CFD Modeling for the design of a large stepped spillway

Overview

The design of large spillway structures requires careful evaluation of hydraulic performance to ensure safe discharge of extreme floods and effective energy dissipation downstream. Complex geometries, high velocities, and the interaction between water and air make these systems difficult to assess without advanced modeling tools.

The Challenge

The design team indicated uncertainties in discharge capacity, the efficiency of energy dissipation in the stilling basin, and had concerns about the potential flooding of the gallery around the bottom discharger. A detailed three-dimensional analysis was needed to evaluate alternative geometries and

Our Contribution

HCS implemented a series of CFD models using OpenFOAM to simulate the spillway crest, chute, and stilling basin. The models resolved free-surface air–water flows under different gate openings and discharges, testing both the original and optimized geometries. The analysis demonstrated that the refined crest profile improved discharge efficiency, while the modified chute successfully eliminated undesired flooding of the bottom discharger gallery. In the stilling basin, the models confirmed that the hydraulic jump remained contained within the structure and that high-velocity zones were properly confined. These results provided key input for guiding future physical model testing and, and helped validate the design before construction.