IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
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You are here : eLibrary : IAHR World Congress Proceedings : 35th IAHR Congress - Chengdu (2013) : THEME 5 - FLUVIAL HYDRAULICS AND RIVER MANAGEMENT : Use of a Three-Dimensional Numerical Model to Improve Estimation of Channel Constriction Energy Loss
Use of a Three-Dimensional Numerical Model to Improve Estimation of Channel Constriction Energy Loss
Author : Jim Ly and Colin D. Rennie
River constrictions are frequently encountered by engineers, and improper understanding can lead to designs that do not adequately protect against flooding. This paper studies river constrictions using the three dimensional Reynolds Averaged Navier Stokes (RANS) model SSIIM. The model was validated using an experimental laboratory constriction test case (Duc and Rodi 2008) by comparing measured and predicted velocity fields. Subsequently, four different degrees of channel constriction were simulated, and energy losses were estimated based on predicted water levels. In order to explain the physics of the energy losses that occur in a constriction, flow patterns near the constriction were examined, focusing on the eddy reattachment length as well as the distribution of turbulent kinetic energy. As expected, as the constriction ratio increases, both energy losses and the turbulent kinetic energy within the flow field increase. Using the results of the 3D model combined with an analytical expression (Henderson 1966), the contraction head loss coefficient (K) is calculated at various levels of constriction. It is demonstrated that K increases with constriction ratio, despite the fact that constriction ratio is considered in the analytical expression. These results can be used to calibrate 1D models such as HEC- RAS that are frequently used in industry. Erroneous K values can lead to unsuitable designs with consequences such as flooding causing loss of life and property.
File Size : 516,392 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 35th IAHR Congress - Chengdu (2013)
Date Published : 18/07/2016
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