Investigation of flow over textured surfaces

• Main Author: Koh, Ti Kiat
• Other Authors: Chan Weng Kong
• Format: Final Year Project
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/75186
• Institution: Nanyang Technological University

Fluid flow is an important aspect in modern day engineering. However, it comes with the issue of energy loss due to friction when fluid contacts a surface. Energy loss is undesirable as more power is required to keep the flow going. Researchers have found that the degree of hydrophobicity influences losses due to friction. The higher the degree of hydrophobicity, the less adhesion there is between fluid and the surface, suggesting lesser drag and thus less energy loss. Therefore, superhydrophobic surfaces are desired for this purpose. Among the many methods to produce superhydrophobic surfaces, solution immersion was found to be a relatively cheap and easy way to do so. Aluminium Alloy(AA) 6061 was the material of choice for this study as it is widely used in fluid flow applications. Studies have shown that concentration of solution used, and duration of etching affect the hydrophobicity of surfaces. However, in those studies, only one round of solution immersion was performed. This experimental study aims to investigate the effect of solution immersion twice on the surface profile, hydrophobicity and drag reducing ability of fabricated surfaces. Various preliminary experiments were conducted on small AA 6061 plates and those with trends were fabricated on large AA 6061 plates for the pressure drop experiment. The chemicals used were Hydrochloric Acid (HCL), Sodium Hydroxide (NaOH) and Ethanol with Stearic Acid (ESA). HCL and NaOH were used to alter the surface of AA 6061 while ESA was used to lower the surface energy of the samples. To determine the drag reducing ability of the fabricated samples, a pressure drop experiment was conducted using water as the medium. In general, samples which were subjected to immersion in HCL followed by NaOH produced superhydrophobic surfaces and demonstrated better drag reduction capability compared to samples that were only immersed in HCL. Data analysed from Scanning Electron Microscope (SEM) and surface roughness profile images concurred with the pressure drop experiment results.