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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 43191 (08)
- University: Sharif University of Technology
- Department: Mechanical Engineering
- Advisor(s): Moosavi, Ali
- Abstract:
- Hydrodynamic mesoscopic equations are solved using boundary integral method to investigate the coarsening dynamics of two dimensional nanodroplets. The dynamics is probed by locating two drops on homogeneous, chemical heterogeneous and physical heterogeneous substrates respectively. For homogeneous substrate, the effect of different parameters like droplets distance, slip boundary condition, surface contact angle and disjoining pressure type on the dynamics is studied. Results reveal that increasing the contact angles to values larger than a critical value may qualitatively change the coarsening process and the profile of the disjoining pressure can appreciably modify the coarsening rate. Changing no slip boundary condition to slip condition and increasing slip length enhance the dynamics. Various kinds of chemical patterns like chemical gradient, stripe and step are considered to see the heterogeneity effect on the dynamics. Obtained results show that the presence of a chemical heterogeneity can enhance or weaken the coarsening dynamics depending on the pattern type and positions of the droplets on the substrate. Also physical heterogeneity in the form of step topography is employed and the effect of different geometrical parameters like step height, drops distance from the step and drops configuration and chemical parameters like wettability and disjoining pressure type is investigated. Decreasing the step height and droplets distance from the step accelerates the dynamics while decreasing surface contact angle reduces the coarsening rate. In the case of step disjoining pressure, crude previously used model is compared with more accurate new developed model to see the differences in the coarsening dynamics. Then thin film equation is solved using finite difference method to probe three dimensional coarsening dynamics. Although comparing the results of three dimensional simulation with two dimensional one reveals qualitative similar behavior which approves the method, there is an enormous difference between two cases quantitatively. Finally, some studied parameters in two dimensional analysis, are also investigated for three dimensional coarsening dynamics
- Keywords:
- Coarsening Dynamics ; Nanodroplets ; Thin Fluid Film ; Chemical Heterogeneous Substrate ; Physical Heterogeneous Substrate
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