Effect of asymmetrical roughness on the settlement behaviour of an object

• Main Author: Tan, Mark Chen Yang
• Other Authors: Chiew Yee Meng
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Environmental engineering
• Online Access: http://hdl.handle.net/10356/77978
• Institution: Nanyang Technological University

An experimental study was conducted to investigate the effects of asymmetrical surface roughness on the settling behaviour of spheres in three separate fluids: water, glycerol and a glycerol-water mixture. Asymmetrical roughness was created on the surface of the spheres using sand of grain size ranging from 0.4mm to 1.54mm. The MATLAB software with the DLTdv digitizing tool was used for video analysis to evaluate the settling profile of the spheres based on their cumulative vertical displacement, cumulative horizontal displacement and settling velocity. The experimental results revealed that the degree of asymmetrical roughness did not significantly affect the settling velocity and cumulative vertical displacement of the spheres. However, the cumulative horizontal displacement was greatly influenced by the degree of asymmetrical roughness present on the roughened hemispheres. Spheres with high degree of asymmetrical roughness displayed more drastic lateral movements from its original settling path. The different boundary layer separation points on each hemisphere resulted in an imbalance in pressure drag, which had a more pronounced effect on the spheres’ lateral movement as compared to its vertical settlement. The limitations in this experimental study has brought up key variables that has to be addressed when exploring the effects of asymmetrical roughness of the settling profile of spheres. Further research has to be done in order to definitively conclude that asymmetrical roughness affects the overall settling profile of spheres immersed in fluids.