Stepped spillway model enables reduction of kinetic energy in a plant

Researchers of Dona Francisca Energética S/A and of UFRGS built, in the laboratory, a stepped spillway model to evaluate the physical characteristics of the water flow, both in the spillway and downstream (lower location, in the case of rivers and creeks and streams, they are the points placed towards its mouth, the stream, downstream), in the dissipation basin, located after the spillway of a hydroelectric plant. The basic function of a stepped spillway is to reduce the kinetic energy downstream of the plant, minimizing the impact speed of the water jet, the cavitation effects (vacuum formation), erosion and fatigue in the riverbed or structures. To prevent damage to hydraulic structures, it is essential that the kinetic energy generated by the flow is mostly dissipated. One of the most widespread methods for energy dissipation is the use of stepped spillway. With the dissipation of energy, it is possible to reduce the bearing capacity (storage capacity) of the dissipation basin, such as length, thickness and anchoring. This may cause a decrease in the total costs of the works of energy dissipation. The data obtained by researchers in the laboratory were used to determine the locations where there were larger fluctuations of pressure on the stairs and where the important pressure fluctuations on the dissipation basin ended. Thus, the researchers concluded that it is possible to evaluate the sites that will be more problematic (due to the hydrodynamic efforts) in the stepped spillway structure and learn, in advance, the values ​​of pressure in a dissipation basin downstream of spillways. This information can be used in future stepped spillway designs, allowing a safer and cheaper design, and becoming part of the information database on stepped spillway structures.