Numerical Simulation of the Rotating Vortex Rope with Code_Saturne

The paper presents numerical simulations of the rotating vortex rope (RVR) inside a Francis turbine draft tube. The computational fluid dynamics (CFD) calculations were carried out using the Code_Saturne software. The geometry of the turbine was obtained from the Francis-99 workshops. The mesh files provided for the Francis-99 workshop II were modified in the Salome's mesh module, SMESH, in order to comply with the Code_Saturne mesh quality criteria. First, steady state numerical simulations using the Frozen Rotor turbomachinery model were performed at best efficiency point (BEP) and part load (PL) on a reduced model of the Francis-99 turbine. The reduced geometry consisted in one runner blade, one splitter blade and part of the draft tube. The post-processing part was carried out in ParaVIEW. The results were validated against experimental data. Secondly a numerical unsteady simulation was performed at PL in the draft tube of the Francis-99 turbine to capture the RVR.