Influence of the tip gap size on the development of the tip-leakage vortex using Large Eddy Simulations
Jean Decaix, Guillaume Balarac, Matthieu Dreyer, Mohamed Farhat, Cécile Münch
Session: Large Eddy Simulation 1
Session starts: Thursday 27 August, 10:30
Presentation starts: 10:30
Room: Room E
Jean Decaix (Univ. of Applied Sciences and Arts, Western Switzerland)
Guillaume Balarac (Univ. Grenoble Alpes, LEGI)
Matthieu Dreyer (Ecole Polytechnique Fédérale de Lausanne, Laboratory for Hydraulic Machines)
Mohamed Farhat (Ecole Polytechnique Fédérale de Lausanne, Laboratory for Hydraulic Machines)
Cécile Münch (Univ. of Applied Sciences and Arts, Western Switzerland)
In hydraulic turbines, the tip-leakage vortex is responsible for flow instabilities and for promoting erosion due to cavitation. To better understand the flow in the tip region, LES computations are carried out to compute the flow around a NACA0009 blade including the gap between the tip and the wall. The influence of the gap size is investigated by computing two gap widths.
The validation of the results is performed by comparisons with experimental data. The simulations are also used to investigate the flow in the tip gap region. Depending on the gap width, the vortex flow topology differs from one case to the other. At large gap widths, the tip-leakage vortex merges with the tip-separation vortex. On the contrary, at small gap widths, the tip-leakage vortex move upward and no tip-separation vortex is clearly identified. Part of these observations are validated by comparisons with experimental visualizations of the cavitating tip-leakage vortex.