach number limit. The equations are then solved by a modified projection method, in which the nonzero velocity divergence is treated as a source term in the pressure Poisson equation. The vaporization model is implemented in a volume-of-fluid (VOF) based code "Gerris" featuring adaptive mesh refinement. The vaporization of a single n-decane droplet in both quiescent and convective air environments of 1000 K at 1 atm is investigated to verify and validate the present model in terms of interface localization and mass conservation. The results demonstrate the accuracy and robustness of the present work. The vaporization of an impulsively started n-decane droplet with large deformation and breakup is also studied. The droplet surface dynamics are captured well, as are the vaporization behaviors.