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PAIDEffect of Sudden Area Expansion on Formation of Cross-Waves in Downstream of Bottom Outlet Tunnel of Dams

Investigation of the air vents in the bottom outlet tunnel of dams due to prevention of vibration and cavitation is an important issue. The air above the water surface should be transmitted through tunnel easily. In the present study, the effect of area expansion after step on formation of cross-waves in downstream tunnel is investigated. The aeration ratio values in the numerical simulation, in the gate openings of 20%, 60%, and 100% are compared with that of physical model results. Numerical results showed a good agreement with experiments. In this study, two-phase turbulent flow is simulated using the K-e model. In addition, for implementation of two-phase flow, the volume of fluid scheme is used.