Investigation of spillway rating curve via theoretical formula, laboratory experiment, and 3D numerical modeling: A case study of the Riam Kiwa Dam, Indonesia

The spillway rating curve of the Riam Kiwa Dam was investigated via theoretical formula, laboratory experiment, and 3D numerical modeling. It is an ogee type with two uncontrolled and five gated spillways with a total length of 77.5 m. The experiment was performed with a scale of 1:50, while the numerical modeling was conducted using FLOW-3D software. Several discharge values (16.67–2,652.7 m³/s) were tested and observed for two different scenarios of gate openings. For the low discharge in Scenario 1, the theoretical formula and FLOW-3D computed the rating curve less accurately with the error values greater than 10%. A similar phenomenon was observed in Scenario 2, where both theoretical formula and FLOW-3D predicted the rating curve accurately with error values less than 10% for the higher discharge. The discharges tend to be overestimated for the water depth values greater than 2 m giving the average discharge deviation of 6% for the PMF condition. FLOW-3D was found to calculate water depth for all scenarios accurately. It shows a promising approach between numerical simulation and physical modeling, to minimize laboratory model construction costs.