Instability of radially spreading extensional flows. Part 1. Experimental analysis

Roiy Sayag, M. Grae Worster

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

We present laboratory experiments that show that fingering patterns can emerge when circular interfaces of strain-rate-softening fluids displace less viscous fluids in extensionally dominated flows. The fingers were separated by regions in which the fluid appeared to be torn apart. Initially, the interface had a large dominant wavenumber, but some of the fingers progressively merged so that the number of fingers gradually declined in time. We find that the transition rate to a lower wavenumber during this cascade is faster the larger is the discharge flux of the displacing fluid. At late times, depending on the discharge flux, the pattern either converged into an integer wavenumber or varied stochastically within a finite range of wavenumbers, implying convergence to a fractional wavenumber. In that stage of the evolution we find that the average wavenumber declines with the discharge flux of the displacing fluid.

Original languageEnglish
Pages (from-to)722-738
Number of pages17
JournalJournal of Fluid Mechanics
DOIs
StatePublished - 1 Jan 2019

Keywords

  • complex fluids
  • instability
  • thin films

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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