Numerical study on jet flow characteristics of high head and large discharge spillways

Sammanfattning: Today scale models are used to design spillway structures for hydropower stations. These are expensive and time-consuming to build and alter. This study investigates the possibilities of using numerical simulations in order to facilitate the spillway design process. It would be possible to save time and resources by altering the spillway parameters in the numerical model and thus find an optimal design, which can be further investigated with a scale model. However, it is complicated to simulate turbulent flows. Therefore the simulated flows in this study are compared to experimental measurements in order to investigate the accuracy of the numerical model. Ansys software Fluent uses Computational Fluid Dynamics (CFD) to calculate turbulent flows and is used as the simulation tool in this study. The simulations were performed on the spillway system of Shuibuya hydropower station. There are five spillway channels with flip bucket terminals and high head. In order to investigate the risk of erosion during large flows the jet throw distance was examined in experiments on a scale model. The same parameter was investigated in this simulation study. The acceptable error margin was set 30 % for the comparison between simulated and experimental measurements. All performed simulations met this criterion. It was therefore concluded that Fluent could be used as a sufficiently good approximation tool when it comes to turbulent flows in spillways.