Study of the secondary droplet breakup mechanism and regime map of Newtonian and power law fluids at high liquid–gas density ratio

Abstract

This work reports the numerical investigation of the secondary breakup of non-Newtonian droplets at different Weber [Formula: see text] and Ohnesorge [Formula: see text] numbers. As part of this work, an in-house coupled level set volume of fluid solver is developed based on OpenFOAM libraries. It uses improved curvature calculation techniques like smoothening and the closest point search method. Flow is assumed to be axisymmetric. Approximately 95 different cases were simulated to investigate the effect of [Formula: see text] and [Formula: see text] numbers on secondary breakup for Newtonian, shear-thinning, and shear-thickening fluids. [Formula: see text] varies from [Formula: see text] to [Formula: see text], and, correspondingly, [Formula: see text] varies from [Formula: see text] to [Formula: see text]. The non-Newtonian rheology is modeled as a power-law fluid, and the power-law index [Formula: see text] ranged from [Formula: see text]. The present work describes the flow field near the droplet and the effects of non-Newtonian parameters and viscosity on the flow field. The various aspects of droplet dynamics like droplet deformation ratio [Formula: see text], deformation rate [Formula: see text], and coefficient of pressure [Formula: see text] are studied and compared with the internal flow theory. A generalized relation for critical Weber number [Formula: see text] is proposed for both Newtonian and non-Newtonian fluids and is shown in a phase diagram plot to map the different regimes of secondary droplet breakup.