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.

混合层和相关的大型湍流结构是湍流浅水流的一些最常见特征。由于它们的准二维性质，大尺度结构也被称为二维相干结构（2DCS）。这些结构的存在引发了流动中的一些并发症，例如床材料的冲刷，影响水容器的可操作性，并导致再循环流内形成污染物捕集区；因此，影响水工建筑物的稳定性，诱发溺水危险，并影响附近的水生环境。像所有湍流现象一样，由于其高度随机性，直接以足够的准确度预测浅水湍流具有挑战性。这项工作提出了一种半耦合模型，旨在预测 2DCS 在明渠流域中的空间分布。所提出的模型求解二维非定常全动量方程，并分析计算输出以预测 2DCS 在流动中的可能位置。模型参数通过实验观察进行校准。然后将模型结果与在 OpenFOAM 中执行的浅水模型和标准湍流模型（k-Ɛ、k-ω 和 LES（大涡模拟））的 CFD 模拟进行比较。在结果之间观察到良好的一致性。所提出的模型在预测大规模湍流结构方面比标准 CFD 模拟快大约五倍。结果还证明了 LES 模型在解决大尺度湍流方面的优越性。