Three-sided spillways are one of the important dam's outlet works that despite their hydraulic limitations, selected as the best option in storage dam under special topographical conditions. Considerable energy losses, the flow high turbulences, and applying great fluctuations shock on walls and bed of the side channel are the hydraulic conditions that must carefully considered in these spillways. In this study, the three-dimensional flow filed of U-shaped spillway and end-sill of the side channel are simulated using Flow3D and the effect of flow turbulences have been modelled by RNG closure. Comparison of the numerical and experimental results revealed that this model with RNG closure has capable to carefully simulate the turbulence flow field on these structures. The effect of making stepped the ogee profile of the three-sided spillway on flow depth and dynamic pressure fluctuations has been numerically evaluated; the non-dimensional turbulence index has been used to investigate the fluctuations of the dynamic pressure. The results revealed making stepped the ogee profile causes to reduce the encounter of the side overfalls, and to increase the flow depth in the side channel, in which this lead to considerable decrease in pressure fluctuation intensity. Three-sided spillways are one of the important dam's outlet works that despite their hydraulic limitations, selected as the best option in storage dam under special topographical conditions. Considerable energy losses, the flow high turbulences, and applying great fluctuations shock on walls and bed of the side channel are the hydraulic conditions that must carefully considered in these spillways. In this study, the three-dimensional flow filed of U-shaped spillway and end-sill of the side channel are simulated using Flow3D and the effect of flow turbulences have been modelled by RNG closure. Comparison of the numerical and experimental results revealed that this model with RNG closure has capable to carefully simulate the turbulence flow field on these structures. The effect of making stepped the ogee profile of the three-sided spillway on flow depth and dynamic pressure fluctuations has been numerically evaluated; the non-dimensional turbulence index has been used to investigate the fluctuations of the dynamic pressure. The results revealed making stepped the ogee profile causes to reduce the encounter of the side overfalls, and to increase the flow depth in the side channel, in which this lead to considerable decrease in pressure fluctuation intensity. Three-sided spillways are one of the important dam's outlet works that despite their hydraulic limitations, selected as the best option in storage dam under special topographical conditions. Considerable energy losses, the flow high turbulences, and applying great fluctuations shock on walls and bed of the side channel are the hydraulic conditions that must carefully considered in these spillways. In this study, the three-dimensional flow filed of U-shaped spillway and end-sill of the side channel are simulated using Flow3D and the effect of flow turbulences have been modelled by RNG closure. Comparison of the numerical and experimental results revealed that this model with RNG closure has capable to carefully simulate the turbulence flow field on these structures. The effect of making stepped the ogee profile of the three-sided spillway on flow depth and dynamic pressure fluctuations has been numerically evaluated; the non-dimensional turbulence index has been used to investigate the fluctuations of the dynamic pressure. The results revealed making stepped the ogee profile causes to reduce the encounter of the side overfalls, and to increase the flow depth in the side channel, in which this lead to considerable decrease in pressure fluctuation intensity.

Keywords: Three-sided spillway, Hydraulic performance, Stepped profile, Numerical simulation

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