Scour below a non-full flowing rectangular culvert outlet

• Main Author: Tan, Bei'er.
• Other Authors: Lim Siow Yong
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/52754
• Institution: Nanyang Technological University

In this study of scour below a non-full flowing rectangular culvert outlet, experiments were conducted to investigate, understand and predict scour hole formation and its geometry. Five sets of experiments with uniform sediment bed particles of median size, d50 1.63 mm and standard deviation, σg of 1.19 but varying tailwater depth levels and flow rates were conducted for 48 hours so that the scour hole formation to reach its equilibrium stage. The effects of scour on the sediment bed were visible as soon as water is being channeled from the reservoir and out of rectangular channel. Dimensional analysis was conducted on the data consolidated to establish the correlations of parameters influencing scour hole formation and its geometry. The tailwater depth, H is an important parameter as it determines the degree of water resistance against the inlet water flow affecting the plunging jet force and the subsequent scour hole formation and its geometry. For high tailwater, backwater effect was observed and water depth at the brink of channel outlet is affect by the tailwater depth. The results showed that the Densimetric Froude Number, Fo is a dominant parameter and its effect shows that whenever Fo increases, all parameters associated with scour hole geometry such as maximum depth of scour, dse, maximum scour length, Lse maximum width of scour, Wse and volume of scour hole, Vse increases at a very steep rate. The study proposed a set of general equations to predict the equilibrium scour hole geometries below a non-full flowing rectangular culvert outlet.