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Numerical Investigation of Droplet Generation in a Microfluidic Flow-Focusing Junction Aiming High-Throughput Droplet Generation

Mardani Boldaji, Fatemeh | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54151 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Taghipoor, Mojtaba; Hosseini, Vahid
  7. Abstract:
  8. Droplet microfluidic platform generates monodisperse droplets in a desired size through immiscible multiphase flows inside microchannels. Droplets are individual reactor and can be used for bio(chemical) analyses. Also, for materials fabrication, droplet microfluidics offers a versatile platform for generation of nano- or micro-sized particles and microcapsules that are widely used in drug delivery. In addition to the monodispersity, high-throughput generation is also necessary in many applications. Therefore, droplets must be formed in stable regimes (dripping and squeezing) in the highest possible frequency. In this study, the flow-focusing geometry, which is the most common geometry in passive method, is investigated numerically to optimize geometry dimensions and flow rate ratio to achieve monodisperse droplets with high frequency generation and high mass flow rate. 3D numerical simulation has been performed with the commercial Computational Fluid Dynamics solver ANSYS Fluent using VOF method. At the first, frequency, diameter and mass flow rate of droplets is analyzed for a specified geometry and then the channel dimensions and orifice shape are changed to detect which geometry have better performance. The results revealed that the ordinary geometry of flow focusing with aspect ratio 1 and the flow rate ratio 5 have higher mass flow rate and generation frequency in dripping regime., Further, an equation for designing the most suitable channel width to create a droplet with a specific diameter was expressed. Finally, to prove the independence of the results from the phases properties, the effect of surface tension and viscosity of the phases on diameter and frequency was investigated and the accuracy of the equation was confirmed
  9. Keywords:
  10. Geometry Optimization ; Volume of Fluid ; Two Phase Flow ; Numerical Simulation ; High-Throughput Determination ; Flow-Focusing Geometry ; Droplet Microfluidic

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