Viscoelastic wetting: Cox-Voinov theory with normal stress effects

Minkush Kansal*, Vincent Bertin, Charu Datt, Jens Eggers, Jacco H. Snoeijer

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

The classical Cox-Voinov theory of contact line motion provides a relation between the macroscopically observable contact angle, and the microscopic wetting angle as a function of contact-line velocity. Here, we investigate how viscoelasticity, specifically the normal stress effect, modifies the wetting dynamics. Using the thin film equation for the second-order fluid, it is found that the normal stress effect is dominant at small scales yet can significantly affect macroscopic motion. We show that the effect can be incorporated in the Cox-Voinov theory through an apparent microscopic angle, which differs from the true microscopic angle. The theory is applied to the classical problems of drop spreading and dip coating, which shows how normal stress facilitates (inhibits) the motion of advancing (receding) contact lines. For rapid advancing motion, the apparent microscopic angle can tend to zero, in which case the dynamics is described by a regime that was already anticipated in Boudaoud (Eur. Phys. J. E, vol. 22, 2007, pp. 107-109).

Original languageEnglish
Article numberA17
JournalJournal of fluid mechanics
Volume985
DOIs
Publication statusPublished - 25 Apr 2024

Keywords

  • UT-Hybrid-D
  • drops
  • viscoelasticity
  • contact lines

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