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Prediction of Flow around a Vertical Circular Pier in a Discordant Bed Channel Confluence

  • WATER RESOURCES AND THE REGIME OF WATER BODIES
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Abstract

Understanding the flow dynamics around the hydraulic structure caused by complex junction flow is still a major challenge. In order to gain a better insight of impact of junction flow and its interaction with structures like circular pier, numerical tests were conducted at 45° and 90° channel confluences with a discordance bed under different flow conditions. Numerical model was applied to solve three-dimensional RANS equation with RNG k–ɛ turbulence closure using CFD (SSIIM2.0) model. The Volume of fluid approach was adopted to capture the air-water interface at the free surface. Model study was validated against the measured data and with literature finding. The present study revealed that several parameters like the channel geometry; hydraulic parameters and the presence of structure influence the hydrodynamics of river confluence. Importantly, results show that the backwater rise has a significant effect on flow dynamics in front of the pier and in the wake region. The flow structures and water surface elevation are significantly changed and does not follow the common flow patterns of confluence owing to the presence of the pier. The results illustrate that the separation zone occurs at the downstream corner of the confluence for all flow ratios and attains its minimum value with 45° channel confluence. The geometry of the separation zone decreases with increasing of flow ratios. Present finding confirms that simulation results fail to match the measured streamwise velocity at the centre line of the flow (w/D = 0), due to the intrinsic shortcomings of RANS modelling for computing recirculating regions.

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Funding

The authors acknowledge the Science and Engineering Research Board (SERB), Ministry of Science and Technology, Government of India for financial support (Grant no. EMR/2016/005371).

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Authors and Affiliations

  1. Department of Civil Engineering, National Institute of Technology Agartala, Tripura, India

    Nabina Khanam & Sushant K. Biswal

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  1. Nabina Khanam
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Correspondence to Nabina Khanam or Sushant K. Biswal.

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Khanam, N., Biswal, S.K. Prediction of Flow around a Vertical Circular Pier in a Discordant Bed Channel Confluence. Water Resour 48, 947–959 (2021). https://doi.org/10.1134/S0097807821060087

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  • DOI: https://doi.org/10.1134/S0097807821060087

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