Threshold criteria for jet flipping below a sluice gate

• Main Author: Wang, Cassandra Weimei
• Other Authors: Lim Siow Yong
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Civil engineering
• Online Access: http://hdl.handle.net/10356/52980
• Institution: Nanyang Technological University

In this project, the threshold criteria for jet-flipping below a sluice gate, on non-cohesive and uniform sediment beds, are explored. All experimental runs were conducted with an apron at both low and high submergence. Jet-flipping is a phenomenon observed when the emerging jet changes direction, from bed jet to surface jet. It was observed that the emerging jet tends to impinge on the sand bed resulting in scour. The other jet flow investigated is the filling phase in jet-flipping,characterized by a surface jet. In this report the various observations and characteristics of the scour and filling process are described and explained in the report. In addition, the influences of certain parameters on the processes are also investigated and relations between the parameters and processes were discussed. In addition, the critical zones whereby jet-flipping phenomenon ceased to occur was charted out and discussed. It was noted that the scour process was characterized by 5 different stages and the maximum scour depth was affected by both the tailwater depth and the densimetric Froude number. Likewise, both parameters had an effect on the fill depth. The frequencies of the jet-flipping cycles were also found to be affected by the tailwater depth and densimetric Froude number. It was noted that jet-flipping cycle frequency decreases with increasing tailwater depth but increases with increasing densimetric Froude number. The critical tailwater depth and densimetric Froude number whereby jet-flipping ceased to occur was also charted out and discussed. It was discovered that the ranges whereby jet-flipping occurs were relatively constant over different discharges and a lower critical tailwater depth exists, in addition to the upper critical tailwater depth. Also, the critical tailwater depth for jet flipping was also dependent on the discharge. As discharge increases, critical tailwater depth increases.