Numerical Simulation and Characterization of a Micro-mixer with Moving Walls

Omidvar, Ahmad Reza | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 49018 (58)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Saeedi , Mohammad Saeed; Sani, Mahdi
  7. Abstract:
  8. Recent advances in micro-technology are finding important applications especially in chemical and biological processes. In these applications, mixing has a profound importance. Due to the inherent low Reynold’s number flow in micro systems, diffusion mixing is the dominant mixing mechanism at these scales. This is in contrary to the high Reynold’s number ordinary applications where turbulent mixing plays the major role. There are two major classes of micro-mixers: passive and active. Passive micro-mixers rely on geometric features to enhance mixing. Active micro-mixers on the other hand, use external excitation to promote and control the rate of mixing. In this work, using numerical tools, we investigate a type of micro-mixer relying on physical boundary deformation as a mixing enhancement measure. In this micro-mixers, some of the walls (boundary or internal) of the micro-channel are made of deformable materials like PDMS. The flexible boundary is equipped with magnets which are driven by external coils. The design of magnetic driving assembly and prediction of the wall deformations is addressed first. Then using the resulting deformations, we have solved fluid domain. Arbitrary Eulerian Lagrangian (ALE) approach embedded in the in-house finite volume code Rayan is used to model fluid flow in the deforming micro-channel. Different mixer designs are proposed and simulated. The mixing efficiencies are compared. The results show that the mixing is enhanced in some cases such as top wall moving, vertical wall moving near the stagnation point and top and bottom walls moving. There are also some cases where the mixing efficiency is smaller than the simple non-deforming (static) mixer such as horizontal and vertical moving obstacle at the middle. We have also figured out that extending the length of the channel after the deforming (dynamic) part magnifies the mixing enhancement effect and efficiencies as high as 99% are attainable
  9. Keywords:
  10. Active Micromixer ; Rayan Code ; Microfluidic System ; Micromixer ; Arbitrary Lagrangian-Eulerian Method ; Deforming Bounding ; Magnetic Actuation

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