Effect of airflow pressure on the droplet breakup in the shear breakup regime

Abstract

In this paper, the coupled level set volume of fluid and the large eddy simulation methods are adopted to perform three-dimensional simulations of the shear breakup of a water droplet. We investigate the effect of airflow pressure (1–3 atm) on the temporary deformation and breakup characteristics, including the breakup initiations, the cross-stream, and streamwise deformations. In addition, special attention is paid to subsequent sub-droplet size distributions, which are generally ignored by many researchers. The results indicate that different morphologies on the surface of the droplets in the shear breakup regime are in relatively good agreement with the available experimental visualizations. Based on the present method, the physical mechanism for the variations in the wake recirculation with the development of Rayleigh–Taylor instability waves is discussed. Furthermore, higher airflow pressures can significantly increase cross-stream and streamwise deformations. However, the corresponding breakup initiations at high airflow pressures are much earlier than those of parent droplets at low airflow pressures. Specifically, a reduction of 12.17% in the mean sub-droplet sizes is obtained as the airflow pressure increases from 1 atm to 2 atm, while a reduction of less than 0.1% in the mean sub-droplet sizes is obtained at higher airflow pressures from 2 atm to 3 atm. Eventually, there are linear growths of the aggregate superficial area ratios (0.996–28.2) and the mass ratios (3.55%–64.29%) of the sub-droplets to the parent droplet.