Study on the interfacial dynamics of free oscillatory deformation and breakup of single-core compound droplet

摘要

Compound droplets are usually taken as microcontainers for biomedical and material encapsulation applications in which a good understanding of the free oscillatory deformation and breakup behavior is essential. In this work, the dynamics of free oscillatory deformation and breakup of a single-core compound droplet with an initial ellipsoidal shell was investigated numerically using the volume-of-fluid method. The effects of droplet diameter and the outer droplet initial deformation parameter are considered. Four outcomes are identified: oscillatory deformation, separation, separation breakup, and breakup. The evolution of the kinetic energy and pressure field of the compound droplet for the four typical outcomes is also analyzed in detail. A clear boundary exists between the first and the latter three outcomes (initial deformation parameters of 0.600-0.773), while the critical factor for the latter three outcomes is the inner and outer droplet diameter ratio. The oscillatory deformation is characterized by the inner and outer droplet undergoing a finite deformation and subsequent oscillatory behavior, with the maximum deformation of the inner and outer droplets being related to the energy transfer between the two, and the outer droplet being a periodic decaying oscillation, while the inner droplet is a large deformation oscillation interspersed with a small deformation oscillation. Separation, separation breakup, and breakup are characterized by breakup at the inner or outer interface during deformation; separation and breakup times are largely dependent on droplet diameter and the initial deformation parameter of the outer droplet; and the neck width at separation is also analyzed in detail.

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