Scale physical model and prototype comparison for a large dam bottom outlet

Scale physical modeling is widely used for large hydraulic structures design. It is recognized as a reliable method to characterize detailed flow conditions at prototype scale. However, similar to numerical models, scale physical models are simplifications of real size flow conditions. That's why, when possible, comparison of scale model data to prototype data has to be done and shared among the scientific and practitioners' community. In this paper, data gained from a large dam bottom outlet operation are compared at prototype and physical model scale (1:35). The structure includes a bottom step aerator, specific downstream channel sidewalls and a complex flip bucket to control the jet impact location in the narrow downstream valley. Prototype tests cover a large range of upstream head with varied gate openings. The comparison shows that, while main flow features have been properly predicted by the scale model, significant differences exist. For instance, flow aeration is much more important on the prototype than on the scale model. Transients have also been properly capture during the experimental tests.