This study discusses the issue of cavitation damage to concrete structures in dam spillways and the potential risks associated with it. Cavitation can cause cracks on the concrete surface, leading to further damage by means of sulfate attack, freeze-thaw, alkali-silica reaction, and others. To prevent this damage, stepped spillways are recommended as they are suitable and cost-effective options for high-volume storage dams that require significant energy dissipation. In this study, a numerical analysis was conducted on the hydraulic characteristics of the skimming flow regime of the stepped spillway of the Zirdan Dam. The study compared the flow characteristics of stepped and smooth spillways. The numerical models used the k-ε RNG turbulence model and the multiphase mixture method, and field data was collected for validation. The results showed that the presence of steps along the spillway caused a significant reduction in the length of the boundary layer, which led to faster aeration and reduced the risk of cavitation and destruction. The cavitation index was found to be higher than the critical limit along the entire length of the stepped spillway, while for the smooth spillway, negative pressures occurred 56 m from the crest of the spillway on the downstream side. The energy dissipation for the stepped spillway was found to be 47% higher than that of the smooth spillway for the design discharge. Overall, the study provides valuable insights into the benefits of stepped spillways in preventing cavitation damage to concrete structures in dam spillways.
Author(s) Details:
Farzin Salmasi,
Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.
John Abraham,
School of Engineering, University of St. Thomas, Minnesota, USA.