CFD investigation of spillway flows and structural stressors : Evaluating operational conditions and aerator integration

Hydropower remains a cornerstone of Sweden’s renewable energy system, with spillways playinga vital role in ensuring dam safety by safely conveying excess water downstream. However, longterm exposure to extreme hydraulic conditions can lead to structural deterioration in spillwaycomponents.This study presents a numerical investigation of hydraulic conditions within a spillway exhibitingsigns of structural deterioration. Using computational fluid dynamics (CFD) in ANSYS Fluent,flow variables were analyzed under various operational and geometric scenarios. The objectivewas to identify mechanisms contributing to material erosion and to evaluate potential mitigationstrategies.A two-dimensional model was initially developed and validated against discharge measurements.Mesh sensitivity studies were conducted to ensure numerical reliability, followed by simulationsassessing the effects of varying tailwater levels and gate configurations. Results indicated thatreduced tailwater levels and partial gate closures amplified damaging hydraulic conditions invarying degrees. In contrast, higher downstream water levels generally improved flow stabilityand reduced risk factors.To address the identified vulnerabilities, a three-dimensional model incorporating an aeratorstructure was developed. The addition of the aerator successfully eliminated critical low-pressurezones near the spillway crest and both reduced- and redirected peak hydraulic loads to the nappeimpact region, significantly lowering cavitation potential and associated risks. Two aerator con-figurations with varying dimensions were tested and produced nearly identical results, highlight-ing the potential for design flexibility and the value of exploring further variations for optimiza-tion.The results suggest that targeted geometric modifications can effectively improve spillway re-silience, offering a foundation for future design improvements and operational guidelines aimedat minimizing long term structural damage.