Effect of weir height on jet flipping scour downstream of a submerged weir

• Main Author: Irsyad Harith Ismail
• Other Authors: Lim Siow Yong
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Civil engineering::Water resources
• Online Access: http://hdl.handle.net/10356/72936
• Institution: Nanyang Technological University

It is important to conduct studies and investigate the effects of scouring downstream of hydraulic structures, particularly in an erodible sediment bed below them. This is because the local scouring will undermine the stability of the hydraulic structures. Hence, this clarifies the reason why we have to get further understanding about the local bed degradation by analysing the scour characteristics and profiles. This study is conducted to investigate the jet flipping scour downstream of an overflowing submerged weir with varying parameters. All experimental runs were conducted under varying weir height, tailwater depth and flowrate while other parameters were kept constant. The results show that jet flipping phenomenon occurs even without the presence of apron length. Based on the results, the jet flipping scour is dependent on weir height, tailwater depth and flowrate. The increase in weir height and decrease in tailwater depth caused an increase in the scour depth. A higher weir height also leads to a decrease in frequency of jet flipping. A notable observation is the results for tailwater depth, h2 = 10mm above the weir height, P, showed that the weir height has no significant influence on the maximum scour depth. It only has influence on the formation of the deposition ridge. On top of that, the changes in the scour profile after each consecutive jet flipping cycles are minimal especially for the surface jet regime. It was also discovered that with a decrease in weir height, the jet flipping frequency increases. Hence, this implies that for any particular weir height, there is a certain range of tailwater depth which can have a significant influence on the maximum scour depth.