JWSS - Journal of Water and Soil Science

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Mahjoob A, Kilanehei F, Khademi K. Numerical Investigation of the Opening of River Bridges Change and Skew on Flow Structure and Afflux: Three-Dimensional Versus One-Dimensional Approaches. jwss 2025; 29 (4) :42-61
URL: http://jstnar.iut.ac.ir/article-1-4509-en.html

One of the most significant hydraulic issues in determining the opening of river bridges is the lack of flow choking due to a reduction in the width of the flood passage. In this paper, determining the required opening for flow passage at a bridge location has been investigated using the concept of specific energy, one-dimensional, and three-dimensional flow modeling. First, the maximum encroachment of the embankments on the sides of the bridge in the river has been determined in such a way that it does not change the flow situation upstream of the bridge, using the concept of specific energy. The dimensions obtained for the bridge opening have been simulated numerically in two one-dimensional and three-dimensional models, and the flow condition at the bridge site and upstream has been evaluated and compared. The results showed that the one-dimensional numerical model predicts, on average, 67 percent higher amount of afflux than the three-dimensional model, while the maximum shear stress obtained from the one-dimensional model is, on average, 33 percent lower than that of the three-dimensional model. The effect of the bridge skewness on the amount of afflux and other hydraulic parameters of the flow, including bed shear stress and maximum velocity, has also been investigated using a three-dimensional model. The afflux was obtained at a 19.2 percent of normal depth at a skew of 40 degrees.