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Ogee spillways with converging training walls are applied to lower the hazard of accidental flooding in locations with limited construction operations due to their unique structure. Hence, this type of structure is proposed as an emergency spillway. The present study aimed at experimental and machine learning-based modeling of the submerged discharge capacity of the converging ogee spillway. Two experimental models of Germi-Chay dam spillway were utilized: one model having a curve axis which was made in 1:50 scale and the other with a straight axis in 1:75 scale. Using visual observation, it was found that the total upstream head, the submergence degree, the ogee-crest geometries and the convergence angle of training walls are the crucial factors which alter the submerged discharge capacity of the converging ogee spillway. Furthermore, two machine-learning techniques (e.g. artificial neural networks and gene expression programming) were applied for modeling the submerged discharge capacity applying experimental data. These models were compared with four well-known traditional relationships with respect to their basic theoretical concept. The obtained results indicated that the length ratio () had the most effective role in estimating the submerged discharge capacity.

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Cavitation is among the most complex and common damages occurring in spillway structures, which is one of the most expensive parts of a dam. The cavitation index, as the one of the most efficient approaches, can be used to analyze this important hydraulic phenomenon. The present study examines the changes in the cavitation index caused by changes in the convergence angle of an ogee spillway's sidewalls with an arc in the plan. To this end, a spillway was constructed on the 1:50 scale. Then, it was tested with four different convergence angles, including 0°, 60°, 90°, and 120°, relative to the spillway's sidewalls and six different flow rates per unit width ranging from 6.74 to 48.42 (l/s)/m. The results indicated that as the flow rate increased, the cavitation index relatively declined at both crest and chute of the spillway while growing at its toe. It was observed that the lowest cavitation index was found to be 1.54 in.X/Hd = 2.42 at an angle of 0° and a flow rate per unit width of 40.52 (L/s)/m.