Numerical investigation of the effects of different step designs on energy dissipation performance for stepped spillways

Stepped spillways are hydraulic structures capable of dissipating a significant portion of the flow energy through steps arranged along the discharge channel. Due to their high energy dissipation capacity, these structures have been used for centuries and have become a frequent subject of academic research. In order to enhance energy dissipation performance, researchers continue to propose different step geometries and investigate their hydraulic efficiency. In this study, the effects of different step geometries on the energy dissipation performance of stepped spillways were investigated numerically using the OpenFOAM software based on the Computational Fluid Dynamics (CFD) method. Firstly, the numerical model was validated using experimental data from classical stepped spillway designs with two different slopes reported in the literature. Then, new step configurations with zigzag labyrinth geometries were analyzed under three different channel slopes (8.9˚, 14.6˚, 26.6˚) and six different flow rates. The results showed that as the discharge increased, the energy dissipation efficiency decreased for all models. It was also concluded that reducing the number of cycle enhanced the energy dissipation performance, and lower channel slopes generally provided higher energy dissipation. Notably, Model 7 with a 14.6° channel slope achieved the highest performance, dissipating 73.85% of the energy at maximum discharge. Model 1, with a 26.6° slope, performed approximately 20% better than the classical stepped spillway model. Among the models with an 8.9° slope, Model 11—which shares the same step geometry as Model 1—also showed promising results. Furthermore, velocity profile analyses demonstrated that the newly designed models were effective in reducing flow velocity on spillway. Ultimately, the study concluded that novel step geometries could offer significant improvements in energy dissipation performance for stepped spillways.