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Droplet formation in a T-shaped microfluidic junction

Liu, Haihu and Zhang, Yonghao (2009) Droplet formation in a T-shaped microfluidic junction. Journal of Applied Physics, 106 (3). 034906. ISSN 0021-8979

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Abstract

Using a phase-field model to describe fluid/fluid interfacial dynamics and a lattice Boltzmann model to address hydrodynamics, two dimensional (2D) numerical simulations have been performed to understand the mechanisms of droplet formation in microfluidic T-juntion. Although 2D simulations may not capture underlying physics quantitatively, our findings will help to clarify controversial experimental observations and identify new physical mechanisms. We have systematically examined the influence of capillary number, flow rate ratio, viscosity ratio, and contact angle in the droplet generation process. We clearly observe that the transition from the squeezing regime to the dripping regime occurs at a critical capillary number of 0.018, which is independent of flow rate ratio, viscosity ratio, and contact angle. In the squeezing regime, the squeezing pressure plays a dominant role in the droplet breakup process, which arises when the emerging interface obstructs the main channel. The droplet size depends on both the capillary number and the flow rate ratio, but is independent of the viscosity ratio under completely hydrophobic wetting conditions. In the dripping regime, the droplet size will be significantly influenced by the viscosity ratio as well as the built-up squeezing pressure. When the capillary number increases, the droplet size becomes less dependent on the flow rate ratio. The contact angle also affects the droplet shape, size, and detachment point, especially at small capillary numbers. More hydrophobic wetting properties are expected to produce smaller droplets. Interestingly, the droplet size is dependent on the viscosity ratio in the squeezing regime for less hydrophobic wetting conditions.

Item type: Article
ID code: 13461
Keywords: lattice boltzmann model, droplet formation, fluid dynamics, flow rate ratio, viscosity ratio, contact angle, capillary number, Mechanical engineering and machinery, Chemical technology, Physics, Mechanical Engineering, Fluid Flow and Transfer Processes
Subjects: Technology > Mechanical engineering and machinery
Technology > Chemical technology
Science > Physics
Department: Faculty of Engineering > Mechanical and Aerospace Engineering
Depositing user: Ms Katrina May
Date Deposited: 18 Nov 2009 11:33
Last modified: 21 Jul 2015 17:59
URI: http://strathprints.strath.ac.uk/id/eprint/13461

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