Vaporization of liquid droplet with large deformation and high mass transfer rate, I: Constant-density, constant-property case

Abstract

A numerical model based on decomposed vaporization mechanisms has been developed for the study of vaporization of liquid droplets with large deformation and high mass transfer rate. In this model, the vaporization-induced volume, energy, and species source terms in the gas phase are modeled using a body-fitted layer placed around the interface on the gas side. In this layer, continuous distributions of volume, energy, and species sources are specified by the conservation laws. A corresponding body-fitted sink layer is placed on the liquid side of the interface to account for mass, energy and species loss in the liquid phase due to vaporization. The formulation retains the advantages of interface localization methods and mitigates the error and complexity caused by the combined treatment of mass/heat transfer and interface localization. The new model is versatile and does not depend on the specific interface localization method, and can thus be implemented in any of the existing methods. As a specific example, the present approach is implemented in a volume-of-fluid (VOF)-based code “Gerris”. A number of test cases concerning liquid vaporization in both quiescent and convective environments are presented, with the constant-density assumption, to verify and validate this model in terms of interface localization. In particular, the vaporization of a single n-decane droplet in a uniform air flow of 1000 K at 1 atm is investigated. The predicted liquid volume evolution demonstrates the robustness and accuracy of interface localization for cases with large density ratio and high vaporization rate. Vaporization of n-decane droplets with large deformation and high mass transfer is also investigated systematically.