Numerical modelling of cavitation erosion
Résumé
The goal of the work is to investigate the possibility of cavitation erosion prediction using computational fluid dynamics (CFD) tools only. For that purpose, a numerical process based on a coupling between CFD and an erosion model is presented and tested in several configurations of cavitating flow on a two-dimensional hydrofoil. The CFD code, which is based on the homogeneous approach, was previously validated on numerous experiments. In the present work, the predictions of velocity and pressure evolutions in the vicinity of the hydrofoil are compared with experimentally measured data. A close agreement is systematically obtained. The erosion model is based on the physical description of phenomena from cavitation cloud implosion, pressure wave emission and its attenuation, micro-jet formation and finally to the pit formation. The coupling between CFD and the erosion model is based on the use of local pressure, void fraction and velocity values to determine the magnitude of damage at a certain point. The results are compared with the experimentally measured damage on the hydrofoil. In the experiments a thin copper foil applied to the surface of the hydrofoil was used as an erosion sensor. A pit-count method was applied to evaluate the damage. The comparison shows that it is possible to use solely CFD tools to predict time evolution of cavitation erosion, including final extent and magnitude, with a very good accuracy.