Abstract
Mixing layers and associated large-scale turbulent structures are some of the most common features of turbulent shallow water flow. Due to their quasi-two-dimensional nature, large-scale structures are also referred to as two-dimensional coherent structures (2DCS). The presence of these structures instigates several complications in the flow, such as scouring of the bed material, affecting the maneuverability of water vessels, and causing the formation of pollutant trapping zones inside recirculating flows; thus, impacting the stability of hydraulic structures, inducing drowning hazards, and affecting aquatic environments in the vicinity. Like all turbulence phenomena, it is challenging to predict shallow water turbulence directly with sufficient accuracy due to its highly random nature. This work proposes a semi-coupled model that aims to predict the spatial distribution of 2DCS in an open channel flow domain. The proposed model solves the 2D unsteady full momentum equations, and the computed outputs are analyzed to predict the possible locations of 2DCS in the flow. The model parameters are calibrated with experimental observations. The model results are then compared with CFD simulations of the Shallow Water model and standard turbulence models (k-Ɛ, k-ω, and LES (Large Eddy Simulation)), performed in OpenFOAM. A good agreement is observed between the results. The proposed model is approximately five times faster in predicting large-scale turbulent structures than standard CFD simulations. Results also demonstrate the superiority of LES models in resolving large-scale turbulence.
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The codes were developed in MATLAB and Python, and the output data can be provided on request.
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All authors contributed to the study's conception and design. Material preparation, data collection, and analysis were performed by [B.K.], and [A.H.]. The first draft of the manuscript was written by [B.K., A.B.] and supervised by [A.K.S.]. All authors read and approved the final manuscript.
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Kalita, B., Baruah, A.J., Handique, A. et al. A semi-coupled model for determining the distribution of two-dimensional coherent structures in open channel flow. Environ Fluid Mech 22, 743–761 (2022). https://doi.org/10.1007/s10652-022-09847-4
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DOI: https://doi.org/10.1007/s10652-022-09847-4