Cavitation Investigation in the Sluice Section of the Sefid Rood Dam Using Flow 3D Software for Environmental Purposes

It is evident that water resources are essential for the existence of living organisms, particularly human life. Outlets are a series of structures employed to transfer water from the dam reservoir to the discharge point downstream. Due to the significance of this section of the dam, the performance analysis of the outlet, including the channel, gates, and their outlet, is sensitive. The presence of pressurized flow in the upstream of the outlet gate, energy dissipation due to various factors, and the very low values concerning the gate opening compared to the water head over the outlet gate cause significant errors in determining various parameters related to the outlets. This includes pressure drops across the gates and their discharge capacities when using theoretical methods. This research aims to investigate pressure distribution at various points along the outlet channel, determine the gate discharge capacity, and calculate its discharge coefficient. It explores the possibility of cavitation occurrence, compares the presented scenarios for post-service and emergency gate operations in the simultaneous operation of two gates, and determines the main loss coefficients in the channel, including frictional losses, conversion losses, and gate losses. This investigation utilizes data obtained from the physical model of the spillway outlet constructed at the Soil and Watershed Conservation Research Center laboratory. The physical model includes the channel and gates (service and emergency), and necessary experiments were conducted. The pressure values at different points, gate discharge rates at three opening levels (60%, 80%, and 100%), were measured in the reservoir, and the results are presented in corresponding tables and graphs. Additionally, the Flow 3D software was employed to numerically model the outlet discharge under three gate openings (60%, 80%, and 100%) for comparison between experimental and numerical results and with previous findings in this research. Subsequently, it will be demonstrated that, under single-gate operation and simultaneous operation, the cavitation index in critical areas, such as gate slots and between gates, in the single- gate mode falls within an acceptable range, practically eliminating the risk of cavitation. However, in simultaneous operation mode, negative pressures occur in some gate openings, posing the possibility of cavitation occurrence.