Evaporation of a deformable droplet under convection

Abstract

Evaporation of a deformable droplet under convection is investigated and the performance of the classical and Abramzon-Sirignano (A-S) models is evaluated. Using the Immersed Boundary/Front-Tracking (IB/FT) method, interface-resolved simulations are performed to examine droplet evaporation dynamics over a wide range of Reynolds ($20 \leq Re \leq 200$), Weber ($0.65 \leq We \leq 9$), and mass transfer ($1 \leq B_M \leq 15$) numbers. It is shown that flow in the wake region is greatly influenced by the Stefan flow, as higher evaporation rates lead to earlier flow separation and a larger recirculation zone behind the droplet. Under strong convection, the models fail to capture the evaporation rate, especially in the wake region, which leads to significant discrepancies compared to interface-resolved simulations. Droplet deformation greatly influences the flow field around the droplet and generally enhances evaporation, but the evaporation rate remains well correlated with the surface area. The A-S model exhibits reasonably good performance for a nearly spherical droplet but its performance deteriorates significantly and generally underpredicts the evaporation rate as droplet deformation increases. The A-S model is overall found to outperform the classical model in the presence of significant convection.