Water surface profiles in open channels

• Main Author: Loh, Siew Hui.
• Other Authors: Lim Siow Yong
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Civil engineering::Water resources
• Online Access: http://hdl.handle.net/10356/15901
• Institution: Nanyang Technological University

Eight textbooks on open channel hydraulics have been reviewed, and it was found that no book is able to provide an absolutely clear explanation on the sketching of water surface profiles in prismatic open channels. Thus, 6-step profile sketching method is introduced to provide a complete procedure of sketching in a simple and understandable manner. As this 6-step method is designed for the gradually varied flow profiles in simple open channels, an experimental study is conducted on the channel transitions cases i.e., channels with an elevated bed or channels with a constriction, in a rectangular channel with mild slope, to assess the applicability of profile sketching using the 6-step method. A comparison is made between the profiles obtained from the experiments to the profiles obtained through sketching using the 6-step method. From the comparative study, both profiles look quite different. Thus, two improvements were suggested proposed to the 6-step method to increase the accuracy of the profiles estimation for both channel elevation and channel constriction. In addition, the effects of the flow rates on the water surface profiles have been studied. The experimental results show that the water surface profile on the raised-bed channel, as well as the constricted channel have similar shape and the flow rate does not affect the overall shape of the profile in both channel elevation and channel constriction. The 6-step profile sketching method is also extended to predict water surface profiles in compound channel. This is an advanced topic and only one textbook out of the eight reviewed described water surface profile in compound channels. A modified 6-step method is used to sketch the surface profiles in the compound channel with three critical depths.