A comparative analysis of CFD methodologies to predict the performance of Francis turbine

Abstract A Francis turbine’s flow characteristics strongly depend on the operating conditions. Accurately predicting the flow field within a turbine unit is challenging due to complex flow phenomena, such as separation around the turbine blades, pressure variations within the runner, and swirling flows in the draft tube. Various CFD methodologies can be employed to predict turbine performance. The present work evaluates the reliability of different CFD simulation methodologies in predicting turbine performance, focusing on the sensitivity of different turbulence models, grid types, and modeling approaches for accurate numerical solutions. Simulations are performed on a high-head Francis turbine under various operating conditions, including part load, Best Efficiency Point (BEP), and high load conditions, each representing a different turbine flow field. The simulation results are compared with experimental data from model tests to confirm the reliability of the numerical simulations for Francis turbines. The results show that the SST k-ω model with a hexahedral mesh (HH) is best suited for overall turbine performance prediction.