Mechanistic Models for Droplet Formation and Breakup

Abstract

Mechanistic models are created to predict the smallest droplet or bubble of a low concentration, inviscid, dispersed fluid that can be formed by shear from the continuous fluid (or droplet impact on a wall) and the largest droplet/bubble that can survive in a shear flow. Weber number criteria are developed for both the smallest and largest droplet/bubbles based on energy and force balances. The droplet deformation is predicted from an energy balance between available energy from drag on the droplet and energy required to deform the droplet. Different droplet deformation geometries are incorporated into the deformation model and compared against available data from the literature. The oblate spheroid deformation was found to provide the better prediction of deformation, terminal velocity, and largest droplet than a sphere, disk or spherical segment. The droplet deformation and breakup models are believed to be applicable to breakup of droplets, bubbles, and dual dispersions in a wide variety of conditions. These relatively simple models compare favorably against experimental data for low viscosity dispersed liquids and have been successfully used to predict liquid carry-over and gas carry-under from various gas/liquid separators. These models have been incorporated into simulation software used to design predict performance of compact separation equipment.