Aerobreakup of a polymeric droplet*

Aerobreakup of a liquid droplet is the process of breaking a droplet into smaller fragments by subjecting it to a high-speed stream of gas. It is encountered in various natural and industrial processes. Aerobreakup of polymeric droplets is of special interest because the properties of any liquid can be engineered by adding a small amount of polymer to control the process of aerobreakup. Polymeric liquids exhibit viscoelastic behavior, and the presence of elasticity in the liquid phase can significantly retard the breakup process. We present a study on the aerobreakup of a polymeric droplet to get a better understanding of the role of liquid elasticity in the breakup process. A wide range of Weber number (∼10²–10⁴) and Elasticity number (∼10^-4–10²) is investigated by subjecting polymeric droplets of different concentrations to the induced airflow behind a moving shockwave. Experiments revealed that elasticity plays an insignificant role in the initial stages of aerobreakup, which involves droplet deformation and the appearance of hydrodynamic instabilities (Kelvin-Helmholtz and Rayleigh-Taylor). The dominant role of elasticity appears in the final stages of aerobreakup in terms of the morphology of the fragmenting liquid mass.