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Micromachines 2017, 8(2), 57;

Droplet Dynamics of Newtonian and Inelastic Non-Newtonian Fluids in Confinement

JamesWeirFluidsLaboratory, DepartmentofMechanical&AerospaceEngineering,UniversityofStrathclyde, Glasgow G1 1XJ, UK
School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Author to whom correspondence should be addressed.
Received: 30 November 2016 / Accepted: 8 February 2017 / Published: 15 February 2017
(This article belongs to the Special Issue Droplet Microfluidics: Techniques and Technologies, Volume II)
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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 capillary 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. View Full-Text
Keywords: droplet dynamics; lattice Boltzmann method; multiphase flows; power–law fluids; droplet deformation; droplet breakup droplet dynamics; lattice Boltzmann method; multiphase flows; power–law fluids; droplet deformation; droplet breakup

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Ioannou, N.; Liu, H.; Oliveira, M.S.N.; Zhang, Y. Droplet Dynamics of Newtonian and Inelastic Non-Newtonian Fluids in Confinement. Micromachines 2017, 8, 57.

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