Effect of tailwater on jet flipping downstream of a sluice gate

• Main Author: Fong, Xi Ning
• Other Authors: Lim Siow Yong
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/60967
• Institution: Nanyang Technological University

Scour has been a problem associated with the operation of hydraulic structures since their debut in the 19th century. This is because scour endanger the stability of hydraulic structure and human safety. Since then, scientists and researchers have been identifying the types of scours and the conditions behind their formation in order to minimize instability. This report aims to study the situations and conditions of scour formation under a sluice gate for two types of uniform sands with median size of 3.19 mm and 1.62 mm respectively. The objective is to study the effect of tailwater depths on the scour formation. Brief introduction of scour, along with studies done by some researchers are included in the literature review. Following that, the method employed for the assessment of scours is elaborated and illustrated. The method illustrates the set-up of the experiment to simulate real time situation efficiently. Scour depths information were collated for experiments with tailwater depths 17.13 cm, 12.5 cm, 10 cm, 7.5 cm and 3.84 cm for the d50 = 3.19 mm red sand and tailwater depths 17.13 cm, 7.5 cm and 3.84 cm for d50 = 1.62 mm yellow sand. Scour depth formation are attained either in steady or unsteady state which is dependent on hydraulic parameters such as volumetric flowrate, apron length and tailwater depth. The steady state is correlated with the existence of only digging phase and unsteady state with the presence of both digging and filling phase. This study also encompasses the aspect of jet flipping which is a condition of unsteady state scouring with sequential digging resulting in increase of scour depth and filling phase, decrease of scour depth. Jet Flipping occurrence is dependent on the magnitude of tailwater depth. Lastly, important conclusions such as jet flipping are dependent on the volumetric flowrate, apron length and tailwater depth are drawn based on the discussions and results done. Recommendations to improve the study are also incorporated.