Effect of viscosity on droplet-droplet collisional interaction

Giulia Finotello*, Johan T. Padding, Niels G. Deen, Alfred Jongsma, Fredrik Innings, J.A.M. Kuipers

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

66 Citations (Scopus)
108 Downloads (Pure)


A complete knowledge of the effect of droplet viscosity on droplet-droplet collision outcomes is essential for industrial processes such as spray drying. When droplets with dispersed solids are dried, the apparent viscosity of the dispersed phase increases by many orders of magnitude, which drastically changes the outcome of a droplet-droplet collision. However, the effect of viscosity on the droplet collision regime boundaries demarcating coalescence and reflexive and stretching separation is still not entirely understood and a general model for collision outcome boundaries is not available. In this work, the effect of viscosity on the droplet-droplet collision outcome is studied using direct numerical simulations employing the volume of fluid method. The role of viscous energy dissipation is analysed in collisions of droplets with different sizes and different physical properties. From the simulations results, a general phenomenological model depending on the capillary number (Ca, accounting for viscosity), the impact parameter (B), the Weber number (We), and the size ratio (Δ) is proposed.

Original languageEnglish
Article number067102
Number of pages13
JournalPhysics of Fluids
Issue number6
Publication statusPublished - 2017


  • Viscosity
  • Collision theories
  • Drop coalescence
  • Surface tension
  • Drop formation


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