Labyrinth spillway

Description

A spillway is a hydraulic structure designed to regulate the water level stored behind a dam or levee, typically discharging excess flow into a downstream riverbed. Several spillway configurations exist, each suited to different site and capacity requirements.

As incoming water raises the reservoir level beyond the dam's storage capacity, the surplus volume must be safely released downstream through the spillway. This project simulates a labyrinth spillway positioned at the center of a channel, designed to manage and control the stored water height behind it.

The 3D geometry was built in Design Modeler, and an unstructured mesh was generated in ANSYS Meshing, producing 464,175 elements. Using ANSYS Fluent's Make Polyhedral function, this element count was later reduced to 99,248, improving computational efficiency without sacrificing accuracy.

Methodology

The simulation is run as a transient (unsteady) case to properly capture the time-dependent behavior of the fluid. A pressure-based solver is used, appropriate for the incompressible working fluid. Gravitational effects are included by applying an acceleration of 9.81 m/s² in the negative Y-direction. Multiphase behavior is captured using the VOF (Volume of Fluid) model to track the interacting fluid phases throughout the simulation.

Conclusion

The water level retained behind the spillway stabilizes at a height equal to the spillway's own height, while any inflow exceeding the dam's storage capacity is directed over it. This excess water passes through the labyrinth spillway and continues downstream, helping maintain a controlled reservoir level.

The contours and animations reveal turbulent behavior as incoming water pushes the stored fluid toward the downstream side. Once the flow overtops the dam structure, it accelerates noticeably before reaching the outlet.