The inexorable resistance of inertia determines the initial regime of drop coalescence

Joseph D. Paulsen, Justin C. Burton, Sidney R. Nagel, Santosh Appathurai, Michael T. Harris, Osman A. Basaran

Research output: Contribution to journalArticlepeer-review

155 Scopus citations


Drop coalescence is central to diverse processes involving dispersions of drops in industrial, engineering, and scientific realms. During coalescence, two drops first touch and then merge as the liquid neck connecting them grows from initially microscopic scales to a size comparable to the drop diameters. The curvature of the interface is infinite at the point where the drops first make contact, and the flows that ensue as the two drops coalesce are intimately coupled to this singularity in the dynamics. Conventionally, this process has been thought to have just two dynamical regimes: a viscous and an inertial regime with a cross-over region between them. We use experiments and simulations to reveal that a third regime, one that describes the initial dynamics of coalescence for all drop viscosities, has been missed. An argument based on force balance allows the construction of a new coalescence phase diagram.

Original languageEnglish (US)
Pages (from-to)6857-6861
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number18
StatePublished - May 1 2012
Externally publishedYes


  • Emulsions
  • Fluid singularity

ASJC Scopus subject areas

  • General


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