Abstract
Open channel junctions are encountered in urban water treatment plants, irrigation and drainage canals, and natural river systems. Junctions are very important in municipal sewerage systems and river engineering. Adequate theoretical description of flow through an open channel junction is difficult because numerous variables are to be considered. Equations of junction models are based on mass and momentum or mass and energy conservation. The objective of this study is to compare two junction models for subcritical flows. In channel branches, we solve numerically the Saint-Venant hyperbolic system by combining Preissmann scheme and double sweep method. We validate our results with HEC-RAS using Nash and Sutcliffe efficiency. In junction models, equality of water stage and complete energy conservation equation from HEC-RAS are compared. Outcome of the research clearly indicates that the complete conservation energy model is more suitable in flow through junction than equality of water stage model in serious situations.
Highlights
Channel junctions are area of separation or meeting of natural or artificial flow networks
HEC RAS is a new version of the hydraulic model previously named HEC-2 that includes a graphical interface for editing, modifying, and visualizing input data, as well as observing the results obtained
Mass and energy conservation model can be approximated by equality of water surface model as used in many packages
Summary
Channel junctions are area of separation or meeting of natural or artificial flow networks. Flow at junction is characterized by tri-dimensional effects and presence of an air-water mixture It includes complicated patterns with a separation zone immediately downstream, low pressure, low turbulence intensities and complex velocity distributions [3]. Mass and energy based models are more easy to implement, avoid solving non linear equations, and provide answer in much less time than solution procedures based on momentum models It can be simplified when physical effects such as boundary effects can be neglected, or when the flow through the junction is subcritical. Several applications like Mike 11, Mouse Model from the Danish Hydraulic Institute (1999), Canoe model from SOGREAH and Insavalor (2009) and InfoWorks from Wallingford Software (2006) use the water stage equality at the junction [11] Other applications such as HEC RAS use directly mass and energy based model. It is currently used in several engineering firms and government agencies [13] [14] [15] and it performs well flow through junction
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