Evaporation of a deformable droplet under convection

TL;DR

This study investigates the evaporation dynamics of deformable droplets under convection using detailed simulations, evaluating the accuracy of classical and Abramzon-Sirignano models across various flow conditions.

Contribution

It provides a comprehensive comparison of evaporation models against interface-resolved simulations for deformable droplets in convective flows.

Findings

Flow in wake region is influenced by Stefan flow and recirculation zones.

Models fail to accurately predict evaporation rates in wake regions under strong convection.

Droplet deformation enhances evaporation but surface area remains a key factor.

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.