Cavitation Simulations of a Tip Leakage Vortex for a NACA0009 Hydrofoil and a Francis Turbine at Stable Full Load Operating Point

In the first part of the study, the ability of homogeneous and inhomogeneous two-phase modeling approach is investigated using a NACA0009 hydrofoil with a cavitating tip leakage vortex. The results indicate that the inhomogeneous model does not increase accuracy of the simulation results. This can be explained by the small diameter of the cavitation bubbles, which results in a strong coupling between liquid and vapor phase. Based on the results for the test case, homogeneous model is applied for two-phase simulations of a Francis turbine at a stable full load operating point. The mesh study demonstrates the need for fine meshes with a size of approximately 50 million elements. While the effect of the cavitation constants can be neglected, the geometry of the runner nut and enabling curvature correction in the SST turbulence model has a relevant impact on simulation accuracy. The use of a transient rotor stator interface is challenging for computational performance. Applying multipass partitioning method increases the speedup by around 10%. Further performance improvement can be achieved with the expert parameter $$parallel \; optimization \; level$$ . All in all, a parallelization on 1200 cores is reasonable.