Droplet dynamics of Newtonian and inelastic non-Newtonian fluids in confinement

Nikolaos Ioannou, Haihui Liu, Mónica S. N. Oliveira, Yonghao Zhang

Research output: Contribution to journalArticle

2 Citations (Scopus)
157 Downloads (Pure)

Abstract

Microfluidic droplet technology has been developing rapidly. However, precise control of dynamical behaviour of droplets remains a major hurdle for new designs. This study is to understand droplet deformation and breakup under simple shear flow in confined environment as typically found in microfluidic applications. In addition to the Newtonian–Newtonian system, we consider also both a Newtonian droplet in a non-Newtonian matrix fluid and a non-Newtonian droplet in a Newtonian matrix. The lattice Boltzmann method is adopted to systematically investigate droplet deformation and breakup under a broad range of capillary numbers, viscosity ratios of the fluids, and confinement ratios considering shear-thinning and shear-thickening fluids. Confinement is found to enhance deformation, and the maximum deformation occurs at the viscosity ratio of unity. The droplet orients more towards the flow direction with increasing viscosity ratio or confinement ratio. In addition, it is noticed that the wall effect becomes more significant for confinement ratios larger than 0.4. Finally, for the whole range of Newtonian carrier fluids tested, the critical apillary
number above which droplet breakup occurs is only slightly affected by the confinement ratio for a viscosity ratio of unity. Upon increasing the confinement ratio, the critical capillary number increases for the viscosity ratios less than unity, but decreases for the viscosity ratios more than unity.
Original languageEnglish
Number of pages14
JournalMicromachines
Volume8
Issue number2
Early online date15 Feb 2017
DOIs
Publication statusE-pub ahead of print - 15 Feb 2017

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Fluids
Viscosity
Microfluidics
Shear thinning
Shear flow

Keywords

  • droplet dynamics
  • lattice Boltzmann method
  • multiphase flows
  • power–law fluids
  • droplet deformation
  • droplet breakup

Cite this

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title = "Droplet dynamics of Newtonian and inelastic non-Newtonian fluids in confinement",
abstract = "Microfluidic droplet technology has been developing rapidly. However, precise control of dynamical behaviour of droplets remains a major hurdle for new designs. This study is to understand droplet deformation and breakup under simple shear flow in confined environment as typically found in microfluidic applications. In addition to the Newtonian–Newtonian system, we consider also both a Newtonian droplet in a non-Newtonian matrix fluid and a non-Newtonian droplet in a Newtonian matrix. The lattice Boltzmann method is adopted to systematically investigate droplet deformation and breakup under a broad range of capillary numbers, viscosity ratios of the fluids, and confinement ratios considering shear-thinning and shear-thickening fluids. Confinement is found to enhance deformation, and the maximum deformation occurs at the viscosity ratio of unity. The droplet orients more towards the flow direction with increasing viscosity ratio or confinement ratio. In addition, it is noticed that the wall effect becomes more significant for confinement ratios larger than 0.4. Finally, for the whole range of Newtonian carrier fluids tested, the critical apillarynumber above which droplet breakup occurs is only slightly affected by the confinement ratio for a viscosity ratio of unity. Upon increasing the confinement ratio, the critical capillary number increases for the viscosity ratios less than unity, but decreases for the viscosity ratios more than unity.",
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Droplet dynamics of Newtonian and inelastic non-Newtonian fluids in confinement. / Ioannou, Nikolaos; Liu, Haihui; Oliveira, Mónica S. N.; Zhang, Yonghao.

In: Micromachines, Vol. 8, No. 2, 15.02.2017.

Research output: Contribution to journalArticle

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AU - Oliveira, Mónica S. N.

AU - Zhang, Yonghao

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