### Abstract

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 language | English |
---|---|

Number of pages | 14 |

Journal | Micromachines |

Volume | 8 |

Issue number | 2 |

Early online date | 15 Feb 2017 |

DOIs | |

Publication status | E-pub ahead of print - 15 Feb 2017 |

### Fingerprint

### Keywords

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

### Cite this

}

*Micromachines*, vol. 8, no. 2. https://doi.org/10.3390/mi8020057

**Droplet dynamics of Newtonian and inelastic non-Newtonian fluids in confinement.** / Ioannou, Nikolaos; Liu, Haihui; Oliveira, Mónica S. N.; Zhang, Yonghao.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Droplet dynamics of Newtonian and inelastic non-Newtonian fluids in confinement

AU - Ioannou, Nikolaos

AU - Liu, Haihui

AU - Oliveira, Mónica S. N.

AU - Zhang, Yonghao

PY - 2017/2/15

Y1 - 2017/2/15

N2 - 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.

AB - 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.

KW - droplet dynamics

KW - lattice Boltzmann method

KW - multiphase flows

KW - power–law fluids

KW - droplet deformation

KW - droplet breakup

UR - http://www.mdpi.com/journal/micromachines

U2 - 10.3390/mi8020057

DO - 10.3390/mi8020057

M3 - Article

VL - 8

JO - Micromachines

JF - Micromachines

SN - 2072-666X

IS - 2

ER -