Experiment-Based CFD Simulation of Flow Pattern at Open-Channel Junctions
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RESEARCH PAPER
Experiment‑Based CFD Simulation of Flow Pattern at Open‑Channel Junctions Reza Goudarzizadeh1 · Seyed Habib Musavi‑Jahromi1 Received: 26 July 2018 / Accepted: 27 December 2019 © Shiraz University 2020
Abstract This paper proposes a numerical 3D flow pattern at the 90° equal-width open-channel junction. The Reynolds stress turbulent model (RSM) is applied to simulate the turbulent flow which is analyzed as a one-phase steady state. The Shumate’s experimental findings are used to test the validity of developed numerical model. Comparison of the simulation results and the experimental data has indicated a close proximity between the flow patterns of the two sets. The average prediction error also showed a range between 3.5 and 10%. Effects of the discharge ratio on the separation zone characteristics have illustrated an inverse relation, where an increase in discharge ratio will entail a decrease in the length and width of the separation zone. The shape index of separation zone has an average value 0.18. Comparison analysis further revealed that the increase in the discharge ratio will lead to a decrease in the maximum value of the bed shear stress. In addition, it clearly provides a powerful numerical model for the flow pattern analysis. Keywords Junction · Separation zone · Shear stress · Numerical modeling · Reynolds stress turbulent model (RSM) List of Symbols ui Velocity components in Cartesian coordinates (u, v, w) u Cartesian velocity in x direction v Cartesian velocity in y direction w Cartesian velocity in z direction U0 Average velocity at downstream end of the main channel P Total pressure 𝜌 Water density gi Gravity acceleration in Cartesian coordinate 𝜏ij Stress tensor H0 Water depth at downstream end of the main channel W Channel width Hr Width of separation zone Lr Length of separation zone Q Total discharge q∗ Ratio of the main channel to total discharge 𝜈 Kinematic viscosity
* Reza Goudarzizadeh [email protected] 1
Faculty of Water Sciences Engineering, Shahid Chamran University of Ahwaz, Ahvaz, Iran
1 Introduction Channel confluences are important components of the river networks and are crucial in the hydraulic engineering. Under conditions where a flow continues in the river network, it has to pass through the confluences. Due to the increase in discharge and mixing of flows at a certain point, a zone with a 3D flow pattern with highest turbulence in the river regime is established. In addition, it creates scouring and sedimentation at the channel confluence. The results revealed a significant morphological change in the vicinity as a research (Borqaee and Nazari 2003; Boyer et al. 2006; Ghobadian 2006). They illustrated a fundamental impact on water abstraction from the river in the affected zone. Various studies have been conducted in this respect, one of which is the work of Taylor (1944) which was based on experiments on a channel junction which produced an equation for the relative depth at the point of confluence. The experimental works carried b
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