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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 56507 (08)
- University: Sharif University of Technology
- Department: Mechanical Engineering
- Advisor(s): Nouri Borujerdi, Ali; Moosavi, Ali
- Abstract:
- The present study's main aim is to investigate the drag-reduction ability of liquid-infused surfaces inspired by the pitcher plant. The present study can be divided into experimental and numerical sections. In the numerical section, the drag reduction ability of these surfaces was investigated in the internal flows. For this purpose, the effect of different parameters, such as Reynolds number, viscosity and density ratio of working fluid and lubricant, overlayer film thickness, and Ohnesorge number representing the interfacial tension, on the drag reduction was investigated. The results revealed that the variation in density ratio and Ohnesorge number had insignificant impact on drag reduction. With the rise of the viscosity ratio between the lubricant and the working fluid, the drag-reduction ability of liquid-infused surfaces decreased. The lowest drag was attributed to the viscosity ratio of 0.01. in this case, compared to the single-phase grooved channel, the pressure drop was 55% lower. According to the results, the drag reduction performance of liquid-infused surfaces was augmented with the rise of the Reynolds number. The numerical study was performed due to the lack of experimental setup required for the drag test of these surfaces in the internal flows. However, the experimental section was devoted to understanding the drag-reduction ability of liquid-infused surfaces in external flows. For this purpose, nine affordable surface features with different scales of roughness, from nanometers to micrometers, were introduced on aluminum substrates. These surface features were modified using stearic acid or octadecyltrichlorosilane and then were infiltrated by liquid lubricants, including silicone oils and paraffine and solid lubricants, such as beeswax and carnauba wax. The contact angle hysteresis of all fabricated surfaces was lower than 10°. Potentiodynamic polarization test showed that the surfaces comprised of aluminum oxide or boehmite had remarkable anti-corrosion performance. Moreover, with the rise of the viscosity of infused lubricant, the anti-corrosion performance was improved. In the antibacterial test, the surfaces infiltrated with liquid lubricants were preferable to those filled with solid ones. Furthermore, the lower the viscosity of the infused lubricant, the more its antibacterial performance. The roughened surfaces possessing copper or zinc oxides could decrease bacterial adhesion by 99.9%. The drag reduction test, which was performed using a designed device in the lab, demonstrated that for a more viscous working fluid, a layered-double hydroxide surface filled with silicone oil with the lowest viscosity had the best performance with the drag reduction rate of 15% at low surface velocities. The drag reduction performance was initially enhanced with the rise of surface velocity but then decreased. For viscous lubricants and solid ones, there was no drag reduction seen whatsoever. For the working fluid with lower viscosity, the anodized surface which was filled with the silicone oil with a viscosity of 5 mPa.s, had the best performance and resulted in a 17% drag reduction. It should be mentioned that the layered-double hydroxide surfaces had the highest durability in the stability tests
- Keywords:
- Hydrophobicity ; Antibacterial Properties ; Anticorrosive Coating ; Drag Reduction ; Friction Reduction ; Lubrication ; Liquid-Infused Surfaces
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