Hydraulic jump in aerated flows

• Main Author: Dy, Raelene Ina Bianchi Mendez
• Other Authors: Chiew Yee Meng
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering::Civil engineering::Water resources
• Online Access: http://hdl.handle.net/10356/68084
• Institution: Nanyang Technological University

One of the issues posed by the transport of water inside closed conduits to underground storage caverns is the effects of the hydraulic jump on the inner surface of these pipes. In particular, hydraulic jumps occurring within the pipes may experience closed conduit conditions within the pipes, which will cause the conduits to experience pressure and may cause adverse effects like scour or erosion to the pipe lining. Due to constraints of time and the construction of the flume, the objective of this study was limited to observing and describing the behavior of the flow and the resulting hydraulic jump inside a closed conduit, with a particular focus on velocity and pressure. This was meant to simulate the conditions under which a hydraulic jump might occur in an underground pipe, where water is brought in from a free-surface to the closed-surface condition. The study was conducted at Nanyang Technological University (NTU), B5 Hydraulics Lab. This project was executed using a flume with dimensions of length 5m x width 20 cm x height 15cm. Sluice gates was located at both the downstream and upstream ends of the flume, to control the location and size of the hydraulic jump. Pressure transducers were used to measure the pressure felt by the channel bed during the jump. To ensure accuracy of the data and to account for the effects of changing atmospheric pressure, the pressure transducers were calibrated every 30 minutes to generate conversion curves from the raw data to water depth in centimeters. The classical hydraulic jumps were verified by comparing the experimental water depth data with the theoretical sequent depth values from the Belangér equation. The closed conduit hydraulic jump data was also verified against the Belangér equation. It was observed that the location of the sequent depths for these hydraulic jumps was beyond the area being recorded in the flume. In addition, the jump toe would move back and forth during experiment runs. This movement manifested in the variance and standard deviation values recorded by the pressure transducers near the jump toe as relatively large values, indicating a wider spread of data. A damping effect was observed from the variance and standard deviation values for the pressure transducers near the supposed horizontal location of the sequent depth, which was towards the downstream end of the jump.