Numerical and Analytical Study of Mixing in Y-shaped Micromixers: Electroosmotic and Poiseuille Flow of PTT Fluids

Reshadi, Milad | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46921 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saeedi, Mohammad Hassan; Mozaffari, Ali Asghar
  7. Abstract:
  8. Dissemination of an analyte under the laminar flows plays a major role in measuring and assessment of biological fluids such as sample preparation in the context of microfluidic systems. Due to the development of manufacturing technology in the Lab-on-a-chip devices, the production of rectangular microchannels with finite aspect ratios and micron and submicron sizes has been provided by which the effect of electrokinetic phenomena on concentration distribution will be magnified in these systems. On the other hand, these biofluids are viscoelastic and show extraordinary flow behaviors, not existing in Newtonian fluids and adopting appropriate constitutive equations these exotic flow behaviors can be modeled and predicted reasonably. Since the recent researches in this field have overlooked such effects, the present work will be conducted analytically and numerically to study the effect of electric double layer, viscoelastic properties, hydrophobicity and channel aspect ratios on cross stream diffusion of the analyte in the combined electroosmotic and pressure driven flows. Also, in the case of microchannels with large aspect ratios, by using Taylor-Arise dispersion phenomenon, the fully analytical solution has obtained to rigorously study the effect of the aforementioned parameters on mixing process. So, three flow scenarios, the favorable, adverse and zero pressure gradients are analyzed. The results demonstrate that the width of the diffusion region near the top and bottom walls of the microchannel becomes broader with the increase in the Debye length. Also, the results of the scaling analysis reveal the decrease in mixing intensity with increasing the Péclet number based on Helmholtz-Smoluchowski velocity and dimensionless Debye–Hückel parameter. As well, the average scaling exponent of this criterion is a descending function with respect to the thickness of the electric double layer. Also in all cases, by shear-thinning enhancement of the viscoelastic fluid, the convective mass transfer grows leading the low residence time for diffusive mixing and results in lower width of the diffusion broadening region in all cross sections of the microchannel
  9. Keywords:
  10. Electroosmotic Flow ; Mass Transfer ; Micromixer ; Viscoelastic Fluids ; Mixing ; Mixing Process ; Microfluidic System ; Phan Thien-Tanner (PTT)Model

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