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Analytical and Numerical Study of Dynamics of Wettability Driven Droplets in Smooth And Corrugated Channels

Esmaili, Ehsan | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43439 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Moosavi, Ali
  7. Abstract:
  8. We studied dynamics of droplets inside channels under surface forces created by chemicalsteps on the channel walls. A multi-component Shan-Chen lattice Boltzmann method isused for this purpose.The effects of parameters such as the channel height, viscosity anddensity ratios on the results were investigated for homogeneous and grooved substrates. Alsoan analytical solution was developed for droplets under chemical heterogeneities in channels with smooth surfaces. The solution considers a general condition, namely, asymmetry of the contact angles on the top and bottom walls, the viscosity of the gas as the second fluid and the effect of the channel height. Then using Shan-Chen lattice Boltzmann method the effects of height, viscosity ratio and wettability pattern on different cases were studied and with the analytical solution were compared. A close agreement between the results were observed.Due to the importance ofgrooved surfaces we then considered channels with grooves with different sizes on hydrophilicand hydrophobic surfaces. It was found that by increasing the height of the grooves dragincreases, similar to the case of constant volumetric force. However, increasing the distancebetween the grooves (w) does not affect the maximum velocity. Dynamics of droplets onhydrophobic surface was also investigated. In contrast to hydrophilic surfaces by increasingthe distance between the grooves the dynamics of the droplets decreases.In addition,we studied the dynamics of nano fluids and nano droplets by applying the appropriate boundaries condition on channels’s wall.Finally an analytical solution was developed and it’s results were compared with numerical datas.

  9. Keywords:
  10. Channels ; Nanofluid ; Droplet Dynamics ; Lattice Boltzmann Method ; Chemical Step Gradient

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