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Numerical Investigation of Motion of Droplets in Micro and Nanochannels

Bedram, Ahmad | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42108 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Moosavi, Ali
  7. Abstract:
  8. In this research, droplet motion in symmetric and asymmetric junctions in micro and nano scales was investigated. Droplets motion in symmetric and asymmetric junctions have many applications in many industries such as chemical and pharmacy. In this research symmetric T-junction in micro and nano sizes was simulated numerically in 2D and 3D formes. Also asymmetric T-junction (with unequal width branches) was simulated numerically in two cases, 2D and 3D. In the asymmetric T-junction, also an analyrical theory was developed. Numerical simulation was performed by using VOF techniqe and analytical theory was developed by thin film theory. For verifying the accuracy of numerical solution, grid independency and time step independency were checked. Also the results of numerical simulation were compared with the results of two analytical researches and very good agreement was found. An obvious property of our research (in compare of former ones) is economic optimization of symmetric and asymmetric T-junction. The results show, in the state that droplet is deforming in symmetric or asymmetric T-junction, if tunnel forms (tunnel is a zone between the upper surface of droplet and wall, that continuous fluid flows in it) large vortexes in the inside of droplet form and mixing in the droplet increases well. Also in micro and nanofluidic symmetric T-junction, for increasing the process speed and decreasing the costs, it should be decreases the droplet length as much as possible and if it isn't possible it should be increases the capillary number as much as possible. Also the results show that for economization of asymmetric T-junction, it should be increases the width ratio of channel as much as possible and if it isn't possible it should be decreases the capillary number as much as possible. With using the analytical theory, two good equations were achieved for calculating the minimum thickness of tunnel (in asymmetric T-junction) in terms of width ratio and capillary number
  9. Keywords:
  10. Drop Breakage ; Analytical Solution ; Symmetric T Junction ; Asymmetric T Junction ; Modified Volume of Fluid (VOF)

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