Numerical Analysis of Stormwater Flow Conditions and Separation Zone at Open-Channel Junctions

Open-channel junctions are critical design elements for many major and minor drainage infrastructures. Typical examples of these structural elements are encountered in stormwater drainage systems, urban water networks, irrigation, and natural or artificial waterways. The analysis of flow behavior and condition of those structures are of considerable use to engineers involved in the design and planning processes. However, these analyses are very challenging due to the interaction among the incoming junctional and main channel flow coupled with the functional parameters involved, such as the angle of confluence, channel width, cross-section, bed slope, flow direction, discharge, and wall roughness. Therefore, the aim of this paper is to illustrate the application of a finite volume/numerical analysis method to model stormwater flow conditions and separation zone at 45 and 90 degrees of open-channel junctions. In general, the simulation results and analysis suggested that for a 90 degrees junction the separation zone area and discharge ratio is indirectly proportional due to recirculating flow, low pressure, and minimum velocities near the T-junction and Y-junction's areas. For a 45 degrees junction, flow separation is the function of divergence angles and flow velocity. Statistical analyses were also applied using the chi-square test to verify the accuracy of the numerical model result used to investigate the dimensions of the separation zone. (C) 2016 American Society of Civil Engineers.