Shock induced aerobreakup of a polymeric droplet

TL;DR

This study investigates how elasticity influences the aerobreakup of polymeric droplets subjected to shock-induced airflow, revealing three distinct breakup modes and highlighting elasticity's role in the final breakup stage.

Contribution

It introduces a comprehensive analysis of viscoelastic droplet breakup modes under shock airflow, emphasizing elasticity's impact on the final stage of breakup, which was less understood before.

Findings

Identified three breakup modes: vibrational, shear-induced entrainment, and catastrophic.

Elasticity significantly affects the final breakup stage, not the initial deformation or instability stages.

Developed a mathematical framework supporting the experimental observations.

Abstract

Droplet atomization through aerobreakup is omnipresent in various natural and industrial processes. Atomization of Newtonian droplets is a well-studied area; however, non-Newtonian droplets have received less attention despite their frequent encounters. By subjecting polymeric droplets of different concentrations to the induced airflow behind a moving shock wave, we explore the role of elasticity in modulating the aerobreakup of viscoelastic droplets. Three distinct modes of aerobreakup are identified for a wide range of Weber number ($\sim 10^2-10^4$) and Elasticity number ($\sim 10^{-4}-10^2$) variation; these modes are: vibrational, shear-induced entrainment and catastrophic breakup mode. Each mode is described as a three stage process. Stage-I is the droplet deformation, stage-II is the appearance and growth of hydrodynamic instabilities, and stage-III is the evolution of liquid mass morphology. It is observed that elasticity plays an insignificant role in the first two stages, but a dominant role in the final stage. The results are described with the support of adequate mathematical analysis.