Numerical Methodology to Predict and Analyze Cavitating Flows in a Kaplan Turbine

Abstract

A computational methodology to predict the cavitation phenomena appearance and evolution in a 5-blades Kaplan turbine scale model was developed. Two different inlet boundary conditions have been tested in both non-cavitating and cavitating regimes: the classical one, the mass flow rate and the new one, the total pressure. The best results were obtained applying a constant total pressure on the inlet. The torque and efficiency drop curves were well-predicted with the proposed calculation methodology and the numerical cavitation structures agreed with experimental observations. Indeed, this new inlet boundary condition allows to keep the machine head constant during the cavitation drop, as in experiments. Unsteady simulations are under investigation to improve the prediction and the analyses of more developed cavitating regimes.